Static compression down-regulates N-cadherin expression and facilitates loss of cell phenotype of nucleus pulposus cells in a disc perfusion culture

Circ0007042 alleviates intervertebral disc degeneration by adsorbing miR-369 to upregulate BMP2 and activate the PI3K/AKt pathway

Background

To identify regulatory ncRNA molecules that can cause differential expression of CDH2 in intervertebral disc degeneration (IDD) and explore whether there are other ways to affect the progression of IDD.

Methods

A primary culture of human nucleus pulposus (NP) cells was established and identified by immunofluorescence. An in vitro IDD model was constructed by compressing human NP cells, and the MTT assay was used to measure cell viability. Changes in the ncRNA group were analysed by RNA-seq. The expression levels of hsa_circ_7042, CDH2, and miR-369-3p were detected by qPCR. Cell apoptosis, senescence, and extracellular matrix (ECM) metabolism were detected by flow cytometry, β-galactosidase staining, and Western blotting. hsa_circ_7042, miR-369-3p, and bone morphogenetic protein 2 (BMP2) were verified by luciferase and RNA immunoprecipitation (RIP) analyses. The PI3K/Akt pathway was validated by transfection of BMP2 siRNA. Furthermore, a mouse model of lumbar spine instability was constructed. circ_7042 adenovirus was packaged and injected into the intervertebral discs of mice, and the influence of circ_7042 overexpression on intervertebral disc degeneration was determined.

Results

Western blotting, qPCR, and flow cytometry analyses confirmed that overexpression of circ_7042 could downregulate miR-369-3p and upregulate the expression of CDH2 and BMP2 in IDD cell and animal models. Additionally, the levels of apoptotic and senescent cells decreased, and ECM degradation decreased. The PI3K/Akt pathway was significantly activated after circ_7042 was overexpressed. The injection of circ_7042-overexpressing adenovirus effectively reduced ECM degradation and the level of apoptosis in NP tissue.

Conclusions

circ_7042 could upregulate the expression of CDH2 and BMP2 by absorbing miR-369-3p, and the increased BMP2 activated the PI3K/Akt pathway, thus improving IDD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02895-7.

Spheroid-Based Tissue Engineering Strategies for Regeneration of the Intervertebral Disc

Degenerative disc disease, a painful pathology of the intervertebral disc (IVD), often causes disability and reduces quality of life. Although regenerative cell-based strategies have shown promise in clinical trials, none have been widely adopted clinically. Recent developments demonstrated that spheroid-based approaches might help overcome challenges associated with cell-based IVD therapies. Spheroids are three-dimensional multicellular aggregates with architecture that enables the cells to differentiate and synthesize endogenous ECM, promotes cell-ECM interactions, enhances adhesion, and protects cells from harsh conditions. Spheroids could be applied in the IVD both in scaffold-free and scaffold-based configurations, possibly providing advantages over cell suspensions. This review highlights areas of future research in spheroid-based regeneration of nucleus pulposus (NP) and annulus fibrosus (AF). We also discuss cell sources and methods for spheroid fabrication and characterization, mechanisms related to spheroid fusion, as well as enhancement of spheroid performance in the context of the IVD microenvironment.

Hydrostatic Pressure Modulates Intervertebral Disc Cell Survival and Extracellular Matrix Homeostasis via Regulating Hippo-YAP/TAZ Pathway

Established studies proved that hydrostatic pressure had multiple effects on the biological behavior of the intervertebral disc (IVD). However, the conclusions of the previous studies were inconsistent, due to the difference in hydrostatic loading devices and observing methods used in these studies. The current study is aimed at investigating the role of dynamic hydrostatic pressure in regulating biological behavior of the notochordal nucleus pulposus (NP) and fibrocartilaginous inner annulus fibrosus (AF) and its possible mechanism using our novel self-developed hydrostatic pressure bioreactor. The differences in the biological behavior of the rabbit IVD tissues under different degree of hydrostatic pressure were evaluated via histological analysis. Results revealed that low-loading dynamic hydrostatic pressure was beneficial for cell survival and extracellular matrix (ECM) homeostasis in notochordal NP and fibrocartilaginous inner AF via upregulating N-cadherin (N-CDH) and integrin β1. In comparison, high-magnitude dynamic hydrostatic pressure aggravated the breakdown of ECM homeostasis in NP and inner AF via enhancing the Hippo-YAP/TAZ pathway-mediated cell apoptosis. Moreover, inner AF exhibited greater tolerance to physiological medium-loading degree of hydrostatic pressure than notochordal NP. The potential mechanism was related to the differential expression of mechanosensing factors in notochordal NP and fibrocartilaginous inner AF, which affects the fate of the cells under hydrostatic pressure. Our findings may provide a better understanding of the regulatory role of hydrostatic pressure on the cellular fate commitment and matrix metabolism of the IVD and more substantial evidence for using hydrostatic pressure bioreactor in exploring the IVD degeneration mechanism as well as regeneration strategies.