Autoradiographic distribution of collagen loss in skin grafts

Mechanical properties of skin graft wounds

In female Wistar rats the mechanical strength development of the wound between a skin graft and the neighbouring intact skin (graft wound) was compared with that of ordinary incisional wounds after 4, 7, 14 and 21 days of healing. In one group of rats a 35 x 20 mm skin graft including the subcutaneous muscle was raised and replaced in situ on the left side of the back and a 35 mm incisional wound was made on the right side. In another group a 35 mm incisional wound was made on the right side of the back only. After 4 days the maximum load, maximum stiffness and relative failure energy of the graft wounds were 49, 43 and 40% less respectively than those of the incisional wounds from the same animals and after 7 days the maximum load and maximum stiffness of the graft wounds were reduced by 26 and 29%. However, after 14 and 21 days no differences in mechanical properties were found between these two types of wounds. Compared with the incisional wound from rats without graft the maximum load, maximum stiffness and relative failure energy of the graft wound were reduced by 57, 58 and 44% after 4 days, 59, 62 and 54% after 7 days, 37, 38 and 29% after 14 days and for maximum load and maximum stiffness a reduction of 33 and 31% was found after 21 days of healing.

Dermal collagen implants

The feasibility of using preparations of cell-free, fibrous dermal collagen, prepared by trypsin-treatment of skin, for the repair of soft body tissues has been examined both as subcutaneous implants and as a replacement for dermis in skin wounds in rats. Increased collagen stability, and suppression or reduction of tissue antigenicity in collagen heterografts, was achieved by crosslinking with weak solutions of aldehydes while still allowing implant recellularization and revascularization. Tritium-labelled collagen turnover studies have shown that maintenance of collagen mass in implants crosslinked with glutaraldehyde occurs primarily by inhibition of loss of original implant collagen. Some of the in vitro growth characteristics of human fibroblasts on animal collagen preparations are also described.

Reconstruction of full-thickness loss skin wounds using skin collagen allografts

Sheets of allogeneic dermal collagen measuring 20 X 15 mm and prepared by trypsin treatment of full-thickness skin were grafted under skin flaps in rats. After 2 to 5 weeks the protective recipient skin was excised and replaced by split-thickness skin isografts which remained viable on their supportive collagen beds. On average such composite grafts maintained 84 per cent of their original size over 3 to 28 weeks and in contrast with split-thickness skin grafts achieved full-thickness reconstruction of the excised skin.

Incorporation of stored cell-free dermal collagen allografts into skin wounds: a short term study

Allogeneic dermal collagen has been evaluated as an alternative to skin autografts for the permanent replacement of lost or damaged skin in the rat. All non-collagenous structures were removed from full-thickness back skin by treatment with a solution of crystalline trypsin. Such dermal collagen preparations were grafted into skin wounds, examined up to 8 1/2 weeks after operation, and compared with excised wounds and skin isografts and allografts of the same initial size. The dermal collagen grafts, particularly when dressed with a sheet of dermal collagen, become recellularised, revascularised and re-epidermalised. Unlike the skin allografts, there was no evidence of cellular rejection. Whereas contracture of the excised wounds was delayed, but not suppressed, by applying a conventional dressing, collagen grafts maintained from 60 to 100 per cent of their original size. In contrast, equivalent skin isografts shrank to 50-60 per cent and showed persistent epidermal hyperplasia.