The histological evaluation was performed at 4 weeks post surgeries. The rats were anesthetized with isoflurane and transcardially perfused with 4% paraformaldehyde in PBS. Spinal cord tissue was cut into paraffin sagittal sections of 7 μm thickness. After the paraffin sections were prepared, the paraffin sections were stained with hematoxylin-eosin (Solarbio, China), as described previously [27 (link)]. Finally, the stained sections were observed under a microscope (Nikon, Japan).