Experiment Of Assessing Expanded Polytetrafluoroethyleneis As A Safe Material Covering Wound Surface

Objective:The problem of the skin source has always been bottlenecks in clinical treatment of extensive burned patients. Now, the wound surface is mostly covered with allograft skin and xenograft skin in clinical practice. It is well known that allogenic skin can temporarily solve the problem of wound covering, but the strong rejection will lead to the restrictions on the use of them. In recent years, many researchers are keen to find some biological material with good biocompatibility to cover large-area burned wound surface to replace the xenograft skin and allograft skin. This experiment is designed to assess the feasibility of high molecular ePTFE as a safe material covering wound.Methods: The back wounds of Sprague Dawley (SD) rats generated by surgical excision were treated with either implant of ePTFE or skin flap obtained from the back of the Wistar rats. The wound healing processes were examined daily for 60 days and representative tissue specimens were biopsyed and analyzed microscopically at different time points to assess the extent of inflammatory response and tissue regeneration. Macrophages, lymphocytes and fibroblasts were quantified. Additionally, IL-2 and IFN-γexpression in the infiltrating mononuclear cells were assessed by immunohistochemistry.Results:(1) Gross Examination of the Wound Healing Process: ePTFE adheres tightly to the wound surface. Minimal inflammation and no adverse effects were observed throughout the experiment.(2) Light Microscopic Examination of the Wound Healing Process The number of macrophages, fibroblasts, lymphocytes in the study group were significantly lower than their counterparts in the control group (P<0.01). There is a significant difference between the autografting and the ePTFE treated group on day 7 (P<0.05). No significant difference was observed between the two groups at any other time points.(3) Immunohistochemical Evaluation of the Healing Process Three days after the wound surface was covered with ePTFE,γ-IFN and IL-2 positive particles gathered under the cuticular layer, especially in the recipient bed. Starting on postoperative day 7, the number of positive signals increased gradually reaching the peak. On day14 the expression level started to decrease.Compared with the allograft group,γ-IFN and IL-2 positive particles increased remarkably on day 3. With time goes by, there are more and more positive particles. On day 14, almost the whole skin has been repelled.Conclusions:(1) The number of macrophages, fibroblasts, lymphocytes in the study group are significantly lower than their counterparts in the control group. That means EPTFE elicits minimal inflammatory response and foreign body reaction.(2) Compared with the allograft group,γ-IFN and IL-2 positive particles increased remarkably. That means EPTFE will unlikely to cause adverse effects when applied to wound surface for a prolonged period of time.