| ObjectiveThe purpose of the study is preliminary assessing of porcine collagenic dermal matrix ( PCDM ) as a dermal substitute. We provide the feasibility of PCDM as dermal substitute in experiment and clinical application by observing histological structure and evaluating cytotoxicity about PCDM. Through observing the morphology, structure, growth character of fibroblasts and vascular endothelial cell and the vascularization of PCDM after PCDM were embedded in the subcutaneous of rats, we supply strategy for modifying structure and investigate the treatment of improving histocompatibility of porcine dermal scaffold.Methods1) Observing histological structure of PCDM by HE staining, immunohistochemistry staining, SEM and TEM. The histological structure of PCDM was compared to that of porcine acellular dermal matrix (PADM)and human acellular dermal matrix (HADM).2) The cell growth curves of L-929 with different concentration were measured by MTT assay in order to decide an appropriated cell seeding concentration. The leaching liquor of PCDM was made and used as test group, blank control group, positive control group and negative control group were set. The effects of different levels of leaching liquor on L-929 were detected by MTT. The cytotoxicity of PCDM was evaluated in vitro according to the national standard of biomaterial. 3) Twenty-four wistar rats were enrolled in the study and were randomly divided into porcine collagenic dermal matrix ( PCDM ), human acellular dermal matrix ( HADM ) groups according to different dermal substitutes grafted underneath the skin of wistar rats. The gross appearance of the grafts was observed, and the tissue biopsies were harvested at 3, 7,14, 30 post grafting day (PGD) for the observation of the revascularization process and their histological changes.Results1) PCDM was pure white and smooth with good tenacity and soft feeling. In the light microscope , the side of papillary dermis was smooth and intact, immunohistochemical staining showed filiform brown region on papillary dermis, it suggest intact basal membrane was remained ,but the cell, blood vessel, appendages of the skin were removed completely, The three dimensional structure of collagenic matrix was intact. The side of reticular dermis was rough, ruptured collagen fiber were seen. In transmission electron microscope, collagenic structure remained as normal porcine dermis was observed. A comparison of PCDM, HADM and PADM by SEM reveals that they all have a tightly packed network of thick collagen bundles, however, the PCDM and HADM appears to have a more loosely packed surface than PADM.2) The number of cells in 5×10~3/well to 1×10~4/well were appropriate for MTT, The cell growth curves of L-929 showed straight line correlation of direct proportion according to the curve of cell number vs OD in a week. the cell proliferation was active and the measured data was stable according to the standard detection method of cytotoxicity, cell proliferation degree of test group were higher than positive control group significantly, the value among test group , blank control group and negative control group was no significant difference. The toxicity grade of PCDM was grade 0-1, there was no significant toxicity to body.3) Gross observation: The incision in each group healed well without local swelling and inflammatory response after grafting. The grafts had a compact contact with the wounds. Fibroblasts, neutrophiles and lymphocytes migrated into the grafts and new capillary sprouts from the receiving beds could be observed after 3PGD.Affluent capillary nets formed in the grafts after 30 PGD.Conclusion1) PCDM prepared by physical-chemical process has no cytotoxicity. It is a safe xenogenic dermal substitute2) FB and VEC proliferated well on PCDM. FB infiltration and new vessels was seen in the interior of PCDM in this study. This find shows PCDM has good histocompatibility and it also suggests that there is no xenogenic barrier to fibroblast migration on porcine collagen.
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