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

Authors: F Zhang, X Liu, B Li, Z Li, S Grad, D Chen, M Gao, S Liu

Address: Innovation Platform of Regeneration and Repair of Spinal Cord and Nerve injury, Department of Orthopaedic Surgery, The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China / Guangdong Provincial Key Laboratory of Orthopaedics and Traumatology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.

E-mail: gaomanm at mail2.sysu.edu.cn

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.

Key Words: Intervertebral disc degeneration, hypoxia inducible factor-1α, CD44, hyaluronic acid, gene regulation.

Publication date: February 3rd 2021

Article download: Pages 142-152 (PDF file)
DOI: 10.22203/eCM.v041a10