OBJECTIVETo evaluate the effects of mixed grafting of allogeneic PADM and autologous STS on wound healing of full-thickness defect in rats.

METHODSFull-thickness defects with size of 6 cm x 4 cm were produced on the back of 12 SD rats, and they were divided into E group (n = 6) and C group (n = 6) according to the random number table. The wounds in E group were grafted with a mix of allogeneic PADM (expansion rate 10: 5) and autologous STS with thickness of 0.2 mm, while those in C group were grafted with autologous STS in the same thickness. The wound healing rate, survival rate, contraction rate, and expansion rate of transplanted skin were observed at post operation week (POW) 2, 3, 4, 6, 8, 12, 20. Tissue samples form wounds and surrounding normal skin were harvested at POW 20 for histopathological observation as follows. The structure of collagen fiber bundle was observed by HE staining, the diameter and gap rate of collagen fiber bundle were also measured. The distribution of type I and III collagen was observed by sircus red staining, and the contents of type I, III collagen and their ratio were also examined. Data were processed with independent samples t test, Levene test, and t' test.

RESULTSSurvival rate of transplanted skin in E group at POW 2 [(76.1 +/- 13.1)%] was obviously lower than that in C group [(94.5 +/- 1.3)%, t' = 3.440, P = 0.018]. Contraction rate of transplanted skin in E, C groups at POW 3 showed significant difference [(34 +/- 8)% vs. (16 +/- 12)%, t = -3.211, P = 0.009]. Compared with those in peri-wound normal skin, collagen fiber bundles in C group showed signs of homogenization, and collagen fibers were thin with irregular arrangement. Collagen fiber structure and arrangement of composite skin in E group were similar to those surrounding normal skin with incomplete degradation of PADM. Diameter of collagen fiber bundle [(9.6 +/- 0.8) microm], gap rate between collagen bundle [(24 +/- 5)%], content of type I collagen [(80.2 +/- 5.4)%] and the ratio of type I to type III collagen (4.3 +/- 1.2) in E group were all increased as compared with those in C group [(7.3 +/- 1.4) microm (t = -3.562, P = 0.005), (17 +/- 4)% (t = -2.760, P = 0.020), (68.1 +/- 8.4)% (t = -2.981, P = 0.014), 2.3 +/- 1.0 (t = -3.204, P = 0.009)], while content of type III collagen [(19.8 +/- 5.4)%] in E group was lower than that in C group [(32.0 +/- 8.4)%, t = 2. 981, P = 0.014]. Above-mentioned indexes of collagen in wound of E group were similar to those of normal skin surrounding the wound.

CONCLUSIONSAllogeneic PADM used as dermal regeneration template is beneficial in improving collagen fiber bundle structure in dermis layer of rats with full-thickness skin wounds when repaired with autologous STS, and it accelerates maturation of regenerative dermal tissue.