Histological studies of subcutaneous and intraperitoneal implants of trypsin-prepared dermal collagen allografts in the rat.

The possibility of using allograft collagen for the permanent replacement of lost or damaged connective tissues has been examined in the rat. The cellular components of skin, which are known to be of major importance in allograft rejection, were removed by treating skin with a solution of crystalline trypsin at 15 degrees C. Non-collagenous structures were largely removed by 7 days, but the purification process continued up to 28 days without damage to the collagen fibrils. Dermal collagen allografts, which were implanted intraperitoneally or subcutaneously and biopsied 3-83 days after operation, became recellularized and revascularized without being being resorbed. In contrast to skin allografts, there was no evidence of cellular rejection of the collagen grafts, even when recipient animals had been sensitized to allogeneic skin from the same donor. Densensitization of collagen to collagenase, by treating dermal collagen with solutions of glutaraldehyde at concentrations ranging from 0.001-1.0 per cent, was also investigated in vitro and by implantation. The best results, in terms of preservation of the collagen bundle architecture and graft recellularization without persisting inflammation, were achieved with collaged pre-treated with a solution of 0.01% glutaraldehyde.