ABSTRACT The goal of this project is to shed light on the etiology of keratoconus (KC) by elucidating the bio-molecular effects of environmental and genetic factors in vivo using a KC murine model with ultraviolet radiation (UV) and in vitro using a novel cornea-on-a-chip model. Keratoconus, a progressive and degenerative disorder characterized by localized thinning near or in the center of the cornea, affects an estimated 300,000 people in the United States and is one of the leading causes of corneal transplant. Though still undetermined, it is widely recognized that genetic and environmental risk factors contribute to KC pathogenesis. Previous work in our lab has uncovered a gene of interest in a multi-generation family affected by KC, PPIP5K2. Subsequent gene-trap and two knockin mouse models of Ppip5k2 demonstrated localized thinning in the center of the cornea but lacked other histopathological and morphological characteristics seen in KC patients. Here we hypothesize that incorporation of an environmental risk factor for KC, namely combined UVA and UVB radiation, in these Ppip5k2 gene-trap and knockin mice may sufficiently produce a reliable KC mouse model. This is especially important to the study of KC as there is currently no sufficient animal model that represents both the underlying pathology and morphological defects of the disorder. On the other hand, we will model the interaction of corneal epithelial and stromal cells using a novel cornea-on-a-chip in vitro model to integrate cellular, genetic, biomechanical, and environmental factors. This cornea-on-a-chip will allow us to study epithelial-stromal interactions in adjacent layers of corneal tissue, specifically when treated with inflammatory factors similar to those produced endogenously as a result of vigorous eye-rubbing and atopy. We hypothesize that KC-related genetic, inflammatory, and biomechanical factors and their interactions affect the epithelial-stromal communication, leading to the loss of stromal cells and corneal thinning. Our preliminary data indicate the promising potential of these in vivo and in vitro models in advancing our understanding of KC pathogenesis. The successful completion of this innovative application will lead to the establishment of in vitro and in vivo models closely mimicking the pathophysiological processes in KC development, eventually helping develop novel therapies for this devastating and critical vision disorder.