Proceedings of The Physiological Society

Experimental Models (Exeter, UK) (2018) Proc Physiol Soc 40, PC02

Poster Communications

Purinergic modulation of cell proliferation within the spinal cord stem cell niche

C. Maclean1, J. Deuchars1, S. Deuchars1

1. School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom.

There is some controversy over the neurogenic potential of the central canal region of the mammalian spinal cord. After injury, this region displays increased proliferation with migration of the newly-proliferated cells to the site of injury and differentiation into astrocytes and oligodendrocytes (1,2). It is thought that ependymal cells are involved in these functions but the role of the cerebrospinal fluid contacting cells (CSFcCs) is not known. Following injury, adenosine triphosphate (ATP) is released and it is known that there are purinergic P2X2 receptors in this region (3), which could be involved as part of a damage recognition system, initiating cell proliferation. This study will look at the role of purinergic signalling in the ependymal cells and CSF-contacting cells (CSFcCs). Spinal cord slices were obtained from Wistar rats anaesthetised with either sodium pentobarbitone 120 mg kg-1 or urethane 2 g kg-1 i.p. and transcardially perfused with sucrose artificial CSF. In acute slices, whole cell patch clamp recordings were made from both ependymal cells and CSFcCs. Local application of ATP (300 μM) elicited fast depolarisations in a subgroup of CSFcCs (21.50 ± 5.16 mV), which was reduced by application of the broad-spectrum purinergic antagonist suramin (50 μM; 9.73 ± 3.03 mV). The P2X2/3,3-specific antagonist A317491 (1 μM) had variable effects on the magnitude of the ATP-triggered depolarisations, with no effect in some, partial reduction and complete reduction of depolarisation in others. Immunohistochemical analysis of the P2X subtypes in this area revealed a sub-population of CSFcCs, predominantly in the ventral area of the region around the central canal that expressed P2X3 in addition to P2X2-containing receptors indicated by previous research. The remainder of the CSFcC population and the ependymal stem cells responded to ATP or UTP with a hyperpolarisation (-5.64 ± 1.98 mV) which was not affected by application of suramin (-5.64 ± 1.98 mV). Modulation of purinergic signalling had no effect on proliferation rate in spinal cord slices over a 4 hour time period, nor did it affect the survival rate of the newly-proliferated cells over 5 days in organotypic slice cultures. In this model, inhibition of purinergic signalling with suramin reduced the migration of newly-proliferated ependymal cells away from the central canal, while inhibition of the breakdown of ATP by ARL 67156 facilitated this migration. The presence of fast acute responses to ATP and a spatial variation in receptor subtypes suggests a role for purinergic signalling in the functioning of the cell types in this area including the response of the cell types to damage.

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