Recombinant leptin administration improves early angiogenesis in full-thickness skin flaps: an experimental study

Leptin is a potent direct angiogenic factor that stimulates endothelial cell migration and activation in vitro, and angiogenesis in vivo. In addition, leptin seems to play an important role in angiogenesis as it promotes the formation of new blood vessels.

To determine the effect of local application of exogenous leptin on the survival of full thickness skin flaps in an experimental animal model.

Ninety Sprague-Dawley rats were used in this study. A full thickness dorsal flap (10 cm x 2 cm) with the pedicle located at the level of the iliac crest was designed. Animals were divided into ten groups of nine animals each. In the distal two thirds of the flap and by means of subdermal injection at 8 different locations, rats were injected with 100 ng/ml leptin, 250 ng/ml leptin, 500 ng/ml leptin, 1000 ng/ml leptin (groups A, B, C and D), 1 microg/ml VEGF (group E), or 1 ml saline (control group), respectively. For each of the four leptin doses used, another animal group was injected with a combination of leptin/antileptin: 100 ng/ml leptin with 150 ng/ml antileptin, 250 ng/ml leptin with 375 ng/ml antileptin, 500 ng/ml leptin with 750 ng/ml antileptin or 1000 ng/ml leptin with 1500 ng/ml antileptin (groups A1, B1, C1 and D1, respectively), in order to study the inhibition of the leptin factor. Nine rats served as controls and were injected with 1 ml saline solution. Rats were sacrificed 3, 7 and 9 days postoperatively. After sacrifice of the animals, the skin was grossly arranged on its appearance, colour and texture. Full thickness skin flaps were dissected for histological examination. A qualitative analysis of angiogenesis in the flap was conducted following a standard hematoxylin and eosin stain. The wound tissue samples from each experimental group underwent immunohistochemical evaluation of microvessel density by endothelial cell staining with mouse anti-rat CD 34 monoclonal antibody.

Immunohistochemical staining revealed that more granulation tissue and improved angiogenesis were observed in group D (1000 ng/ml leptin) flaps compared to those in the VEGF, leptin/antileptin and saline groups. In addition, skin flap survival rate in group D (1000 ng/ml leptin) and group E (1 microg/ml VEGF) were significantly better than those of the other groups. The most impressive formation of new blood vessels was noted in the groups with the higher leptin doses. Surgical wounds in the control, as well as in the leptin/antileptin groups, did not demonstrate any new vessels.

Exogenous administration of recombinant leptin increases early skin flap angiogenesis in an experimental animal model. Local application of leptin could efficiently improve survival of ischemic skin flaps.