Osteogenic protein-1 attenuates apoptosis and enhances matrix synthesis of nucleus pulposus cells under high-magnitude compression though inhibiting the p38 MAPK pathway

Exploration of the mode of death and potential death mechanisms of nucleus pulposus cells

Intervertebral disc degeneration (IVDD) is a common chronic orthopaedic disease in orthopaedics that imposes a heavy economic burden on people and society. Although it is well established that IVDD is associated with genetic susceptibility, ageing and obesity, its pathogenesis remains incompletely understood. Previously, IVDD was thought to occur because of excessive mechanical loading leading to destruction of nucleus pulposus cells (NPCs), but studies have shown that IVDD is a much more complex process associated with inflammation, metabolic factors and NPCs death and can involve all parts of the disc, characterized by causing NPCs death and extracellular matrix (ECM) degradation. The damage pattern of NPCs in IVDD is like that of some programmed cell death, suggesting that IVDD is associated with programmed cell death. Although apoptosis and pyroptosis of NPCs have been studied in IVDD, the pathogenesis of intervertebral disc degeneration can still not be fully elucidated by using only traditional cell death modalities. With increasing research, some new modes of cell death, PANoptosis, ferroptosis and senescence have been found to be closely related to intervertebral disc degeneration. Among these, PANoptosis combines essential elements of pyroptosis, apoptosis and necroptosis to form a highly coordinated and dynamically balanced programmed inflammatory cell death process. Furthermore, we believe that PANoptosis may also crosstalk with pyroptosis and senescence. Therefore, we review the progress of research on multiple deaths of NPCs in IVDD to provide guidance for clinical treatment.

Rosuvastatin: A Potential Therapeutic Agent for Inhibition of Mechanical Pressure-Induced Intervertebral Disc Degeneration

Background

Intervertebral disc degeneration (IDD) underlies the pathogenesis of degenerative diseases of the spine; however, its exact molecular mechanism is unclear.

Purpose

To explore the molecular mechanism of mechanical pressure (MP)-induced IDD and to assess the role and mechanism of Rosuvastatin (RSV) inhibits MP-induced IDD.

Methods

SD rat nucleus pulposus cells (NPCs) were cultured in vitro and an apoptosis model of NPCs was constructed using MP. Proliferative activity, reactive oxygen species content, apoptosis, and wound healing were detected in each group of NPCs, respectively. The expression of relevant proteins was detected by qPCR and Western Blot techniques. 18 SD rats were randomly divided into control, pressure and RSV groups. Elisa, qPCR, Western Blot and immunohistochemical staining techniques were used to detect changes in the content of related proteins in the intervertebral discs of each group. HE staining and Modified Saffron-O and Fast Green Stain Kit were used to assess IDD in each group.

Results

MP treatment at 1.0 MPa could significantly induce apoptosis of NPCs after 24 h. MP could significantly inhibit the proliferative activity and wound healing ability of NPCs, and increase the intracellular reactive oxygen species content and apoptosis rate; pretreatment with RSV could significantly activate the Nrf2/HO-1 signaling pathway and reverse the cellular damage caused by MP; when inhibit the Nrf2/HO-1 signaling pathway activation, the protective effect of RSV was reversed. In vivo MP could significantly increase the content of inflammatory factors within the IVD and promote the degradation of extracellular matrix, leading to IDD. When the intervention of RSV was employed, it could significantly activate the Nrf2/HO-1 signaling pathway and improve the above results.

Conclusion

RSV may inhibit MP-induced NPCs damage and IDD by activating the Nrf2/HO-1 signaling pathway.

Unraveling the mechanisms of intervertebral disc degeneration: an exploration of the p38 MAPK signaling pathway

Intervertebral disc (IVD) degeneration (IDD) is a worldwide spinal degenerative disease. Low back pain (LBP) is frequently caused by a variety of conditions brought on by IDD, including IVD herniation and spinal stenosis, etc. These conditions bring substantial physical and psychological pressure and economic burden to patients. IDD is closely tied with the structural or functional changes of the IVD tissue and can be caused by various complex factors like senescence, genetics, and trauma. The IVD dysfunction and structural changes can result from extracellular matrix (ECM) degradation, differentiation, inflammation, oxidative stress, mechanical stress, and senescence of IVD cells. At present, the treatment of IDD is basically to alleviate the symptoms, but not from the pathophysiological changes of IVD. Interestingly, the p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway is involved in many processes of IDD, including inflammation, ECM degradation, apoptosis, senescence, proliferation, oxidative stress, and autophagy. These activities in degenerated IVD tissue are closely relevant to the development trend of IDD. Hence, the p38 MAPK signaling pathway may be a fitting curative target for IDD. In order to better understand the pathophysiological alterations of the intervertebral disc tissue during IDD and offer potential paths for targeted treatments for intervertebral disc degeneration, this article reviews the purpose of the p38 MAPK signaling pathway in IDD.

Andrographolide Inhibits Static Mechanical Pressure-Induced Intervertebral Disc Degeneration via the MAPK/Nrf2/HO-1 Pathway

Purpose

To explore the molecular mechanism by which andrographolide (ADR) inhibits static mechanical pressure-induced apoptosis in nucleus pulposus cells (NPCs) and to assess the role of ADR in inhibiting IDD.

Methods

Hematoxylin-eosin (HE), toluidine blue, and immunofluorescence staining were used to identify NPCs. An NPC apoptosis model was constructed using a homemade cell pressurization device. The proliferation activity, reactive oxygen species (ROS) content, and apoptosis rate were detected using kits. The expression of related proteins was detected using Western blot. A rat tailbone IDD model was constructed using a homemade tailbone stress device. HE staining and safranine O-fast green FCF cartilage staining were used to observe the degeneration degree of the intervertebral disk.

Results

ADR inhibits static mechanical pressure-induced apoptosis and ROS accumulation in NPCs and improves cell viability. ADR can promote the expression of Heme oxygenase-1 (HO-1), p-Nrf2, p-p38, p-Erk1/2, p-JNK, and other proteins, and its effects can be blocked by inhibitors of the above proteins.

Conclusion

ADR can inhibit IDD by activating the MAPK/Nrf2/HO-1 signaling pathway and suppressing static mechanical pressure-induced ROS accumulation in the NPCs.

Regulating the fate of stem cells for regenerating the intervertebral disc degeneration

Lower back pain is a leading cause of disability and is one of the reasons for the substantial socioeconomic burden. The etiology of intervertebral disc (IVD) degeneration is complicated, and its mechanism is still not completely understood. Factors such as aging, systemic inflammation, biochemical mediators, toxic environmental factors, physical injuries, and genetic factors are involved in the progression of its pathophysiology. Currently, no therapy for restoring degenerated IVD is available except pain management, reduced physical activities, and surgical intervention. Therefore, it is imperative to establish regenerative medicine-based approaches to heal and repair the injured disc, repopulate the cell types to retain water content, synthesize extracellular matrix, and strengthen the disc to restore normal spine flexion. Cellular therapy has gained attention for IVD management as an alternative therapeutic option. In this review, we present an overview of the anatomical and molecular structure and the surrounding pathophysiology of the IVD. Modern therapeutic approaches, including proteins and growth factors, cellular and gene therapy, and cell fate regulators are reviewed. Similarly, small molecules that modulate the fate of stem cells for their differentiation into chondrocytes and notochordal cell types are highlighted.

Duhuo jisheng decoction suppresses matrix degradation and apoptosis in human nucleus pulposus cells and ameliorates disc degeneration in a rat model

ETHNOPHARMACOLOGICAL RELEVANCE

The lower back pain (LBP) caused by intervertebral disc (IVD) degeneration brings a heavy burden to society. A classic treatment method of Chinese medicine, fangji-duhuo jisheng decoction (DHJSD), has been effective in the clinical treatment of LBP, although the underlying mechanism remains unknown.

AIM OF THE STUDY

In this work, the main objective was to study the effects of DHJSD on in vitro IVD degeneration of human nucleus pulposus (NP) cells after pressure treatment and on an in vivo interrupted IVD degeneration rat model.

MATERIALS AND METHODS

The effects of DHJSD on the viability of NP cells were detected using Cell Counting Kit-8. RT-qPCR, western blotting, TUNEL assay, transmission electron microscopy, and immunofluorescence staining were performed to explore the molecular mechanism underlying protection against compression-induced matrix degradation and apoptosis in NP cells by DHJSD. Furthermore, the effects of DHJSD on IVD degeneration in a rat IDD model were also determined.

RESULTS

We found that DHJSD increased the viability of NP cells in a concentration- and time-dependent manner. Furthermore, DHJSD significantly reduced compression-induced NP matrix degeneration and apoptosis, activated autophagy, and inhibited the p38/MAPK signaling pathway in NP cells subjected to compression. Autophagy inhibitor 3-MA and p38/MAPK signaling pathway activator anisomycin reversed the beneficial effects of DHJSD in NP cells, indicating that DHJSD protects against IVD degeneration by autophagy activation and P38/MAPK signaling pathway inhibition. Furthermore, DHJSD treatment effectively delayed IVD degeneration in a puncture-induced IDD rat model.

CONCLUSIONS

DHJSD prevents compression-induced matrix degradation and cell apoptosis through regulating autophagy and the P38/MAPK signaling pathway. The mechanism underlying the effects of DHSJD elucidated in this study provides a new direction for LBP treatment.

Upregulation of the long noncoding RNA lncPolE contributes to intervertebral disc degeneration by negatively regulating DNA polymerase epsilon

Long noncoding RNAs (lncRNAs) are critical regulators of gene transcription. Our previous results have demonstrated that iron deficiency accelerates intervertebral disc degeneration (IDD) by affecting the stability of the DNA polymerase epsilon (Polε) complex. Here, we discovered that the novel lncRNA lncPolE functions as a negative regulator of Polε. The expression of lncPolE in IDD tissues was upregulated compared to its expression in healthy control tissues, and this was in contrast to the PolE1 expression levels. The increased lncPolE level was significantly correlated with the severity of IDD. Ectopic expression of lncPolE in human nucleus pulposus cells (hNPCs) was able to decrease PolE1 levels and cause apoptosis, while the specific knockdown of lncPolE in primary NP cells (pNPCs) from IDD patients can restore PolE1 levels. Interestingly, iron depletion or supplementation can affect the expression of lncPolE. Further analyses indicated that the downregulation of DNA methylation in the promoter region of lncPolE caused its overexpression. Collectively, our results suggest that the aberrant expression of lncPolE contributes to the pathogenesis of IDD by negatively regulating PolE1 in iron deficient conditions, and this may provide a new avenue to alleviate IDD progression in clinical treatment.

Mechano growth factor attenuates mechanical overload-induced nucleus pulposus cell apoptosis through inhibiting the p38 MAPK pathway

Mechanical overload is a risk factor of disc degeneration. It can induce disc degeneration through mediating cell apoptosis. Mechano growth factor (MGF) has been reported to inhibit mechanical overload-induced apoptosis of chondrocytes. The present study is aimed to investigate whether MGF can attenuate mechanical overload-induced nucleus pulposus (NP) cell apoptosis and the possible signaling transduction pathway. Rat NP cells were cultured and subjected to mechanical overload for 7 days. The control NP cells did not experience mechanical load. The exogenous MGF peptide was added into the culture medium to investigate its protective effects. NP cell apoptosis ratio, caspase-3 activity, gene expression of Bcl-2, Bax and caspase-3, protein expression of cleaved caspase-3, cleaved PARP, Bax and Bcl-2 were analyzed to evaluate NP cell apoptosis. In addition, activity of the p38 MAPK pathway was also detected. Compared with the control NP cells, mechanical overload significantly increased NP cell apoptosis and caspase-3 activity, up-regulated gene/protein expression of pro-apoptosis molecules (i.e. Bax, caspase-3, cleaved caspase-3 and cleaved PARP) whereas down-regulated gene/protein expression of anti-apoptosis molecule (i.e. Bcl-2). However, exogenous MGF partly reversed these effects of mechanical overload on NP cell apoptosis. Further results showed that activity of the p38 MAPK pathway of NP cells cultured under mechanical overload was decreased by addition of MGF peptide. In conclusion, MGF is able to attenuate mechanical overload-induced NP cell apoptosis, and the p38 MAPK signaling pathway may be involved in this process. The present study provides that MGF supplementation may be a promising strategy to retard mechanical overload-induced disc degeneration.

Nucleus pulposus cell apoptosis is attenuated by CDMP-2 through regulating oxidative damage under the hyperosmotic environment

Disc nucleus pulposus (NP) cell experiences periodic osmolarity alterations during daily activities, which has been proved to affect cell biology in vitro The present study was aimed to investigate the effects of cartilage-derived morphogenetic protein-2 (CDMP-2) on NP cell apoptosis under the hyperosmolarity culture and the potential mechanism. Isolated rat NP cells were cultured in the in situ-osmolarity medium or hyperosmolarity medium for 3 days. CDMP-2 was added into the hyperosmolarity medium to investigate its effects on NP cell apoptosis. Cell apoptosis rate, caspase-3 activity, gene expression of Bcl-2, Bax, and caspase-3, and protein expression of Bcl-2, Bax, and cleaved caspase-3 were analyzed to evaluate NP cell apoptosis. Additionally, the intracellular reactive oxygen species (ROS) and the total superoxide dismutase (SOD) activity were analyzed to investigate the potential role of oxidative damage in this process. In the hyperosmolarity culture, NP cells showed a significantly increased cell apoptosis rate and caspase-3 activity, an up-regulated expression of Bax and caspase-3/cleaved-caspase-3 and a down-regulated expression of Bcl-2. However, CDMP-2 partly inhibited these effects of hyperosmolarity culture on NP cells. Additionally, the hyperosmolarity culture significantly increased ROS content and decreased the total SOD activity compared with the in situ-osmolarity culture, whereas exogenous CDMP-2 partly decreased the ROS content and increased the total SOD activity in the hyperosmolarity culture. In conclusion, CDMP-2 is effective in attenuating hyperosmolarity environment-induced NP cell apoptosis, and this process may be mediated through inhibiting oxidative stress damage. The present study indicates that CDMP-2 may be helpful to retard hyperosmolarity niche-mediated disc degeneration.