Revascularization of skeletal muscle transplanted into the hamster cheek pouch: intravital and light microscopy.

Small fiber bundles from the extensor digitorum longus (EDL) muscle were transplanted into the hamster cheek pouch to observe the process of revascularization. We tested the hypothesis that blood vessels of a graft degenerate and that revascularization results from the ingrowth of blood vessels from the cheek pouch into the graft. Degeneration and regeneration of muscle fibers followed a pattern similar to that reported for autografts of whole muscles in rats. Blood vessels in the graft that were adjacent to vascularized host tissue survived. At 1 day, surviving blood vessels in the graft had normal structure but erythrocytes were packed tightly in the lumen. At 2 days, sprouts from surviving graft vessels had grown into the cheek pouch. Between 2 and 2.5 days, anastomoses of blood vessels from the graft with those of the cheek pouch reestablished circulation. After circulation was established, the blood vessels contained well-spaced erythrocytes. By 3 days, blood vessels which increased in number and diameter throughout the graft occupied 40-60% of the graft. Over the next 24 hr, blood vessels in the graft regressed toward the control value. We conclude that blood vessels in muscle grafts in the cheek pouch survive transplantation, and that circulation in grafts is reestablished by the anastomoses of blood vessel sprouts from the graft with the blood vessels of the host.