Authors:
Eric S. Hager, Neil Moudgill, Steven McIlhenny, Ping Zhang, Thomas Tulenko, Thomas Tulenko, Joseph Lombardi, Robert Larson, Paul DiMuzio.
Summary:
Objectives: Vascular graft function may be improved by seeding with adult stem cells (ASC) differentiated into an endothelial cell-like phenotype (EC); however, cellular attachment has been inefficient. Shear stress improves EC attachment by upregulation of integrins (α5β1, αvβ3) and veCadherin. We hypothesize that shear stress improves stem cell attachment to vascular basement membrane components similar to EC.
Methods: Adult stem cells isolated from human fat (CD13+29+90+) and differentiated towards EC by culture in EGM-2 media for 2 weeks were exposed to physiological shear stress for 48h (12 dynes). α5β1 and αvβ3 integrin expression was measured using ELISA; veCadherin was measured via RT-PCR. Cell attachment to tissue culture plates pre-coated with collagen I, fibronectin, or gelatin was measured by absorbance spectroscopy after staining with crystal violet. Mature human EC were used as controls.
Results: ASC expressed both integrins, but at reduced levels compared to EC [Figure 1]; veCadherin was not seen on ASC. Shear stress significantly upregulated α5β1 expression but not that of αvβ3. ASC attachment was significantly improved by all three pre-coats, with collagen I showing the best attachment [Figure 2]. Shear stress significantly improved ASC attachment to both collagen I and fibronectin-coated plates, but not to gelatin or uncoated control.
Conclusions: These data suggest that: 1) human adult stem cells differentiated towards EC express integrins important for cell attachment, but at reduced levels compared to EC, 2) this expression is upregulated by shear, and 3) this upregulation corresponds to improved attachment to basement membrane components specific to the α5β1 integrin. Thus, shear stress may be useful in improving the retention of these cells to tissue engineered vascular grafts.
Source:
2008 Vascular Annual Meeting; 4:20 PM, 06/07/08