Small intestinal submucosa as a graft to increase rectum diameter.

BACKGROUND: The purpose of our study was to assess the biocompatibility of the porcine small bowel submucosa and its ability to increase the rectal diameter compared with a formal transverse coloplasty. METHODS: We assigned 36 New Zealand male rabbits to four experimental groups: groups C1 and C2 were treated with transverse coloplasty and groups S1 and S2 were treated with a patch of a porcine small intestine submucosa. We killed the animals in the C1 and S1 groups on the 7th postoperative day, and the animals in the C2 and S2 groups on the 30th postoperative day. We evaluated outcomes on the basis of animal survival, clinical course, anastomosis bursting pressures, morphometric examination, and histologic and immunohistochemical assessment. RESULTS: Morphometric examination showed a significant increase in colonic diameter in animals in the S2 group. We found no statistical difference regarding anastomosis bursting pressure between the C1 and S1 groups, and the C2 and S2 groups. On the 30th postoperative day, histologic examination showed total epithelium coverage of the grafts, and the immunohistochemical study showed an organized smooth muscular layer covering the graft. The higher concentration of collagen ticker fiber, type I, was seen in the S2 and C2 groups, but there was no statistical difference between them. CONCLUSIONS: The implanted graft proved superior to transverse coloplasty regarding the increase in distal colon diameter. Remarkable regeneration, marked fibroplasia, and epithelium coverage occurred throughout the graft on the 30th postoperative day.

Tuna cornea as biomaterial for cardiac applications.

Among available biomaterials, cornea is almost completely devoid of cells and is composed only of collagen fibers oriented in an orderly pattern, which contributes to low antigenicity. Thunnus thynnus, the Atlantic bluefin tuna, is a fish with large eyes that can withstand pressures of approximately 10 MPa. We evaluated the potential of this tuna cornea in cardiac bioimplantation. Eyes from freshly caught Atlantic bluefin tuna were harvested and preserved in a fixative solution. Sterilized samples of corneal stroma were embedded in paraffin and stained with hematoxylin and eosin, and the histologic features were studied. Physical and mechanical resistance tests were performed in comparison with bovine pericardial strips and porcine mitral valves. Corneal material was implanted subcutaneously in 7 rats, to evaluate in vivo calcification rates. Mitral valves made from tuna corneal leaflets were implanted in 9 sheep. We found that the corneal tissue consisted only of parallel collagen fibers without evidence of vascular or neural structures. In tensile strength, the tuna corneal specimens were substantially similar to bovine pericardium. After 23 days, the rat-implanted samples showed no calcium or calcium salt deposition. Hydrodynamic and fatigue testing of valve prototypes yielded acceptable functional and long-term behavioral results. In the sheep, valvular performance was stable during the 180-day follow-up period, with no instrumental sign of calcification at the end of observation. We conclude that low antigenicity and favorable physical properties qualify tuna cornea as a potential material for durable bioimplantation. Further study is warranted.