| Summary: | <p> Low back pain (LBP) is the leading cause of disability worldwide, and intervertebral disc (IVD) degeneration is the most common diagnosis for non-specific LBP. A need exists to develop and understand an animal model of LBP with similarities to the human condition that can be used to understand underlying pathophysiology and as a screening tool in therapeutic studies. Although a wealth of previous research exists regarding the causes of IVD degeneration, no studies to date have directly related molecular measures to a functional pain behavior in an induced lumbar IVD injury model. Therefore, the purpose of this project was to determine the predictive causes of pain in a lumbar IVD puncture rat model. Pain behavior, IVD degeneration, IVD height, intradiscal pro-inflammatory cytokine expression, and dorsal root ganglia (DRG) Substance P (SubP) expression were measured and their relationships analyzed with single and multi-variate regressions. Using a multi-variate step-wise linear regression model, IVD height was the only predictive factor for pain behavior in this rat model. This suggests the induced annular injury utilized in this model produces pain via DRG impingement by foraminal stenosis or by increased motion segment instability. TNF-α injection also increased pain, suggesting an additional inflammatory pain component in this model. These neuropathic and nociceptive pain contributions of the model share many characteristics with the human IVD degeneration condition and therefore this model has much potential to identify mechanisms of IVD degeneration-related pain and therapeutic screening. </p>
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