A mouse model to study the wound healing response following filtration surgery

Background: Failure of trabeculectomy is attributed to an exaggerated wound healing response at the episcleral level. We have developed a simple technique in mice that creates corneoscleral wounds and used it to study the role of growth factors in wound healing associated with loss of fistular patency. In addition, the effect of suramin on the wound healing response has been investigated. Materials and methods: Using black C57B1/6 mice, we created a fistula from the subconjunctival space to the anterior chamber by external penetration with a 25-gauge needle through the bulbur conjunctiva. Eyes were examined by light microscopy at different times following surgery and evaluated for the presence of growth factors in the sclerosing wound by immunohistochemistry. In an additional group, suramin (1.0 mg/ml) was applied topically five times. Results: The limbal/scleral wounds closed rapidly. Granulation tissue consisting mostly of fibroblasts developed within the first 2 days, and the collagen component increased over time. By 4 weeks, the wound was completely healed. We found that within 1 day after surgery GF β2 reached high intensity. TGF β1 and PDGF A reached maximal intensity by day 2 and remained elevated for about a week. PDGF B was present at moderate intensity even before surgery. Myofibroblastic differentiation was observed from days 2 to 7. Suramin-treated wounds showed a decrease of cells and delay in fibroblast maturation. TGF β1 and TGF β2 levels persisted longer than in the controls, while PDGF A and PDGF B levels were lower than in the controls at all time points. Conclusions: The mouse corneoscleral wound model that we have developed mimics the process of wound healing and fistulizing surgery that takes place in other animal models and in human eyes in which the outcome of the surgery is poor. Our analysis of the appearance of growth factors associated with wound healing demonstrates that PDGF A as well as TGF β1 and TGF β2 appear early in the process at high levels and are potential targets for interventive strategies to ensure channel patency. Suramin has a distinct effect on the wound healing process and expression of growth factors and may be a promising substance for clinical use.