Fibrosis reduces the quality of life for millions and negatively impacts vision in the cornea by causing haze and scarring, in the lens by causing Posterior Capsular Opacification (PCO), and in the retina by causing fibrovascular membrane contraction leading to macular holes. During the previous funding period we showed that in the mouse and chick lens, as in the cornea, there is an innate population of mesodermal cells that are CD45+ and that these cells go to the leading edge of an injured lens epithelium to regulate migration of the epithelium to repair the wound in a mock cataract surgery model. This same population can be induced to express ?-SMA, acquiring a myofibroblast phenotype associated with causing PCO. The fact that these innate repair cells express CD45 suggests they are leukocytes. Because the lens was believed to consist exclusively of ectodermally derived cells, these data change our fundamental understanding of the lens and how it is formed and maintained. In this proposal, we propose to: 1) Establish that the lens contains a diverse resident population of mesodermally derived leukocytes with tissue specific properties, by identifying the leukocyte type(s) present in the lens and cornea that modulate the repair process following injury to ocular epithelia, examining how leukocytes impact the rate of epithelial sheet movement and the reestablishment of a normal epithelium following wounding of the lens and cornea, assessing the ability of injury-induced cytokines to mediate lens leukocyte activation, determining whether immune surveillance is induced in the lens following injury to other ocular tissues, and investigating the hypothesis that lens leukocyte activation in response to injury can recruit leukocytes from the outside the lens. 2) Establish that integrin-matrix signaling converts resident immune cells in the lens and cornea to myofibroblasts by investigating the role played by tenascin-C in the provisional matrix needed for FN(EDA+) expression and assembly, examining the mechanism by which FN(EDA+) signals myofibroblast differentiation, determining the mechanism by which ?9 integrin mediates myofibroblast differentiation, investigating whether collagen assembly and stiffening modulate persistence of the myofibroblast phenotype in the lens. Leukocyte integrins are known to mediate immune cell migration after injury and leukocytes can convert into ?-SMA expressing myofibroblasts. The proposed studies use well-characterized lens and cornea models to study myofibroblast formation and persistence from innate leukocytes with the goal of developing new treatments that induce myofibroblasts to revert into non-pathologic cells and or to undergo apoptosis to reduce the burden of scarring diseases in vision.
The knowledge gained from our studies of a novel population of mesenchymal progenitor cells, innate to epithelial tissues, that upon wounding are activated to form the repair cells that modulate the wound response, is expected to reveal novel targets for enhancing wound repair and tissue regeneration. Furthermore, our findings that the progeny of these cells also are a principal source of myofibroblasts, a cell type associated with fibrotic diseases such as PCO and corneal scarring, suggest that the results of our studies also will have a major impact on understanding mechanisms of fibrotic disease to prevent this cell- type from persisting and causing blinding diseases.
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