Sonic Hedgehog Signaling Promotes Survival and Lineage Specific Differentiation of Transplanted Neural Precursor Cells and Improves Motor Recovery After Thoracic Spinal Cord Injury in Rats

Transplanted neural precursor cells (NPCs) can support repair after spinal cord injury (SCI) but often face poor survival and limited differentiation within the hostile post-injury microenvironment. We tested whether subacute activation of Sonic hedgehog (Shh) signaling improves NPC engraftment and functional recovery over the duration of 6 weeks. Female Wistar rats underwent T9/T10 clip-contusion SCI and were assigned to vehicle, Shh-only, NPC-only, Shh + NPC, or sham groups (n = 8 per SCI arm, n = 5 sham, total n = 37). GFP + NPCs (4 × 105) were grafted at 7 days post injury. Recombinant Shh or vehicle was delivered intrathecally via osmotic pumps for 7 days thereafter. Outcome measures included pathway activation (GLI1, SMO), NPC differentiation (NeuN, Olig2, Nestin, GFAP), astrogliosis (GFAP), CSPG deposition, immune cell infiltration (CD3, Iba1), apoptosis (cleaved Caspase-3), and locomotion (BBB, Gridwalk, CatWalk) over 6 weeks. Shh delivery increased GLI1/SMO expression and, when combined with NPCs, significantly elevated NPC-derived neurons and oligodendrocytes while preserving undifferentiated NPCs. Combined therapy reduced astrogliosis, CSPG deposition, T-cell and macrophage/microglial densities, cyst size and apoptotic cells compared with controls. These histological benefits were accompanied by improved locomotor scores in BBB, Gridwalk and selected CatWalk parameters. Our findings highlight the synergistic effects of Shh pathway activation and NPC transplantation in promoting neuroregeneration after SCI. The data support Shh as an adjunct to NPC transplantation for SCI repair.