Potential roles of lncRNA-Cox2 and EGR1 in regulating epidural fibrosis following laminectomy

Z.-Y. Qian, F. Jiang, J. Tang, D.-W. Ge, H.-T. Chen, S.-N. Zheng, X.-J. Cao, Y.-B. Ge, L. Yang

Department of Orthopedics, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China. leiyang@njmu.edu.cn

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• Orthopedics

OBJECTIVE: Epidural fibrosis, one of the common complications after spinal surgery, seriously affects the surgical decompression effect. Effectively inhibiting the fibrous tissue hyperplasia is pivotal to reduce the scar adhesion. Previous studies showed that early growth response 1 (EGR1) is associated with the fibroblast reactivity induced by transforming growth factor-beta (TGF-β) and plays a vital regulatory role in scar formation; however, the upstream targets and mechanisms still remain unclear. In this work, it was found that the level of long non-coding ribonucleic acid (lncRNA)-cyclooxygenase-2 (COX2) was significantly negatively correlated with EGR1 expression and the severity of the scar. Therefore, it was conjectured that lncRNA-COX2 may decrease fibroplasia and scar formation by negatively regulating EGR1.

MATERIALS AND METHODS: TGF-β was used to activate the embryonic and adult rat fibroblasts. Rats underwent laminectomy to establish the epidural fibrosis model. The changes in the levels of fibroplasia-related genes were measured and analyzed through messenger RNA (mRNA), lncRNA, and micro RNA expression profile chips. Quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) was applied to determine the levels of EGR1 and lncRNA-COX2, and Western blotting was adopted to detect the content of EGR1, collagen I (Col-1), Col-3, and alpha-smooth muscle actin (α-SMA). The scar formation was reflected by hematoxylin and eosin (HE) staining and Masson staining, and the expression level of α-SMA in the scar tissues was measured via immunohistochemistry. Finally, micro-magnetic resonance imaging (MRI) was utilized to examine the different degrees of epidural fibroplasia.

RESULTS: It was found that the reactivity of embryonic rat fibroblasts to the TGF-β stimulation was different from that of adult rat fibroblasts. LncRNA-COX2 was highly expressed in the embryonic rat fibroblasts, but lowly expressed in the adult rat fibroblasts, which had negative correlations with the EGR1 level in embryonic and adult rat fibroblasts. In addition, it was revealed that the expression of EGR1 in the adult rat fibroblasts was remarkably higher than that in the embryonic rat fibroblasts after the activation with TGF-β. Meanwhile, the level of lncRNA-COX2 was lowered after the activation, especially in the adult rat fibroblasts. It was discovered in the in-vivo model that the degree of fibroplasia was positively associated with EGR1 level and negatively correlated with lncRNA-COX2 level.

CONCLUSIONS: The results of this research elucidated that the down-regulation of lncRNA-COX2 is involved in the epidural scar formation and related to the elevated EGR1 level which regulates the activation of fibroblasts and secretion of massive extracellular matrixes, suggesting that lncRNA-COX2 may modulate the role of fibroblasts in scar formation as an upstream action target of EGR1.

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