Synergistic Enhancement of Peripheral Nerve Regeneration via Ibudilast-Primed Three-Dimensional Spheroid Culture of Human Adipose-Derived Stem Cells.

Background: Peripheral nerve regeneration relies on Schwann cell activation and neurotrophic support. Although adipose-derived stem cells (ADSCs) show therapeutic potential through paracrine mechanisms, their clinical application is often limited by donor-dependent heterogeneity in therapeutic efficacy. Accordingly, strategies to standardize and potentiate their secretory function are essential. This study investigated a safety-optimized strategy to achieve this by combining three-dimensional (3D) spheroid culture with ibudilast, a clinically approved phosphodiesterase inhibitor. Methods: Human ADSCs were cultured in 2D or 3D conditions with varying ibudilast concentrations. Safety was confirmed via CCK-8 assays, and trophic factor secretion was quantified by RT-qPCR and ELISA. To rigorously validate functional outcomes, conditioned media were applied to a dual-model system comprising immortalized rat (RSC96) and primary human Schwann cells (HSwCs), assessing migration and the expression of regeneration-associated genes. Results: Ibudilast demonstrated no cytotoxicity. While 3D culture alone enhanced secretion compared to 2D controls, the addition of ibudilast provided a synergistic boost, resulting in a 6- to 14-fold increase in NGF, VEGF, and IGF-1 levels compared to 3D spheroids alone. Notably, conditioned media from these primed spheroids significantly accelerated HSwCs migration and induced robust upregulation of myelination-related genes (specifically PMP22 and EGR2), with trophic effects sustained for up to 72 h. Conclusions: Ibudilast-primed 3D spheroids synergistically amplify the neuroregenerative secretome of ADSCs. By utilizing a repurposed, safe small molecule to overcome functional variability and maximize potency without genetic manipulation, this strategy represents a highly translatable candidate for peripheral nerve repair.