Dorsal root ganglion axons facilitate and guide cortical neural outgrowth: In vitro modeling of spinal cord injury axonal regeneration

BACKGROUND: Spinal cord injury (SCI) patients represent a heterogeneous group, with injuries ranging from partial compression to complete transection. Patients with complete injuries are unlikely to exhibit recovery and suffer from paralysis as well as the loss of bowel and bladder function. One treatment option is the formation of a bridge through a lesion site, whereby transplanted cells or biocompatible scaffolds guide the regenerating axons across the site of injury. Moreover, the viability of transplanted dorsal root ganglia (DRGs) into rat spinal cord has been previously demonstrated. OBJECTIVE: We aim to demonstrate the feasibility of using DRG axons as a bridging tool to help guide the axonal growth of cortical neurons. METHODS: Cortical neurons were isolated from embryonic rats and two aggregated populations were cultured at increasing distances in isolation and in a co-culture with DRG explants. Growth rates of the sprouting axons and connections between the two populations were observed over a period of twelve days. RESULTS: DRG explants demonstrated the ability to grow robust axonal connections that can connect two explants separated by up to 10 mm, however, CNAs could not achieve connections in distances greater than 2 mm. The co-culture of CNAs with DRG explants facilitated axonal growth between two populations of CNAs at distances they cannot otherwise traverse. CONCLUSIONS: Our findings support the use of DRG axons to facilitate the growth of cortical neurons in a process of axon-facilitated axon regeneration. We believe these results could have implications for the treatment of SCI.