Dissecting the Human Diabetic Bone Marrow Niche

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PROJECT ABSTRACT Approximately one-third of all diabetic patients develop a diabetic foot ulcer (DFU), of which 50% will result in a lower extremity amputation due to infection. The medical cost, utilization of emergency care, medical disability, and increased mortality due to DFUs is disproportionately higher in disadvantaged communities. Current treatment for DFUs is only 50% effective at preventing amputation because we lack fundamental knowledge regarding the mechanisms driving the failure of DFUs to heal. Type 2 diabetes (T2D) is associated with impaired innate immunity function during wound healing. The innate immune system is primarily derived from bone marrow hematopoietic stem cells (HSCs). To study the effect of T2D on the development of human innate immunity, I have developed a novel method to harvest and expand human HSCs and mesenchymal progenitor cells (MSCs) directly from bone marrow tissue explants collected from T2D and non-T2D donors that underwent lower extremity amputation. The tissue explant culture recapitulates the bone marrow niche through the co-culture and expansion of human MSCs and HSCs. My preliminary data demonstrates that an adipocyte-rich bone marrow microenvironment comprises a specialized niche for a previously unrecognized HSC population and suggests that bone marrow adipocytes may influence the functional properties of the human innate immune system development through the leptin signaling pathway. The proposed work will define the effect of T2D on bone marrow-derived innate immunity development (Aim 1 and 2). These studies will be complemented by investigating the role of leptin, an inflammatory cytokine produced by adipocytes, in the dysregulation of normal immune cell development (Aim 3). This work will be performed under the continual mentorship of Dr. Silvia Corvera, an expert in adipose tissue signaling and metabolic disease. I will further build upon relationships with my co-mentors, Dr. Louis Messina, Dr. Michael Brehm, Dr. Jennifer Wang, and Dr. Katherine Fitzgerald, who are renowned for their knowledge and expertise in HSCs, humanized immune mouse models, innate immunity in diabetes, and immunology respectively. This work will be conducted at University of Massachusetts Chan School of Medicine. The results of the proposed work will provide fundamental understanding of the human diabetic innate immune system and have the potential to translate these findings into development of in vivo pre-clinical models for DFUs and novel immunotherapies (or other targeted treatments) to treat non-healing DFUs. If funded, this award will allow me to complete a rigorous training plan to expand my research across disciplines, learn new techniques, and acquire knowledge and skills to establish an independent laboratory focused on targeting the diabetic immune system to enhance wound healing, thereby ultimately preventing lower extremity amputations.