Stem cell-derived secretome and dental pulp stem cells enhance sciatic nerve regeneration in a rat sciatic neurotmesis model using chitosan nerve conduits

Introduction: Peripheral nerve injuries remain a major clinical challenge, often leading to long-term motor and sensory deficits. Stem cell-based and cell-free approaches, combined with biomaterial scaffolds, have emerged as promising strategies for nerve repair. Methods: This study evaluated the regenerative potential of human dental pulp stem cells (hDPSCs), their conditioned medium (hDPSCs-CM), and the combination of hDPSCs with olfactory mucosa mesenchymal stem cell conditioned medium (OM-MSCs-CM) in a rat model of sciatic nerve neurotmesis repaired with a chitosan-based nerve guide conduit (Reaxon®). Twenty-seven rats were allocated into experimental groups, including an uninjured control (contralateral limb), an end-to-end neurorrhaphy surgical control group, and treatment groups repaired with Reaxon® alone or combined with hDPSCs, hDPSCs-CM, or hDPSCs with OM-MSCs-CM suspended in Matrigel®. Following nerve transection, a 9-10 mm sciatic nerve gap was created. Functional recovery was monitored over 20 weeks through motor, nociceptive, behavioral, gait, stereological, histomorphometric, and electrophysiological evaluations. Results: All treatments promoted progressive motor recovery and partial restoration of nociceptive function compared to the untreated condition, although the magnitude of improvement differed among groups. The hDPSCs-CM-treated group (CMDP) showed the most favorable overall outcomes, including the lowest muscle mass loss, higher compound muscle action potential amplitudes, and functional indices approaching control values, indicating enhanced reinnervation and neuromuscular preservation. Histomorphometric and stereological analyses confirmed active regeneration across all groups, characterized by microfasciculation and thinner myelin sheaths typical of regenerating fibers. Discussion: Despite incomplete recovery, the combination of biological therapies with chitosan conduits provided an effective environment for axonal regrowth and functional improvement. These findings highlight the relevance of CMDP as a potent biological adjunct in peripheral nerve repair and support the development of cell-free, clinically translatable strategies for neuroregeneration.