Tissue engineered heart valves re-endothelialized under simulated physiological conditions: Preclinical testing

Introduction: The regenerative ability of implanted decellularized heart valves is still discussed controversial. The aim of this study was to evaluate the in-vivo integration capacity of decellularized in comparison to re-endothelialized pulmonary valves (PV) in the sheep model.

Methods: Twelve ovine PV were decellularized using a detergent solution (0.5% Na-deoxycholate/0.5% SDS). The luminal surface of six decellularized PV was repopulated with autologous jugular vein endothelial cells (EC; 1.2×10E7) and cultivated in a pulsatile bioreactor under simulated physiological conditions prior implantation. Six decellularized and six reendothelialized PV were implanted into the ortho position. Three of each were echocardiographically investigated and harvested after 3 and 6 months, respectively. For morphological evaluation of explanted PV, H&E-, Elastica van Gieson-, von Kossa-, DAPI-staining, collagen IV-, perlecan-, eNOS–, procollagen-I-, α-actin-immunostaining, and electron microscopy were performed.

Results: All implanted PV were functionally competent without insufficiency, stenosis, macroscopic degeneration or thrombosis. Microscopic evaluation showed a confluent EC monolayer on the valve surface expressing eNOS in the reseeded group and absence of EC in the decellularized group. In both groups the matrix of the explanted valves were comparable repopulated with interstitial cells expressing α-actin and procollagen-I. All valves were free of calcification.

Conclusion: Despite competent function, re-endothelialization of detergent-decellularized valves with autologous EC under simulated physiological conditions prior implantation is a prerequisite for total EC coverage of the valves up to six months post implantation, whereas the valve repopulation with interstitial cells in-vivo occurs most likely by cell migration inside the scaffold.