An Experimental Study On Changes Of Acute Skin Injury Wound By β-ray And Its Epidermal Stem Cells Expression

ObjectiveTo research the dynamic change of surface markers beta1integrin and p63of theepidermal stem cells in local wounds at different times after SD rat skin with acutebeta ray injury. The experiment investigated the mechanism of skin damage andwound healing by beta ray and provided a certain theoretical basis in clinicaltreatment.Methods102normal rats of2to3months old, either male or female, weight180to220g, weredivided into3groups randomly. The irradiation group: n=48, irradiated the bare skinof rats’ buttocks singly with6MeV high energy electron beam produced by a linearaccelerator, the irradiation diameter was3cm, the total absorbed dose was35Gy, tobuild animal models of acute deep Ⅱ degree beta ray skin injury wound. The scaldgroup: n=48, put a test tube with the diameter of2.5cm filled with hot water in awater-bath of electric heating and constant temperature set at91℃, pressed the rats’bare buttocks gently on the mouth of the tube to touch the water closely for8seconds,to build animal models of skin deep second-degree thermal burns as a comparisonwith ordinary scald. The normal group: n=6, normal rats, were for normal skin tissuesamples cutting.1d,3d,7d,14d,21d,28d,35d after irradiation and scald, took thewound tissue samples of6rats’ buttocks each time, fixed and embedded to make thepathological section. The local wounds were observed by naked eyes andhistopathology technology. The epidermal stem cell surface markers beta1integrin andp63expression were detected by immunohistochemistry methods (SP method) andimage analysis.Results1. To observe rats of the irradiation group by naked eyes, the buttock skin appeared dry peeling and some of the irradiation sections appeared congestive erythema3-5days after the irradiation;7-14days after the irradiation, the colour of the erythemagradually became deep, forming skin necrosis zones the same size as the irradiationarea, local skin swelled and the rats were irritable;14-21days after the irradiation, thenecrotic skin fell off and formed ulcer, the surface of the wound was dry and the edgeof the wound was red and swollen;21-28days after the irradiation, new epitheliumgrew around the wound gradually but grew slowly;28-35days after the irradiation,the surface of the wound gradually contracted but healed slowly and the hair in theneonatal skin zone grew slowly. The scald group: after the scald, the local skin turnedwhite immediately, low gloss, mild swelling, but no blister forming;3days after thescald, the wound was gray, the boundary was clear and no exudation;5-7days afterthe scald, the wound was dry and began to scab;9-14days after the scald, the colourof the eschar became deep, the wound gradually contracted and the edge of the woundwasn’t red, swollen or exudating;21days after the scald, decrustation, the wound wasmoist and the area gradually reduced;28days after the scald, the wound healed, withsparse hair growth.2. Histopathology showed that the irradiation group, after1-7days by irradiating,epithelial cells and hair follicle epithelial swelled, the number of skin cells decreased,dermis and subcutaneous tissue appeared congestive reaction, collagen arrangementdisordered; after14days by irradiating, epidermis disappeared, stratum basale anddermis were damaged, some of the sebaceous glands and hair follicles were destroyed,vascular congestion, endothelial cells swelled and fell off; after21-28days byirradiating, the collagen fiber denatured, dissolved, fractured and arrangementdisordered under the necrotic tissue layer, fibroblasts loose form of mass cell gathered,deformity fibroblasts were formed, few new capillary and inflammatory cells existed,granulation tissue hyperplasia was poor; after35days by irradiating, epidermisdiddn’t cover the wound completely, a few angiogenesis and collagen arrangementdisordered. The scald group: after1-3day by scald, epidermis and most of the dermaltissue coagulative necrosis, collagen fibers integrated into the film, endothelial cellsswelling, wound was infiltrated by inflammatory cells and lots of the hair follicles, sebaceous glands and sweat gland were destroyed. In the deep dermis, residual hairfollicles were visible; after7days by scald, some of the necrotic tissue separated fromnomal tissues and scattered granulation tissue formed; after14days by scald,granulation tissue grew actively, meanwhile, epidermal cell proliferated; after21daysby scald, necrosis tissue fell off, a amount of new skin tissue could be observed;28-35days later, epidermis covered the wound completely and hair follicles andsebaceous glands grew out.3. Immunohistochemistry showed that the expression of beta1integrin and p63positive cells: the IOD of p63positive cells from the serial sections of the same tissuesamples were higher than the IOD of beta1integrin positive cells, and the changerules of the two were consistent. Compared with the normal group,1day afterirradiation and scald, the IOD of positive cells both in the irradiation group and thescald group starts to rise. For the scald group,1to21days later, the IOD of positivecells showed the statistical significance (P<0.05);14to21days after scald, the IODof positive cell continued increasing to the summit and then decreased gradually withthe wound healing;28to35days after scald, the wound healed completely and theIOD of positive cells got close to that of the normal group, then there was nostatistical significance for the IOD differences between the scald and normal groups(P>0.05). For the irradiation group, there was no apparent increase of the positivecells compared with the normal group after1to7days of irradiation, then there wasno statistical significance for the IOD differences between the irradiation and normalgroups (P>0.05); after14to35days of irradiation, skin necrosis zones formed, woundappeared, and positive cell expression increased, there was statistical significancecompared with the normal group (P<0.05). Compared with the scald group, beta1integrin and p63positive cells, in the irradiation group, continued low expression, theIOD value increased slowly; after the1,3,7,14and21days, at the five time point,the difference was statistically significant between the irradiation and scald groups (P<0.05).Conclusions 1. Irradiating the bare skin of rats’ buttocks singly with6MeV high energy electronbeam produced by a linear accelerator, the total absorbed dose was35Gy, which wassuccessfully used to establish animal models of acute skin injury by beta ray.2. During the process of acute injury wound healing of local skin caused by a largedose of beta ray external irradiation, compared with the deep Ⅱ degree scald woundhealing, the proliferation and differentiation of epidermal stem cells slowed down andcouldn’t form a pronounced peak, which may be one of the reasons of repeated delayand prolonged healing of the acute beta ray skin injury wound.