Plasma exosome proteomics reveals upregulation of CILP-1 in concave side of paraspinal muscle in adolescent idiopathic scoliosis.

Abstract

Background: There is insufficient attention to the pathogenesis of abnormal radiological changes and molecular mechanism in the paraspinal muscles in AIS patients.

Methods: Proteomics of plasma exosomes were applied for identification of differentially expressed proteins (DEPs) in AIS patients through liquid chromatography mass spectrometry (LC-MS/MS). Bioinformatic analysis were performed to explore biomarkers. The muscle density (HU value) of the concave and convex sides of paravertebral muscles in AIS patients was compared. HE staining were applied for investigation of pathological changes of paravertebral muscles. Cartilage intermediate layer protein-1 (CILP-1), TGF-β1/Smad pathway and the downstream proteins were compared between the concave and convex side of paraspinal muscle. C2C12 cells were incubated with TGF-β1 or Smad3 phosphorylation inhibitor (SIS3) to further clarify the correlation between CILP-1 and TGF-β1/Smad pathway.

Results: A total of 2437 proteins were identified, among which DEPs were enriched in immune response and extracellular matrix-receptor interaction, while CILP-1 was screened out. HU value of concave multifidus muscle (MF) in apical vertebrae area was significantly lower when compared with both convex MF and control group. Muscle fibrosis, increased CILP-1, TGF-β1 phosphorylation of Smad2/3 and downstream proteins could be observed in the concave side of paraspinal muscle. TGF-β1 stimulation resulted in upregulation of CILP-1 and ECM related proteins, which could be partially inhibited by SIS3.

Discussion: We confirmed the asymmetric expressions of CILP-1 and TGF-β1/Smad signaling pathways in the paravertebral muscles of AIS patients. In C2C12 cells, TGF-β1 induced up-regulation of CILP-1 expression via Smad3 phosphorylation.