Ubiquitin-dependent proteolysis of CXCL7 leads to posterior longitudinal ligament ossification

Abstract

Ossification of the posterior longitudinal ligament (OPLL), a spinal ligament, reduces the range of motion in limbs. No treatment is currently available for OPLL, which is why therapies are urgently needed. OPLL occurs in obesity, is more common in men, and has an onset after 40 years of age. The mechanisms underlying OPLL remain unclear. In this study, we performed a serum proteomic analysis in both OPLL patients and healthy subjects to identify factors potentially involved in the development of OPLL, and found reduced levels of a protein that might underlie the pathology of OPLL. We isolated the protein, determined its amino acid sequence, and identified it as chemokine (C-X-C motif) ligand 7 (CXCL7). Based on these proteomics findings, we generated a CXCL7 knockout mouse model to study the molecular mechanisms underlying OPLL. CXCL7-null mice presented with a phenotype of OPLL, showing motor impairment, heterotopic ossification in the posterior ligament tissue, and osteoporosis in vertebrate tissue. To identify the mechanisms of CXCL7 deficiency in OPLL, we searched for single nucleotide polymorphisms and altered DNA exons, but no abnormalities were found. Although miR-340 levels were found to be high in an miRNA array, they were insufficient to reduce CXCL7 levels. Ubiquitin C-terminal hydrolase1 (UCHL1) was found to be overexpressed in CXCL7-null mice and in the sera of patients with OPLL, and was correlated with OPLL severity. Post-translational modifications of proteins with ubiquitin and ubiquitin-like modifiers, orchestrated by a cascade of specialized ubiquitin activating enzyme (E1), ubiquitin conjugating enzyme (E2), and ubiquitin ligase (E3) enzymes, are thought to control a wide range of cellular processes, and alterations in the ubiquitin–proteasome system have been associated with several degenerative disorders. In addition, the OPLL tissue of CXCL7-null mouse and its primary cells expressed the antibody to ubiquitin (linkage-specific K48). Our data clearly show decreased CXCL7 levels in patients with OPLL, and that OPLL developed in mice lacking CXCL7. Tumor necrosis factor receptor-associated factor (TRAF)6 expression was decreased in CXCL7-null mouse primary cells. Furthermore, K48 polyubiquitination was found in posterior longitudinal ligament ossified tissue and primary cells from CXCL7-null mice. We performed a phosphoproteomics analysis in CXCL7-deficient mice and identified increased phosphorylation of mitogen-activated protein kinase kinase (ME3K)15, ubiquitin protein ligase E3C (UBE3C) and protein kinase C (PKC) alpha, suggesting that ubiquitin-dependent degradation is involved in CXCL7 deficiency. Future studies in the CXCL7-null mouse model are, therefore, warranted to investigate the role of ubiquitination in the onset of OPLL. In conclusion, CXCL7 levels may be useful as a serum marker for the progression of OPLL. This study also suggests that increasing CXCL7 levels in patients can serve as an effective therapeutic strategy for the treatment of OPLL.

Deep Learning Algorithm Based on Analysis the Effect of Posterior Cervical Vertebral Canal Decompression Angioplasty in the Treatment of Ossification of Posterior Longitudinal Ligament of Cervical Spine by CT Image

“…Some researchers have proposed that, combining pixel information of different scales can extract the best size information; some researchers believe that, reducing the size of the convolution kernel can improve the running speed of the neural network. [7][8][9][10] The CT image reconstruction algorithm can effectively remove image noise and improve image quality, assisting physicians in diagnosing diseases. With the rapid development of deep learning, many deep learning networks are used to process CT images.…”

Effects of oophorectomy on the lumbar spine of Wistar rats submitted to vibratory platform treatment

“…Research shows that individuals with metabolic disorders present osteoporosis, with stiffening and thickening of the posterior longitudinal ligament from the age of forty years. However, there are not any data to indicate the onset of morphological changes after instilling injury 32,33 . Since changes have been observed that point to a reduction in the thickness of the ALL, it may be an indication of positive effects, i.e.…”

Association between periodontitis and ossification of the posterior longitudinal ligament: a case report

“…Prior to this study, we induced the growth of ligament-like tissue from mesenchymal stem cells [ 1 ] and created a mouse model for ossification of the posterior longitudinal ligament (OPLL) for the study of ligament diseases [ 2 ]. In transgenic mice, ligament-like tissue derived from mesenchymal stem cells was found to be strongly expressed in the spinal ligament, anterior cruciate ligament of the knee joint, and periodontal ligament.…”

“…OPLL is an incurable disease of unknown cause in which the spinal ligament ossifies, resulting in limited range of motion and reduced function of the extremities. A previous proteomic study [ 2 ] identified a partial defect in the chemokine C-X-C motif ligand 7 (CXCL7) and low serum levels among patients. OPLL is classified into continuous, segmental, mixed, and circumscribed subtypes.…”