The effect of hyaluronic acid on nucleus pulposus extracellular matrix production through hypoxia-inducible factor-1α transcriptional activation of CD44 under hypoxia

Abstract

Intervertebral disc degeneration (IDD) is the leading cause of low-back pain. Implantation of hyaluronic acid (HA) is potentially a therapeutic strategy for IDD, but its pharmacological effects and mechanism under hypoxic conditions remain unclear. In this study, the expression of extracellular matrix genes and proteins were enhanced in nucleus pulposus cells (NPCs) in the presence of HA under hypoxic condition, as shown by real-time reverse transcription-polymerase chain reaction, immunofluorescence staining, and dimethylmethylene blue assays. Moreover, the expression of CD44 was increased in the presence of both HA and hypoxia compared to either alone. Using a bioinformatic database, hypoxia inducible factor-1α (HIF-1α), a key transcription factor in the hypoxic condition, was found to have 4 predicted binding sites on the CD44 promoter. CD44 expression was significantly increased by treatment with cobalt chloride or dimethyloxalylglycine. Over-expression of HIF-1α in NPCs significantly up-regulated the expression of CD44. The binding site of HIF-1α in the CD44 promoter region, was identified by promoter truncation experiments and chromatin immunoprecipitation assays. Taken together, these results indicated that hypoxic conditions positively potentiated the ability of NPCs matrix synthesis in the presence of HA, which correlated with the increasing CD44 expression by HIF-1α transcriptional activation.

Single-Cell RNA-Seq Analysis of Cells from Degenerating and Non-Degenerating Intervertebral Discs from the Same Individual Reveals New Biomarkers for Intervertebral Disc Degeneration

“…The membrane receptors for hyaluronan CD44 play important roles in cartilage homeostasis [ 106 , 107 ]. In fact, increasing CD44 expression has previously been correlated with matrix synthesis in NP cells of degenerating IVDs [ 108 ]. FN1 is a glycoprotein present at the cell surface and in the extracellular matrix that increases with disc degeneration [ 109 ].…”

Intradiscal injection for the management of low back pain

“…Especially, hyaluronic acid-based hydrogels have been drawing increasing attention as the ideal candidates for IDD, 92 because of their potential to repair and regenerate the NP through providing a three-dimensional microenvironment for the implanted cells, 93 restoring biomechanical properties, 94 reducing inflammation response, and nociceptive behavior, 95 promoting ECM synthesis, 96 and promoting stem cell differentiation to NP-like cells. 97 Animal experiments revealed that the injection of hyaluronic acid hydrogel not only restored the height of the intervertebral disc but also reduced inflammation and promoted the synthesis of ECM.…”

“…(1) Providing a three-dimensional microenvironment for the implanted cells (2) Restoring biomechanical properties; (3) Reducing inflammation response and nociceptive behavior; (4) Promoting the synthesis of ECM; (5) Promoting stem cell differentiation to NP-like cells. [92][93][94][95][96][97] Improving VAS, ODI, SF-36 scores, and disc quality quantified by Pfirrmann grading and apparent diffusion coefficient on diffusion MRI in the short and long term.…”

The biological effect of cobalt chloride mimetic-hypoxia on nucleus pulposus cells and the comparability with physical hypoxia in vitro

“…Nucleus pulposus tissue contain abundant ECM including collagen II (COL2) and aggrecan (ACAN) that are responsible for maintaining the mechanical load of IVD [26,27]. Over the years, many studies have shown that hy- poxia could induce various cell types to enhance COL2 and ACAN expression via HIF1α, including NPCs [10,[28][29][30][31][32]. Matrix metalloproteinases (MMPs) are endopeptidases of the ECM that have the ability to degrade almost all known components of the ECM in IVDs.…”