Combined effects of aging and type 2 diabetes on wound healing in a humanized mouse model

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Abstract Aging is a powerful risk factor for the development of chronic, non-healing foot ulcers in people with type 2 diabetes (T2DM). Diabetic foot ulcers in older adults with T2DM have devastating consequences, leading to increased risks of amputation and all-cause mortality. There is a compelling, unmet need to develop therapies to treat these non-healing wounds in this population; however, an appropriate animal model for use in the development of biotherapeutics and stem cell therapies with a high degree of translatability to human disease does not exist. Therefore, the overall goal of this proposal is to develop an aged-T2DM humanized mouse model to study the mechanisms by which the combined effects of aging and T2DM dysregulate the human immune system of T2DM patients during wound healing and to test therapeutics based on these new insights. To achieve this goal, two Specific Aims are proposed. The purpose of Specific Aim 1 is to develop a humanized mouse model engrafted with CD34+ hematopoietic stem cells (HSCs) from aged-T2DM human donors to study wound healing. The hypothesis is that humanized mice engrafted with CD34+ HSCs from older adults with diabetes faithfully recapitulate the non-healing wound phenotype and skewed polarization of wound- infiltrating macrophages that has been documented in human T2DM patients. This model is based on our published and unpublished findings that T2DM and aging impair wound healing by an oxidant stress- dependent HSC autonomous mechanism. Thus, the aging-T2DM-associated impairment in wound healing will be conferred by the donor HSCs from aged-T2DM patients. The purpose of Specific Aim 2 is to determine the effect of ATLAS therapy on wound healing in humanized mice engrafted with aged-T2DM HSCs. The hypothesis is that ATLAS treatment of HSCs derived from aged T2DM human donors prior to engraftment into NSG-SGM3 mice reduces HSC oxidant stress and increases nitric oxide bioavailability that restores normal macrophage number and polarization in wounds. Our results show that in a T2DM murine model of wound healing ATLAS, a combination of L-arginine, tetrahydrobiopterin, and L-ascorbate, decreases HSC oxidative stress and increases HSC NO bioavailability that restores normal wound healing. The development of the proposed humanized mouse model bridges a major gap between murine wound healing models and human non-healing foot ulcers in older adults with T2DM; thus, the creation of a highly translatable tool to develop novel biological therapies to treat non-healing wounds in older adults with T2DM fulfills a major unmet need for these patients. As a consequence of the results of this project, we hope to greatly reduce the suffering from this devasting problem that disproportionately affects older adults worldwide.