Autologous bone marrow mononuclear cell transplantation therapy improved symptoms in patients with refractory diabetic peripheral neuropathy via the mechanisms of paracrine and immunomodulation

Abstract Background: We recently reported that transplantation of autologous bone marrow mononuclear cells (BM-MNCs) may be an effective and promising therapy to treat refractory diabetic peripheral neuropathy (DPN) in patients with type 2 diabetes mellitus (T2DM). This study was designed to investigate the potential mechanisms of BM-MNCs therapy.Methods: This clinical study recruited 60 patients with DPN, 30 T2DM patients without complications, 30 healthy control participants. All clinical parameters, the levels of inflammatory markers and growth factors in three groups were compared. All patients with DPN received one intramuscular injection of BM-MNCs and clinical follow-ups after the therapy for 2 days, 1, 4, 12, 24, and 48 weeks. Then they were divided into the responder and non-responder groups based on the improvement of nerve conduction velocity. Binary logistic regression was performed to evaluate the corresponding prognostic factors for BM-MNCs treatment.Results: Patients in DPN group had higher level of tumor necrosis factor-α (TNF-α) and lower level of vascular endothelial growth factor (VEGF) than those in control group. DPN group had the highest level of soluble intercellular adhesion molecule-1 (sICAM-1) among three groups. The level of nerve growth factor (NGF) in DPN group was slightly lower than that in DM group. Neuropathic symptoms were significantly improved after BM-MNCs injection. Thirty five of 54 patients with DPN (64.8%) reached the primary endpoint, and were regarded as the responders. Compared to non-responders, responders were younger, had a longer history of diabetes, and had higher numbers of mobilized CD34+ cells and BM-MNCs. The levels of TNF-α and sICAM-1 decreased just after BM-MNCs injection in both groups and slowly reverted to baseline levels. The durations of downtrend of TNF-α and sICAM-1 in responder group lasted longer than that in non-responder group. Serum level of VEGF in responder group increased immediately after BM-MNC therapy, and reached the highest point after the injection for 12 weeks. On the other hand, VEGF levels in the non-responder group only increased slightly. The number of applied CD34+ cells (OR=1.567, 95% CI 1.106-2.222, p=0.012) and duration of diabetes (OR=0.760, 95% CI 0.597-0.967, p=0.025) were the independent predictors of responding to BM-MNCs therapy. No adverse event associated with the treatment was observed during follow-up observations.Conclusions: BM-MNCs transplantation is an effective and promising therapeutic strategy to treat refractory DPN. The immune regulation and paracrine function of BM-MNCs may contribute to the improvement of DPN.