This study is based on the premise that wound angiogenesis plays an essential role in either the formation of normal cutaneous scar or its extreme variants, hypertrophic scar and keloid. The characteristic feature of tissue hypoxia frequently reported in both hypertrophic scar and keloid could be attributed t an aberrant angiogenic process during the early granulation tissue phase of would healing. The regulation of wound angiogenesis is not well-understood; however, recent studies on animal wound models suggest a possible role of vascular endothelial growth factor (VEGF) in neovessel formation and an increased vascular permeability at the wound site. The proposed study will examine whether or not VEGF and its receptor(s) play a role int he remodeling and maintenance of dermal microvasculature in both normal dermal tissue (defined as normal skin and normal scar) and abnormal scar (hypertrophic scar and keloid). The hypothesis is that the expression of VEGF receptor as well as its biological activity is altered as a function of the tissue of origin (normal dermal tissue versus abnormal scar). The long-term objectives of this work are to determine why hypoxia exists in abnormal scar and to explore possibility of regulating the angiogenic process in both early and late stage of wound healing, thereby preventing its formation.
The specific aims are; 1) To confirm that vascular endothelial growth factor receptor is expressed on human microvascular endothelium of normal dermal tissues and abnormal scar tissues and to establish whether such expression is altered as a function of the tissue of origin. 2) To study the binding kinetics of vascular endothelial growth factor (VEGF) and its receptor and to establish whether differences in receptor binding affinity, receptor number and receptor type exist between these microvascular endothelial cells (MEC). 3) To determine whether VEGF induce protein tyrosine phosphorylation in MECs and to establish whether the tyrosine kinase activity differs as a function of the tissue of origin. 4) To examine the in vitro angiogenic effect exerted by VEGF on human MECs in terms of growth proliferation and blood vessel sprouting. The experimental plan will assess two variables; VEGF receptor(s) expression and biological function using both cultured human dermal MECs and frozen tissues. Methodologically, VEGF receptor(s) expression and biological function will be assessed by immunohistochemistry/immunocytochemistry, radioimmunobinding assay, in situ hybridization, polymerase chain reaction, Northern hybridization, immunoprecipitation, affinity crosslinking an phosphorylation assay.
