MicroRNA-887-3p Inhibited MDM4 Expression and Proliferation but Promoted Apoptosis of Intervertebral Disc Annulus Fibrosus Cells in Rats

Abstract

ObjectiveTo investigate the effects of microRNA (miRNA, miR)-887-3p on the proliferation and apoptosis of rat intervertebral disc annulus fibrosus cells and its underlying molecular mechanism.MethodsAnnulus fibrosus tissues were obtained from 8-week-old SPF-grade SD male rats, centrifuged to prepare and identify annulus fibrosus cells. Rats in the experiment were randomly divided into four groups: a Normal group consisting of primary annulus fibrosus cells without any treatment; a Control group treated with 10 ng/mL interleukin-1β (IL-1β) for 24 hours to establish a degenerative cell model; an interference group (miR-887-3p inhibitor) transfected with miR-887-3p inhibitor using Lipo3000 based on the Control group; and an overexpression group (miR-887-3p mimics) transfected with miR-887-3p mimics using Lipo3000 based on the Control group. CCK-8 assay was used to assess cell viability; flow cytometry was used to measure cell apoptosis rates; real-time fluorescence quantitative PCR (qPCR) was used to detect the expression levels of miR-887-3p and murine double minute 4 (MDM4) mRNA; Western blotting was used to measure the protein expression levels of MDM4, Bcl-2, and Caspase-3.ResultsImmunofluorescence staining of isolated and cultured cells revealed a Collagen I positive rate of over 90% in rat intervertebral disc annulus fibrosus cells, indicating a cell purity level greater than 90%. Real-time fluorescence qPCR results showed that after establishing an annulus fibrosus degenerative cell model using IL-1β, the expression level of miR-887-3p significantly increased compared to the Normal group (P<0.001). Compared to the Control group, transfection with miR-887-3p inhibitor resulted in a significant decrease in its expression level (P<0.001). The CCK-8 assay showed that compared to the Normal group, cell viability significantly decreased in the Control group (P<0.001). Compared to the Control group, cell proliferation ability significantly increased after miR-887-3p inhibition, and significantly decreased after overexpression of miR-887-3p. Flow cytometry results revealed that compared to the Normal group, the apoptosis rate in the Control group significantly increased (P<0.001). Compared to the Control group, the cell apoptosis rate significantly decreased in the miR-887-3p interference group (P<0.001) and increased in the overexpression group (P<0.001). Western blotting analysis showed that compared to the Normal group, Bcl-2 expression level significantly decreased (P<0.001) and Caspase-3 expression level significantly increased (P<0.001) in the Control group. Compared to the Control group, Bcl-2 and MDM4 expression levels significantly increased (P<0.01), and Caspase-3 expression level significantly decreased (P<0.01) in the miR-887-3p interference group; whereas in the overexpression group, Bcl‑2 and MDM4 expression levels significantly decreased (P<0.05), and Caspase-3 levels significantly increased (P<0.05). Real-time fluorescence qPCR and protein immunoblotting results showed that after interfering with miR-887-3p, the expression of MDM4 protein and mRNA increased (P<0.001); after overexpressing miR-887-3p, their expression decreased (protein, P<0.01; mRNA, P<0.001).ConclusionMiR-887-3p may modulate the cell proliferation and apoptosis of rat intervertebral disc annulus fibrosus cells by regulating MDM4 expression, thereby influencing the development and progression of disc degeneration.

Keywords

• mir-887-3p
• intervertebral disc annulus fibrosus cells
• degenerative model
• cell proliferation
• apoptosis
• rats