Shear Conditioning of Adipose Stem Cells for Reduced Platelet Binding to Engineered Vascular Grafts

Conferring antithrombogenicity to tissue-engineered vascular grafts remains a major challenge, especially for urgent bypass grafting that excludes approaches based on expanding autologous endothelial cells (ECs) that requires weeks of cell culture. Adipose-derived stem cells (ASCs) are available from most patients in sufficient number for coronary bypass graft seeding and may be effective as allogeneic cells. We thus compared the adhesion and platelet binding of human ASCs that were shear conditioned with constant and pulsatile shear stress (SS) after seeding the cells on a biologically engineered matrix suitable for arterial grafts. A monolayer of cells was maintained up to 15 dyn/cm² constant SS and up to 15 dyn/cm² mean pulsatile SS for 6 days of shear flow. Platelet binding was reduced from 83% to 6% of surface area and nitric oxide production was increased 23-fold with 7.5-15 dyn/cm² constant SS, but not pulsatile SS, relative to cells cultured statically on the matrix for 6 days. The reduction in platelet binding varied from no reduction to maximum reduction over a constant shear range of ∼2 to 4 dyn/cm², respectively. Collectively, the study supports the potential use of ASCs to seed the luminal surface of a vascular graft made from this biologically engineered matrix to confer an antithrombogenic surface during the development of an endothelium from the seeded cells or the surrounding blood and tissue.