Fibronectin Matrix Mimetics Promote Full-Thickness Wound Repair in Diabetic Mice

Abstract

During tissue repair, fibronectin is converted from a soluble, inactive form into biologically active extracellular matrix (ECM) fibrils through a cell-dependent process. ECM fibronectin promotes numerous cell processes that are critical to tissue repair and regulates the assembly of other proteins into the matrix. Nonhealing wounds show reduced levels of ECM fibronectin. To functionally mimic ECM fibronectin, a series of fibronectin matrix mimetics was developed by directly coupling the matricryptic, heparin-binding fragment of the first type III repeat of fibronectin (FNIII1H) to various sequences from the integrin-binding domain (FNIII8–10). The recombinant proteins were produced as glutathione-S-transferase (GST)-tagged fusion proteins for ease of production and purification. Full-thickness, excisional wounds were produced in genetically diabetic mice, and fibronectin matrix mimetics were applied directly to the wounds. A significant enhancement of wound closure was observed by day 9 in response to GST/III1H,8–10 versus GST-treated controls (73.9%±4.1% vs. 58.1%±4.7% closure, respectively). Two weeks after injury, fibronectin matrix mimetic-treated wounds had developed a multi-layered epithelium that completely covered the wound space. Furthermore, significant increases in granulation tissue thickness were observed in response to treatment with GST/III1H,8–10 (4.05±0.93-fold), GST/III1H,8,10 (2.91±0.49-fold), or GST/III1H,8^RGD (3.55±0.59-fold) compared with GST controls, and was accompanied by dense collagen deposition, the presence of myofibroblasts, and functional vasculature. Thus, the recombinant fibronectin matrix analogs normalized the impairment in repair observed in this chronic wound model and may provide a new approach to accelerate the healing of diabetic wounds.