Sonic Hedgehog Agonists Induce Repair Schwann Cells

Peripheral nerve regeneration relies on repair Schwann cells (SCs) to support axonal regrowth and functional recovery. This study aimed to identify drugs that promote this repair phenotype, which is regulated by the expression of the transcription factor c-Jun. Purmorphamine (PUR) and Smoothened agonist (SAG) are both Sonic Hedgehog (SHH) agonists that have been implicated in promoting regeneration after neurological injury in animal models. Here, we have demonstrated that SHH agonists significantly increased c-Jun expression in rat primary SCs and promoted morphological and functional changes consistent with the repair SC phenotype, including an elongated bipolar morphology and increased secretion of neurotrophic factors. Notably, PUR consistently demonstrated a greater potency in driving these effects compared with SAG at the same concentrations. We also identified 2.5 µM PUR as an effective dosage producing these measurable effects in vitro. Coculturing dorsal root ganglion (DRG) neurons with PUR-treated SCs resulted in a marked increase in neurite elongation, suggesting that cell-based or contact-dependent features of repair SCs contribute to axon growth. These findings demonstrate that SHH agonists effectively reprogram SCs into a repair phenotype, which constitutes a potential therapeutic strategy for enhancing nerve regeneration and functional recovery in peripheral nerve injury treatment.