CB1 cannabinoid receptor enrichment in the ependymal region of the adult human spinal cord.

Cannabinoids are involved in the regulation of neural stem cell biology and their receptors are expressed in the neurogenic niches of adult rodents. In the spinal cord of rats and mice, neural stem cells can be found in the ependymal region, surrounding the central canal, but there is evidence that this region is largely different in adult humans: lacks a patent canal and presents perivascular pseudorosettes, typically found in low grade ependymomas. Using Laser Capture Microdissection, Taqman gene expression assays and immunohistochemistry, we have studied the expression of endocannabinoid system components (receptors and enzymes) at the human spinal cord ependymal region. We observe that ependymal region is enriched in CB1 cannabinoid receptor, due to high CB1 expression in GFAP+ astrocytic domains. However, in human spinal cord levels that retain central canal patency we found ependymal cells with high CB1 expression, equivalent to the CB1(HIGH) cell subpopulation described in rodents. Our results support the existence of ependymal CB1(HIGH) cells across species, and may encourage further studies on this subpopulation, although only in cases when central canal is patent. In the adult human ependyma, which usually shows central canal absence, CB1 may play a different role by modulating astrocyte functions.