| Objective: To observe the impact of IHH-PC used in SD rats'subcutaneous vascular net free skin, which include the process of peripheral revascularization, vascular cell increment and the survival skin area. Skin transplantation is a main treatment of Hand Surgery, Burn and Plastic Surgery. The routine free skin contains full thickness skin graft skin and intermediate thickness free skin graft. The subcutaneous vascular net free skin contains epidermis, the dermis layer, the subdermal vascular plexus and little subcutaneous adipose tissue. It is rich in elastic fibers, gland, capillary and little adipose tissue, so it's more soft, elasticity, antifriction than routine free graft, has much better sensory compare to routine free graft, and no needs to repair thick fat compare to skin flap. The basis of successful skin graft is the establishment of blood supply, and vessel formation (angiogenesis in the proliferation and the formation process) is the foundation and key factor of the blood supply. The free skin's mode of blood supply establishment contains peripheral revascularization establishment and base revascularization establishment. Some experiments indicate that the free skin's peripheral revascularization establishment is the main route of blood supplement, but it's peripheral blood supply is not enough, so it will appear some partial necrosis when it cover major area nonvascular wound surface. Intermittent hypobaric hypoxia preconditioning has significant organism protection against such as ischemia, anoxia and ischemia/reperfusion injuries. We have found that many DNA and mRNA, growth factor, protein involved in the protection process, such as VEGF. VEGF is one of the most effective angiogenesis factor, which can accelerate the growth of endothelial cells, promote the formation of new capillaries, increase the number of capillary, thereby improving wound microcirculation. This study researched how intermittent hypobaric hypoxia preconditioning influence the survival area and the establishment of blood supply of the skin graft when it's basal blood supply had been interdicted, provided experimental evidence for free skin graft apply to major area of nonvascular wound surface in clinical operation.Methods: 45 healthy SD rats were randomly divided into three groups, GroupA: contrast(Con), GroupB: intermittent hypobaric hypoxia(IHH), GroupC: intermittent hypobaric hypoxia preconditioning(IHH-PC). All rats were cut 1×1 cm~2, 2×2 cm~2, 3×3 cm~2 free skin, which is located in relative same position in dorsum area. The formation process of the subcutaneous vascular network skin is as follows: cut skin, subcutaneous tissue, in the deep fascia superficial skin surface will be set off, bleeding wound thoroughly and repair the majority of subcutaneous films, retain subcutaneous fat about 2 to 3 mm, then the basement were filled by the Skin Flake silica membrane in order to block the basement blood supply, at last skin were reversed and sutured directly. The IHH rats were put into a hypobaric chamber to get 7 days IHH mimicking 5000m altitude, 6hrs/day, after cut free skin, respectively. The IHH-PC rats were put into a hypobaric chamber to get 7 days IHH mimicking 5000m altitude, 6hrs/day before cut free skin, respectively. The time put in and get out the hypobaric chamber is regular respectively, the temperature is 17-20℃. The contrast rats were kept in the same environment as IHH and IHH-PC rats with free access to food and water except hypoxic exposure. We investigated the outcomes after 7 days. MEASURES: 1. observed the color, texture, flexibility situation of the free skin. 2. survival skin area: after one week, according the digital camera recording, measuring the longest diameter and the most width survived skin area, measured the percentage of survival. 3. histologic observation: get pathological section in a margin of the surrounding free skins, HE staining, selected five high-power microscope vision randomly, measured the number of new vascular.Results: General observation: 45 rats all survived after the whole feeding, if the skin texture stiffen, lose flexibility or the color change into black, this is the standards for judging skin necrosis. Survival area of 1 cm~2: group A 0.89000 cm~2, B and C: 0.90000, 0.91000 cm~2, there is no difference in the three groups. Survival area of 4cm~2: Group A 2.53000 cm~2, B and C: 2.9500,3.4900cm~2, there are significance of survival area and average width(P<0.05), the survival area and average width of groupC is larger than groupA,B, groupB is larger than groupA. Survival area of 9cm~2: Group A 4.2800 cm~2, B and C: 5.0700, 6.0200cm~2, there are significance of survival area and average width(P<0.05), the survival area and average width of groupC is larger than groupA,B, groupB is larger than groupA. 2. Histological observation: In group A, most of the cuticular layer is damaged. There are a large number of inflammatory cell. We can see rare of neogenic micrangium. In group B, some layer of skin is damaged and can see a number of inflammatory cell and some big vessels in the demis layer. In group C, the layer of skin was kept, we only can see a little inflammatory cell, and we also see a lot of capillary and big vessels. Under the microscope of 100 times, selected five perspectives in each section randomly, measured the numbers of vessels, on the average. Cut scope of 1 cm~2: Group A 2.81, B and C 3.19,5.03; cut scope of 4 cm~2: Group A 2.69, B and C 3.24,5.44; cut scope of 9 cm~2: Group A 2.73, B and C 3.64,5.52.There are significance of capillary numbers in three groups(P<0.05), the capillary number of groupC is larger than groupA,B, groupB is larger than groupA.conclusion: After intermittent hypobaric hypoxia preconditioning on the subcutaneous vascular net free skin, strengthening the capacity of resistance to ischemia, anoxia, promote the process of revascularization establishment as the same time. We find that IHH has the similar efficacy as IHH-PC.
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