The hemodynamic and molecular mechanism study on the choke vessels in the multi-territory perforator flap transforming into true anastomosis

Abstract

Background: The aim of this study was to explore the hemodynamic and morphological changes of the choke vessels, and to investigate the role of HIF-1α in the flap adaptation to hypoxic and choke vessel transformation after multi-territory perforator flap transplantation.

Methods: Animal model of single pedicle multi-territory perforator flap was established in the back of SD rats and the blood supply characteristics were studied by gelatin-oxide perfusion technique. HE staining and stereomicroscope were used to observe vascular changes. Afterward, the influence of hypoxia on cell proliferation and apoptosis were detected by MTT assay and flow cytometry, respectively. Besides, the expression of HIF-1α, iNOS and VEGF expression of HUVECs under hypoxia were detected by qRT-PCR and Western blot.

Results: The results revealed that all the choke vessels immediately began to expand after operation. The day after operation, some of the choke vessels continued to grow and expand, turning into the true anastomosis, while the others gradually dwindled and finally disappeared. Compared with the control group, the day after transplantation, the expression levels of both HIF-1α and iNOS were significantly increased. The only different was that HIF-1α was then maintained a high level, iNOS was significantly decreased aftertimes. What's more, the expression of VEGF was increased to the maximum at 3 days after operation and then decreased. In HUVECs, hypoxia increased the expression of HIF-1α, iNOS and VEGF protein. Besides, it also promoted the proliferation and inhibited the apoptosis. In addition, we also found that hypoxia-induced VEGF and iNOS upregulation is mediated by HIF-1α overexpression and HIF-1α knockout can reverse the effects induced by hypoxia.

Conclusions: We found that HIF-1α may participate in the early vascular dilatation of transregional skin flap by inducing iNOS expression and promoting the reconstruction of choke vessels through increase VEGF expression.

Keywords: Choke vessels; HIF-1α; Perforator flap; VEGF; iNOS.