In vivo cell repopulation and differentiation in decellularized and allogenically transplanted aortic valves

The purpose was the attainment of acellular valve substitutes amenable to acquire postimplantation autogenic-like characters with concurrent non-thrombogenicity, anticalcific and suitable mechanical properties, and growth capacity. Valved aortic conduits were excised from 3-month-old minipigs. Decellularization was performed with defined procedure including detergents Triton X-100 and Colate and endonuclease Benzonase®. Surgical replacements were performed at pulmonary position in 3 12-month-old minipigs. Postoperative conditions were clinically monitored. Samples were explanted after 6 and 12 months and processed for (i) immunohistochemical detection of markers vWF, CD31, vimentin, alpha-SMA, and (ii) transmission electron microscopy. Besides favorable postoperative functional outcomes, proper compensatory implant growth occurred (30-35% increase in diameters). Both aortic wall and valve leaflet surfaces were completely coated by an adhering monolayer of vWF+/CD31+ endothelium-like cells with the presence of a weak basal lamina and early/mature intercellular tight junctions. At the valve aortic aspect, many of these cells were clearly involved in prominent ECM formation resulting in the appearance ofd a subendothelial layer with a distinct organized texture of fibrillin microfibrils and elaunin fibers. In addition, a lot of vimentin+ and/or alpha-SMA+ interstitial cells exhibiting fibroblast-like, myofibroblast-like or smooth myocyte-like features populated the leaflet stroma, most of them showing ultrastructural features consistent with prominent collagen fibrillogenesis. In conclusion, this decellularization procedure allowed to produce promising bioprosthetic valved conduits, being glutaraldehyde-free and permitting "in vivo" spontaneous cell repopulation by cells expressing phenotypes mimicking those in native conditions and tissue growth/remodelling.