Abstract 18140: Blood-Derived Endothelial Progenitor Cells (EPCs) Create Biocompatible Lining for Titanium Blood-Contacting Surfaces
Background: Synthetic cardiovascular implants cause contact activation of coagulation. Endothelial seeding provides an anti-thrombotic and biocompatible coating, but is limited by the lack of easily available autologous cells that adhere under flow. Blood derived, late-outgrowth EPCs function like endothelial cells (ECs) and represent a promising source of ECs. We hypothesize that (1) peripheral blood-derived EPCs adhere to titanium (Ti) surfaces in mechanical circulatory assist devices under arterial shear stress, (2) spread faster on fibronectin-precoated Ti (Fn-Ti), (3) present an anti-thrombotic profile, and that (4) Ti tubes can be uniformly seeded to achieve a confluent monolayer.
Methods and Results: Ti was electron-evaporated on glass slides. Porcine late-outgrowth EPCs from 10 swine were characterized with flow cytometry and fluorescently labeled before seeding. Platelet adhesion was reduced 590-fold on EPC-coated Ti relative to uncoated Ti (p<0.0001, n=15 experiments, 2-sample t-test). EPCs spread significantly faster after 8 hours on Fn-Ti (area=3,582±101.0μm2) compared to uncoated Ti (area= 2,518±89.3 μm2) (p<0.001, n=1,662 cells, 2-way ANOVA). However, EPCs adhered strongly to uncoated Ti in a laminar flow circuit under physiological shear stress of 15dynes/cm2 over 48 hours (97.3±0.82% cell retention, n=8 experiments). In addition EPCs elongated under shear stress (roundness of 0.896±0.0038 to 0.523±0.0075, p<0.0001, n=700 cells, paired t-test) and produced 8.2-fold more NO as compared to static conditions (p<0.0001, n=98 NO measurements, mixed model). For subsequent in-vivo studies, Ti tubes were seeded with EPCs in a rotating seeding device for 30 minutes. Following static culture for 24 hours, EPCs with an initial area of 179.8±5.8μm2 spread significantly to an area=2,351.9±72.1μm2, forming a confluent monolayer inside the Ti tubes (p<0.0001, n=700 cells, paired t-test, n=7 experiments).
Conclusions: EPCs adhere to and spread on Ti surfaces under physiological flow and remain functional. Therefore, it is feasible to coat implants, such as Ti-coated Nitinol stents and circulatory assist devices, with EPCs to prevent contact activation and thromboemboli formation in areas of low flow and stasis.
- © 2010 by American Heart Association, Inc.