Expression of ANGPTL4 in Nucleus Pulposus Tissues Is Associated with Intervertebral Disc Degeneration

Abstract

Objective. Angiopoietin-like protein 4 (ANGPTL4), encoding a glycosylated secreted protein, has been reported to be closely related to many kinds of diseases, including diabetes, tumor, and some musculoskeletal pathologies, such as rheumatoid arthritis, osteoarthritis, and osteoporosis. The aim of the current study is to investigate the role of ANGPTL4 in intervertebral disc degeneration and analyze the association of ANGPTL4 expression with Pfirrmann grades. Methods. A total of 162 nucleus pulposus tissues were collected from lumbar intervertebral disc herniation patients undergoing interforaminal endoscopic surgery. Real-time quantitative PCR and western blot were performed to determine the mRNA and protein expression of ANGPTL4 in nucleus pulposus samples. Statistical analysis was performed to analyze the association of ANGPTL4 expression with Pfirrmann grades. Results. Based on the clinical data of 162 patients, results showed that Pfirrmann grades were significantly associated with patients’ age ( $r=0.162$ , $P=0.047$ ) and were not significantly associated with patients’ gender ( $P>0.05$ ). RT-qPCR and western blot results showed that the mRNA ( $r=0.287$ , $P<0.05$ ) and protein ( $r=0.356$ , $P<0.05$ ) expressions of ANGPTL4 were both closely associated with Pfirrmann grades. The expression of ANGPTL4 was remarkably increased in the groups of high IVDD Pfirrmann grades. Conclusion. The results demonstrated that ANGPTL4 expression was positively associated with the Pfirrmann grades and the severity of intervertebral disc degeneration. ANGPTL4 may be served as a candidate biomarker for intervertebral disc degeneration.