The peripheral nervous system undergoes sufficient stress when affected by diabetic conditions, chemotherapeutic drugs, and personal injury. Consequently, peripheral neuropathy arises as the most common complication, leading to debilitating symptoms that significantly alter the quality and way of life. The resulting chronic pain requires a treatment approach that does not simply mask the accompanying symptoms but provides the necessary external environment and neurotrophic factors that will effectively facilitate nerve regeneration. Under normal conditions, the peripheral nervous system self-regenerates very slowly. The rate of progression is further hindered by the development of fibrosis and scar tissue formation, which does not allow sufficient neurite outgrowth to the target site. By incorporating scaffolding supplemented with secretome derived from human mesenchymal stem cells, it is hypothesized that neurotrophic factors and cellular signaling can facilitate the optimal microenvironment for nerve reinnervation. However, conventional methods of secretory vesicle production are low yield, thus requiring improved methods to enhance paracrine secretions. This report highlights the state-of-the-art methods of neuropathy treatment as well as methods to optimize the clinical application of stem cells and derived secretory vesicles for nerve regeneration.

Peripheral neuropathy (PN) is a debilitating condition characterized by chronic pain, numbness, and motor dysfunction, with limited treatment options. Ischemic stroke can cause central neuropathy, which may also induce PN. Human mesenchymal stem cells (hMSCs) have shown promise in therapeutic applications, but limitations in cell viability, immune response, and efficacy persist. Extracellular vesicles (EVs), which facilitate cell-free intercellular communication, offer a promising alternative for nerve regeneration. Electrical stimulation (ES) has emerged as a method to enhance EV secretion, and this study investigates its potential for promoting EV production from human adipose tissue-derived mesenchymal stem cells (hASCs) and human Schwann cells (hSCs). In this study, hASCs, hSCs, and lipopolysaccharide (LPS)-induced inflamed hSCs were subjected to one hour of low-frequency direct current (DC) electrical stimulation (100 mV/mL) for 7 days. EVs were isolated using differential ultracentrifugation and characterized through nanoparticle tracking analysis (NTA). Gene expression was analyzed via qRT-PCR to evaluate markers associated with EV biogenesis as well as pro- and anti-inflammatory cytokines. Our results demonstrate that ES significantly increases EV secretion from both hASCs and hSCs, with a notable upregulation of genes involved in both the endosomal sorting complex required for transport (ESCRT)-dependent and ESCRT-independent pathways of EV biogenesis. Additionally, ES modulates inflammation-related markers, promoting anti-inflammatory gene expression and reducing pro-inflammatory gene levels. Notably, LPS-induced hSCs exhibited a phenotype shift from myelinating to non-myelinating cells, producing EVs capable of modulating the inflammatory microenvironment. However, prolonged exposure to ES led to a decrease in EV secretion and changes in EV size distribution, suggesting potential cellular adaptation or membrane stress. This study highlights the potential of ES as a scalable, cell-free strategy to enhance EV production, offering new insights into its therapeutic applications for peripheral neuropathy and nerve regeneration.