P. Shoureshi1, K. Chang1, F. Lay1, Z. Alikhassy Habibabady2, J. M. Abraham1, A. K. Ahmed1, R. Sebastian3, J. W. Harmon1 1Johns Hopkins University School Of Medicine,Dept Of Surgery,Baltimore, MD, USA 2Massachusetts General Hospital,Cardiac Surgey,Boston, MA, USA 3George Washington University School Of Medicine And Health Sciences,General Surgery,Washington, DC, USA
Introduction:
Hypoxia-inducible factor-1 (HIF-1) is a transcriptional activator that orchestrates the cellular response to hypoxia. Its actions in dermal wounds promote angiogenesis and improve healing. In plastic and reconstructive surgery, surgical skin flaps are frequently used to repair acquired and congenital disabilities. Necrosis of the distal flap is a common complication resulting from insufficient blood supply to the distal flap. Improving blood flow to such flaps utilizing HIF-1 is an attractive strategy for improving flap survival. To explore the feasibility of a local injection of 3194bp plasmid-encoded to express a human degradation resistant HIF-1 (Nature Technology Company, Lincoln, NE) to improve the viability of dermal pedicle flaps by increasing angiogenesis in aged rats
Methods:
One-year-old Sprague Dawley rats were prophylactically injected intradermally in the marked region of dermis where the flaps would be made. The treatment group received 50μl of 1μg/μl HIF-1α DNA plasmid while the control group received a 50μl saline sham injection. Seven days after treatment, each rat had two 1.6×8 cm isolated pedicle flaps raised with a silicone implanted in between the skin flap and muscle layer. Surviving flap area and blood perfusion measured by laser Doppler imaging were compared for the treatment and control groups. Immunohistochemistry was assessed on tissues stained with CD 31. Levels of human HIF mRNA were measured with qRT-PCR.
Results:
Necrotic area of the skin flap assessed photographically was significantly less in the treatment compared to the control group (the Necrotic area on day 1: 0.4 ±1.2 vs. 2.3±2.5, day 7: 1.0±2.3 vs. 4.0±4.6, day 14: 1.0±2.0 vs. 2.5±2.8, Tukey test, p<0.001). CD31 showed angiogenesis with a significant increase in the number of vessels present per high power field (t-Test, p=0.027). We confirmed that the DNA plasmid was being transcribed using qRT-PCR in skin tissues 24 hours after treatment was administered. Human HIF mRNA from the plasmid was expressed at 25X the level of endogenous rat HIF.
Conclusion:
Local injection of HIF-1α DNA plasmid promotes angiogenesis and viability of dermal pedicle flaps significantly. This approach has a potential for clinical application in different fields of surgery
