Decellularized Porcine Aortic Roots: Histopathology Features in an Experimental Animal Model of Right Ventricular Outflow Tract Reconstruction.
Stefania Rizzo, Laura Iop, Alessandro Gandaglia, Maurizio Marchini, Michele Spina, Gaetano Thiene, Gino Gerosa, Cristina Basso. University of Padua, Italy; University of Udine, Italy
Background: The ideal valve conduit for right ventricular outflow tract (RVOT) reconstruction is still missing. Structural valve deterioration due either to immunological reactions or dystrophic calcification is still a major challenge.
Design: TRICOL de-cellularized porcine α-Gal negative aortic roots were used to replace RVOT in nine 12 month old vietnamese pigs. As a control group, four animals had their RVOT resected and immediately reimplanted (sham operation). Both groups underwent serial echo evaluation prior to surgery, at 15 days, and every 3 months. The explanted valved conduits were analysed by histology, immunohistochemistry and electron microscopy.
Results: Intraoperative deaths occurred in 2 cases and 1 controls, excluded from further analysis. In the study group, death due to graft-related causes occurred in 2 (i.e. infective endocarditis 48 days and 9 months after implantation), whereas the remaining 5 survived with a favourable outcome and proper growth of implants (up to 35% increase in diameters) and limited inflammation. Only in 1 case (6 month after implantation) vimentin+ and α-SMA+ interstitial cells were observed within the leaflets, showing ultrastructurally collagen fibrillogenesis and elastogenesis; in the remaining cases (at 6 and 12 months) very few vimentin+ and α-SMA+ cells were detected within the leaflets, mainly at insertion level. Endothelization (CD31+ and vWF+) was evident only at insertion level, whereas the free margins of the leaflets were not covered by endothelial cells. Thrombus deposition and features of subacute infective endocarditis were detected on the luminal surfaces in 3 cases. Tissue positivity for stem cell markers and cell pattern of graft derived-primary cultures suggested cell repopulation originating from recipient bone marrow mesenchymal stem cells.
Conclusions: α-Gal negative TRICOL decellularized porcine aortic roots might represent a valuable solution for RVOT reconstruction. Although these glutaraldehyde-free valved vascular conduits seem permissive for spontaneous cell repopulation and tissue growth, the incomplete re-endothelialization with the high incidence of thrombus formation and infective endocarditis suggests the need of further studies to assess the late re-cellularization and growing capabilities.
Wednesday, March 2, 2011 1:00 PM
Poster Session VI # 38, Wednesday Afternoon