Human corneal fibrosis: An in vitro model

Purpose. Corneal injury may ultimately lead to a scar by way of corneal fibrosis, which is characterized by the presence of myofibroblasts and improper deposition of extracellular matrix (ECM) components. TGF-β1 is known to stimulate overproduction and deposition of ECM components. Previously, an in vitro three-dimensional (3-D) model of a corneal stroma was developed by using primary human corneal fibroblasts (HCFs) stimulated with stable vitamin C (VitC). This model mimics corneal development. The authors postulate that with the addition of TGF-β1, a 3-D corneal scar model can be generated. Methods. HCFs were grown in four media conditions for 4 or 8 weeks: VitC only; VitC+TGF-β1 for the entire time; VitC+TGF-β1 for 1 week, then VitC only for 3 or 7 weeks; and VitC for 4 weeks, then VitC+TGF-β1 for 4 weeks. Cultures were analyzed with TEM and indirect immunofluorescence. Results. Compared with the control, addition of TGF-β1 increased construct thickness significantly, with maximum increase in constructs with TGF-β1 present for the entire time- 2.1- to 3.2-fold at 4 and 8 weeks, respectively. In all TGF-β- treated cultures, cells became long and flat, numerous filamentous cells were seen, collagen levels increased, and long collagen fibrils were visible. Smooth muscle actin, cellular fibronectin, and type III collagen expression all appeared to increase. Cultures between weeks 4 and 8 showed minimal differences. Conclusions. Human corneal fibroblasts stimulated by VitC and TGF-β1 appear to generate a model that resembles processes observed in human corneal fibrosis. This model should be useful in examining matrix deposition and assembly in a wound-healing situation.