Abstract
BackgroundCell therapy for the treatment of intervertebral disc degeneration (IDD) faces serious barriers since tissue-specific adult cells such as nucleus pulposus cells (NPCs) have limited proliferative ability and poor regenerative potential; in addition, it is difficult for exogenous adult stem cells to survive the harsh environment of the degenerated intervertebral disc. Endogenous repair by nucleus pulposus mesenchymal stem cells (NPMSCs) has recently shown promising regenerative potential for the treatment of IDD. Notochordal cells (NCs) and NC-conditioned medium (NCCM) have been proven to possess regenerative ability for the treatment of IDD, but this approach is limited by the isolation and passaging of NCs. Our previous study demonstrated that modified notochordal cell-rich nucleus pulposus (NC-rich NP) has potential for the repair of IDD. However, whether this can protect NPMSCs during IDD has not been evaluated.MethodsIn the current study, tumor necrosis factor (TNF)-α was used to mimic the inflammatory environment of IDD. Human NPMSCs were cocultured with NC-rich NP explants from healthy rabbit lumbar spine with or without TNF-α. Cell proliferation and senescence were analyzed to investigate the effect of NC-rich NP explants on TNF-α-treated NPMSCs. The expression of mRNA encoding proteins related to matrix macromolecules (such as aggrecan, Sox-9, collagen Iα, and collagen IIα), markers related to the nucleus pulposus cell phenotype (including CA12, FOXF1, PAX1, and HIF-1α), and senescence markers (such as p16, p21, and p53), senescence-associated proinflammatory cytokines (IL-6), and extracellular proteases (MMP-13, ADAMTS-5) was assessed. The protein expression of CA12 and collagen II was also evaluated.ResultsAfter a 7-day treatment, the NC-rich NP explant was found to enhance cell proliferation, decrease cellular senescence, promote glycosaminoglycan (GAG), collagen II, and CA12 production, upregulate the expression of extracellular matrix (ECM)-related genes (collagen I, collagen II, SOX9, and ACAN), and enhance the expression of nucleus pulposus cell (NPC) markers (HIF-1α, FOXF1, PAX1, and CA12).ConclusionModified NC-rich NP explants can attenuate TNF-α-induced degeneration and senescence of NPMSCs in vitro. Our findings provide new insights into the therapeutic potential of NC-rich NP for the treatment of IDD.
Highlights
Cell therapy for the treatment of intervertebral disc degeneration (IDD) faces serious barriers since tissue-specific adult cells such as nucleus pulposus cells (NPCs) have limited proliferative ability and poor regenerative potential; in addition, it is difficult for exogenous adult stem cells to survive the harsh environment of the degenerated intervertebral disc
Significantly lower numbers of nucleus pulposus mesenchymal stem cell (NPMSC) were detected in the coculture group compared with that in the tumor necrosis factor (TNF)-α-treated group on days 5 and 7, while in both TNF-α-treated NPMSCs, a higher cell number was observed in the notochordal cell (NC)-rich NP coculture group, with a significant difference at day 7 (P < 0.05; Fig. 5b). These results suggested that NC-rich NP can NC-rich NP explants enhance the expression of NP cell markers in TNF-α-treated NPMSCs carbonic anhydrase 12 (CA12) is known as a specific marker of NP cells; here, we examined the expression of this marker in TNF-α-treated NPMSCs with or without coculture with NC-rich NP explants
Data are expressed as mean ± SD values (n = 4). *p < 0.05 these results indicate that NC-rich NP can promote matrix synthesis in TNF-α-treated NPMSCs
Summary
Cell therapy for the treatment of intervertebral disc degeneration (IDD) faces serious barriers since tissue-specific adult cells such as nucleus pulposus cells (NPCs) have limited proliferative ability and poor regenerative potential; in addition, it is difficult for exogenous adult stem cells to survive the harsh environment of the degenerated intervertebral disc. Notochordal cells (NCs) and NC-conditioned medium (NCCM) have been proven to possess regenerative ability for the treatment of IDD, but this approach is limited by the isolation and passaging of NCs. Our previous study demonstrated that modified notochordal cellrich nucleus pulposus (NC-rich NP) has potential for the repair of IDD. NPCs have limited proliferative ability and poor regenerative potential; exogenous adult stem cells cannot survive in the degenerated IVD environment due to the associated harsh conditions such as strong forces, acidic pH, hypoxia, hyperosmolarity, and limited nutrients [6]. Studying endogenous repair might provide us with a new method for regenerative therapy to treat IDD
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