Cartilage intermediate layer protein is regulated by mechanical stress and affects extracellular matrix synthesis

Exosomes from M2c macrophages alleviate intervertebral disc degeneration by promoting synthesis of the extracellular matrix via MiR-124/CILP/TGF-β

Immuno-inflammation is highly associated with anabolic and catabolic dysregulation of the extracellular matrix (ECM) in the nucleus pulposus (NP), which dramatically propels intervertebral disc degeneration (IVDD). With the characteristics of tissue remodeling and regeneration, M2c macrophages have attracted great attention in research on immune modulation that rebuilds degenerated tissues. Therefore, we first demonstrated the facilitating effects of M2c macrophages on ECM anabolism of the NP in vitro. We subsequently found that exosomes from M2c macrophages (M2c-Exoss) mediated their metabolic rebalancing effects on the ECM. To determine whether M2c-Exoss served as positive agents protecting the ECM in IVDD, we constructed an M2c-Exos-loaded hyaluronic acid hydrogel (M2c-Exos@HA hydrogel) and implanted it into the degenerated caudal disc of rats. The results of MRI and histological staining indicated that the M2c-Exos@HA hydrogel alleviated IVDD in vivo in the long term. To elucidate the underlying molecular mechanism, we performed 4D label-free proteomics to screen dysregulated proteins in NPs treated with M2c-Exoss. Cartilage intermediate layer protein (CILP) was the key protein responsible for the rebalancing effects of M2c-Exoss on ECM metabolism in the NP. With prediction and verification using luciferase assays and rescue experiments, miR-124-3p was identified as the upstream regulator in M2c-Exoss that regulated CILP and consequently enhanced the activity of the TGF-β/smad3 pathway. In conclusion, we demonstrated ameliorating effects of M2c-Exoss on the imbalance of ECM metabolism in IVDD via the miR-124/CILP/TGF-β regulatory axis, which provides a promising theoretical basis for the application of M2c macrophages and their exosomes in the treatment of IVDD.

In Situ Cell Signalling of the Hippo-YAP/TAZ Pathway in Reaction to Complex Dynamic Loading in an Intervertebral Disc Organ Culture

Recently, a dysregulation of the Hippo-YAP/TAZ pathway has been correlated with intervertebral disc (IVD) degeneration (IDD), as it plays a key role in cell survival, tissue regeneration, and mechanical stress. We aimed to investigate the influence of different mechanical loading regimes, i.e., under compression and torsion, on the induction and progression of IDD and its association with the Hippo-YAP/TAZ pathway. Therefore, bovine IVDs were assigned to one of four different static or complex dynamic loading regimes: (i) static, (ii) "low-stress", (iii) "intermediate-stress", and (iv) "high-stress" regime using a bioreactor. After one week of loading, a significant loss of relative IVD height was observed in the intermediate- and high-stress regimes. Furthermore, the high-stress regime showed a significantly lower cell viability and a significant decrease in glycosaminoglycan content in the tissue. Finally, the mechanosensitive gene CILP was significantly downregulated overall, and the Hippo-pathway gene MST1 was significantly upregulated in the high-stress regime. This study demonstrates that excessive torsion combined with compression leads to key features of IDD. However, the results indicated no clear correlation between the degree of IDD and a subsequent inactivation of the Hippo-YAP/TAZ pathway as a means of regenerating the IVD.

MiR-330-5p inhibits intervertebral disk degeneration via targeting CILP

BACKGROUND

Intervertebral disk degeneration (IDD) is caused by nucleus pulposus (NP) degeneration and extracellular matrix (ECM) remodeling and cartilage intermediate layer protein (CILP) expression has been confirmed to be increased in IDD. This study is mainly conducted to clarify the mechanism of CILP in the NP cell degeneration and ECM remodeling in IDD.

METHODS

CILP expression in the degenerated NP tissues and cells is quantified by quantitative real-time PCR and western blot. CILP function is assessed by cell cycle assay, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and flow cytometry, β-galactosidase staining, and the detection of ECM-related molecules aggrecan, collagen type I, collagen type II, MMP-3, and MMP-9 expression is accomplished by qRT-PCR. The potential mechanism is authenticated by dual-luciferase reporter gene assay.

RESULTS

CILP was increased in the degenerated NP tissues and cells, and the knockdown of CILP promoted the NP cell cycle, increased cell activity, and repressed cell apoptosis and repressed cell senescence and ECM production. Moreover, miR-330-5p targeted the CILP 3'-untranslated region, and miR-330-5p negatively regulated CILP expression. Moreover, the overexpression of miR-330-5p repressed NP cell degeneration and ECM remodeling to relieve IDD by downregulating CILP.

CONCLUSION

MiR-330-5p represses NP cell degeneration and ECM remodeling to ameliorate IDD by downregulating CILP.

Genetic Predictors of Early-Onset Spinal Intervertebral Disc Degeneration: Part Two of Two

Understanding genetic indicators is a fundamental aspect to characterizing the pathophysiology of chronic diseases such as intervertebral disc degeneration (IVDD). In our previous spinal genetics review, we characterized some more common genetic influencers in the context of IVDD. In this second part of our two-part comprehensive spinal genetics review, we characterize the more infrequently studied genes that have pathophysiological relevance. In doing so, we aim to expand upon the current gene-library for IVDD. The genes of interest include: asporin, cartilage intermediate layer protein, insulin-like growth factor 1 receptor, matrix metallopeptidase 9, and thrombospondin 2. Findings show that these genetic indicators have trends and polymorphisms that may have causal associations with the manifestation of IVDD. However, there is a narrow selection of studies that use genetic indicators to describe correlations to the severity and longevity of the pathology. Nevertheless, with the continued identification of risk genes involved with IVDD, the possibilities for refined models of gene therapies can be established for future treatment trials.

Cartilage intermediate layer protein affects the progression of intervertebral disc degeneration by regulating the extracellular microenvironment (Review)

Intervertebral disc degeneration (IDD), which is caused by multiple factors, affects the health of individuals and contributes to low back pain. The pathology of IDD is complicated, and changes in the extracellular microenvironment play an important role in promoting the process of degeneration. Cartilage intermediate layer protein (CILP) is a matrix protein that resides in the middle of human articular cartilage and is involved in numerous diseases that affect cartilage. However, there is no detailed review of the relationship between CILP and degenerative disc disease. Growing evidence has revealed the presence of CILP in the extracellular microenvironment of intervertebral discs (IVDs) and has suggested that there is a gradual increase in CILP in degenerative discs. Specifically, CILP plays an important role in regulating the metabolism of the extracellular matrix (ECM), an important component of the extracellular microenvironment. CILP can combine with transforming growth factor-β or insulin-like growth factor-1 to regulate the ECM synthesis of IVDs and influence the balance of ECM metabolism, which leads to changes in the extracellular microenvironment to promote the process of IDD. It may be possible to show the correlation of CILP with IDD and to target CILP to interfere with IDD. For this purpose, in the present study, the current knowledge on CILP was summarized and a detailed description of CILP in discs was provided.