ANGIOGENESIS AND REINNERVATION IN SKIN FLAPS - THE EFFECTS OF ISCHEMIA EXAMINED IN AN ANIMAL-MODEL

In clinical flap transplantation, ischaemia may alter reinnervation pa tterns either directly or by affecting angiogenesis. This study presen ts the effects of ischaemia on innervation in totally denervated, tran siently (30 minutes) or prolongedly ischaemic skin flaps studied immun ohistochemically with antisera to PGP 9.5, CGRP and VWF. Following tra nsient ischaemia, an increase in PGP-immunoreactive (PGP-IR) and CGRP- IR nerve fibres in distant skin by day 12 was followed by increased in nervation in immediately adjacent skin. The latter increase was mainta ined up to 24 days which allowed near normal innervation at the suture margin and in adjacent flap tissue, 0.5 cm from the margin. There was concomitant reinnervation from the pedicle by day 24. In prolongedly ischaemic flaps, an earlier and more prolonged increase in innervation was seen in the entire surrounding skin, with innervation around the suture line at 24 days resembling that in the transiently ischaemic fl aps despite initial complete nerve fibre depletion in this area. Hyper trophic nerve fibre clusters were seen in fibrotic areas overlying the pedicle. Vascular changes were similar in both groups with vasculariz ation preceding reinnervation. There were no significant differences i n reinnervation between the transiently and prolongedly ischaemic flap s at 24 days, despite considerable initial variations. Ischaemia, CGRP , mediators of chronic inflammation and epidermal factors appeared to stimulate angiogenesis and reinnervation.