Injured adult motor and sensory axons regenerate into appropriate organotypic domains of neural progenitor grafts

Jennifer N Dulin,Ken Kadoya,Mark H Tuszynski,Andrew F Adler,Paul Lu,Daniel Gibbs,James W Fawcett,Hans Strobl,Hiromi Kumamaru,Gunnar H D Poplawski,Corinne Lee-Kubli

doi:10.1038/s41467-017-02613-x

Abstract

Neural progenitor cell (NPC) transplantation has high therapeutic potential in neurological disorders. Functional restoration may depend on the formation of reciprocal connections between host and graft. While it has been reported that axons extending out of neural grafts in the brain form contacts onto phenotypically appropriate host target regions, it is not known whether adult, injured host axons regenerating into NPC grafts also form appropriate connections. We report that spinal cord NPCs grafted into the injured adult rat spinal cord self-assemble organotypic, dorsal horn-like domains. These clusters are extensively innervated by regenerating adult host sensory axons and are avoided by corticospinal axons. Moreover, host axon regeneration into grafts increases significantly after enrichment with appropriate neuronal targets. Together, these findings demonstrate that injured adult axons retain the ability to recognize appropriate targets and avoid inappropriate targets within neural progenitor grafts, suggesting that restoration of complex circuitry after SCI may be achievable.

Highlights

Neural progenitor cell (NPC) transplantation has high therapeutic potential in neurological disorders
As well as previous transplantation studies utilizing dissociated rodent spinal cord NPCs, donor cells are obtained from E14 rat embryos[7,15,25,26,27,28,29,30], at which stage the spinal cord contains a mix of neural stem cells (NSCs), progenitors and post-mitotic cells[28,31]
To characterize the types of neural progenitors that are present in the cell suspension used for grafting, we dissociated E14 spinal cords using previously described methods[26], cultured cells for 24 h, and characterized expression of NPC-specific transcription factors (Fig. 1a–e)

Summary

Introduction

Neural progenitor cell (NPC) transplantation has high therapeutic potential in neurological disorders. The successful integration of graft-derived neurons into injured host circuitry appears to depend on the regional identities of grafted neurons; for example, graft-derived visual cortical neurons transplanted into the lesioned visual cortex integrate into injured host circuitry, whereas neurons with motor cortical identity fail to integrate into visual cortex[5] These findings suggest that specific, functionally restricted connections from graft to host are spontaneously formed. We show that dissociated NPC grafts self-assemble neuronal clusters with laminar organization of distinct dorsal spinal cord interneuronal subtypes, recapitulating the laminar cytoarchitecture of the intact spinal cord dorsal horn These organotypic dorsal horn-like structures are preferentially innervated by regenerating host sensory afferent axons, but are entirely avoided by regenerating host corticospinal axons. Injured, regenerating adult axons retain their developmental ability to distinguish between functionally appropriate and inappropriate targets within NPC grafts

Methods

Results

Conclusion