The care for human skin wounds, including stasis and pressure ulcers, diabetic ulcers and burn wounds, costs the United States ~$11 billion/year. For example, the number of lower extremity amputations is approaching 100,000 in the US due to non-healing diabetic ulcers, in which a single surgical procedure and hospitalization alone can cost $65,000. The currently available treatments show moderate or little efficacy and yet are very expensive, such as RegranexTM (PDGF-BB). Treating a single diabetic foot wound costs up to $28,000 within a 24-month period. Thus, there has been a pressing need to develop new and more cost-effective wound healing agents. Until recently, the heat shock protein-90alpha (Hsp90a) has been known as an ATP-dependent intracellular chaperone protein with more than 100 client targets inside the cell. However, studies from the past five years in our laboratory have unveiled a surprising need for skin cells to secrete Hsp90 a under pathological or stressful conditions like those found in the wound milieu, such as hypoxia and newly appearing cytokines. We found that both human keratinocytes and dermal fibroblasts rapidly secrete Hsp90a. The secreted Hsp90a promotes cell motility through binding to the LDL-Receptor Related Protein-1 (LRP1) receptor. More intriguingly, the pro-motility activity resides between the middle domain and the linker region of Hsp90 a, independent of its N-terminal ATPase activity. Unlike conventional growth factors, the Hsp90 a -induced cell migration cannot be inhibited by TGF2, the abundant inhibitor of cell migration and proliferation present in the wound. These new findings (which have generated publications such as Bandyopahdhay et al. JCB, 2006, Li et al. EMBO, 2007, Cheng et al. MCB, 2008 and Woodley et al. JCS, 2009 and a US patent, US 2010/0035815A1, application for the topical use of recombinant Hsp90 a for skin wound healing) provide an explanation for the first time of which factor really drives dermal cells (dermal fibroblasts and endothelial cells) to migrate into the TGF2-rich wound bed, because these cells must move into the wound to deposit new connective tissue materials and build new blood vessels (remodeling). Pre- clinically, topical application of recombinant Hsp90 a significantly accelerated the wound-healing rate by ~45% in mice. In parallel, FDA-approved RegranexTM (used to treat diabetic ulcers) showed much less (~17%) effect. These new findings led to our hypothesis that secreted Hsp90a, but not conventional growth factors, is the driving force of both epidermal and dermal cell migration against TGF2 inhibition to heal wounds. In this proposed study, we will 1) first narrow down the minimum peptide/amino acid requirements in human Hsp90a for binding to the LRP-1 receptor and promoting skin cell motility as the full-length Hsp90 a in vitro and 2) establish the candidate peptide using a pig wound healing model for future clinical studies. Our goal is to develop a recombinant Hsp90a peptide into a novel and more effective wound-healing agent.
Skin ulcers and non-healing wounds are a major healthcare problem due to the lack of effective therapy. Recently, we unexpectedly found that hypoxia induces human keratinocytes (HKs) to secrete an intracellular chaparone protein called heat shock protein alpha (Hsp90 a). The secreted Hsp90 a stimulates, via an autocrine mechanism, HK and the nearby dermal cell, through a paracrine mechanism, migration by binding to the LDL Receptor-Related Protein-1 (LRP1) receptor, even in the presence of TGF2. This proposal will test the hypothesis that the mechanism of hypoxia> Hsp90 a secretion>LRP1 stimulation>cell motility is an essential driving force for wound healing. We will develop topical Hsp90a peptide-based therapy and Hsp90a -secreting cell-based therapy for healing skin wounds.
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