Treatment of diabetic peripheral neuropathy with engineered mesenchymal stromal cell-derived exosomes enriched with microRNA-146a provide amplified therapeutic efficacy.

Diabetic peripheral neuropathy (DPN) is one of the most prevalent chronic complications of diabetes mellitus with no effective treatment. We recently demonstrated that mesenchymal stromal cell (MSC)-derived exosomes (exo-naïve) alleviate neurovascular dysfunction and improve functional recovery. MicroRNA (miRNA), one of the exosomal cargos, downregulates inflammation-related genes, resulting in suppression of pro-inflammatory gene activation. In the present study, we developed engineered MSC-exosomes loaded with miR-146a (exo-146a) and compared the therapeutic effects of exo-146a with exo-naïve in diabetic (db/db) mice with DPN. Exo-146a possesses a high loading capacity, robust ability to accumulate in peripheral nerve tissues upon systemic administration, and evokes substantially enhanced therapeutic efficacy on neurological recovery compared with exo-naïve. Treatment of DPN in diabetic mice with exo-146a for two weeks significantly increased and decreased nerve conduction velocity, and thermal and mechanical stimuli threshold, respectively, whereas it took four weeks of exo-naive treatment to achieve these improvements. Compared with exo-naïve, exo-146a significantly suppressed the peripheral blood inflammatory monocytes and the activation of endothelial cells via inhibiting Toll-like receptor (TLR)-4/NF-κB signaling pathway. These data provide a proof-of-concept about both the feasibility and efficacy of the exosome-based gene therapy for DPN. The translation of this approach to the clinic has the potential to improve the prospects for people who suffer from DPN.