Injury-responsive coding genes are recognized as a major cornerstone in wound healing. As much as 97% of human DNA does not encode for protein and has been called junk. microRNAs (miRs) represent a class of non-coding (nc) genes that can not only be no longer regarded as junk but they represent a key regulatory mechanism that control the functionality of large sets of coding target genes. miRs themselves do not encode protein but the function of one-third of the coding human genome is regulated by miRs. miRs are evolutionarily conserved, approximately 22-nucleotide single-stranded RNAs that post-transcriptionally silences genes by inducing mRNA degradation or by inhibiting translation. Thus, miR biology connects mRNA to their biological function. Yet, information on the significance of miRs in wound healing is scanty. In 2008, our group reported the first work on how miRs may regulate wound angiogenesis and has since then actively published in the field of miRs and wound healing. This proposal builds on our recent published observation that wound-responsive repression of cutaneous miR-200b turns on wound angiogenesis which is de-regulated during diabetes mellitus. Endothelial cells of patients with adult onset (type-2) diabetes feature elevated miR-200b. Consistent findings were noted in diabetic mice. These data lead us to question the mechanism of how miR-200b accumulates in the setting of diabetic wounds (AIM1) and how the resultant miR-200b-dependent downstream pathways mitigate wound angiogenesis (AIMS 2&3). The following 3 aims are proposed:
AIM 1 Investigate the molecular mechanisms causing aberrant induction of endothelial miR-200b in diabetic wounds. 1.1 Loss of GATA2 induces endothelial miR-200b expression; 1.2 Diabetic wound-associated p53 activation supports endothelial miR-200b expression.
AIM 2 Determine the significance of elevated endothelial miR-200b in disruption of VEGF signaling. 2.1 Aberrant induction of endothelial miR-200b blocks VEGF expression in diabetic wounds. 2.2 Loss of diabetic wound-site endothelial VEGFR1 is caused by high miR-200b. 2.3 miR-200b silences diabetic wound-site CAGE and impairs VEGF signaling.
AIM 3 Establish the molecular mechanisms underlying dysregulated miR-200b in impairing endothelial cell turnover and impaired angiogenesis in diabetic wounds. 3.1 miR-200b-ZEB1 signaling enhances endothelial apoptosis in diabetic wound-edge. 3.2 High endothelial miR-200b in diabetic wound-edge tissue drives endothelial apoptosis via a Bcl-2 dependent mechanism. 3.3 miR-200b silences CXCL1 and IL-8 and impairs endothelial cell proliferation in diabetic wounds causing impaired angiogenesis.
In the United States, skin wounds affect 6.5 million patients placing a major burden, estimated at US $25 billion annually, on society. Poor vascular supply of the wound tissue is a major contributor to wound chronicity specifically in diabetic ulcers. The proposed project aims address a novel regulatory mechanism (microRNA) that simultaneously governs multiple pathways related to vascularization of the wound tissue. Specifically, the proposal focuses on microRNA200b as a key regulator of wound perfusion.
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