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.

The use of decellularized allografts was safe and with good medium-term results up to 4 years. There was a tendency to lower late gradients in the SDS decellularized allografts after 12 months.

Two types of monofilament polypropylene meshes of markedly different construction, configuration and pore size were compared and used to repair full-thickness muscle defects in the abdominal wall of 22 mongrel dogs to assess their biocompatibility with host tissues. The defects were repaired with Prolene (Ethicon) woven mesh (pore size = 164 x 96 microns) and with an experimental, extruded mesh called T mesh (pore size = 3 mm x 4 mm). On the 30th postoperative day, the animals were sacrificed, and the segments of the abdominal wall containing the implanted meshes were excised. Although the Prolene mesh had greater tensile strength before implantation, 30 days after implantation, the T mesh showed similar tensile strength to Prolene mesh. The collagen densitometry showed a significant increase of total and mature collagen type I deposition in the T mesh. This suggests that the increased mature collagen type I deposition significantly increases the tensile strength of the reinforced mesh tissue and that the larger pore in the T mesh contributed to this finding by allowing increasing fibber orientation within the pores as a result of in vivo tension.

In heavily pretreated patients, HDB results in a relatively high response rate. It can also be used safely in patients with renal impairment who are not suitable for HDM.

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.

BackgroundIn the past, successful use of decellularized xenogenic tissue was shown in the pulmonary circulation. This study, however, evaluates a newly developed decellularized equine pericardial patch under high pressure circumstances.Material/MethodsSeven decellularized equine pericardial scaffolds were implanted into the descending aorta of the juvenile sheep. The implanted patches were oversized to evaluate the durability of the decellularized tissue under high surface tension (Law of Laplace). After 4 months of implantation, all decellularized patches were inspected by gross examination, light microscopy (H&E, Serius red, Gomori, Weigert, and von Kossa straining), and immunohistochemical staining.ResultsThe juvenile sheep showed fast recovery after surgery. There was no mortality during follow-up. At explantation, only limited adhesion was seen at the surgical site. Gross examination showed a smooth and pliable surface without degeneration, as well as absence of aneurysmatic dilatation. Light microscopy showed a well preserved extracellular scaffold with a monolayer of endothelial cells covering the luminal side of the patch. On the outside part of the patch, a well developed neo-vascularization was seen. Host fibroblasts were seen in all layers of the scaffolds. There was no evidence for structural deterioration or calcification of the decellularized equine pericardial scaffolds.ConclusionsIn the juvenile sheep, decellularized equine tissue showed no structural deterioration, but regeneration and remodeling processes at systemic circulation.

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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