oa Fibronectin Coating Triggers In Vivo Recellularization of Tissue-Engineered Aortic Conduits

Strategies that aim at an acceleration of in vivo neoendothelialization and medial repopulation are warranted to increase the integrity and functionality of tissue-engineered cardiovascular implants. Proactive coating of decellularized implants represents a promising approach, however, little is known about the in vivo fate of coated agents over time. Detergent-decellularized aortic rat conduits (n = 24) were coated with covalently Alexa488-labelled (green emission) fibronectin (FN; 50 µg/ml, 24 hours) and implanted in the infrarenal aorta of wildtype Wistar rats (Group A; n = 12). Uncoated implants served as controls (Group B; n = 12). Before implantation and at postoperative day 1 and week 1, 4 and 8, fluorescence-based detection of FN coating was performed. Cellular repopulation was examined by histology and immunohistochemistry. All rats survived without clinical or sonographic signs of lower body malperfusion. Confocal microscopy of the aortic conduits revealed bright green FN fluorescence before and 1 day after implantation on the luminal as well as on the adventitial surface. The signal intensity decreased after 1 week, but was still present after 4 and 8 weeks. Four weeks after the operation, the luminal surface in the perianastomotic regions of Group A was completely neoendothelialized (vWF+) and a myofibroblast hyperplasia (αSMA+) with increased ratio of intima-to-media (I/M) thickness occurred. After 8 weeks I/M was significantly increased in Group A versus Group B (p < 0.01). At the same time point, medial repopulation starting at the adventitial zone was observed in group A, while only marginal repopulation occurred in group B (p < 0.001). In both groups vonKossa staining revealed sparse medial calcification and staining against inflammatory cell markers (CD3 & CD68) was negative. In our standardized rat transplantation model, a biofunctional protein coating of cardiovascular implants in the systemic circulation proved feasible and persistent up to 8 weeks. FN surface coating of aortic conduits induced a significantly increased medial recellularization, originating from the adventitial surface. The role of intimal hyperplasia and the relevance thereof needs further investigation.