eCM (Eur Cell Mater / e Cells & Materials) eCM Open Access Scientific Journal
 ISSN:1473-2262         NLM:100973416 (link)         DOI:10.22203/eCM

2021   Volume No 41 – pages 121-141

Title: Osmotic adaptation of nucleus pulposus cells: the role of aquaporin 1, aquaporin 4 and transient receptor potential vanilloid 4

Authors: JW Snuggs, RAD Bunning, CL Le Maitre

Address: Biomolecular Sciences Research Centre, Sheffield Hallam University, City Campus, Howard Street, Sheffield S1 1WB, UK.

E-mail: C.Lemaitre at

Abstract: The microenvironment of the nucleus pulposus is hyperosmotic and fluctuates diurnally due to mechanical loading. Changes in extracellular osmolality result in cell volume alterations, responsiveness to such changes is essential for cellular homeostasis. Aquaporins allow movement of water across cell membranes and control water permeability in response to osmotic gradients. Furthermore, transient receptor potential vanilloid 4 has been shown to sense osmotic and mechanical stimuli resulting in changes to intracellular Ca2+. It has been shown previously that aquaporin 1 and 4 expression decreases during disc degeneration. Here, the expression of transient receptor potential vanilloid 4 by human nucleus pulposus cells during disc degeneration, and the roles of aquaporin 1, 4 and transient receptor potential vanilloid 4 in regulating responses to osmotic gradients was investigated. Transient receptor potential vanilloid 4 was expressed by the majority of human nucleus pulposus cells and not affected by disc degeneration. Aquaporin 4 staining co-localised with primary cilia. Nucleus pulposus cells modulated their rate of volume change, water permeability and Ca2+ influx in response to extracellular osmolality. These responses were inhibited by chemical inhibition of aquaporin 4, transient receptor potential vanilloid 4, and to a lesser extent aquaporin 1; suggesting that both aquaporins and transient receptor potential vanilloid 4 play important roles in the fundamental adaptation of nucleus pulposus cells to their osmotic environment. Co-localisation with primary cilia indicates these proteins may function synergistically to achieve adaptation, which may be lost during disc degeneration, when aquaporin 1 and 4 expression is reduced.

Key Words: Aquaporin, TRPV4, nucleus pulposus, osmotic adaptation, water permeability.

Publication date: February 02th 2021

Article download: Pages 121-141 (PDF file)

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