Spontaneous regeneration of intrinsic spinal cord axons in a novel spinal cord slice culture model.

A substantial problem in research concerned with axonal repair is the use of a wide variety of lesion models and the complexity associated with the respective in vivo lesion paradigms. Organotypic slice cultures are a potential in vitro alternative because the cytoarchitectonic tissue organization is well preserved and the slices can be maintained in culture for several weeks. Until now no spinal cord slice culture model for the study of axonal growth has been available. Here we present a spinal cord slice culture model that is well suited for the study of axonal growth. The spinal cord slices were cut not in the transverse but in the sagittal longitudinal plane such that several spinal cord segments were included in the slice culture. In these cultures the typical ventro-dorsal polarity of the spinal cord was maintained and intrinsic spinal cord axons formed a strong fibre tract extending along the longitudinal axis of the slice. The axons became myelinated during the culture period and synaptic contacts were present in these cultures. After mechanical lesions the intrinsic spinal cord axons had a substantial potential for axonal growth and regeneration. The number of regenerating axons crossing the lesion site decreased with increasing maturation of the culture, but even in mature cultures a small number of crossing fibres were present. This slice culture model could provide an important tool for several aspects of spinal cord research in the fields of axonal growth and regeneration, synapse formation, formation of intrinsic spinal cord circuits and myelination.