Dysregulated miR-98 Contributes to Extracellular Matrix Degradation by Targeting IL-6/STAT3 Signaling Pathway in Human Intervertebral Disc Degeneration

Abstract

Intervertebral disc degeneration (IDD) is associated with dysregulated expression of microRNAs (miRNAs). However, the precise molecular mechanisms underlying this disorder remain unclear. Therefore, we tested the hypothesis that miRNAs modulate IDD through effects on the IL-6/STAT3 signaling pathway, a potential regulator of IDD. The miRNA expression profile was determined in nucleus pulposus (NP) tissues from patients with IDD and controls, employing miRNA microarray and quantitative real-time PCR (RTqPCR). Biological functions of differential expression miRNAs were further investigated using immunofluorescent staining. Luciferase reporter assays and Western blotting were performed to determine miRNA targets. We identified 41 miRNAs that were differentially expressed in patients compared with controls. Following RT-qPCR confirmation, miR-98 was significantly downregulated in degenerative NP tissues. Moreover, its level was inversely correlated with grade of disc degeneration. Through gain-of-function and loss-of-function studies, miR-98 was shown to significantly promote type II collagen expression in NP cells. Interleukin-6 (IL-6) was identified as a target of miR-98. Knockdown of IL-6 induced effects on NP cells similar to those induced by miR-98. In contrast, IL-6 treatment abrogated the effects induced by miR-98 upregulation. Moreover, miR-98 dramatically suppressed expression of STAT3 target gene, MMP2. IL-6 treatment antagonized this effect, whereas knockdown of IL-6 by IL-6 short hairpin RNA (shIL-6) induced inhibitory effects on the expression of p-STAT3 and its main target genes, similar to miR-98. The mRNA level of IL-6 was inversely correlated with that of miR-98 in degenerative NP tissues. These results suggest the downregulation of miR-98 could promote IDD through the IL-6/STAT3 signaling pathway. Our findings also highlight miR-98 as a novel hopeful therapeutic target for IDD.

Mesenchymal stem cells deliver exogenous miR‐21 via exosomes to inhibit nucleus pulposus cell apoptosis and reduce intervertebral disc degeneration

“…Recently, many studies have reported that different miRNAs regulate NPC apoptosis through their targets in the degenerated IVD. Pro-apoptotic miRNAs include miR-494, miR-138, miR-27a and miR-15a [5,[23][24][25], and anti-apoptotic miRNAs include miR-98, miR-155 and miR-125a [26][27][28]. However, little is known about which miRNAs are associated with TNF-a induced NPC apoptosis.…”

The Role of MicroRNAs and Their Targets in Osteoarthritis

“…Interestingly, this miRNA represses Smad3 resulting in the inhibition in cancer metastasis [160]. Furthermore, miR-98 is highly expressed in OA chondrocytes but has no confirmed target; however, it is an important regulator in intervertebral disc degeneration, where it targets IL-6 [161]. Several miRNAs that are downregulated in OA samples also have unidentified roles in chondrocyte homeostasis.…”

MicroRNA-494 promotes apoptosis and extracellular matrix degradation in degenerative human nucleus pulposus cells

“…Although the molecular mechanisms underlying IDD are not fully understood, it is well established that apoptosis, ECM degradation, cell proliferation, and the inflammatory response contribute to IDD development [7, 8]. Some miRNAs that regulate these processes have been linked to IDD [16, 34, 35]. For example, miR-27b causes the loss of type II collagen by directly targeting MMP13, leading to IDD development [36].…”

“…For example, miR-27b causes the loss of type II collagen by directly targeting MMP13, leading to IDD development [36]. MiR-146a suppresses IL-1β-induced MMP-13, ADAMTS4, and ADAMTS-5 expression in NP cells [34], and miR-98 downregulation contributes to the loss of type II collagen in IDD [35]. In this study, we found that miR-494 overexpression increased the levels of MMP3, MMP13, ADAMTS4, and ADAMTS5 and decreased that of type II collagen, aggrecan and sGAG; these effects were reversed by inhibiting miR-494.…”