Circular RNA PDK1 targets miR‐4731‐5p to enhance TNXB expression in ligamentum flavum hypertrophy

Abstract

Hypertrophic ligamentum flavum (LF) is a main factor responsible for lumbar spinal stenosis (LSS); however, the exact mechanisms of the pathogenesis of these processes remain unknown. This study aimed to elucidate whether circular RNAs and microRNAs regulate the pathogenesis of LF and LSS, especially focusing on circPDK1 (hsa_circ_0057105), a circRNA targeting pyruvate dehydrogenase kinase 1 and differentially expressed in LF tissues between lumbar disk herniation and LSS patients. The circPDK1/miR-4731 and miR-4731/TNXB (Tenascin XB) interactions were predicted and validated by luciferase reporter assay. Colony formation, woundhealing, and MTT assays were used for estimating cell proliferation and migration.Protein expression levels were evaluated using Western blotting. TNXB expression was verified using immunohistochemistry (IHC). Overexpressing circPDK1 promoted the proliferation, migration, and expression of fibrosis-related protein (alpha smooth muscle actin (α-SMA), lysyl oxidase like 2 (LOXL2), Collagen I, matrix metalloproteinase-2 (MMP-2) and TNXB) in LF whereas miR-4731-5p showed opposite effects. The expression of TNXB was promoted by circPDK1; contrary results were observed with miR-4731-5p. Co-overexpression of miR-4731-5p partially reversed the proliferative and fibrosis-prompting effects of circPDK1 or TNXB. The circPDK1-miR-4731-TNXB pathway may be proposed as a regulatory axis in LF hypertrophy, which might shed light on in-depth research of LSS, as well as providing a novel therapeutic target for LF hypertrophy-induced LSS.

Exploring lncRNA Expression Patterns in Patients With Hypertrophied Ligamentum Flavum

“…Growing evidence shows that noncoding RNAs, including lncRNAs, play a role in the development and progression of various disorders, including spinal diseases [ 9 , 29 ]. Previous studies have investigated molecular mechanisms underlying LFH; however, the role of lncRNAs in LFH progression is only partially understood [ 22 , 23 , 30 , 31 ]. Here, we investigated the expression patterns of lncRNAs in LFH and LFN tissues by lncRNA sequencing.…”

LOXL2 in Cancer: A Two-Decade Perspective

“…Although not related to the cancer field, it is worth mentioning that in a cell model of hypertrophic flavum ligamentum, LOXL2 mRNA is targeted by miR-4731, and LOXL2 downregulation is relieved by circPDK1 [ 90 ].…”

Circular RNA circ_0003609 ameliorates hypertrophied ligamentum flavum by regulating the miR-155/SIRT1 axis

“…Circular RNAs (circRNAs), which are classified as noncoding RNA, exploit covalent bonds to form closed-loop structures [3,4]. Studies showed that circRNAs significantly impact the progression of fibrotic diseases [5][6][7]. The study of Zhang et al demonstrated that circPDK1 promoted the propagation, dissemination, and fibrosis of LF cells [7].…”

“…Studies showed that circRNAs significantly impact the progression of fibrotic diseases [5][6][7]. The study of Zhang et al demonstrated that circPDK1 promoted the propagation, dissemination, and fibrosis of LF cells [7]. The expression profile of circRNA has revealed a significant downregulation of circ_0003609 in both HLF tissues and cells [8].…”

“…circRNAs function as carriers for microRNAs (miRNAs) to regulate gene expression and have a role in the development of diseases [9,10]. For example, circPDK1 acted as a sponge for miR-4731 and exerted a role in the development of HLF [7]. A previous study demonstrated that the level of miR-155 was significantly elevated in the LF of patients with lumbar spinal stenosis compared to those with lumbar disc herniation [11].…”