Dynamic Compression Promotes the Matrix Synthesis of Nucleus Pulposus Cells Through Up-Regulating N-CDH Expression in a Perfusion Bioreactor Culture

Abstract

Background/Aims: An adequate matrix production of nucleus pulposus (NP) cells is an important tissue engineering-based strategy to regenerate degenerative discs. Here, we mainly aimed to investigate the effects and mechanism of mechanical compression (i.e., static compression vs. dynamic compression) on the matrix synthesis of three-dimensional (3D) cultured NP cells in vitro. Methods: Rat NP cells seeded on small intestinal submucosa (SIS) cryogel scaffolds were cultured in the chambers of a self-developed, mechanically active bioreactor for 10 days. Meanwhile, the NP cells were subjected to compression (static compression or dynamic compression at a 10% scaffold deformation) for 6 hours once per day. Unloaded NP cells were used as controls. The cellular phenotype and matrix biosynthesis of NP cells were investigated by real-time PCR and Western blotting assays. Lentivirus-mediated N-cadherin (N-CDH) knockdown and an inhibitor, LY294002, were used to further investigate the role of N-CDH and the PI3K/Akt pathway in this process. Results: Dynamic compression better maintained the expression of cell-specific markers (keratin-19, FOXF1 and PAX1) and matrix macromolecules (aggrecan and collagen II), as well as N-CDH expression and the activity of the PI3K/Akt pathway, in the 3D-cultured NP cells compared with those expression levels and activity in the cells grown under static compression. Further analysis showed that the N-CDH knockdown significantly down-regulated the expression of NP cell-specific markers and matrix macromolecules and inhibited the activation of the PI3K/Akt pathway under dynamic compression. However, inhibition of the PI3K/Akt pathway had no effects on N-CDH expression but down-regulated the expression of NP cell-specific markers and matrix macromolecules under dynamic compression. Conclusion: Dynamic compression increases the matrix synthesis of 3D-cultured NP cells compared with that of the cells under static compression, and the N-CDH-PI3K/Akt pathway is involved in this regulatory process. This study provides a promising strategy to promote the matrix deposition of tissue-engineered NP tissue in vitro prior to clinical transplantation.

Hydrostatic pressure mimicking diurnal spinal movements maintains anabolic turnover in bovine nucleus pulposus cells in vitro

“…Since CDH2 is a cell-cell contact molecule, proliferation of NP cells may efficiently occur within cell clusters, increasing to establish cell-cell contact. Although early studies showed that CDH2 expression increases under cyHP and decreases under coHP (Wang et al, 2017;Xu et al, 2018), the present study results indicated that repetitive HOsm/HP elicited a significantly larger increase in CDH2 compared to cyHP and coHP loading. The effects of repetitively alternating cyHP and coHP on CDH2 expression will be clarified in further studies.…”

Integrins, cadherins and channels in cartilage mechanotransduction: perspectives for future regeneration strategies

“…They are discussed in detail in Section 'Mechanotransduction at the cell-matrix interface'. Conversely, cell-to-cell contacts in the early phase of the articular chondrocyte life cycle and also in the NP contain neural (N)-cadherins (Refs[104][105][106][107][108][109][110][111][112]. Apart from supporting mesenchymal cell condensation, cadherin-based junctions act as important signalling platforms for the integration of mechanobiological information from different cellular pathways.…”

BMSC-Derived Exosomes Alleviate Intervertebral Disc Degeneration by Modulating AKT/mTOR-Mediated Autophagy of Nucleus Pulposus Cells

“…Numerous studies have shown that the Akt-mTOR signaling pathway is an important pathway to regulate the biological functions of various cells [32][33][34], including the regulation of the biological function of NPCs [35][36][37]. The Akt-mTOR signaling pathway is also involved in the progression of various human degenerative diseases, including the degeneration of nucleus pulposus cells [38].…”