The results with the juvenile sheep model showed that decellularized heart valves are recellularized in vivo. Host endothelial cells form a monolayer on the inner surface of the valve matrix. Furthermore, host fibroblasts repopulate the valve matrix and produce collagen; thus, a remodeling potential can be expected.
Objective: A challenging issue is to create a heart valve with growth and remodeling potential, which would be of great interest for congenital heart valve surgery. This study was performed to evaluate the growth and remodeling potentials of a decellularized heart valve. Methods: In 4 juvenile sheep (age 12 ± 1 weeks) with a weight of 24.3 ± 4.4 kg, a 17-mm diameter decellularized porcine valve was implanted as pulmonary valve replacement. Valve growth was evaluated by transthoracic echocardiography. At explantation, valves were evaluated by gross examination, light microscopy (hematoxylin and eosin, von Kossa, Sirius red, Weigert and Gomori staining), electron microscopy and immunohistochemistry. Atomic absorption spectrometry was performed to evaluate calcium content. Results: All animals showed fast recovery. The mean follow-up was 9.0 ± 1.8 months. All sheep at least doubled their weight (54.3 ± 9.2 kg). Echocardiography showed no regurgitation and a flow velocity of 0.7 ± 0.1 m/s at the latest follow-up. The valve diameter increased from 17.6 ± 0.5 to 27.5 ± 2.1 mm (p < 0.018). Gross examination showed a similar wall thickness of the implanted valve and native pulmonary wall, with smooth and pliable leaflets. Histology showed a monolayer of endothelial cells, fibroblast ingrowth and production of new collagen. No calcification was seen at von Kossa staining, confirmed by low calcium content levels of the valve wall and leaflets at atomic absorption spectrometry. Conclusions: This glutaraldehyde-free heart valve showed not only the absence of calcification, but also remodeling and growth potential.
This study evaluated decellularized stentless porcine xenografts into the aortic position of seven juvenile sheep. The hemodynamic performance were analyzed by means of echocardiographic examination. Post mortum, specimens were evaluated by gross examination, light microscopy, and immunohistochemical staining. Explantations were performed at up to four months. Echocardiographic evaluation examination showed a maximum flow velocity of 0.94m/s with absence of regurgitation. Gross examination showed smooth and pliable leaflets endothelial cells covered the valve wall and leaflets, deeper layers presented ingrowth of host interstitial cells. There was no evidence for calcification. Our preliminary results showed excellent hemodynamics. Regeneration by host cells and absence of calcifications was observed at 4 months follow-up within the systemic circulation.
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