ARVO 2016 Annual Meeting Abstracts 160 Stem Cell Engineering and Fundamental Mechanisms Sunday, May 01, 2016 3:15 PM–5:00 PM Exhibit/Poster Hall Poster Session Program #/Board # Range: 1130–1150/B0349–B0369 Organizing Section: Retinal Cell Biology Program Number: 1130 Poster Board Number: B0349 Presentation Time: 3:15 PM–5:00 PM Xeno-free defined conditions for differentiation of proteininduced pluripotent stem cells towards retinal precursor cells Ramesh Kaini, Heuy-Ching H. Wang. Ophthalmology, United States Army Inst of Surgical Rsrch, San Antonio, TX. Purpose: Induced pluripotent stem cells (iPSCs) have been successfully differentiated into different retinal cell types, thus instilling hopes for stem cell-based therapy in various retinal degenerative diseases and trauma. However, iPSCs used in these studies were reprogrammed using retroviral or lentiviral approaches and differentiated using animal derived products that may have potential risks of oncogenesis, zoonotic disease transmission, and immune rejection. Therefore, we sought to differentiate genetic integration free, protein-induced pluripotent stem cells (piPSCs) towards retinal lineage and generate clinical-grade retinal precursor cells in defined xeno-free conditions. Methods: Commercially available piPSCs were maintained in xeno-free TeSR-E8 medium and vitronectinXF coated culture plates for at least 5 passages. piPSCs were differentiated towards retinal lineage by using a modified protocol by Sridhar A et al. Cells were dissociated using ReLeSRTM and then generated as uniform sized EBS of 9000 cells/EB using Aggrewell. EBs were gradually transitioned to neural induction medium (NIM) on day 3 of differentiation and maintained in suspension culture in rotary cell culture system (Synthecon) for 7 days. EBs were plated on vitronectinXF coated plates on day 8. On Day 17, aggregates were dislodged and transferred to rotary cell culture system in retinal differentiation medium (RDM). Results: piPSCs maintained in vitronectinXF coated plates with TeSR-E8 medium retained the expression of pluripotent markers, including OCT4, Nanog, SSEA-3, and TRA-1-60 after five passages. During retinal differentiation, piPSCs acquired expression of various neural and retinal specification markers including Otx2, Sox2, LHX2, RAX, PAX6, and CHX10 at different time points of differentiation. Conclusions: In this study, we have confirmed the capacity of piPSCs to differentiate into retinal precursor cells using a modified xeno-free retinal differentiation protocol. Our results suggest that pluripotent stem cells developed using protein-based reprogramming can be a viable option for generating a safe source of patient-specific cells for retinal regenerative therapies. Commercial Relationships: Ramesh Kaini; Heuy-Ching H. Wang, None Program Number: 1131 Poster Board Number: B0350 Presentation Time: 3:15 PM–5:00 PM Generating cone photoreceptor-like cells by inhibiting BMP and Activin/TGFβ signaling in early primitive ectoderm-like cells Kimberly A. Wong1, 2, Michael Trembley6, Ichiro Hiratani5, David M. Gilbert4, Andrea S. Viczian3, 2. 1Neuroscience & Physiology, SUNY Upstate Medical University, Syracuse, NY; 2Center for Vision Research, SUNY Upstate Medical University, Syracuse, NY; 3Ophthalmology, SUNY Upstate Medical University, Syracuse, NY; 4Biological Science, Florida State University, Tallahassee, FL; 5RIKEN Center for Developmental Biology, Kobe, Japan; 6 Pharmacology & Physiology, Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, Rochester, NY. Purpose: Photoreceptor cells derived from mouse embryonic stem (mES) cells are an attractive source for studying photoreceptor-replacement therapies; however, current studies have been unsuccessful in generating a sufficient number of cone photoreceptors, due to a lack of understanding about how cones are specified. In Xenopus, we have found that inhibition of bone morphogenetic protein (BMP) and Activin/TGFβ signaling pathways in primitive ectoderm is sufficient to bias cells to retinal progenitor cells. We hypothesize that a similar treatment with BMP and Activin/ TGFβ inhibitors will direct mES-derived primitive ectoderm to become retinal progenitors, including cone photoreceptors. Methods: Mouse D3 ES cells were treated with conditioned media in suspension and transformed into primitive ectoderm-like (EPL) spheroids. Cultures were then supplemented with Noggin, or the chemical inhibitors dorsomorphin and SB431542, to inhibit BMP and Activin/TGFβ signaling, respectively. After differentiation, we assayed for the presence of various neural and retinal cell types by immunofluorescence and qRT-PCR. We also conducted this assay with transgenic Crx-GFP ES cells, which allowed for visual identification and sorting of GFP+ photoreceptor precursors. Results: If first converted to primitive ectoderm, treatment with high concentrations of BMP and activin/TGFβ inhibitors resulted in a dose-dependent reduction of pluripotency markers and increase in neural and retinal progenitor markers. Interestingly, we found that 99% of the inhibitor-treated aggregates expressed markers for photoreceptors (crx), and 93% of aggregates expressed cone-specific opsins (M-opsin, S-opsin). Within these spheres, 62 ±12% of cells were crx+ photoreceptor progenitors, and that 23.8 ± 0.7% of cells expressed S-opsin after 9 days of culture. Conclusions: These findings suggested that first restricting mES cells to a primitive ectoderm lineage creates an environment where BMP and activin/TGFβ inhibition can induce significant cone photoreceptor generation in vitro. These results allow a better understanding of the signaling responsible for directing cells towards photoreceptor lineages. We are currently developing a method to differentiate cone and rod progenitors in our cultures, in order to identify cone-specific signaling factors. Commercial Relationships: Kimberly A. Wong, None; Michael Trembley, None; Ichiro Hiratani, None; David M. Gilbert, None; Andrea S. Viczian, None Support: NEI Grant EY019517, Research to Prevent Blindness Unrestricted Award, and the Lions of District 20-Y1 Program Number: 1132 Poster Board Number: B0351 Presentation Time: 3:15 PM–5:00 PM BMP/SMAD-signaling is necessary for the formation of proliferating Müller glia-derived progenitors Levi Todd, Isabella Palazzo, Natalie Squires, Andrew J. Fischer. Neuroscience, The Ohio State University, Columbus, OH. These abstracts are licensed under a Creative Commons Attribution-NonCommercial-No Derivatives 4.0 International License. Go to http://iovs.arvojournals.org/ to access the versions of record. ARVO 2016 Annual Meeting Abstracts Purpose: Müller glia are the predominant glial cell type in the retina and normally perform homeostatic functions. However, in response to acute retinal injury or treatment with growth factors, Müller glia can become proliferating neurogenic progenitors with the ability to replace lost neurons. Therefore, understanding the mechanisms that orchestrate the ability of Müller glia to transition into Müller gliaderived progenitor cells (MGPCs) is imperative to harnessing the regenerative capacity of the retina. This study investigates whether BMP/SMAD-signaling influences the formation of neurogenic MGPCs in the in vivo chick retina. Methods: All experiments utilized hatched chicks (7-21 days old). Compounds were delivered via intraocular injections where one eye served as the “experimental” eye and the contralateral eye served as the “control”. Compounds included recombinant BMP4 to activate BMP/SMAD-signaling, the small molecule inhibitor DMH1 to selectively block the BMP receptor, and recombinant FGF2 to activate MAPK-signaling and stimulate proliferating Müller glia. Retinas were damaged by a single injection of N-Methyl-D-aspartate (NMDA). Intraocular injections of BrdU/EdU were applied during experimental paradigms to label proliferating cells. Following injection paradigms, retinas were harvested and processed for indirect immunofluorescence and digital photomicroscopy. Significance of difference (*p<0.05; n≥5) was determined by using a paired, twotailed t-test. Results: We found that pSMAD1/5/8, a readout of active BMP/ SMAD-signaling, accumulates selectively in Müller glia in response to injections with BMP4, NMDA or FGF2. We found that DMH1 specifically inhibits the up-regulation of pSMAD induced by BMP4. We also found that inhibition of BMPR1 suppressed the formation of proliferating MGPCs in NMDA and FGF2-treated retinas. Evidence is provided using immunohistochemistry that inhibition of BMP/ SMAD-signaling may impact the formation of MGPCs by disrupting Müller glia’s ability to up-regulate cFos, pS6 (a readout of mTorsignaling), and the retinal stem cell factor Pax6. Conclusions: Our data suggests that active BMP/SMAD-signaling is necessary for the formation of MGPCs. This work provides novel data that the BMP/SMAD-signaling is an important component of the network of cell-signaling pathways that regulate the formation or MGPCs and retinal regeneration. Commercial Relationships: Levi Todd, None; Isabella Palazzo, None; Natalie Squires, None; Andrew J. Fischer, None Support: NIH-EY022030-3 Program Number: 1133 Poster Board Number: B0352 Presentation Time: 3:15 PM–5:00 PM Differential effects of early BMP4 exposure on optic vesicle production across multiple hiPSC lines Jishnu Saha1, Elizabeth E. Capowski1, Divya Sinha1, Jee Min1, Joe Phillips1, 3, David M. Gamm2, 3. 1Waisman Center, University of Wisconsin-Madison, Madison, WI; 2Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI; 3McPherson Eye Research Institute, University of WisconsinMadison, Madison, WI. Purpose: To test the effect of brief, early BMP4 treatment (Kuwahara et al. (2015) Nat Commun. 6:6286) on the production of 3-D optic vesicle-like structures (OVs) from multiple hiPSC lines. Methods: hiPSC lines derived from 8 individuals were maintained on Matrigel in mTesR1 and differentiated to OVs according to our established stepwise protocol, which minimizes the use of exogenous factors (Meyer et al. (2011) Stem Cells 29: 1206; Phillips et al. (2012) IOVS 53:2007). On day 6 of differentiation, each line was treated with or without 55 ng/ml BMP4, followed by 1:1 media exchanges every 3 days until day 16, when neuroectodermal colonies were lifted from the culture plates. Efficiency of hiPSC-OV production was assessed by counting OVs and non-OV neurospheres at day 25. Results: In the absence of BMP4, one of the hiPSC lines routinely generated >50% OVs (high producer), 6 generated <10% OVs (low producer), and one never generated OVs or any other neuroectodermal derivative (non-producer). The low producing lines had the greatest responses to BMP4 treatment, significantly increasing OV production an average of 8.4 ± 2.1-fold (p = 0.0038) per 6 well starting plate of undifferentiated hiPSCs. The non-producing hiPSC line also responded to BMP4 treatment by generating neuroectoderm, but did not yield OVs. However, the high producing line showed no difference in OV production with or without BMP4 treatment. Conclusions: BMP4 treatment is capable of significantly increasing the yield of OVs in low producing hiPSC lines. These results extend the previously published findings of Kuwahara et al. (2015) and demonstrate both the utility and the limitations of this culture modification. Commercial Relationships: Jishnu Saha; Elizabeth E. Capowski, None; Divya Sinha, None; Jee Min, None; Joe Phillips, None; David M. Gamm, None Support: Foundation Fighting Blinding Wynn-Gunn TRAP (Translational Research Acceleration Program) Research Award, Research to Prevent Blindness, Retina Research Foundation (Kathryn and Latimer Murfee and Emmett A. Humble Chairs) McPherson Eye Research Institute (Sandra Lemke Trout Chair), NIH P30HD03352, and NIH R01EY21218 Program Number: 1134 Poster Board Number: B0353 Presentation Time: 3:15 PM–5:00 PM The role of SIX6 in the development of optic vesicle-like structures derived from human pluripotent stem cells Jessica A. Cooke1, Akshayalakshmi Sridhar1, Sarah Ohlemacher1, Jason S. Meyer1, 2. 1Biology, IUPUI, Indi, IN; 2Stark Neurosciences Research Institute, Indiana University, Indianapolis, IN. Purpose: Three-dimensional optic vesicle-like structures are capable of being derived from human pluripotent stem cells (hPSCs). Highly enriched for retinal progenitor cells, these populations express a number of transcription factors associated with retinal development. Among these is the homeobox transcription factor SIX6, which is highly expressed in retinal progenitor cells yet its precise role in early retinogenesis remains largely unclear. In the current study, efforts were undertaken to elucidate the role(s) of SIX6 in the formation of hPSC-derived three-dimensional optic vesicle-like structures. Methods: hPSCs were differentiated to yield three-dimensional optic vesicle-like structures following existing protocols. Following differentiation, optic vesicle-like structures were readily identified and isolated apart from non-retinal forebrain populations of cells. The retinal progenitor nature of these cells was confirmed by both immunocytochemistry and qRT-PCR. To identify a role for SIX6, the gene was either overexpressed or knocked down in hPSCs using a lentiviral vector and its effects on proliferation and differentiation were characterized. Results: Within the first thirty days of differentiation, hPSCderived optic vesicle-like structures were isolated and the retinal progenitor nature of these cells was confirmed by their expression of developmental transcription factors including CHX10, RAX, and PAX6. Analysis of the expression of SIX6 within these cells demonstrated a specific localization within hPSC-derived optic vesicle-like structures, in which nearly all cells were SIX6positive. Further analysis of the role of SIX6 by overexpression and These abstracts are licensed under a Creative Commons Attribution-NonCommercial-No Derivatives 4.0 International License. Go to http://iovs.arvojournals.org/ to access the versions of record. ARVO 2016 Annual Meeting Abstracts knockdown demonstrated important roles in the proliferation and differentiation of hPSC-derived optic vesicle-like structures. Conclusions: Overall, the results of this study build a foundation for understanding the role of SIX6 in retinal development. SIX6 was highly expressed specifically within optic vesicle-like structures, indicating an important role in the establishment of a retinal fate, as well as the differentiation of retinal cell types. Such results help to establish hPSCs as a valuable in vitro model system for studies of human retinogenesis, with important implications for the differentiation of specific cell types for translational applications. Commercial Relationships: Jessica A. Cooke, None; Akshayalakshmi Sridhar, None; Sarah Ohlemacher, None; Jason S. Meyer, None Support: NEI RO1 EY024940 Program Number: 1135 Poster Board Number: B0354 Presentation Time: 3:15 PM–5:00 PM Elucidating the role of RAX in human retinogenesis with pluripotent stem cells Akshayalakshmi Sridhar1, Casey A. Miller1, Kimberly Ho-A-Lim1, Jessica A. Cooke1, Sarah Ohlemacher1, Jason S. Meyer1, 2. 1Biology, Indiana Univ Purdue Univ Indianapolis, Indianapolis, IN; 2Stark Neurosciences, Indiana University, Indianapolis, IN. Purpose: Human pluripotent stem cells (hPSCs) allow for the unprecedented ability to recapitulate the earliest stages of human retinogenesis, including the establishment of a definitive retinal fate from a more primitive neural progenitor source. Recent studies have clearly illustrated this ability, with hPSCs possessing the capacity to give rise to three-dimensional optic vesicle-like structures in vitro. In this role, hPSCs provide an attractive in vitro model for elucidating complex mechanisms of human retinogenesis in an easily accessible in vitro system. Methods: hPSCs were directed to a retinal lineage as via previously described, resulting in three-dimensional optic vesicle-like structures. Initially, the expression patterns of critical eye field transcription factors were analyzed over a timecourse of differentiation via immunocytochemistry and quantitative RT-PCR. Lentiviralmediated overexpression and shRNA knockdown approaches were also utilized to evaluate the role of critical transcription factors in retinal differentiation. Additionally, DNA methylation analyses were performed to identify epigenetic modifications associated with early retinal fate determination. Results: At early stages of differentiation, RAX was observed to be expressed broadly throughout most cells, followed by its restriction to a subpopulation of cells shortly thereafter. This restriction was closely associated with the onset of more definitive retinal transcription factors such as SIX6 and CHX10. Interestingly, the expression of RAX was also absent from any cells adopting a non-retinal forebrain phenotype, suggesting a critical role for RAX in retinal specification. Methylation analysis of the RAX promoter suggested that epigenetic mechanisms could potentially account for the restricted expression of RAX in early retinal differentiation. Overexpression and knockdown of RAX further demonstrated its requirement in the establishment of a retinal fate, as well as the specification of particular retinal cell types. Conclusions: Overall, the results of this study help to demonstrate the suitability of hPSCs as an effective in vitro model of human retinogenesis, with RAX demonstrated to be critical for the initial establishment of a retinal fate as well as the specification of particular retinal cell types. Such results help to establish hPSCs as a valuable in vitro model system for studies of human retinogenesis. Commercial Relationships: Akshayalakshmi Sridhar, None; Casey A. Miller; Kimberly Ho-A-Lim, None; Jessica A. Cooke, None; Sarah Ohlemacher, None; Jason S. Meyer, None Support: NEI R01 EY024940, BrightFocus Foundation Grant G2012027, Indiana CTSI (NIH/NCRR Grant UL1TR001108) Program Number: 1136 Poster Board Number: B0355 Presentation Time: 3:15 PM–5:00 PM Development of a step-wise protocol for the generation of human induced pluripotent stem cell-derived choroidal endothelial cells Allison E. Songstad, Luke A. Wiley, Erin R. Burnight, S Scott Whitmore, Emily E. Kaalberg, Megan J. Riker, Edwin M. Stone, Robert F. Mullins, Budd A. Tucker. Stephen A. Wynn Institute for Vision Research, Carver College of Medicine, University of Iowa, Iowa City, IA. Purpose: Age-related macular degeneration (AMD) involves dysfunction of choroidal endothelial cells (CEC), retinal pigment epithelial cells (RPE), and photoreceptor cells (PRs). Human induced pluripotent stem cell (iPSC)-based strategies to replace PRs and RPE are a major scientific focus. However, success of these approaches may require the replacement of damaged and lost CECs, which degenerate early in the pathogenesis of AMD. The purpose of this study is to design a step-wise differentiation protocol to generate iPSC-derived CECs. Methods: Fibroblasts from a patient with normal ocular history were isolated from a skin biopsy and reprogrammed into iPSCs via transduction with a non-integrating Sendai virus driving expression of OCT4, SOX2, KLF4, and c-MYC. Pluripotency was assessed via TaqMan Scorecard Assay and immunocytochemistry (ICC). RNA sequencing analysis of cultured monkey RF/6A CECs and 2-D gel/ mass spec analysis of RF/6A-conditioned medium identified seven secreted proteins known to be involved in vascular development. Using the Taguchi statistical strategy, media were developed using combinations of the seven proteins to drive CEC differentiation. In a separate strategy, each protein was eliminated one at a time from the differentiation protocol to identify those that were crucial for CEC differentiation. The iPSC-CECs from both methods were characterized via rt-PCR and ICC for EC- and CEC-specific markers. Results: Using each approach, patient-specific iPSCs cultured in media containing CTGF, TWEAKR, and VEGF-B differentiated into CECs that expressed the EC-specific markers CD31, CD34, eNOS, FOXA2, ICAM1, TIE2, and VE-Cadherin, and the CEC-restricted markers CA4 and TTR. CTGF is required for CEC differentiation, whereas TWEAKR and VEGF-B enhanced CEC differentiation. CTNNB1, PDPN, RTN4, and SHC1 did not play a major role in CEC differentiation. The iPSC-CECs fed CTGF, TWEAKR, and VEGF-B formed vascular tube networks morphologically identical to those formed in primary human CEC cultures. Conclusions: We describe two strategies used to develop a stepwise differentiation protocol for the derivation of CECs from patientspecific iPSCs. In addition to being useful for cell replacement, patient-specific CECs, in combination with RPE and PRs, will be invaluable to accurately interrogate the pathophysiology of AMD. Commercial Relationships: Allison E. Songstad, None; Luke A. Wiley, None; Erin R. Burnight, None; S Scott Whitmore, None; Emily E. Kaalberg, None; Megan J. Riker, None; Edwin M. Stone, None; Robert F. Mullins, None; Budd A. Tucker, None Support: Wynn Institute Endowment for Vision Research, Elmer and Sylvia Sramek Charitable Foundation, NIH RO1 - EY 024605 These abstracts are licensed under a Creative Commons Attribution-NonCommercial-No Derivatives 4.0 International License. Go to http://iovs.arvojournals.org/ to access the versions of record. ARVO 2016 Annual Meeting Abstracts Program Number: 1137 Poster Board Number: B0356 Presentation Time: 3:15 PM–5:00 PM A flow cytometry sorting method for the production of high fidelity retinal pigmented epithelial cells Lisa R. Conti, Monte J. Radeke, Carolyn Radeke, Tyler Jean, Stephanie LaBouve, Pete J. Coffey. Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA. Purpose: Establishing renewable sources of retinal pigmented epithelial cells (RPE) and creating patient-specific cell lines that produce high fidelity RPE is valuable to the field of degenerative eye research. Prevailing techniques for iPSC-derived RPE (iPSCRPE) production rely on manual dissection or passive enrichment by passage. These methods are often labor intensive, variable and restricted to cell lines with a propensity to produce high quantities of pigmented cells. This study sought to determine whether granularity, conferred by pigment, is sufficient to purify iPSC-RPE cells from mixed differentiated cultures via flow cytometry. Methods: Five iPSC lines were established from fRPE donor lines. Following differentiation using three methods, cells were dissociated and sorted based on side and forward scatter-properties. Pigmented cells were collected and, following an expansion step, transcriptome profiles were compared to their fRPE counterparts. Cultures were further subject to immunocytochemistry (ICC) characterization. Results: A single round of sorting yielded cell populations that formed uniform pigmented epithelial monolayers. Intra-donor specific transcriptome comparison between iPSC-RPE and fRPE cell lines revealed gene markers consistent with strong RPE cell signatures. In the few cases where sorted cultures displayed heterogeneous pigment patterns, contaminant cell marker signatures, confirmed with ICC, coincided. In these cases, a second round of sorting established culture purity. High fidelity, high purity RPE cultures were expandable up to 1000 fold. To date, we have applied this enrichment method to generate seven iPSC-RPE lines, producing banks that range from 3 to 55 million cells per line Conclusions: Sorting based on pigment is an effective technique for enriching iPSC-RPE cell lines. Notably, sorting is applicable to iPSC lines with limited pigmented cell production, providing a resource where samples are scarce. Further, this technique can eliminate the need for cell line termination following failed enrichment attempts. In all, we have established a flow cytometry pigment based method for the reliable, user-independent production of high fidelity RPE. Commercial Relationships: Lisa R. Conti, None; Monte J. Radeke, None; Carolyn Radeke, None; Tyler Jean, None; Stephanie LaBouve, None; Pete J. Coffey Support: CIRM LA1-02086, Garland Initiative for Vision Research, Arnold and Mabel Beckman Initiative for Macular Research Program Number: 1138 Poster Board Number: B0357 Presentation Time: 3:15 PM–5:00 PM Adipose tissue derived mesenchymal stem cells migrate towards RPE, rescue apoptotic RPE under oxidative stress, and have the potential to differentiate into RPE Aya Barzelay, Sebastian Katz, Shira Wheisthal, Moshe Ben - Hemo, Anat Loewenstein, Adiel Barak. Division of Ophthalmology, Tel Aviv Medical Center, Tel Aviv, Israel. Purpose: Oxidative stress plays a cardinal role in the pathophysiology of AMD, and leads to apoptosis of RPE. Adipose tissue derived mesenchymal stem cells (ASCs) may serve as a therapeutic tool to regenerate RPE. Here we evaluated the activity of ASCs when exposed to RPE under oxidative stress in vitro; we assessed their migratory capacity towards injured RPE, and their ability to prevent apoptosis of RPE. We also studied the differentiation potential of ASCs into RPE. Methods: Human ASCs were harvested from subcutaneous fat of patients undergoing abdominoplasty. Primary cultures of human RPE cells were subjected to oxidative stress by exposure to 1.5mM hydrogen peroxide (H2O2). Conditioned medium of “stressed” RPE was collected. The migratory capacity of ASCs towards conditioned medium of “stressed” RPE or towards conditioned medium of normoxic RPE was determined by a scratch assay. In order to study the preventive effect of ASCs on apoptosis of RPE, “stressed” RPE were treated with ASCs’ conditioned medium or with standard, nonconditioned medium. H2O2 induced RPE apoptosis was measured by Annexin V/ propidium iodide staining and flow cytomtery analysis. Finally, the differentiation potential of ASCs into RPE was evaluated by culturing ASCs with 10nM nicotine amide. Results: ASCs exhibited enhanced migration towards RPE that were subjected to oxidative stress (193%±0.4 increase cells per area, p<0.05). Treatment of “stressed” RPE with ASCs’ conditioned medium prevented H2O2 induced apoptosis (50±0.7% decrease cells number, p <0.05). After two weeks in differentiation medium, ASCs underwent marked morphological changes forming spheroid bodies in culture and upregulating early eye field markers (PAX6 2.2±0.1, RX 2.1±0.8, BF1 4.7±0.7, NestinA 2.3 ±0.38 folds). Conclusions: ASCs migrate towards RPE under oxidative stress and reduce H2O2 induced apoptosis of RPE. Moreover, ASCs demonstrate a differentiation potential into RPE evident by a morphological change and upregulation of eye field markers. These data may imply to a therapeutic potential of ASCs in regenerating RPE. ASCs exhibited enhanced migration when exposed to conditioned medium of RPE under oxidative stress (A- 0 hrs, C-24 hrs) compared to control(B-0 hrs, D-24 hrs). These abstracts are licensed under a Creative Commons Attribution-NonCommercial-No Derivatives 4.0 International License. Go to http://iovs.arvojournals.org/ to access the versions of record. ARVO 2016 Annual Meeting Abstracts was observed by IF staining until 2 weeks after implantation. Longterm expression of Phagocytosis-related receptors was observed 1 month and 4 months after implantation Conclusions: Subretinal implanted hESC-RPE cell might not conduct its biology function in short-term after implantation. Microenvironment of degenerated retina or surgical trauma might attribute to the delayed expression of functional receptors of hESCRPE cell. Commercial Relationships: LI ZHANG; Danhong Zhu, None; Hossein Nazari Khanamiri, None; Biju Thomas, None; Mark S. Humayun, None After two weeks in culture with differentiation medium, ASCs exhibited morphological change forming spheroid bodies. Commercial Relationships: Aya Barzelay, None; Sebastian Katz, None; Shira Wheisthal, None; Moshe Ben - Hemo, None; Anat Loewenstein, None; Adiel Barak, None Support: Moxie foundation grant Program Number: 1139 Poster Board Number: B0358 Presentation Time: 3:15 PM–5:00 PM Expression of phagocytosis-related receptors of subretinal implantated hESC-RPE cells in RCS rats LI ZHANG1, 2, Danhong Zhu2, Hossein Nazari Khanamiri3, 2, Biju Thomas2, Mark S. Humayun2. 1Eye Center, Second Affiliated Hospital, Medical School of Zhejiang University, Hangzhou, China; 2 Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA; 3University of Texas Medical Branch, Galveston, TX. Purpose: Retinal degeneration, including retinitis pigmentosa and age-related macular degeneration, are leading cause of blinding diseases worldwide. Efficient phagocytosis of photoreceptor outer segment (POS) fragments by retinal pigment epithelial (RPE) cells, which depends on the apical distribution of the integrin family adhesion receptor αvβ5 and Mer tyrosine kinase (MerTK) receptors, plays a key role in biological renewal and maintenance of retina health. hESC-RPE cell based treatment for retinal degeneration is heading towards clinical trial. How does the implanted hESC-RPE cell conduct its biology function and express functional-related receptors, remains currently unknown. This study aimed to observe the expression of functional-related receptors of hESC-RPE after implanted into the subretinal space of retinal degenerated animal model. Methods: Polarized monolayer hESC-RPE cell cultured on an ultrathin scaffold were transplanted into the subretinal space of RCS rats, which has been wildly used as an animal model of retinal degeneration. Eyeball samples were fixed and dissected at different time point (1 week, 2 weeks, 1 month and 4 months) after implantation. Optical coherence tomography (OCT) and H&E staining were used to assess the position of implanted scaffold in retina. Expression of human cell marker (TRA-1-85) and RPE specific marker (RPE65) were observed by Immunofluorescence (IF) staining. Phagocytosis-related receptors, including Integrin αvβ5, MerTK and Rhodopsin were stained with corresponding antibodies. Results: OCT and H&E staining confirmed the presence of monolayer of hESC-RPE attached to parylene up to 4 months postimplantation. No expression of Integrin αvβ5, MerTK or Rhodopsin Program Number: 1140 Poster Board Number: B0359 Presentation Time: 3:15 PM–5:00 PM Utilization of an extracellular flux assay to measure mitochondrial respiration in hPSC-RPE Divya Sinha1, 2, Gyda C. Beeson3, Molly M. Wilson1, Janis T. Eells4, Craig C. Beeson3, David M. Gamm5, 2. 1Waisman Center, University of Wisconsin-Madison, Madison, WI; 2McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI; 3Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC; 4Department of Biomedical Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI; 5Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI. Purpose: Human pluripotent stem cell-derived RPE (hPSC-RPE) cells are being utilized to model retinal disease in vitro, as well as to potentially treat patients with certain blinding disorders via cell transplantation. In vivo, RPE cells form a highly metabolically active monolayer that performs several important functions requiring efficient mitochondrial oxidative metabolism. Thus, efforts to monitor and optimize hPSC-RPE health should at least in part take into account mitochondrial function. Toward this end, we examined the behavior of hPSC-RPE in a well-established, rigorous extracellular flux (XF) assay after optimizing critical assay parameters. Methods: RPE cells were differentiated from human embryonic stem cells (hESC) or human induced pluripotent stem cells (hiPSCs) using protocols established by our lab. Pure monolayer cultures of hPSC-RPE were dissociated and then re-seeded at densities of 5000, 10000 or 30000 cells per well on XFe96-well microplates, and cultured for time periods varying from 1 day to two weeks. An XFe96 extracellular flux analyzer (Seahorse Bioscience) was used to measure basal respiration, ATP-coupled and maximal mitochondrial respiration via oxygen consumption rates (OCR). Data was analyzed using XF Wave software (Seahorse Bioscience). Results: A seeding density of 30,000 cells/well on Seahorse 96-well microplates works optimally to reproducibly measure OCR for hPSC-RPE. At lower seeding densities, confluent monolayers are not formed in 1-2 days resulting in variable OCRs. Basal OCR levels can reach greater than 100 pmol/min when seeded hPSC-RPE cells are maintained longer than 3 days in culture and maximal OCR can be 1.5 – 3-fold of basal. Conclusions: Efforts to optimize the XF assay for hPSC-RPE succeeded in producing highly robust and reproducible results when seeding density and length of time in culture were taken into consideration. hPSC-RPE demonstrated active mitochondrial respiration in these assays, indicative of overall excellent cell health. Commercial Relationships: Divya Sinha, None; Gyda C. Beeson, None; Molly M. Wilson, None; Janis T. Eells, None; Craig C. Beeson, None; David M. Gamm, None These abstracts are licensed under a Creative Commons Attribution-NonCommercial-No Derivatives 4.0 International License. Go to http://iovs.arvojournals.org/ to access the versions of record. ARVO 2016 Annual Meeting Abstracts Support: Research to Prevent Blindness Catalyst Award, International Retina Research Foundation, Foundation Fighting Blindness, NIH R01EY024588, Retinal Research Foundation Emmett A. Humble Distinguished Directorship, McPherson Eye Research Institute (Sandra Lemke Trout Chair), Carl and Mildred Reeves Foundation, NIH P30HD03352, Muskingum County Community Foundation, Choroideremia Research Foundation, SIG 1S10OD018039-01 for Seahorse XFe96 analyzer, Support Grant P30 CA014520 to SMSSF (core service of the University of Wisconsin Carbone Cancer Center) Program Number: 1141 Poster Board Number: B0360 Presentation Time: 3:15 PM–5:00 PM Rescue of MerTK retinitis pigmentosa using a human induced pluripotent stem cell disease model Conor M. Ramsden1, 2, Britta Nommiste1, Amelia Lane1, Michael Powner1, Amanda-Jayne F. Carr1, Andrew Webster1, Anthony T. Moore1, Lyndon da Cruz2, Pete Coffey1. 1Ophthalmology, Institute of Ophthalmology, London, United Kingdom; 2Vitreoretinal, Moorfields Eye Hospital, London, United Kingdom. Purpose: Inherited retinopathies are fast becoming the leading cause of blindness in developed countries. In order to counter this heterogeneous group of diseases, adequate disease models need to be developed in order to better understand pathology and to test potential therapies. Induced pluripotent stem cells offer us a new and radicle way to recapitulate the disease in the dish and give us almost limitless material to drive discovery. Methods: Fibroblast derived stem cells were used to generate RPE from a patient suffering from retinitis pigmentosa due to a deficiency in MerTK. The MerTK deficiency arises from a nonsense mutation causing a premature stop codon. These RPE cells were fully characterised and then exposed to a drug screen of read-through agents to force expression of the whole length protein. Results: Two candidate read-through agents were able to force translation through the premature stop codon. The G418 and PTC124 compounds had the best effect at restoring a full length MerTK protein phenotype. Conclusions: These findings represent a promising avenue of drug discovery in order to treat this rare and devastating disease. Commercial Relationships: Conor M. Ramsden, None; Britta Nommiste, None; Amelia Lane, None; Michael Powner, None; Amanda-Jayne F. Carr, None; Andrew Webster, None; Anthony T. Moore, None; Lyndon da Cruz, None; Pete Coffey, None Support: MRC/CIRM - G1000730 Program Number: 1142 Poster Board Number: B0361 Presentation Time: 3:15 PM–5:00 PM Maintenance of phenotype following Expansion of iPS cell derived RPE cultures through multiple passages Alan D. Marmorstein, Benjamin Gillies, Lori Bachman, Joshua Upton, Samuel Cross, Adiv A. Johnson, Lihua Y. Marmorstein. Ophthalmology, Mayo Clinic, Rochester, MN. Purpose: The use of induced pluripotent stem (iPS) cells in research on the retinal pigment epithelium (RPE) is limited by the ability to grow sufficient numbers of iPSC-derived RPE cells. Methods for the differentiation of iPSC-derived RPE require expensive media supplements, frequent feeding, extended periods of growth, and yet often yield small numbers of cells. This study sought to define conditions for the growth of large numbers of iPS-derived RPE cells using inexpensive media. Methods: The iPS cell line 006-BIOTR-0001 was obtained from the Mayo Clinic BioTrust and cultured in mTeSR1™ media on Geltrex™ coated plates. Differentiation of iPSCs to RPE was performed on Matrigel™ coated plates following a protocol using defined media. Differentiation was assessed using morphologic, biochemical, and functional criteria. Cells were then subject to additional passages during which they were switched to DMEM containing 1% FBS at 0, 7, 14, or 28 days after plating. Cells were passaged using one of 4 different enzymatic preparations. Results: iPSC-derived RPE formed a pigmented monolayer of hexagonal cells 60-80 days after initiation of differentiation. Differentiated cells formed monolayers of cuboidal epithelia with apical microvilli, melanin granules, and junctional complexes. The RPE marker protein Best1 was expressed and localized to the basolateral plasma membrane. Western blot demonstrated that cells expressed RPE markers Best1, CRALBP, PEDF, and RPE65. 80 days into the differentiation protocol we passaged cells at a 1:3 ratio using Accumax, Tryp LE, trypsin/EDTA, or dispase. Phenotype was best preserved using Accumax or Tryp LE. Cells were then transferred from DMEM containing B27 supplement to DMEM containing 1% FBS at 0, 7, 14, or 28 days, followed by passaging at 30 or 60 days using Accumax (1x). Following passage feeding was reduced from daily to 3x/week. Phenotype was preserved through at least 3 additional passages in cells following transfer to DMEM/1% FBS and was most effective after cells were preconditioned to DMEM/ FBS for at least 16 days prior to passage. Conclusions: Using these data we have developed a protocol that permits a single 6 cm plate of iPSCs to yield up to 81 x 6 cm plates of iPSC-derived RPE cells in as little as 170 days with the majority of those plates maintained in DMEM/FBS and fed three times per week. Commercial Relationships: Alan D. Marmorstein; Benjamin Gillies, None; Lori Bachman, None; Joshua Upton, None; Samuel Cross, None; Adiv A. Johnson, None; Lihua Y. Marmorstein, LAgen Laboratories LLC (I), LAgen Laboratories LLC Program Number: 1143 Poster Board Number: B0362 Presentation Time: 3:15 PM–5:00 PM Xeno- and feeder-free differentiation of human pluripotent stem cells to ocular epithelial cells Heidi Hongisto, Tanja Ilmarinen, Alexandra Mikhailova, Heli Skottman. BioMediTech, University of Tampere, Tampere, Finland. Purpose: As human pluripotent stem cells (hPSCs) provide a promising cell source for ocular cell replacement therapy applications, more standardized and xenogeneic-free culture and differentiation protocols for hPSCs are desired. We aimed to develop robust, xeno- and feeder cell-free culture system for undifferentiated hPSCs and efficient differentiation methods thereafter to produce ocular epithelial cells suitable for clinical transplantation. Methods: Several human embryonic stem cell (hESC) and human induced pluripotent stem cell (hiPSC) lines were transferred to the hPSC culture system based on the Essential 8TM (E8, Thermo Fisher Scientific) culture medium and human recombinant laminin matrix. Differentiation to retinal pigment epithelial cells (RPE) was performed with two xeno-free media: X-VIVOTM 10 (Lonza) and xeno-free differentiation medium (XF-RPEbasic) using both embryoid body and adherent differentiation methods on a combination of extracellular matrix (ECM) proteins. Cells were analyzed for differentiation efficiency, RPE gene (RT-PCR) and protein (immunofluorescence staining and confocal microscopy) expression, barrier properties (TER) and functional maturity (phagocytosis assay and ELISA). Results: Human PSCs were successfully maintained in the defined, xeno- and feeder-free culture system using single cell passaging. These abstracts are licensed under a Creative Commons Attribution-NonCommercial-No Derivatives 4.0 International License. Go to http://iovs.arvojournals.org/ to access the versions of record. ARVO 2016 Annual Meeting Abstracts The hPSCs demonstrated correct undifferentiated morphology, hPSC marker expression, full pluripotency, and normal karyotype. Prolonged culture led to recurrent karyotype changes conveying culture and differentiation advantage. Both RPE differentiation media enabled efficient differentiation to RPE that was enhanced by small molecule induction in a media and cell line specific manner. A combination of ECM proteins mimicking the natural RPE basement membrane allowed for proliferation and maturation of tight epithelial monolayers with excellent TER values, correct expression and localization of RPE proteins and RPE functionality. Xeno-free cryopreservation protocols for both pluripotent hPSCs and hPSCRPE were optimized for cell banking. Conclusions: A robust and reproducible, xeno- and feeder-free culture method for hPSCs as well as RPE differentiation and cryobanking was established. The method allows for easy transition to Good Manufacturing Practice-quality for generation of clinical grade cells, and can also be used to generate corneal epithelial cells. Commercial Relationships: Heidi Hongisto, None; Tanja Ilmarinen, None; Alexandra Mikhailova, None; Heli Skottman, None Program Number: 1144 Poster Board Number: B0363 Presentation Time: 3:15 PM–5:00 PM Differentiation of Human Embryonic Stem cells into Photoreceptor Precursor – In-Vitro and In-Vivo Study Yossi Mandel1, 2, Yoav Chemla2, Astar Shamul2, Amos Markus2, Nairouz Farah1, 2, Ron S. Goldstein2. 1Optometry and Visual Science, Bar Ilan University, Israel, Ramat Gan, Israel; 2The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Israel, Ramat Gan, Israel. Purpose: There are several methods for inducing the differentiation of human embryonic stem cells (hESCs) into photoreceptors precursors. Herein, we studied photoreceptors generation in twodimensional (2D) or a three-dimensional (3D) cell culture model. In addition, we studied the retention of labeled photoreceptor cells in the subretinal space of rats by fluorescence imaging of the retina. Methods: hESCs (H9, US National Stem Cell Bank) differentiation into photoreceptor precursors was investigated in two cell culture models: a 2D model where photoreceptor differentiation was induced in monolayer cultures over 17 days using media including Dkk1, Noggin and IGF1, or a 3D model, where differentiation was induced in suspension cultures over 21 days with media containing endo-IWR 1, SAG, CHIR 99021. Differentiation was studied by immunostaining (CRX, PAX6) and mRNA expression (CRX,VSX2,PAX6). Cells that were subjected to the differentiation protocol were labeled by infection with GFP-expressing adenovirus and then injected into the subretinal space of Long-Evans rats (100,000 cells/8 µl). The retention of the cells was studied over a month by repeated fluorescence imaging of the retina by a Micron-IV Phoenix rodent imaging system. Results: hESC were differentiated into photoreceptor precursors in the 2D and 3D both models, as was revealed by staining or expression of CRX. Higher efficiency was found in the 3D model as compared to the 2D with up to 80 percent of cells stained for CRX. Transplanted cells diffused evenly in the subretinal space without producing cells clumps. Retention of cells was low with less than 10% of the transplanted cells being be detected by fluorescence imaging at 1 month post transplantation. Conclusions: Both 2D and 3D protocols were efficient in photoreceptor generation with some advantage of the 3D over the 2D method. Retention of injected cells differentiated from hESC in the subretinal space of rats is poor. Further studies should be conducted in order to improve the transplantation protocol. Commercial Relationships: Yossi Mandel; Yoav Chemla, None; Astar Shamul, None; Amos Markus, None; Nairouz Farah, None; Ron S. Goldstein, None Program Number: 1145 Poster Board Number: B0364 Presentation Time: 3:15 PM–5:00 PM Modulation of photoreceptor outer segment phagocytosis and degradation by environmental stressors in an hiPSC-derived model system Sonal Dalvi1, Ali Hashim1, Chad Galloway1, Leslie MacDonald1, Ruchira Singh1, 2. 1Department of Ophthalmology and Biomedical Genetics, University of Rochester, Rochester, NY; 2Center for Visual Science, University of Rochester, Rochester, NY. Purpose: Macular degenerative diseases are multifactorial, the sum of both genetic as well as environmental factors which often affect the retinal pigment epithelium (RPE) cells. Amongst environmental factors, iron toxicity has been implicated in age related macular degeneration (AMD) while cigarette smoke is the number one preventable factor contributing to AMD. The ability to derive RPE from human inducible pluripotent stem cells (hiPSCs) now allows investigation of the additive effect of environmental factors within the genetic background of macular disease patients. This study utilized hiPSC-RPE cells in culture to evaluate the effect of environmental stressors (iron overload, cigarette smoke) on maculopathy-associated physical and functional attributes of RPE cells. Methods: Established monolayers of hiPSC-RPE were treated either chronically (1 week –1 month) or acutely (24 h) with exogenous iron (ferric ammonium citrate, FAC) or cigarette smoke extract (CSE). Subsequently, morphologic, gene/protein expression and functional characteristics of hiPSC-RPE-treated with environmental stressors (FAC, CSE) were compared to untreated control hiPSC-RPE. Results: The expression of genes involved in the pigmentation (TYRP1, SILV) and iron homeostasis (FTH1, SLC40A1) pathway(s) were altered in long-term FAC-treated hiPSC-RPE compared to untreated control hiPSC-RPE. Furthermore, both FAC and CSE treatments affected the rate of photoreceptor outer segment (POS) phagocytosis/degradation in hiPSC-RPE cultures. Interestingly, the effect of FAC and/or CSE was different in RPE cultures that had been chronically stressed with POS compared to RPE cultures without any prior POS exposure. Conclusions: Two significant contributing factors in the progression of macular degenerative disease, iron toxicity and cigarette smoke, alter an obligate function of RPE, phagocytosis/degradation of POS, in hiPSC derived RPE. In addition, chronic iron supplementation also alters metal ion homeostasis, plausibly contributing to RPE dysfunction in hiPSC-derived cultures. Altogether, our data show that hiPSC-RPE cultures are a suitable platform to study the effect of environmental stressors on RPE physiology and thus may be a suitable tool to dissect the contribution of gene vs. environment in specific eye diseases, like macular degeneration. Commercial Relationships: Sonal Dalvi, None; Ali Hashim, None; Chad Galloway, None; Leslie MacDonald, None; Ruchira Singh, None Support: Brightfocus Foundation Macular Degeneration Research Grant, David Bryant Trust, Knight Templar Eye Foundation Research Starter Grant, Research to prevent Blindness (Career Development Award, Singh- PI), Research to Prevent Blindness (unrestricted grant, Feldon- PI) Retina Research Foundation Pilot Study Grant, University Research Award (University of Rochester). These abstracts are licensed under a Creative Commons Attribution-NonCommercial-No Derivatives 4.0 International License. Go to http://iovs.arvojournals.org/ to access the versions of record. ARVO 2016 Annual Meeting Abstracts Program Number: 1146 Poster Board Number: B0365 Presentation Time: 3:15 PM–5:00 PM Micro-culture arrays to control the generation of retinal organoids Sarah Decembrini1, Nathalie Brandenberg2, Sylke Hoehnel2, Yvan Arsenijevic1, M.P. Lutolf2. 1Unit of Gene Therapy & Stem Cell Biology, Jules-Gonin Eye Hospital, FAA, Lausanne, Switzerland; 2Laboratory of stem cell and bioengineering, institute of bioengineering, school of life sciences, Lausanne, Switzerland. Purpose: The feasibility to recapitulate mammalian retinogenesis in vitro by growing self-organizing retinal organoids from pluripotent stem cells was recently demonstrated by our and other laboratories. We observed that retinal organoids are not completely synchronized in culture, resulting in retinas with different sizes, shapes, and apicalbasal orientation suggesting the need to improve the adopted cell culture conditions. Methods: We attempt here to standardize an approach, based on microwell arrays, that can be used to screen compounds to reproducibly generate retinal organoids meanwhile saving time, space and materials. Different biomaterials were tested as culture substrates of microwell arrays. The stiffness, quantity of hydrogels, well shape and size, volume of the reaction and medium composition as well as the effect of cell number were evaluated in respect to the efficiency to generate retinal organoids. Results: Different qualities and stiffness of hydrogels were tested in order to establish the best culture substrate supporting retinal organoid generation. Agarose, noble agarose, polyethylene-glycol (PEG) and polydimethylsiloxane (PDMS) were assessed. The results highlight the higher propensity of 5% w/vol PEG, to generate retinal organoids in comparison to all the other tested materials. AggreWellTM (Stemcell Technologies) served in primis as template to construct the desired well topography. Flat- or V- bottom wells, round or square with a diameter of 400 or 800 µm were tested. The shape and size of the microwells tested were not able to support the generation of the retinal organoids. A standard photolithography was developed to generate an unlimited well size and geometry. The optimal microwell size and shape was identified in 1.5mm height (1.7 max), 1.7mm width, U-bottom wells. Such microwells allow the aggregate formation in less than 6 hours. Different medium conditions, supplements, matrigel concentrations and surviving factors were assessed to fine-tune the retinal organoid production. The results suggest the requirement of factors to induce retinal organoids different than those utilized with plastic wells revealing some distinctive properties of the microwells that are currently under investigation. Conclusions: We conclude that the microwell plates support the survival and differentiation of retinal organoids and can be used to screen morphogens aimed to improve the development of retinal organoids. Commercial Relationships: Sarah Decembrini; Nathalie Brandenberg, None; Sylke Hoehnel, None; Yvan Arsenijevic, None; M.P. Lutolf, None Program Number: 1147 Poster Board Number: B0366 Presentation Time: 3:15 PM–5:00 PM Self organization of human induced pluripotent stem cell (iPSC) derived retinal progenitor cells on a 3D scaffold Laurel T. Tainsh2, 1, Deepti Singh1, 2, SHAO-BIN WANG2, 1, Maryam Ghiassi-Nejad2, 1, Bo Chen2, Ron A. Adelman2, Lawrence J. Rizzolo1, 2. 1Surgery, Yale University, New Haven, CT; 2 Ophthalmology, Yale University, New Haven, CT. Purpose: Stem cell-derived retinal progenitor cells (RPC) have potential for treating retinal degenerations. Although RPC can form retina-like neurospheres, planar structures would be more appropriate for implantation. We investigated whether RPC could be reconfigured on a planar scaffold. Methods: Human iPSCs were differentiated in DMEM/F12 supplemented with N2 and B27 according to published protocols. After 3 or 8 weeks of differentiation, retinal cups (RCs) were seeded as intact spheres or after dissociation with trypsin onto a scaffold composed of gelatin, hyaluronic acid, and chondroitin sulfate. Differentiation of intact and dissociated RCs on scaffolds was monitored with qPCR at monthly time points for up to 14 weeks as compared to control RCs grown in suspension. Immunohistochemistry, confocal microscopy, and scanning electron microscopy were used to assess cell penetration, proliferation, and differentiation within scaffolds. In some experiments, RPC scaffolds were co-cultured with RPE. Effects on the RPE were assessed by the transepithelial electrical resistance (TER). Results: Intact RCs attached as clusters and proliferated to invade the scaffold forming distinct subdomains expressing ganglion cell, interneuron, and photoreceptor markers. Intact cell clusters on scaffolds continued to grow in size for up to 6 weeks. Trypsinized RCs populated the scaffold more uniformly reforming as clusters on the surface and laminating within scaffold pores. Scaffolds seeded with dissociated RCs remained uniformly populated for up to 14 weeks. RT-qPCR results showed that both intact and dissociated RCs on scaffolds differentiate along a timeline as well or better than RCs grown in suspension. Intact and dissociated RCs expressed eyefield, ganglion cell, interneuron, and early photoreceptor markers such as recoverin, but did not express the more mature photoreceptor markers opsin and rhodopsin. With co-culture TER increased 3x for the RPE, while PAX6 decreased and OTX2 increased in the RPC. Conclusions: Both intact and dissociated iPSC derived RCs penetrate, proliferate, and differentiate within HA scaffolds. Dissociating RCs with trypsin before seeding results in a more uniformly populated, laminated, and planar scaffold. Co-culture furthered the maturation of RPE and RPC. Ongoing experiments aim to optimize this approach. Commercial Relationships: Laurel T. Tainsh, None; Deepti Singh; SHAO-BIN WANG, None; Maryam Ghiassi-Nejad, None; Bo Chen, None; Ron A. Adelman, None; Lawrence J. Rizzolo, None Support: NIH CTSA TL1TR000141, Department of Defense MR130036, CT Regenerative Medicine Research Fund 14-SCBYale-18, Leir Family Fund, Alonzo Family Fund Program Number: 1148 Poster Board Number: B0367 Presentation Time: 3:15 PM–5:00 PM Integrin and extracellular matrix (ECM) protein expression in differentiating neural retina generated from human ES cell (hESC) cultures Debjani Phillips1, 2, Douglas Streeten3, Isabel Pinilla4, 3, William J. Brunken5, 6, David M. Gamm7, 2. 1Waisman Center, University of Wisconsin Madison, Madison, WI; 2McPherson Eye Research Institute, Madison, WI; 3University of Wisconsin Madison, Madison, WI; 4Ophthalmology, University Hospital Lozano Blesa, Zaragoza, Spain; 5Ophthalmology, Upstate Medical University, Syracuse, NY; 6SUNY Eye Institute, Syracuse, NY; 7Department of Ophthalmology and Visual Sciences, University of Wisconsin Madison, Madison, WI. Purpose: During retinal development, integrin heterodimers associate with ECM proteins to regulate axon guidance, spatial organization and ECM assembly, thus directing cell fate. The β1 integrin subunit has been implicated in the expansion of neural progenitor cells and is integral for maintaining the collective integrity These abstracts are licensed under a Creative Commons Attribution-NonCommercial-No Derivatives 4.0 International License. Go to http://iovs.arvojournals.org/ to access the versions of record. ARVO 2016 Annual Meeting Abstracts of the developing retina. Using our established hESC model of retinal development, we sought to profile the expression of β1 integrin and its partners, α1-6 integrins and αv integrin, and the ECM proteins with which they associate at varying stages of human neural retinal differentiation. Methods: Optic vesicles (OVs) generated from H9CRX17tdTomato hESCs were differentiated to day (D) 45, D67, D92 and D100. Expression of β1 integrin subunit, its associated α integrin subunits, and the ECM proteins fibronectin, collagen IV and laminin were observed using immunocytochemistry (ICC). Levels of integrin expression on developing CRX+ cells were analyzed by flow cytometry. The CRX+ population was gated according to tdTomato reporter expression levels. Results: The β1 integrin subunit levels remained elevated at D45 and D100 of differentiation. In contrast, expression levels of α integrin subunits were low or undetectable at D45 but increased at D100. Fibronectin, collagen IV, and laminin expression were prevalent during differentiation of hESCs into neural retina and integrins appeared clustered alongside tdTomato-expressing CRX+ cells. Conclusions: Our hESC-OV neural retina model is a useful tool for identifying integrins and ECM proteins that have the capacity to contribute to development and perhaps fate determination of neural retinal cells. Positive identification of the β1 integrin subunit along with all of its associated α integrin subunits in these 3-D cultures provides further evidence of their utility as models of human retinal development. Knowledge of the expression profiles of integrins and their ECM binding partners during different stages of development improves our understanding of the developing human retina and provides guidance for the manipulation of culture techniques in order to direct cells to a desired fate. Commercial Relationships: Debjani Phillips, None; Douglas Streeten; Isabel Pinilla, None; William J. Brunken, None; David M. Gamm, None Support: Retinal Research Foundation Emmet A. Humble Distinguished Directorship, McPherson Eye Research Institute (Sandra Lemke Trout Chair), Carl and Mildred Reeves Foundation, NIH P30HD03352, Muskingum County Community Foundation, Choroideremia Research Foundation Program Number: 1149 Poster Board Number: B0368 Presentation Time: 3:15 PM–5:00 PM Scaffold Composition Affects the Proliferation and Differentiation of Retinal Progenitor Cells Maryam Ghiassi-Nejad1, Deepti Singh1, SHAO-BIN WANG1, Laurel T. Tainsh1, Bo Chen2, Ron A. Adelman2, Lawrence J. Rizzolo1. 1 Surgery/Ophthalmology, Yale University, New Haven, CT; 2 Ophthalomology, Yale University, New Haven, CT. Purpose: Retinal progenitor cells (RPC) can form neurospheres that resemble retinal structure, but their small spherical geometry limits their utility for experimentation and implantation into diseased retinas. We examined different scaffolds for biocompatibility, and ability to foster stem cell growth and differentiation. Methods: Scaffolds were fabricated from electrospun polycaprolactone (PCL) or from alginate or gelatin that was decorated with hyaluronic acid and chondroitin sulfate. The later scaffolds were freeze-dried to create large pores, rehydrated, and sectioned into discs varying from 60-120 microns thick. Pore size was evaluated by scanning electron microscopy, and potential toxicity was tested by implanting the scaffolds into mouse retinas. Human embryonic stem cells (WA09) were differentiated, and in some experiments, co-cultured with human fetal (hfRPE). The cell differentiation was monitored using qRT-PCR and immunofluorescence every two weeks for two months. The cultures were followed up to three months and monitored by quantitative RT-PCR (qPCR) or immunofluorescence. Results: Scaffolds had interconnected pores 50-100 micron in diameter, but for PCL pores were flattened in the XZ plane. Stem cells penetrated PCL only 20-30 micron, and the cultures were not uniform. RPC were able to differentiate on PCL and gelatin scaffolds, but growth and differentiation was impaired on alginate scaffolds. We proceeded with gelatin-based scaffolds. Scaffolds degraded slowly in culture, but were degraded within three weeks following implantation into the subretinal space. There was no evidence of overt inflammation, retinal edema, or degeneration. When plated at low density and co-cultured with hfRPE, RPC transformed from spherical cells to broad, flattened cells that extended neurite-like projections. When plated at high density, cells uniformly populated the full thickness of scaffolds as thick as 120 microns and expressed retinal markers. Conclusions: Scaffolds based on freeze-dried gelatin were most successful at satisfying 3 criteria: full penetration of the scaffolds, uniform cell density in the xy-plane, and no cytotoxicity upon implantation. Retinal lamina began to form, but further experimentation is required to achieve the structures found in neurospheres. Commercial Relationships: Maryam Ghiassi-Nejad, None; Deepti Singh, None; SHAO-BIN WANG, None; Laurel T. Tainsh, None; Bo Chen, None; Ron A. Adelman, None; Lawrence J. Rizzolo, None Support: Dept. of Defense MR 130036, CT Regan Med Rsch Fund 14-SCB-Yale-18: Leir Family Fund: Alonzo Family Fund; Richard K Greshon Fellowship. Program Number: 1150 Poster Board Number: B0369 Presentation Time: 3:15 PM–5:00 PM Evaluating the effects of ECM and elastic modulus on human pluripotent stem cell-derived photoreceptor enrichment Jee Min1, Joe Phillips1, 2, William Daly3, 4, William Murphy3, 4, David M. Gamm5, 2. 1Waisman Center, University of Wisconsin - Madison, Madison, WI; 2McPherson Eye Research Institute, Madison, WI; 3Department of Materials Science and Engineering, University of Wisconsin Madison, Madison, WI; 4Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI; 5Department of Ophthalmology and Visual Sciences, University of Wisconsin - Madison, Madison, WI. Purpose: Human pluripotent stem cell (hPSC)-based photoreceptor replacement strategies require efficient generation and isolation of photoreceptors, as well as the removal of proliferative retinal progenitor cells (RPCs). Extrinsic factors such as the extracellular matrix (ECM), as well as the stiffness (elastic modulus) of the extracellular environment are known to modulate cellular adherence, differentiation, and maturation. The purpose of this study was to determine the potential of these extrinsic factors to promote photoreceptor enrichment while reducing the number of RPCs. Methods: Using our established protocols, hPSC-derived optic vesicle-like (OV) structures were generated, isolated, and differentiated to day 80. OVs were then dissociated and plated onto various substrates and maintained for one week. Two experiments were performed to evaluate the following substrates: Experiment 1) 96 well plates were pre-coated with ECMs and adhesion promoting molecules, including fibronectin, laminin, vitronectin, collagen, matrigel, poly-L-lysine (PLL), poly-D-lysine (PDL), and poly-Lornithine (PLO). Experiment 2) Polyethylene glycol based (PEG) hydrogels were spotted onto 384 well plates. A slow degrading and a fast degrading MMP-labile crosslinker, and a non MMPlabile cross-linker were added to PEG at varying concentrations to These abstracts are licensed under a Creative Commons Attribution-NonCommercial-No Derivatives 4.0 International License. Go to http://iovs.arvojournals.org/ to access the versions of record. ARVO 2016 Annual Meeting Abstracts vary stiffness and degradability of the hydrogel. Furthermore, the optimal concentration of integrin binding peptides were also probed. Quantitative immunocytochemistry analysis was performed on the Operetta High Content Screening System to determine the number of photoreceptors (RECOVERIN+) and RPCs (Ki67+) in both experiments. Results: Initial results suggested that PLO and PLL promoted the greatest degree of photoreceptor enrichment and RPC reduction in experiment 1. In experiment 2, medium stiffness Tryptophan crosslinked hydrogels with a high concentration of IKVAV provided the most photoreceptor enrichment and RPC reduction. Conclusions: In this study, high content screening was used to identify target substrates for photoreceptor enrichment. Knowledge gained from this study can be used to improve photoreceptor production and isolation methods. Additionally, these results are also being used to inform hydrogel design, as transplanting photoreceptors in an encapsulating hydrogel may improve transplant efficiency and cell survival. Commercial Relationships: Jee Min, None; Joe Phillips, None; William Daly, None; William Murphy, None; David M. Gamm, None Support: Foundation Fighting Blindness Wynn-Gund TRAP Award, NIH RO1 EY21218, Retinal Research Foundation Emmett A. Humble Distinguished Directorship, McPherson Eye Research Institute (Sandra Lemke Trout Chair), Research to Prevent Blindness, Carl and Mildred Reeves Foundation, NIH P30HD03352, Muskingum County Community Foundation, Choroideremia Research Foundation These abstracts are licensed under a Creative Commons Attribution-NonCommercial-No Derivatives 4.0 International License. Go to http://iovs.arvojournals.org/ to access the versions of record.