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Janice Walker, Brigid Bleaken, Mary Ann Stepp, A Menko; Increased Matrix Rigidity Drives Repair Cell Transdifferentiation into Myofibroblasts in a PCO Model. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5944.
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© ARVO (1962-2015); The Authors (2016-present)
A major cause of the lens fibrotic disease Posterior Capsule Opacification (PCO) ), a secondary complication to cataract surgery, is the induction of contractile myofibroblasts. We previously identified that a subpopulation of mesenchymal repair cells innate to the lens mediate wound repair in response to mock cataract surgery. These cells have a great potential to transdifferentiate into contractile myofibroblasts, the cell type associated with lens fibrotic disease. Typically, changes in the cells’ microenvironment, like aberrant production of collagen I, promote appearance of myofibroblasts and therefore the progression of fibrotic disease. Here, we examined the effects of matrix rigidity on repair cell transdifferentiation into myofibroblasts.
Ex vivo mock cataract surgery/PCO explants were placed onto collagen I gels of increasing rigidity (0.5, 1.5 and 2.5 mg/ml). These explants were flattened by cuts in the anterior epithelium. Repair cells migrate to the cut edge where they come in direct contact with and migrate onto the collagen substrate. Transdifferentiation to a myofibroblast phenotype was measured at day 3 in culture by immunostaining for the myofibroblast marker αSMA. Cultures were co-labeled for the mesenchymal marker vimentin and for F-actin.
No αSMA stress fiber containing myofibroblasts were detected on low rigidity collagen gels (.5mg/ml) but were present on the higher rigidity collagen gels (1.5 and 2.5mg/ml). Myofibroblast formation was the greatest on the most rigid collagen I microenvironment. Therefore, increasing collagen I rigidity induced greater transdifferentiation of repair cells into αSMA stress fiber containing myofibroblasts in a dose-dependent manner. There appeared to be greater elaboration of αSMA-positive stress fibers on the most rigid collagen gels. Interestingly, vimentin filaments, a significant cytoskeletal element of the repair cells, co-aligned with the αSMA stress fibers.
The aberrant transdifferentiation of repair cells to disease causing myofibroblast following mock catraract surgery results from a mechanotransduction signal imparted by a rigid microenvironment. These studies highlight the importance of the microenvironment and mechanical signaling as important therapeutic targets for lens fibrotic disease.
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