The microvascular composition of the healing wound compared at skin sites with nutritive versus arteriovenous perfusion

Background. In the rat, there is a significantly greater blood flow respons e to wounding at the back, a site perfused mainly by small capillaries, tha n at the paw, which has a much higher density of arterioles and venules. Materials and methods. We characterized the microvascular composition of wo unds at the two skin sites in 11 Wistar Kyoto rats using a quantitative ima ging program. Blood flow was compared using laser Doppler technology. Results. Prior to wounding, skin blood flow was much greater at the paw (7. 1 +/- 0.5 ml 100 g tissue(-1) min(-1)) than at the back (2.1 +/- 0.1 ml 100 g tissue(-1) min(-1), P < 0.01) at baseline. Seven days after wounding, bl ood flow both at the center (8.3 +/- 1.4 mi 100 g tissue(-1) min-l) and at the perimeter of the back wound (4.1 +/- 0.5 ml 100 g tissue(-1) min(-1)) h ad increased substantially. In contrast, skin blood flow at the perimeter o f the paw wound had increased moderately (12.7 +/- 2.0 ml 100 g tissue(-1) min(-1)), but there was no change at the center of the wound (6.9 +/- 0.9 m l 100 g tissue(-1) min(-1)). There were three times more microvessels per m m(2) at the paw site (39.3 +/- 3.6) than at the back (13.1 +/- 1.5) prior t o wounding. The wound granulation tissue was very vascular; the numerical d ensity of vessels was identical at back (166 +/- 9) and at paw (154 +/- 6), Despite the marked increase in blood how at the perimeter of the back woun d, there was no difference in the microvascular density (15.2 +/- 1.4) comp ared to baseline, nor was there a difference at the paw perimeter (39.4 +/- 3.6) compared to baseline. Conclusions. This study demonstrates that the microvascular constitutions o f granulation tissues at the paw and back are identical, Thus, the rise in flow at the back wound and reduction in flow at the paw wound are entirely consistent with similar microvascular compositions of these two sites. Yet, there is increased how at the back wound perimeter where there is no signi ficant change in microvascular constitution compared to unwounded skin. The refore, a microvascular structure no different from that prior to wounding functions very differently after wounding. Clearly vasoregulatory factors i mpact on the wound to modify flow through the microvascular network. (C) 19 98 Academic Press.