Experiment Study On Effect Of RhGH On Survival Of Free Skin Flaps In The Rat

AimThe purpose of the present study was to determine the effects of recombinant human growth hormone (rhGH) on survival of a free abdominal skin flap and on angiogenesis of subdermal vessels of the flaps in the rat and to understand its effects on the whole survival of skin flaps thoroughly so as to provide the rationale for its clinical use.MethodsTwenty Wistar rats weighting 350-400g were employed as experimental animals and were divided two groups at random,each group have ten rats (males and female were random). Remove hair in the area where the skin would be operated, A abdominal free skin flap was designed at every rat and the pedical was the left lateral inferior epigastric artery and vein. there are ten injection points at right lateral. two groups were received respectively the following treatment: group rhGH( n=10): rhGH were injected into the subcutaneous fascial layer in the area where the flap would be dissected at the dose of 0.lIU/kg;we elevated the flap in the next , cutted the right lateral inferior epigastric artery and vein and marked the left lateral inferior epigastric artery and vein with 8-0 suture line, then cutted the left lateral inferior epigastric artery and vein ; and after sewed skin flap in original lateral we inosculated the left lateral inferior epigastric artery and vein with 11-0 sutural line to its original bed ;group normal saline(n=10):we did the same operation with normal saline instead of rhGH ; On postoperative 7 day, all the animals were anaethetized by drug ,and were taken photograph, the survival area of skin flaps was measured with micro-image analystor. And on postoperative 14 day two samples were harvested from each group for pathological check and immunohistochemical test. Flap survival was studied, histologic studies were performed and blood vessel density was measured. The data from the experiment were analyzed statistically.ResultsAfter seven days recovery, the area of flap survival was measured. Mean flap survival area in group rhGH was 47.65±3. 93 cm2,group normal saline was 29.97±2.89 cm2 , There was significant difference between group rhGH and group normal saline(P<0.05).The survival rate was measured 14 days postoperatively. Mean flap survival rate in group rhGH was 84.00±4.96%, group normal saline was 52.40±5.99%. There was significant difference between group rhGH and group normal saline(P<0.05). The data demonstrate that preoperative treatment with subdermal rhGH injection into the flap at flap elevation can induce angiogenesis and enhance skin paddle survival in a musculocutaneous flap. Under the microscope,the tissue inflammatory reactions in the experiment group were not so severe as that in the control group. Immunohistochemical staining demonstrated that there was distabition and active expression of VEGF at the epidermis, the dermis, the hair-follicle, the sebaceous glands, the sweat gland, the endothelial cell, the fibroblast cell in the both group flaps and there wasdistabition and active expression of VEGF-R only at the endothelial cell. The active expression of VEGF and VEGF-R of rhGH group was strong,and that in control group was weak. The difference between the two groups was very significant statistically .The distribution of VEGF in middle segment of rhGH group was widespread,and that in control group was limit. The blood vessel density and blood vessel diameter in middle segment of both groups were measured 7 days postoperatively. Mean flap blood vessel density in middle segment of rhGH group was 29.35士2.52 and that in control group was 18.15士2.69. There was difference between both groups statistically. ( P<0.05).ConclusionsThese results support the notion that rhGH rescues tissue at risk of hypoxic damage by inducing angiogenesis and can improve the ratio of the longth and width of the flaps .The use of rhGH holds promise as a method of improving the survival of the ischemic random skin flaps and it is applicable to give rhGH subcutaneous injection. It makes rhGH therapy simple and practical and will be promising future in the tissue transplantation. The higher survival ratio of the flap might owe to the mechanism that rhGH perhaps helps the flap tissue to produce more VEGF and more VEGF-R in the flap. The mechanism might be that rhGH could accelerate flap vascularization and protect flaps from ischemia -reperfusion injury. All these changes improve the local angiogenesis and microcirculation,promote wound healing and increase the survival area of the flap in the experiment。...