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Purinergic signalling in a latent stem cell niche of the rat spinal cord

Abstract

The ependyma of the spinal cord harbours stem cells which are activated by traumatic spinal cord injury. Progenitor-like cells in the central canal (CC) are organized in spatial domains. The cells lining the lateral aspects combine characteristics of ependymocytes and radial glia (RG) whereas in the dorsal and ventral poles, CC-contacting cells have the morphological phenotype of RG and display complex electrophysiological phenotypes. The signals that may affect these progenitors are little understood. Because ATP is massively released after spinal cord injury, we hypothesized that purinergic signalling plays a part in this spinal stem cell niche. We combined immunohistochemistry, in vitro patch-clamp whole-cell recordings and Ca2+ imaging to explore the effects of purinergic agonists on ependymal progenitor-like cells in the neonatal (P1–P6) rat spinal cord. Prolonged focal application of a high concentration of ATP (1 mM) induced a slow inward current. Equimolar concentrations of BzATP generated larger currents that reversed close to 0 mV, had a linear current–voltage relationship and were blocked by Brilliant Blue G, suggesting the presence of functional P2X7 receptors. Immunohistochemistry showed that P2X7 receptors were expressed around the CC and the processes of RG. BzATP also generated Ca2+ waves in RG that were triggered by Ca2+ influx and propagated via Ca2+ release from internal stores through activation of ryanodine receptors. We speculate that the intracellular Ca2+ signalling triggered by P2X7 receptor activation may be an epigenetic mechanism to modulate the behaviour of progenitors in response to ATP released after injury.

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Acknowledgments

This work was supported by grants FCE 2369 and FCE 100411 from ANII to N.M., and grants FCE 103356 from ANII and R01NS048255 from the National Institute of Neurological Disorders and Stroke to R.E.R. N.M. was a recipient of an ANII fellowship. The antibody rat-401 developed by S. Hockfield was obtained from the Developmental Studies Hybridoma Bank developed under the auspices of the NICHD and maintained by The University of Iowa, Department of Biology, Iowa City, IA 52242.

Author information

Correspondence to Raúl E. Russo.

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The authors declare that they have no conflicts of interest.

Ethical approval

All procedures performed in this study involving animals were in accordance with the ethical standards of the local Committee for Animal Care and Research at the Instituto de Investigaciones Biológicas Clemente Estable. Every precaution was taken to minimize animal stress and the number of animals used.

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Marichal, N., Fabbiani, G., Trujillo-Cenóz, O. et al. Purinergic signalling in a latent stem cell niche of the rat spinal cord. Purinergic Signalling 12, 331–341 (2016). https://doi.org/10.1007/s11302-016-9507-6

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Keywords

  • Stem cells
  • Purinergic signalling
  • P2X7 receptors
  • Ca2+ waves
  • Ependyma
  • Spinal cord