Nanomedicine-Based Targeting of Inflammatory Macrophages in Diabetic Wound Repair

ABSTRACT The inability of wounds to heal in diabetic patients is the leading cause of lower extremity amputation in the United States. Chronic, localized inflammation is believed to be a causative factor in the slow healing of diabetic wounds, and macrophage cells are implicated as primary mediators of this inflammation. In non-diabetic patients, macrophages are initially in a pro-inflammatory state in wounds and shift over time to an anti-inflammatory phenotype that promotes tissue repair. In diabetic patients, the inflammatory macrophage phenotype persists, resulting in impairment of angiogenesis, granulation tissue formation, and wound contraction required for healing. Systemically administered pharmacological agents that are anti-inflammatory or immunomodulatory do not improve healing in the clinic or in preclinical animal models and, in fact, further impair healing, likely due to off- target effects in other immune or structural cells that facilitate tissue repair. This proposal focuses on the development of drug carriers based on targeted nanomaterials to reroute the delivery of pharmacological agents selectively to inflammatory macrophages in wounds after local administration to eliminate off-target effects. We are particularly focused on inhibiting overactive pathways that generate inflammatory prostaglandins. In our preliminary data, we show that polysaccharide-based nanocarriers can deliver cyclooxygenase 2 inhibitors to wound macrophages to potently diminish inflammatory cytokine expression and expedite wound healing in diabetic mouse models. Aim 1 of this proposal is to optimize formulations that maximize the efficiency of targeted delivery to inflammatory macrophages in wounds using fluorescent and radioisotopically labeled nanocarriers, evaluated in vivo by nuclear imaging and ex vivo by flow cytometry, gamma well counting, and fluorescence microscopy. Aim 2 is to optimize the efficacy and drug release rate of a therapeutic formulation that targets different regulatory pathways of prostaglandin synthesis toward diabetic wound healing. Aim 3 is to evaluate efficacy and off-target effects in multiple murine acute and chronic wound healing models of type 2 diabetes, as well as monocyte-derived macrophages from diabetic patients. Fundamental outcomes of this work will be an understanding of nanomaterial transport in wounds and receptor-mediated mechanisms to target macrophage subpopulations, as well as an understanding of the role of prostaglandin-driven inflammatory processes in macrophages within diabetic wounds. The nanocarrier delivery agents are based on materials already in broad clinical use, which may expedite clinical testing of the resulting therapeutic agents if preclinical results are promising. This work will be undertaken by an interdisciplinary team comprising bioengineers (Andrew Smith Lab) who focus on nanomaterial-based drug delivery and imaging agents, experts in molecular and cellular immunology and mechanisms of diabetic wound healing (Katherine Gallagher Lab), and experts in nuclear imaging and radiopharmacology (Wawrzyniec Dobrucki Lab).