Co-regulation of developmental vascular anomalies by fibronectin and collagen

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Project Summary The term vascular anomaly encompasses a broad spectrum of diseases, including the extremely common vasoproliferative disorder infantile hemangioma, and more rare pathologies such as cerebral cavernous malformation. Together, these diseases are estimated to affect more than 10% of the world’s population, and most often occur in children under the age of 5. Several forms of vascular anomalies exhibit an increase in expression of the extracellular matrix protein fibronectin, despite their cause being traced to disparate genetic mutations. Normal adult vascular basement membrane is comprised mainly of laminin and collagen and lacks fibronectin. Thus, the presence of fibronectin in infantile hemangioma, cavernous angioma/cerebral cavernous malformation, Sturge-Weber associated hemangioma, and VHL-disease associated hemangioma, among others, could contribute to a heretofore unidentified pathological mechanism. Fibronectin can stimulate endothelial proliferation and neo-angiogenesis in vitro, however, the role of fibronectin in the pathogenesis of vascular malformations has not been directly determined. Of the many cellular interactions mediated by fibronectin, its interaction with collagen is one of the least understood. Fibronectin and collagen appear to act synergistically to promote angiogenesis, and our new preliminary data show that blocking this interaction inhibits angiogenic tube formation. As the interaction between fibronectin and collagen has not been studied in an endothelial context, several fundamental questions remain about the role of this interaction in normal endothelial cells and in the development of vascular anomalies. Thus, we hypothesize that the fibronectin/collagen interaction regulates neo-angiogenesis and contributes to the formation of vascular anomalies. In this proposal, we will determine the contribution of fibronectin/collagen binding to matrix deposition and stability in endothelial cell cultures, and how this interaction regulates the formation of new vessels in vitro and in vivo by examining whether a peptide inhibitor of this interaction, R1R2, reduces the presence of collagen in the matrix, increases collagen internalization, and inhibits tube formation in vitro and new vessel growth in vivo. In addition, we will determine whether fibronectin/collagen binding contributes to the abnormal vessel formation in mouse models of cerebral cavernous malformation and hemangioma. Together, these data will determine the role of the fibronectin/collagen interaction in normal angiogenesis and the development of vascular anomalies, provide proof-of-principle that a common mechanism underlies the pathogenesis of vascular anomalies, and support further studies of R1R2 as a therapeutic agent.