Interactive Effects of IL-1β and TGF-β on Urokinase-Type Plasminogen Activator and α-Smooth Muscle Actin Expression by Corneal Fibroblasts.

PURPOSE

Corneal fibroblasts appear to differentiate into cells with opposing functions of collagen degradation and collagen synthesis in response to various stimuli during corneal wound healing process. Interleukin-1β (IL-1β) is a proinflammatory cytokine and promotes collagen degradation by corneal fibroblasts by upregulating their production of urokinase-type plasminogen activator (uPA). Transforming growth factor-β (TGF-β) induces the differentiation of corneal fibroblasts into myofibroblasts that express α-smooth muscle actin (α-SMA) and increase collagen synthesis, resulting in tissue contraction and remodeling. To investigate how these two factors might cooperatively regulate collagen metabolism during stromal wound healing, we investigated the potential interaction between IL-1β and TGF-β in the regulation of uPA and α-SMA expression by corneal fibroblasts.

METHODS

Human corneal fibroblasts were cultured in a three-dimensional gel of type I collagen. The uPA was detected by fibrin zymography and immunofluorescence staining, whereas α-SMA was detected by immunoblot analysis and immunofluorescence staining. Collagen gel contraction was assessed by measurement of gel diameter.

RESULTS

TGF-β not only downregulated uPA abundance in corneal fibroblasts under the basal condition, but also attenuated the upregulation of uPA expression by IL-1β. Conversely, IL-1β inhibited both the upregulation of α-SMA expression in these cells and the cell-mediated collagen gel contraction induced by TGF-β.

CONCLUSIONS

Our results show that IL-1β and TGF-β interact to regulate the expression of uPA and α-SMA as well as collagen gel contraction mediated by corneal fibroblasts cultured in a collagen gel. They highlight the phase-dependent effects of cytokines and growth factors on collagen metabolism during corneal wound healing.