Abstract
BACKGROUND: The therapeutic potential of human umbilical cord mesenchymal stem cells (HUCMSCs) for diabetic peripheral neuropathy (DPN) and the underlying mechanisms involving transient receptor potential vanilloid 1 (TRPV1) signaling remain incompletely defined. OBJECTIVE: This study aimed to elucidate the role of the TRPV1-[Ca(2+)]i-AMPK signaling axis in mediating the beneficial effects of HUCMSCs on neuropathic pain and Schwann cell (SC) dysfunction in DPN. METHODS: A murine model of DPN was established. Mechanical allodynia and thermal hyperalgesia were assessed using Von Frey filaments and the KW-LB hot plate test, respectively. Primary mouse SCs were isolated and cultured under high glucose (HG) conditions. Intracellular calcium ([Ca(2+)]i) levels were quantified by flow cytometry. Protein expression (TRPV1, p-TRPV1, AMPK, p-AMPK, cleaved-caspase-3, Bax, Bcl-2, Drp1, PGC-1α, TFAM, Mfn2) was analyzed via Western blotting. Apoptosis and cell proliferation were evaluated using TUNEL staining and the CCK-8 assay, respectively. Specific inhibitors (AMG9810 for TRPV1 and compound C for AMPK) were employed to probe pathway involvement. RESULTS: HUCMSC administration significantly alleviated mechanical allodynia and thermal hyperalgesia in diabetic mice. In vitro, HUCMSC coculture counteracted HG-induced effects in SCs by: (1) increasing the p-TRPV1/TRPV1 ratio and [Ca(2+)]i influx (effects blocked by AMG9810); (2) reducing apoptosis (decreased cleaved-caspase-3/Bax, increased Bcl-2); (3) enhancing the p-AMPK/AMPK ratio (attenuated by both AMG9810 and compound C); and (4) promoting mitochondrial homeostasis, increasing PGC-1α, TFAM, and Mfn2 expression, mitochondrial membrane potential and ATP levels, and decreasing Drp1 expression. These mitochondrial improvements were reversed by compound C. CONCLUSION: HUCMSCs ameliorate diabetic neuropathic pain primarily through activation of the TRPV1-[Ca(2+)]i-AMPK signaling pathway in SCs, which may provide a new molecular target for enhancing the clinical therapeutic effect of HUCMSCs on DPN.