Histologic changes of nonbiodegradable and biodegradable biomaterials used to repair right ventricular heart defects...

Nonbiodegradable synthetic materials have been widely used to repair cardiac defects. Material-related failures, however, such as lack of growth, thrombosis, and infection, do occur. Because a biodegradable scaffold can be replaced by the patient's own cells and will be treated as a foreign body for a limited period, we compared four biodegradable materials (gelatin, polyglycolic acid (PGA), and copolymer made of epsilon-caprolactone and l-lactic acid reinforced with a poly-l-lactide knitted [KN-PCLA] or woven fabric [WV-PCLA]) with a nonbiodegradable polytetrafluoroethylene (PTFE) material. An animal heart model was tested that simulates the in vivo clinical condition to which a synthetic material would be used.

The five patches were used to repair transmural defects surgically created in the right ventricular outflow tracts of adult rat hearts (n = 5, each patch group). The PTFE patch group served as a control group. At 8 weeks after implantation, the biomaterials were excised. Patch size, patch thickness, infiltrated cell number, extracellular matrix composition, and patch degradation were evaluated.

The PTFE patch itself did not change in size except for increasing in thickness because of fibroblast and collagen coverage of both its surfaces. Host cells did not migrate into the PTFE biomaterial. In contrast, cells migrated into the biodegrading gelatin, PGA, and KN-PCLA and WV-PCLA scaffolds. Cellular ingrowth per unit patch area was highest in the KN-PCLA patch. The KN-PCLA patch increased modestly in size and thinness. The WV-PCNA patch did not change in size or thickness. Fibroblasts and collagen were the dominant cellular infiltrate and extracellular matrix formed in the biodegrading scaffolds. The in vivo rates of biomaterial degradation, thinning, and expansion were material specific. All the subendocardial patch surfaces were covered with endothelial cells. No thrombi were seen.

The unique, spongy matrix structure of the PCLA patch favored cell colonization relative to the other patches. The strong, durable outer poly-l-lactide fabric layers in these patches offered physical, biocompatible, and bioresorbable advantages relative to the other biodegradable materials studied. Host cells migrated into all the biomaterials. The cells secreted matrix and formed tissue, which was endothelialized on the endocardial surface. The biomaterial degradation rates and the tissue formation rates were material related. The PCLA grafts hold promise to become a suitable patch for surgical repair.