A wide range of CNS injuries and neurodegenerative diseases results in various degree of cell death and neuroinflammation. Several therapeutic approaches have been evaluated for treatment of CNS impairment, and stem cell therapy is one of the promising means to achieve this aim. Cell-based therapies have recruited different types of stem cells to replace lost cells or to repair damaged areas. Studying the behavior of these cells after implantation and the feasibility of the mode of administration are two main debatable topics in cell-based therapies .
This investigation revealed that CSF, due to its beneficial environment, can retain viability of epidermal neural crest stem cells, and these cells continue to express a neural crest stem cell molecular signature after 72 hours of cultivation in the CSF milieu. According to our findings in the current study, CSF can be a suitable route of administration for EPI-NCSCs in CNS injuries and neurodegenerative diseases.
Previous studies have shown that EPI-NCSCs, as adult-resident stem cells in the bulge of the hair follicle, presents a number of advantages that make it an appropriate cell type for autologous transplantation. These readily accessible stem cells can generate several types of cells without known tumorigenic effects. Furthermore, their potential for regeneration of peripheral nerves and spinal cord injuries was demonstrated previously . As neural crest stem cells are ontologically related to spinal cord stem cells, EPI-NCSCs are particularly attractive types of stem cell for treatment of spinal cord injury . Several studies in mouse models of spinal cord injury showed that EPI-NCSC grafts resulted in significant improvement in sensory connectivity and touch perception. These cells modulate scar formation by contributing to the vascularization and by producing multiple metalloproteases and other extracellular proteases that degrade different types of extracellular matrix molecules [24–28]. In this study, a highly pure population of EPI-NCSCs were obtained by virtue of their migratory ability through a minimally invasive procedure from the bulge of hair follicles. Isolated cells expressed both neural crest marker SOX10 and stem cell marker Nestin abundantly, which verifies their origin and multipotency.
Besides an appropriate cell type, the practicality of different routes of administration is another prominent factor in cell-based therapy. Cerebrospinal fluid, beyond its important role in the maintenance of extracellular ionic balance and providing a fluid cushion for the CNS, was recently implicated in carrying secreted proteins widely throughout life. Lately several studies have demonstrated the crucial role of CSF in neurogenesis at the brain-cerebrospinal fluid interface, regarding its various signaling factors [17, 20]. Therefore it is not considered just as a watery fluid that bathes the brain and spinal cord. Moreover, CSF, owing to its circulatory system, which is in close contact with different parts of the CNS, provides a practical way for EPI-NCSCs transplantation. Above all, CSF-constituent proteins can play an instructive role in fate determination of EPI-NCSCs, as longSAGE gene-expression profile of these cells earlier revealed, EPI-NCSCs express some relevant growth-factor receptors that can convey CSF signals inside the cells .
Our data from culturing EPI-NCSCs in CSF has indicated that these cells can survive in this environment, and the expression of their pertinent markers proceeds for at least 72 hours, adequate for delivering cells to different parts of brain and spinal cord under in vivo conditions. Interestingly, EPI-NCSCs express early lineage markers like β-tubulin ІІІ and GFAP, which demonstrate that these cells can differentiate into either a neuronal or a glial lineage. Moreover, our investigation disclosed that CSF provides a trophic environment for proliferation of isolated EPI-NCSCs. However, the proliferation rate of these cells in CSF was significantly lower than that of cells in primary explants and expansion medium. This acquired trait of EPI-NCSCs after their cultivation in CSF is an attractive feature in cell-based therapy, because tumorigenicity of stem cells is one of the main setbacks of this approach.
Furthermore, our data show that CSF not only decreases the proliferation of EPI-NCSCs but also does not promote their differentiation toward any specific destiny, because the expression of early lineage genes in this medium diminished comparison with the primary explant. This condition can be appropriate for transplanted cells because it allows cells to differentiate according to instructive signals of their prospective target site.
It is noteworthy that the behavior of EPI-NCSCs in the current investigation was studied after their cultivation in healthy CSF, and this result may vary in different pathologic conditions. However, previously, Bai and his colleagues [29, 30] showed that the injection of neural stem cells through the CSF is a practical method to graft cells into traumatic and diseased lesions of the spinal cord. Consistently, Satake et al. in 2004  reported that transplanted mesenchymal stem cells can survive after a lumbar CSF injection and migrate into a previously created thoracic spinal cord injury.