A complication of diabetes is the inability of wounds to heal in diabetic patients. Diabetic wounds are refractory to healing due to the involvement of activated matrix metalloproteinases (MMPs), which remodel the tissue resulting in apoptosis. There are no readily available methods that identify active unregulated MMPs. With the use of a novel inhibitor-tethered resin that binds exclusively to the active forms of MMPs, coupled with proteomics, we quantified MMP-8 and MMP-9 in a mouse model of diabetic wounds. Topical treatment with a selective MMP-9 inhibitor led to acceleration of wound healing, re-epithelialization, and significantly attenuated apoptosis. In contrast, selective pharmacological inhibition of MMP-8 delayed wound healing, decreased re-epithelialization, and exhibited high apoptosis. The MMP-9 activity makes the wounds refractory to healing, whereas that of MMP-8 is beneficial. The treatment of diabetic wounds with a selective MMP-9 inhibitor holds great promise in providing heretofore-unavailable opportunities for intervention of this disease.
Diabetic foot ulcers (DFUs) are a significant health problem. A single existing FDA-approved drug for this ailment, becaplermin, is not standard-of-care. We previously demonstrated that upregulation of active matrix metalloproteinase (MMP)-9 is the reason that the diabetic wound in mice is recalcitrant to healing and that MMP-8 participates in wound repair. In the present study, we validate the target MMP-9 by identifying and quantifying active MMP-8 and MMP-9 in human diabetic wounds using an affinity resin that binds exclusively to the active forms of MMPs coupled with proteomics. Furthermore, we synthesize and evaluate enantiomerically pure ( R)- and ( S)-ND-336, as inhibitors of the detrimental MMP-9, and show that the ( R)-enantiomer has superior efficacy in wound healing over becaplermin. Our results reveal that the mechanisms of pathology and repair are similar in diabetic mice and diabetic humans and that ( R)-ND-336 holds promise for the treatment of DFUs as a first-in-class therapeutic.
Diabetic foot ulcers are a complication of diabetes for which treatment options are limited and not effective, resulting in 73,000 lower-limb amputations in the United States every year. Wound healing is a complex process with a highly orchestrated cascade of events, in which the extracellular matrix (ECM) interacts with growth factors and cells. Matrix metalloproteinases (MMPs) are involved in all wound healing events, in particular MMP-8 and MMP-9, whose physiological functions are to degrade damaged collagen type I and to facilitate keratinocyte migration and re-epithelialization, respectively. Under the hypoxic and inflammatory environment of diabetic wounds, increased reactive oxygen species (ROS) and upregulation of MMP-9 results in wounds that are recalcitrant to healing. We have determined that MMP-8 plays a role in the body's response to wound healing and that MMP-9 is the pathological consequence of the disease with detrimental effects. Thus, selective inhibition of MMP-9, while leaving MMP-8 activity unaffected, is desirable. ND-336 has such inhibitory profile and is a promising strategy for treatment of diabetic foot ulcers.