Histologic Analysis And Vascularization Evaluation In Porcine Acellular Dermal Matrix Processed With Matrix Metalloproteinase

ObjectiveOn the base of the improvement of a mechanical method, making porcine dermal reticular layer, decellularization by Dispase Ⅱ and TritonX-100, and treated with matrix metalloproteinase-7(MMP-7) to reduce the immunogenicity of xenogenic (porcine) acellular dermal matrix(Xeno-ADM), the dermal scaffold structure of P-ADM-pm is kept along with larger interspace of collagenous fibers or collagen fibril to some degree. The current study is to investigate histologic changes and vascularization in porcine acellular reticular layer dermal matrix processed with matrix metalloproteinase-7(P-ADM-pm), porcine acellular reticular layer dermal matrix processed with Dispase Ⅱ and TritonX-100(PADM), which were implanted in rats. In addition, the mechanism of the dermal scaffolds in reconstruction, and the theoretical basis for the clinical application prospect were discussed.MethodsUsing a mechanical method to abtain62pieces of Porcine dermal reticular layer,0.5-0.6mm thick,1cm×1.5mm each, were randomly divided into group A (with decellularization, P-ADM) and group B (with processing by MMP-7after decellularization, P-ADM-pm). One piece of each group was used for sampling test. Thirty adult male Wistar rats were selected. Subcutaneous implantation of materials were performed in rats’dorsa. P-ADM and P-ADM-pm were transplanted into the left and right fascia lacuna, respectively. The implant (n=6) were harvested at3、7、 14、21and28days postoperation respectively. Gross observation, HE staining, masson staining, immunohistochemical staining, scanning electron microscopy (SEM) examination and transmission electron microscopy (TEM) examination were performed to observe host cells, microvessels infiltration and histologic changes in implant.Results(1) Sampling test revealed that a few hair, epithelial root sheath, nuclei, cell debris, vimentin, laminin and collagen Ⅳ were observed in P-ADM but not in P-ADM-pm. The interspace among collagen fiber bundles or collagen fibers was larger in group B than that of group A.(2) Gross observation suggested that at7days after implantation, the two groups were encapsulated by a thin layer of connective tissue. With the time of implantation, the microvessels increased and coarsened, and the group B had more than those in group A. At21days, the microvessels of the two groups decreased, and the group B appeared pink.(3) The microscopic observation showed that group A had intense inflammatory response, of which morphosis of collagen fibers was disorganized after14days. However, group B had less inflammatory response, and host cells, especially fibroblasts and microvessels infiltration into implant were more significant than those in group A (P<0.05). Also, morphosis of implant collagen fibers in group B maintained in normal. SEM examination showed that fibroblasts and new collagen fibrils, as well as the position relationship between the new and original collagen fibrils, were observed in group B at14days.ConclusionsThe host response to P-ADM-pm parallels normal wound healing, and P-ADM-pm as implantable scaffold material plays a good template conduction role and clinical application prospects.