Identification of significant gene biomarkers of low back pain caused by changes in the osmotic pressure of nucleus pulposus cells

Abstract

The incidence of intervertebral disc (IVD) degeneration disease, caused by changes in the osmotic pressure of nucleus pulposus (NP) cells, increases with age. In general, low back pain is associated with IVD degeneration. However, the mechanism and molecular target of low back pain have not been elucidated, and there are no data suggesting specific biomarkers of low back pain. Therefore, the research aims to identify and verify the significant gene biomarkers of low back pain. The differentially expressed genes (DEGs) were screened in the Gene Expression Omnibus (GEO) database, and the identification and analysis of significant gene biomarkers were also performed with various bioinformatics programs. A total of 120 patients with low back pain were recruited. Before surgery, the degree of pain was measured by the numeric rating scale (NRS), which enables comparison of the pain scores from individuals. After surgery, IVD tissues were obtained, and NP cells were isolated. The NP cells were cultured in two various osmotic media, including iso-osmotic media (293 mOsm/kg H 2 O) to account for the morbid environment of NP cells in IVD degeneration disease and hyper-osmotic media (450 mOsm/kg H 2 O) to account for the normal condition of NP cells in healthy individuals. The relative mRNA expression levels of CCL5, OPRL1, CXCL13, and SST were measured by quantitative real-time PCR in the in vitro analysis of the osmotic pressure experiments. Finally, correlation analysis and a neural network module were employed to explore the linkage between significant gene biomarkers and pain. A total of 371 DEGs were identified, including 128 downregulated genes and 243 upregulated genes. Furthermore, the four genes (CCL5, OPRL1, SST, and CXCL13) were identified as significant gene biomarkers of low back pain (P < 0.001) based on univariate linear regression, and CCL5 (odds ratio, 34.667; P = 0.003) and OPRL1 (odds ratio, 19.875; P < 0.001) were significantly related to low back pain through multivariate logistic regression. The expression of CCL5 and OPRL1 might be correlated with low back pain in patients with IVD degeneration disease caused by changes in the osmotic pressure of NP cells.IVD is fibro-cartilage tissue located between vertebrae and is composed of the nucleus pulposus, annulus fibrosus and endplate 1 . NP survives in a special ecological niche containing no distribution of blood vessels and nerves in which the osmotic pressure is significantly higher than that of plasma, enabling proteoglycans to be present in high concentrations 2,3 . Increasing with age, the osmotic pressure changes, and the interverbal disc degenerates 4,5 , which may be related to low back pain 6,7 . Previous studies have shown that the osmotic environment can influence the gene expression of NP cells 7 ; thus, we hypothesized that there are pain-related genes among these affected genes, which might provide new therapeutic strategies and drug targets for low back pain.In addition, the NRS is ubiquitous in the clinic as a means of evaluating low bac...

Engineered Peptide-Functionalized Hydrogels Modulate the RNA Transcriptome of Human Nucleus Pulposus Cells In Vitro

“…HCAR2 has been implicated in macrophage recruitment and inflammatory responses and protein expression of hydroxycarboxylic acid receptor-2 (HCAR2) has been found in chondrocytes and peripheral nerve among other tissues [84][85][86] . Similarly, ADRA2C and SST have been found to be biomarkers in chronic pain for temporomandibular disorder and low back pain [87][88][89] . Although a study found low ADRA2C expression in cartilage, a recent report found a decrease in expression of this protein was associated with IVD degeneration 51,90 .…”

The nucleus pulposus microenvironment in the intervertebral disc: the fountain of youth?

“…A recent bioinformatic analysis identified significant gene biomarkers of LBP caused by changes in the osmotic pressure of NP cells, providing a reference for future in-depth research (Zhao et al, 2020).…”

“…Recently, in vitro studies have shown that static compression stress induces mitochondrial apoptosis in NP progenitor cells Yuan et al, 2018). Apart from the induction of apoptosis and senescence, stress stimuli seem to be critical for the normal functioning of progenitor cells (Hosseini et al, 2015;Kobayashi et al, 1989;Zhao et al, 2015). As an illustration of this, fluid-shear stress can give rise to overexpression of ECM components synthesised by AF progenitor cells (e.g.…”

“…non-ECM related) (Baer et al, 2003;Cao et al, 2009;Cao et al, 2011;Hsieh et al, 2005;Hwang et al, 2014;Jackson et al, 2011a;Korecki et al, 2008). Moreover, it is well documented that disc degeneration first occurs in the NP region of the IVD (Wang et al, 2014;Zhao et al, 2007). In this context, this full microenvironment (i.e.…”

Global gene expression and chromatin accessibility of the peripheral nervous system in animal models of persistent pain

“…Among the 28 GPCR genes upregulated following CCI and CFA, several are known to be involved in abnormal generation of action potentials and altered pain thresholds (e.g., Gal1r, Gabbr2, Grm7, Gpr158, Chrm2, Chrm3, Cnr1, Oprl1, Oprm1, Mrgpre) as well as clinical pain conditions such as neuralgia (e.g., Htr2a, Htr2b, Ptger4, Mrgprx1) (Fig. 2D) [25][26][27][28][29][30][31][32][33][34][35]. Conversely, of the genes identified as transcriptional regulators, the number downregulated was 10-fold higher than the number upregulated (Fig.…”