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Diffusion limits of an in vitro thick prevascularized tissue.
Craig K Griffith1, Cheryl Miller, Richard C A Sainson
1Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92697-2715, USA.
Tissue Engineering
|March 2, 2005
Summary
Engineered tissues thicker than 2 mm can now be created by forming in vitro capillary networks. This vascularization strategy overcomes oxygen diffusion limits, enabling thicker tissue constructs for regenerative medicine.
Area of Science:
- Biomaterials Science
- Tissue Engineering
- Vascular Biology
Background:
- Current tissue engineering is limited to thin constructs (< 2 mm) due to oxygen diffusion constraints.
- In vivo capillary networks supply oxygen and nutrients to thicker tissues, suggesting in vitro vascularization as a potential solution.
Purpose of the Study:
- To develop a system for generating capillary-like networks within thick fibrin matrices for tissue engineering applications.
- To investigate the influence of key parameters on in vitro vascular network formation.
Main Methods:
- Human umbilical vein endothelial cells on microcarrier beads were embedded in fibrin gels at varying distances (Delta) from fibroblast monolayers.
- The distance from the growth medium (C) containing growth factors was also manipulated.
- Capillary network formation was assessed over 6-8 days.
Main Results:
- Visible capillary lumens sprouted within 2-3 days and grew over 500 microm within 6-8 days.
- Network formation showed a strong inverse correlation with Delta, with optimal formation at 1.8 mm.
- Oxygen tension remained high (> 125 mmHg) in thick constructs, indicating oxygen diffusion was not limiting.
Conclusions:
- In vitro oxygen diffusion is not a limiting factor for developing centimeter-thick tissue constructs.
- Fibroblast-derived soluble mediators are essential for stable capillary formation but diffuse slower than nutrients.