Roles of Growth Factors on Corneal Morphogenesis

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Morphogenesis of cornea, conjunctiva and eyelids during vertebrate eye development involves the migration of mesenchymal cells of neural crest origin and the differentiation of cells of the surface ectoderm. The bi-directional mesenchyme-epithelium interactions via growth factors are essential for morphogenesis during development and homeostasis in adults. TGF-betas and FGF- 7 play pivotal roles in modulating functions of mesenchymal cells of neural crest origin and differentiation of ectoderm cells during ocular morphogenesis. These functions are exemplified by severe clinical manifestations observed as follows: in Tgfb2-/- mice resembling Axenfeld-Reiger's anomaly in human; by biglycan transgenic (KeraprBgn/+) mice of keratocan promoter (Kerapr) exhibiting secondary limbal deficiency; and by FGF-7 transgenic mice of alphaA-crystalline promoter (alphaACpr) resulting in conjunctivalization of corneal surface. These observations raise intriguing questions such as: 1). When do mesenchymal cells commit to becoming endothelial cells? 2). Are eyelid stromal cells also of neural crest origin? 3). What is the role of TGF- beta and FGF-7 signaling in eye development and corneal homeostasis and wound healing? 4). What are the molecular and cellular mechanisms of phenotypes observed in KeraprBgn/+ transgenic mice? To address these questions, we will create tetracycline inducible transgenic mouse models that overexpress the dominant negative mutant of type II TGF-beta receptor, active TGF-beta1 and FGF-7 under the control of Kerapr, and FGF-7 under the control of alphaCApr. With these models we will examine the role of TGF-beta signaling on corneal morphogenesis during development and homeostasis and further characterize the KeraprBgn/+ mice to examine the hypothesis that excess biglycan perturbs TGF-beta signaling during eyelid morphogenesis. Specific Aim 1 is to elucidate roles of TGF-beta signaling on eye morphogenesis during development, homeostasis and wound healing using tet-O TbetaRIIdn/+ KeraprrtTA/+ and tet-O TGFbeta1/+ KeraprrtTA/+ mice. Specific Aim 2 will elucidate ocular surface epithelial differentiation using alphaACprrtTA/+ tet-OFGF7/+ and KeraprrtTA/+ tet-OFGF7/+ mice that overexpress FGF-7. Specific Aim 3 will Elucidate the Role of Excess Biglycan on Eyelid Formation during Development of KeraprBgn/+ mice. The proposed studies will yield useful information for a better understanding of the role of TGF-beta and FGF-7 on corneal development and homeostasis, leading to the design of better treatments for corneal diseases, e.g., epithelial debridement, incision, alkali burn.