TU/e
/technische universiteit eindhoven
/department of biomedical engineering
Image Analysis and Interpretation 1 [8P148]
Student: Desirée Abdurrachim
DCL Projects BME
Quantification of collagen architecture –
3D Thickness Structure
The most common treatment for heart valve diseases is the replacement of the valve.
Classical heart valve substitutes are mechanical prosthetic valves with components
manufactured of non-biologic material (e.g. polymer, metal, carbon, fig 1a) and
biological valves (fig 1b) which are constructed, at least in part, of either human
(homografts) or animal tissue (xenografts). The major drawback of these heart valve
replacements is that they are unable to grow, repair and remodel.
Tissue engineering (TE) is a promising technique to overcome these drawbacks. In this
approach, autologous cells are seeded on a pre-shaped biodegradable scaffold (fig 1c) and
cultured in a bioreactor under conditions that mimic the physiological environment of the
tissue. To date, tissue engineered heart valve replacements show promising results when
implanted at the pulmonary position in animal studies [1]. However these valves lack the
mechanical integrity to withstand the pressures at the aortic side.
A
B
C
Fig. 1: Examples of heart valve protheses. a)
Mechanical heart valve (Medtronic). b)
Biological heart valve of non living fixed
tissue (Hancock). c) Living tissue engineered
tri-leaflet heart valve based on human marrow
stromal cells [1].
Fig. 2: 2-photon image (200x200 μm)
of an unstrained TE construct. Blue:
cells; green: collagen fibers; purple:
scaffold
The protein primary responsible for the load-bearing properties of heart valves is
collagen. The strength collagen provides to these tissues depends on collagen fiber
Den Dolech 2 – PO Box 513 - NL 5600 MB Eindhoven – The Netherlands
Tel. +31-40-2475537, Fax +31-40-2472740
URL: www.bmt.tue.nl
TU/e
/technische universiteit eindhoven
/department of biomedical engineering
content, thickness, length, and orientation. A promising way of improving the mechanical
integrity of tissue engineered valves is to optimize collagen remodeling (i.e. changes in
fiber content, thickness, length, cross-links and orientation) via mechanical conditioning
strategies. The way remodeling takes place is strongly influenced by mechanical
straining. In a study by Mol [2] the influence of different strain levels on the strength of
tissue engineered constructs is shown. The Young’s modulus increases with applied
strain. Previous research by Billiar [3] has shown that collagen architecture rather then
collagen content determines the mechanical properties in aortic valve cusps. Determining
the relationship between mechanical straining and collagen architecture may be helpful to
improve the mechanical properties of tissue engineered aortic heart valves.
Previous work
TE constructs were made of a biodegradable polymer scaffold seeded with human donor
cells and conditioned by different loading protocols. After culture, the collagen fibers in
the samples were stained with a recently developed collagen probe [4] and imaged by 2photon microscopy (fig. 2).
In a BME master study by Florie Daniels, several algorithms, developed in the
Biomedical Image Analysis Group, were applied in a feasibility study to automatically
quantify the 3D orientation of the collagen fibers in these samples. The local orientation
in the images was estimated by determining principal curvature directions from the 3D
Hessian matrix in each voxel, followed by scale selection and spatial context
enhancement. To enhance the collagen fibers, a preprocessing step was performed by
coherence enhancing diffusion. The results were promising, and have been submitted to a
conference.
Project activities:
o literature study
o programming in Mathematica
o discussion with tissue-engineering group
Aim of follow-up project:
The aim of this internship is to extend this work to quantify the (multi-scale) 3D
thickness of collagen architecture in 3 D engineered tissues, as a function of the design
parameters of the engineered tissue (stretching, temperature etc.).
The project includes the following steps:
- acquisition from the tissue engineering group a large series of 2-photon microscopy
images of engineered heart valve tissue;
- evaluation and possibly development of robust quantitative 3D thickness analysis
algorithms.
Den Dolech 2 – PO Box 513 - NL 5600 MB Eindhoven – The Netherlands
Tel. +31-40-2475537, Fax +31-40-2472740
URL: www.bmt.tue.nl
TU/e
/technische universiteit eindhoven
/department of biomedical engineering
References:
[1] Hoerstrup S.P., Kadner A., Milnitchouk S., Trojan A., Eid K., Tracy J., Sodian R.,
Visjager R., Kolb S.S., Grunenfelder J., Zund G. Turina M.I., Tissue Engineering of
functional Trileaflet Heart Valves From Human Marrow Stromal Cells. Circulation,
106: 134-150. 2002.
[2] Mol A., Functional tissue engineering of human heart valve leaflets, 2005, ISBN 90386-2956-7.
[3] Billiar K.L., Sacks M.S., Biaxial Mechanical Properties of the Native and
Glutaraldehyde-Treated Aortic Valve Cusp: Part II-A Structural Constitutive Model.
J.Biomed. Eng.,122:137-335, 2000.
[4] Nash-Krahn K., Bouten C.V.C., van Tuijl S., van Zandvoort M.A.M.J., Merkx M.,
Fluorescently labeled collagen binding proteins allow specific visualization of
collagen in tissue and live cell culture. Analytical Biochem., 350: 177-185, 2006.
[5] Daniels, F., Quantification of Collagen Orientation in 3D Engineered Tissue.
TU/eMSc thesis, July 2006. http://www.bmi2.bmt.tue.nl/image-analysis/Education.
Deliveries:
o Project report (as Mathematica notebook), in English
o Report (15 minutes per student) to the BMIA group, in English
Assessment:
A grade will be given for the average of the overal work, the report and the presentation.
 If necessary more information: URL link to a single HTML-page for the specific
assignment. On this page there can be a link to a PDF document or literature
references and pictures.
Desired foreknowledge of the participating students (BMT):
o Front-End Vision & Multi-Scale Image Analysis (8D010)
o Programming in Mathematica
Project coordinator:
Prof. Bart M. ter Haar Romeny
Biomedical Image Analysis
Email: B.M.terHaarRomeny@tue.nl
ir. Mirjam Rubbens
Tissue Engineering
Email: m.p.rubbens@tue.nl
Time: Semester 1B
Den Dolech 2 – PO Box 513 - NL 5600 MB Eindhoven – The Netherlands
Tel. +31-40-2475537, Fax +31-40-2472740
URL: www.bmt.tue.nl
TU/e
/technische universiteit eindhoven
/department of biomedical engineering
Location project: BioMIM lab, WH 3.2A
Project time schedule:
 Time period (blocks): semester 1B
 Kick-off meeting (date/time/place): 16 October 2006, 10:00-11:00, WH2.106.
 Intermediate meeting, incl. evaluation (date/time/place): every two weeks, even
week Monday, 10:00-11:00, WH2.106.
 Delivery of written results in StudyWeb folder of this project (date):
 Final meeting with oral presentation and project evaluation (date/time/place):
 Feedback + end of the project (date):
Den Dolech 2 – PO Box 513 - NL 5600 MB Eindhoven – The Netherlands
Tel. +31-40-2475537, Fax +31-40-2472740
URL: www.bmt.tue.nl