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The objective of this study was to evaluate the survival of skin grafts on graft beds of immediate excision and early wound excision at various time periods after burns and to establish the appropriate timing of burn excision and grafting in a rabbit model. Eight groups of male Japanese white rabbits (n = 5 per group) were established. Animals of all groups were given a 5 x 10-cm full-thickness burn on their shaved back and received the autografting 3, 6, 12, 18, 24, 48, and 72 hours and 5 days after receiving burns, respectively. Weekly skin-graft evaluation was performed for 5 weeks after grafting by measurement of the secondary skin graft contracture (in size) and the survival area of grafts, with use of computerized planimetry. In addition, relative quantitative analysis of exudation on the burned wound was evaluated. Our results indicated that the exudate-related graft loss and graft contracture varied according to the timing of wound excision. The wound contractures of the grafts were maximal in both the 18-hour and 24-hour groups at 2, 3, 4, and 5 weeks after grafting. The 18-hour and 24-hour groups exhibited significantly greater graft loss than the 72-hour and 5-day groups (P < .05). An apparent increase in the amount of exudation on the graft bed was shown in the 18- and 24-hour groups vs the other groups (P < .05). A reverse correlation was detected between the survival area of the skin graft and the degree of exudation of the graft bed. In conclusion, the survival area and secondary contraction of skin grafts are associated with the degree of tissue edema of the graft bed in immediate excision and early excision in the rabbit model. The adverse affect of edema leakage on the graft bed for skin graft survival was shown. We believe that immediate excision or early wound excision and grafting performed within 12 hours after burn or 48 hours later should be considered in the rabbit model.

The induction of donor-specific tolerance to skin allografts was investigated in rabbits using bone marrow transplantation techniques reported to be effective in mice. Various routes of bone marrow transplantation (i.e., intravenous, portal venous, or intraosseous) were also examined. In regimen A, the animals were treated with portal venous injection of bone marrow cells from the donor on day 0 and intravenous injection of bone marrow cells from the same donor on posttransplant day 5. In regimen B, the animals were treated with portal venous and intraosseous injections of donor bone marrow cells on day 0 and intravenous injection of bone marrow cells from the same donor on posttransplant day 5. In regimen C, the animals were given intraosseous injection of donor bone marrow cells on day 0 and intravenous injection of bone marrow cells from the same donor on posttransplant day 5. It was found that regimens B and C were more effective than regimen A in prolonging allograft survival. The results demonstrate that induction of allograft tolerance can be achieved by bone marrow transplantation in a rabbit model. This protocol deserves further study in other large animal models.

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