Generation of Novel Microcarriers for Expansion of Human Mesenchymal Stem Cells
Dave Splan, Grishma Patel, Heather Woolls and Mark Szczypka, Pall Life Sciences, 4370 Varsity Drive, Ann Arbor Michigan 48108
RESULTS
Human bone marrow-derived mesenchymal stem cells expanded on this new microcarrier type reached
acceptable cell densities in spinner cultures under a variety of environmental conditions. Harvest efficiencies
achieved in small scale cultures were excellent, and cell identity was maintained. Conditions optimized in smallscale spinners were successfully employed in environmentally-controlled bioreactor. Cell harvesting optimization
studies at larger scale are currently underway. Results to-date indicate that this novel microcarrier type will
provide a superior substrate for large-scale propagation of MSCs under various environmental conditions.
Figure 1
Key Drivers for Novel Microcarrier Development
Utility
“Universal” substrate for many
cells under multiple conditions
Regulatory
Anticipated need to transition
to animal component-free systems
Core
Microcarrier Material
Cross-linked
Collagen
polystyrene
FACT III
Cross-linked
polystyrene
Plastic
Plastic Plus
ProNectin◆ F
Hillex® II
Cross-linked
polystyrene
Cross-linked
polystyrene
Cross-linked
polystyrene
Cross-linked
modified
polystyrene
Relative
Density
1.02-1.04
Industry Direction
Optimization of surfaces for
specific manufacturing processes
Surface
Treatment
Type 1 porcine
gelatin coating
Charged surface
with Type 1
porcine gelatin
coating
Uncharged
Animal
Protein Free
1.02-1.04
1.02-1.04
X
Charged surface
1.02-1.04
X
Recombinant
protein
Cationic amine
1.02-1.04
X
1.1
X
Surface Modification
Standard Portfolio of Microcarriers
Porcine Type A Gelatin
Positive Charge
ProNectin®
F
Prototype Microcarriers
Assortment of Proteins
Peptides
and Peptides
ed Species
s
Additional Charged
Surfaces can be modified to promote growth of different cell types. Common substrates used on synthetic surfaces
include various charged moieties, natural and recombinant proteins, and synthetic peptides. All of these rigid polystyrene
microcarriers provide an excellent substrate for growth of multiple cell types in stirred-tank reactors.
Two new types of microcarriers were generated and surface characteristics optimized. These include a peptide-coated
microcarrier and a charged microcarrier which promotes rapid cell attachment and growth.
Figure 2
Optimization of Charged Prototype Microcarriers
Charge Density
Low
Medium
High
Charge
cells/cm2
Vero
Cell Attachment
100
80
60
40
20
0
hMSC
Low
Medium
High
1 Hour
B. Cell Growth
1.6E+04
1.4E+04
1.2E+04
1.0E+04
8.0E+03
6.0E+03
4.0E+03
2.0E+03
0.0E+00
14
12
10
8
6
4
2
0
hMSC
Low
Medium
High
Day 5
Cells/cm 2
Day 5
hMSC
c1
c2
c3
Day 5
Peptide concentrations were varied and cell attachment and growth was assessed. A. Microcarriers were coated
with recombinant peptide at various concentrations (C1 to C3). Visual observation of attachment kinetics
indicates that the concentration of peptide used to coat microcarriers influenced the attachment efficiency as
greater numbers of unattached cells were observed at the C1 coating concentration when compared to C2 and
C3 (Arrows highlight unattached cells). Optimal attachment was achieved at C3 coating concentration.
B. Growth of Vero and hMSC in serum-containing media was optimal on C3-coated microcarriers.
Figure 4
Novel Microcarrier Performance in Bioreactors
Growth Curve
1.0E+05
9.0E+04
8.0E+04
7.0E+04
6.0E+04
5.0E+04
4.0E+04
3.0E+04
2.0E+04
1.0E+04
0.0E+00
0
2
Collagen
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Glucose Concentrations
3
4 5 6 7
Day
Charged
Peptide
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Final Cell Harvest
0 1 2 3 4 5 6 7
Day
Day
12
10
8
6
4
2
0
Cell Yield
hMSCs grown in serum-containing medium were harvested and
plated to flatware. Standard adipogenic and osteogenic differentiation
assays were performed. Cells retained their ability to differentiate into
adipocytes (left panels) and osteocytes (right panels) when grown on
charged or peptide-coated microcarrier types.
Figure 5
Simple and Efficient Harvest of Cells from Rigid Prototype Microcarriers
Figure 6
Growth of hMSCs in Xeno-Free Medium
on Charged Microcarriers
Figure 7
Cells Retain Differentiation Capacity after
Growth on Microcarriers
hMSC were grown on
charged microcarriers in
xeno-free medium in a 2 L
stirred-tank reactor. Three
medium exchanges (80% of
total volume) were performed
over the culture (arrows).
Cells were harvested after
97% Harvest E
Efficiency
fficiency on Day 7
7 days of growth. A harvest
efficiency of 97% with
greater than 95% viability was achieved.
hMSCs grown in serum-containing medium were
harvested and plated to flatware. Standard adipogenic and
osteogenic differentiation assays were performed. Cells
retained their ability to differentiate into adipocytes (left
panels) and osteocytes (right panels) when grown on
charged or peptide-coated microcarrier types.
CONCLUSION
Percent
8
7
6
5
4
3
2
1
0
Cells/Bead
Units
A.
C3
100
3.5E+04
3.0E+04
2.5E+04
2.0E+04
1.5E+04
1.0E+04
5.0E+03
0.0E+00
Cells grown on microcarriers in
bioreactors can be harvested using
modifications of standard enzymatic
harvest methods. Microcarriers are
allowed to settle via gravity, medium
removed, and cell-laden microcarriers
Slurry generated by
Microcarriers retained
Single-cell suspension
washed twice with calcium and
enzymatic dissociation
on screen in single
magnesium-free phosphate buffered
and exposure to
pass throug
h system
through
moderate shear force
saline (PBS). Microcarrier pellet is
exposed to TrypLE◆ until cells begin to detach from microcarriers and the slurry is passed through a recirculation
loop to dislodge cells from microcarriers. This mixture is passed through a sterile bag containing a screen which
captures microcarriers in bag and allows cells to pass into a secondary vessel as a single-cell suspension.
Drivers for Novel
Microcarrier Development
Raw Material
Availability and
costs of substrates
C2
70
C1
60
Vero
V
ero
Cells per cm2
(x104)
A spherical microcarrier with a chemistry that promotes rapid attachment and superior growth of multiple cell
types under a variety of environmental condition has recently been developed. The microcarrier chemistry was
optimized through an iterative process using these parameters to guide development. Cell attachment and
growth in medium containing high concentrations of serum was quantified, and microcarriers that provided the
best substrate for attachment and growth were selected for further analysis. Once an optimal surface chemistry
was achieved, the ability to expand human bone marrow-derived mesenchymal stem cells in stirred reactors
was tested. Initial growth and optimization studies were performed in small scale spinners. Cell densities,
doubling times and maintenance of identity and function were ascertained after culture in stirred tank culture.
Favorable conditions identified at small scale were then examined in environmentally-controlled bioreactors.
Cell harvest efficiencies at small scale and bioreactor levels were optimized.
[Peptide]
Attachment %
B. Cell Growth
3.5E+05
3.0E+05
2.5E+05
2.0E+05
1.5E+05
1.0E+05
5.0E+04
0.0E+00
Glucose (g/L)
EXPERIMENTAL APPROACH
A. Cell Attachment
mL
Cells per m
L (x 106)
Multipotent stem cells have been isolated from multiple sources including, bone marrow, adipose tissue,
placenta, umbilical cord and cardiac tissue. It is predicted that large numbers of therapeutically-active cells
isolated from these tissue sources will be required to treat patients inflicted with various disorders. Experimental
evidence suggests that these various cell types can exhibit distinct characteristics depending upon tissue
source and method of expansion: differential expression of cellular markers is sometimes detected, doubling
times and expansion limits can differ, and physical differences that influence the ability of cells to adhere to
various synthetic surfaces are observed. A novel prototype microcarrier recently developed by Pall promotes
rapid attachment and growth of multiple cell types in stirred-tank reactors. Additionally, peptide-coating provides
an alternative animal component-free substrate for cell expansion. These desirable attributes manifest in both
serum-containing and animal component-free medium formulations.
Figure 3
Optimization of Peptide-Coated Prototype Microcarriers
Cells per cm2
BACKGROUND AND NOVELTY
Charge densities were varied and cell attachment and growth was
assessed. A. Analytical techniques were used to measure charge density
of microcarriers. Microcarriers of increasing charge were designated as
low, medium or high charged. Attachment of African green monkey cells
(Vero) and human bone marrow-derived mesenchymal stem cells (hMSC)
was assessed in small-scale dynamic cultures in medium containing high
serum concentrations. Results of cell attachment assays reveal that
microcarriers with the highest charge density promoted the greatest
attachment efficiency under the conditions tested. B. Growth of hMSC
was quantified after five days of culture in serum-containing medium
in dynamic culture. The greatest cell densities were achieved on
microcarriers that contained the highest charge.
Contact: 800.717.7255 (USA and Canada) • 1.516.484.5400 (Outside USA and Canada) • www.pall.com/biopharm • E-mail: biopharm@pall.com
Surface Optimization
Two novel animal protein-free microcarrier types that support excellent attachment and growth of human mesenchymal
stem cells were generated.
Charged Prototype: Optimal surface charge density which promotes rapid cell attachment and subsequent growth
was identified.
Peptide-coated Prototype: Peptide concentrations and coating conditions that support efficient growth of hMSCs
were identified.
Cell Growth in Small Scale Spinner Cultures
Excellent growth of cells was achieved. Cell harvest at small scale demonstrated efficient removal of cells with standard
enzymatic treatment.
Bioreactor Cultures and Cell Harvest
Cell growth on novel microcarrier types was similar to that achieved with commercially-available collagen-coated
microcarriers. Environmental conditions optimized to support excellent growth and harvest efficiencies from two liter
bioreactors yielded reached 1 to 2.5 billion cells.
Excellent harvest efficiencies from microcarriers are obtained using enzymatic treatment and application of moderate
shear force. Harvest efficiencies of 97% with >95% viability were obtained with hMSC.
Cell Characterization
Human mesenchymal stem cells retain ability to differentiate into adipocytes and osteocytes after growth on novel
microcarrier types.
© 2015, Pall Corporation. Pall,
, and Hillex are trademarks of Pall Corporation. ® indicates a trademark registered in the USA. ◆ProNectin is a trademark of Sanyo Chemical Industries and TrypLE is a trademark of Life Technologies Corporation
5/15, GN15.6281