Human induced pluripotent stem cell-derived mesenchymal stromal cells regenerate diabetic ischemic muscle

Chronic limb threatening ischemia (CLTI), the most severe stage of peripheral arterial disease, affects over 500,000 patients in the United States and is associated with a 25% annual risk of amputation. Diabetic CLTI patients experience exceedingly high rates of lower extremity amputation. Many of these patients fail or are not suitable for revascularization, yet no effective non-surgical therapies exist for this population. This study examined how human induced pluripotent stem cell (hiPSC)-derived mesenchymal stromal cells (MSC) interrupt ischemic limb changes and stimulate muscle regeneration in a diabetic murine CLTI model. Mice treated with hiPSC-MSC demonstrated muscle regeneration, angiogenesis, and decreased inflammation. RT-qPCR expression of embryonic myosin heavy chain 3 (p < 0.01) and myoblast determination protein 1 (p = 0.03) mRNA was increased in ischemic muscle, at 30- and 7-days post-hiPSC-MSC injection, respectively, indicating muscle regeneration. Vascular endothelial growth factor-A mRNA expression was also increased at 7 days (p = 0.04), signifying increased angiogenic signaling. Treatment with hiPSC-MSC decreased expression of the nicotinamide adenine dinucleotide phosphate oxidase subunit p47phox at 30 days (p = 0.02), suggesting decreased oxidative stress. Finally, hiPSC-MSC-treated mice had increased mRNA expression for the anti-inflammatory markers, including regulatory T cell (Treg) marker Foxp3 (p = 0.01) at 7 days and M2-biased macrophage marker CD206 at 7 and 30 days (p = 0.04 and p = 0.02, respectively). Our hiPSC-MSC preparation promoted muscle regeneration, partially through Treg-mediated M1 to M2 macrophage polarization. The use of hiPSC-MSC to improve CLTI outcomes in diabetic patients appears promising and warrants further study.