TGF-β1, in association with the increased expression of connective tissue growth factor, induce the hypertrophy of the ligamentum flavum through the p38 MAPK pathway.
Hypertrophy of the ligamentum flavum (LF) is one of the key pathomechanisms of lumbar spinal stenosis (LSS). Transforming growth factor (TGF)-β1 is abundantly expressed in hypertrophied degenerative LF tissues from LSS. However, the molecular mechanisms underling the association between TGF-β1 and LF hypertrophy have not yet been fully elucidated. In this study, we investigated the important role of the mitogen-activated protein kinase (MAPK) pathway in the pathogenesis of LSS by analyzing the expression of connective tissue growth factor (CTGF) and extracellular matrix (ECM) components (collagen I and collagen III) in TGF-β1-treated LF cells. Cell growth assay revealed that TGF-β1, in association with CTGF, enhanced the the proliferation of LF cells, and we found that TGF-β1 also elevated CTGF expression and subsequently enhanced the mRNA expression of collagen I and collagen III. The increased mRNA expression levels of CTGF, collagen I and collagen III were abolished by p38 inhibitors. Both immunofluorescence imaging and western blot analysis of p38 and p-p38 revealed the increased expression and phosphorylation of p38. Silencing the expression of p38 by siRNA in LF cells decreased the protein expression of p38, p-p38 and CTGF, as well as the mRNA expression of CTGF, collagen I and collagen III. Taken together, our findings indicate that TGF-β1, in association with the increased expression of CTGF, contribute to the homeostasis of the ECM and to the hypertrophy of LF through the p38 MAPK pathway.
Department of Orthopaedic Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong 510282, P.R. China.
Yan-Lin
YL
Cao
Department of Orthopaedic Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong 510282, P.R. China.
Yang
Y
Duan
Department of Orthopaedic Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong 510282, P.R. China.
Li-Xin
LX
Zhu
Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong 510282, P.R. China.
Ye-Nan
YN
Zhan
Department of Orthopaedic Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong 510282, P.R. China.
Shao-Xiong
SX
Min
Department of Orthopaedic Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong 510282, P.R. China.
An-Min
AM
Jin
D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D024061:Collagen Type III / Q000235:genetics / Q000378:metabolism; D055513:Connective Tissue Growth Factor / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D006984:Hypertrophy; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D017843:Ligamentum Flavum / Q000201:enzymology* / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000473:pathology; D020935:MAP Kinase Signaling System; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D024042:Collagen Type I; D024061:Collagen Type III; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053773:Transforming Growth Factor beta1; D055513:Connective Tissue Growth Factor; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases