Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Physiology and Pharmacology

Collaborative Specialization

Developmental Biology

Supervisor

Séguin, Cheryle

Abstract

Transient Receptor Potential Cation Channel Subfamily V Member 4 (TRPV4) is a cell membrane Ca2+ channel that regulates intracellular calcium levels in response to mechanical stimuli. Recent studies have demonstrated that TRPV4 is required for the induction of extracellular gene expression in murine intervertebral disc (IVD) cells in response to mechanical load. We investigated the role of TRPV4 in age associated IVD degeneration and spine development using novel knockout mice. Spine samples were harvested from NotoCre;Trpv4fl/fl and WT mice at embryonic day 13.5 (E13.5) as well as postnatal day 1 and postnatal day 21 samples using histological analysis. NotoCre;Trpv4fl/fl mice demonstrated no difference in IVD structure compared to WT mice at each of the observed timepoints. In Col2Cre;Trpv4fl/fl (Trpv4-/-) mice used to asses age-associated disc degeneration, 24-month-old male Trpv4-/-mice showed gross changes in IVD structure at the L4/5 and L5/6 spinal levels compared to WT. Conversely, in 24-month female mice TRPV4 loss appeared to have a protective effect against IVD degeneration. This suggests that the loss of TRPV4 within the IVD may have a sex-specific effect in age-associated disc degeneration. Furthermore, 24-month-old female WT mice demonstrated significantly increased Trpv4 gene expression compared to male WT mice of the same age. Gene expression analysis of 24-month-old male mice, demonstrated a trend of increased expression of inflammatory markers Mmp-13, IL-1beta and IL-6 in Trpv4-/-samples compared to WT. Altogether, these results further support the role of TRPV4 as an important mechanoreceptor within the IVD, that contributes to the adaptive response of the disc to mechanical load.

Summary for Lay Audience

My work mainly involves the spinal disease intervertebral disc degeneration. This disease has been clinically shown to be responsible for the occurrence of low back pain around 40% of the time. Low back pain has been proven to cause suffering for many people due to the combination of requisite, medical costs, severe pain and decreased quality of life. Intervertebral disc degeneration is the structural breakdown of the intervertebral disc, an important tissue located in between each vertebra of the spine. The intervertebral disc serves as a shock absorber, to help the spine deal with all the force placed on it and to provide the spine with flexibility. In the cells of the intervertebral disc, there are proteins that are important for helping to respond to the forces acting on the spine. In my project we have selectively bred mice to not have a specific signalling protein (TRPV4). This allows us to look at the effect of this protein on age-associated disc degeneration. In my research I examined mice at 12, 18 and 24 months-of-age, the latter of which is around the end of a mouse’s lifespan. I took images of all the spines of these mice and used an intervertebral disc degeneration scoring system to determine how much of the disease each mouse was experiencing. I compared the scores of the genetically mutated mice (that did not have the protein of interest) with regular mice (that did have the protein). I found that at 24 month-of-age, male mice without the protein had much more disc degeneration than the male mice that still had the protein. Furthermore, I found that in 24-month-old female mice, not having the protein actually protected against disc degeneration. This was an interesting and unexpected sex-specific difference. Nexts steps for this research could include exposing male and female intervertebral disc cells to either testosterone or estrogen and examine protein activity levels. This will indicate whether the difference that I had previously observed was driven by sex hormones.

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Available for download on Saturday, August 30, 2025

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