Bowman's membrane is a major component of the cornea that has been little studied - with virtually no information available as to whether this unique extracellular matrix has functional and regulatory properties. If it does have such properties, it will be important to elucidate these, since, (1) this layer is lost/ablated during certain types of injuries and laser corrective procedures, and (2) none of the synthetic corneal prosthesis that have been devised includes a Bowman's membrane equivalent which may be necessary to provide a long-term, functional prosthesis. In addition, most of the animal models in current use for corneal wounding studies (e.g., rabbits and rodents), may not be directly applicable to the human since the corneas of these species lack a Bowman's membrane. However, our previous studies on the chicken eye have shown that the cornea of this species has all of the major features of human cornea, including a Bowman's Membrane that is indistinguishable from that of the human. Thus we will use this species as an animal model for the human cornea. This application is based in part on our observation that a unique aspect of Bowman's membrane - which differentiates it from all other matrices we have examined - is the presence of type V Collagen in a form that exposes on the molecule potentially functional domains, such as ones that bind regulatory factors. We propose to examine whether Bowman's membrane, and its type V Collagen, may have unique properties that regulate certain aspects of corneal epithelial behavior (e.g., migration, proliferation and differentiation). To test this, the behavior of the corneal epithelium will be examined in vivo and in vitro on corneal surfaces in which excimer laser ablation has been used to selectively expose, as the matrix substratum for the epithelium, Bowman's Membrane or the epithelial basal lamina or the stroma proper.Other experiments will examine whether recombinant type V Collagen can substitute for Bowman's membrane, and, if so, whether the regulatory properties of the molecule involve its binding of specific growth factors. If Bowman's membrane and its type V Collagen do serve as a source of such factors, to reach the epithelium these must be able to pass across the corneal epithelial basal lamina, and this will also be tested. These experiments should provide clinically relevant information on the short and long term effects of this matrix on corneal wound healing and subsequent corneal maintenance following excimer laser corrective procedures, and wounding in general. They should also provide information as to whether, in a fabricated synthetic cornea, it will be advantageous - or even necessary - to include a subepithelial layer of type V Collagen to provide a Bowman's membrane equivalent.
