Skin blood flow response in the rat model of wound healing: expression of vasoactive factors.
BACKGROUND
Although the microvascular blood flow response to wounding is predominantly vasodilation at skin sites with nutritive capillary perfusion (NUTR), there is a significant vasoconstrictive response at sites with high arteriovenous perfusion (AV). There may be a difference between NUTR and AV sites in the vasoactive factors which mediate the blood flow response to wounding. We measured the levels of mRNA expression of several potential mediators of the blood flow response to assess this possible difference.


METHODS
We measured skin blood flow at wounds placed at the back, a NUTR site, and at the paw, an AV site, in 12 Wistar Kyoto rats. Measurements were performed at baseline and then at 7 days post wounding. There was a significant increase in blood flow at back wound sites, with a rise from 4.1 +/- 0.3 ml/min/100 g to 9.8 +/- 1.9 ml/min/100 g. At the undisturbed wound perimeter, outside the zone of granulation tissue, flow rose to 7.3 +/- 1.1 ml/min/100 g. At the paw wound site, Day 0 flow was 8.8 +/- 0.8 ml/min/100 g. At 7 days, there was a significant decrease in flow at wound center to 5.5 +/- 0.5 ml/min/100 g. We measured the levels of inducible nitric oxide synthetase (iNOS), endothelin, endothelin receptor, vascular endothelial growth factor (VEGF), and keratinocyte growth factor (KGF) gene mRNAs using reverse transcriptase PCR.


RESULTS
There was a 10-fold increase in NOS mRNA in granulation tissue of both wounds on Day 7. There was a lesser but still substantial increase in the wound perimeter tissue. Levels of endothelin mRNA in the wound and wound perimeter were significantly lower at the paw than at the back. At baseline, the level of endothelin receptor B (ETrB) mRNA was greater at the back than at the paw. Wounding resulted in a substantial increase in EtrB mRNA levels in granulation tissue, reaching the same level at the back and paw wounds. There was also a substantial rise in EtrB mRNA levels at the paw wound perimeter, so that there was a reversal of the baseline condition, with paw levels actually surpassing the levels at the back perimeter.


CONCLUSIONS
Thus, we have found significant changes in mediators both of vasoconstriction and vasodilation affecting the healing wound. These changes affect NUTR and AV sites in different ways. These results demonstrate the complexity of the regulatory processes controlling microvascular blood flow in wound healing.
Rendell
Marc S
MS
The Creighton Diabetes Center, Omaha, Nebraska 68131, USA. rendell@asndi.com
Johnson
Mark L
ML
Smith
Denae
D
Finney
David
D
Capp
Christopher
C
Lammers
Rebecca
R
Lancaster
Scott
S
D000818:Animals; D016228:Endothelial Growth Factors / Q000235:genetics / Q000378:metabolism*; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism*; D006097:Granulation Tissue / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008222:Lymphokines / Q000235:genetics / Q000378:metabolism*; D008833:Microcirculation; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011921:Rats, Inbred WKY; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism*; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply*; D014018:Tissue Distribution; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D014945:Wound Healing / Q000502:physiology*
D016228:Endothelial Growth Factors; C496455:Fgf7 protein, rat; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D012333:RNA, Messenger; D017466:Receptors, Endothelin; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat