Persistence of FoxJ1⁺ Pax6⁺ Sox2⁺ ependymal cells throughout life in the human spinal cord

Abstract

Spinal cord ependymal cells have stem cell properties in mice. They surround the central canal and keep expressing spinal cord developmental transcription factors. Similar cells exist in young humans however their persistence with aging is debated. We clarified this issue by collecting 17 spinal cords from organ donors, aged between 37 and 83 years old. We examined the presence of ependymal cells using immunohistochemistry on lightly-fixed tissue. We found the presence of cells expressing the typical ependymal marker FOXJ1 in the spinal cord central region in 100% of cases. In addition, a lumen surrounded by FOXJ1+ cells was observed in half of the cases. Like in mice, these human ependymal cells maintain the expression of SOX2 and PAX6 proteins together with RFX2 a master transcriptional regulator of ciliogenesis and ARL13B, a regulatory GTPase enriched in cilia. Reminiscent of the situation observed in mice and in young human spinal cord, a fetal-like regionalization of neurodevelopmental transcription factors was observed in three donors aged over 75 years: MSX1 and ARX/FOXA2 was preferentially expressed by dorsal and ventral ependymal cells, respectively. These results provide new evidence for the persistence of ependymal cells expressing neurodevelopmental genes throughout human life. The persistence of these cells in humans opens new opportunities to regenerate the spinal cord.