Scar ablation combined with LP/OEC transplantation promotes anatomical recovery and P0-positive myelination in chronically contused spinal cord of rats

We have successfully removed an existing glial scar in chronically contused rat spinal cord using a rose Bengal-based phototoxic method. The purpose of this study is to examine if scar ablation benefits the anatomical recovery by cell/tissue transplantation, and thus provides a more permissive physical and biochemical environment for axonal growth, which may lead to functional recovery. Immediately after scar ablation, we transplanted lamina propria (LP) of the olfactory mucosa alone or in combination with cultured olfactory ensheathing cells (OEC) into the lesion cavity 6 weeks after contusion injury (NYU impactor device, 25 mm height setting) at spinal cord segment T10 of adult female Long–Evans rats. Sixteen weeks after scar ablation and transplantation, we found that the initial repaired tissue significantly expanded, companied by remarkable reduction or disappearance of the lesion cavity and integration of repaired tissue with the spared tissue, thus resulting in histological repair of damaged cord tissue at the injury epicenter. Glial scar reformation was effectively prevented after ablation due to the tissue repair. In addition, at the injury epicenter P0 (myelin glycoprotein P-zero)-positive myelination formed by Schwann cells, which are known to myelinate regenerating and demyelinated axons, were significantly increased in number compared with the control animals. However, when evaluated with BBB open-field scale a significant improvement of locomotor function was not observed in this study; the possible reasons were discussed.

Research highlights
► We ablated existing glial scar with photochemistry in chronically contused rat spinal cord.
► Then we transplanted olfactory lamina propria and olfactory ensheathing cells into lesion cavity.
► Tissue repair and robust P0-positive myelination implying axonal regeneration were found.
► However, no significant functional recovery was observed.
► It may need physical therapy to promote the functional recovery.