Insulin-like growth factor-1 treatment prevents anti-Fas antibody-induced apoptosis in endplate chondrocytes

Smad7 Is Highly Expressed in Human Degenerative Discs and Participates in IL-1β-Induced Apoptosis of Rat AF Cells via the Mitochondria Pathway

Background. Abnormal Smad7 expression can lead to apoptosis in different cell types. Previously, we found high expression of Smad7 in rat degenerative discs. However, the exact role of Smad7 in the apoptosis of disc cells and the possible underlying mechanism remain unclear. Methods. Degenerative and nondegenerative human lumbar intervertebral discs were collected from patients during operation. The expressions of SMAD7 mRNA and protein in the different components of these discs were measured with real-time PCR and Western blotting, respectively. Annulus fibrosus (AF) cells were isolated and cultivated from the discs of young healthy rats. Smad7 in the AF cells was overexpressed with adenovirus and knocked down with siRNA. IL-1β was used to induce apoptosis in the AF cells. Loss-and-gain cell function experiments were performed to show the effect of Smad7 on the apoptosis of AF cells. The function recovery experiments were performed to verify whether Smad7 regulates the apoptosis of AF cells through the mitochondria-mediated pathway. Results. Both the mRNA and protein expressions of Smad7 were significantly higher in the different components of human degenerative discs than in those of the nondegenerative discs. IL-1β stimulated apoptosis while upregulating the Smad7 expression in the AF cells in vitro. Overexpression of Smad7 in AF cells exaggerated the IL-1β-induced apoptosis in the cells while knockdown of Smad7 expression suppressed this apoptosis. With the exaggerated apoptosis in the AF cells with Smad7 overexpression, both active cleaved caspase-3 and cleaved caspase-9, the ratio of Bax/Bcl-2, and Cyt-c increased significantly. However, the inhibitor of caspase-9, Z-LEHD-FMK, significantly diminished the apoptosis in these cells. Conclusion. Smad7 is highly expressed in human degenerative discs and participates in IL-1β-induced apoptosis of rat AF cells via the mitochondria pathway. Smad7 may be a potential target for the prevention and treatment of degenerative disc disease.

Modulation of cartilage's response to injury: Can chondrocyte apoptosis be reversed?

Osteoarthritis is characterized by a chronic, progressive and irreversible degradation of the articular cartilage associated with joint inflammation and a reparative bone response. More than 100 million people are affected by this condition worldwide with significant health and welfare costs. Our available treatment options in osteoarthritis are extremely limited. Chondral or osteochondral grafts have shown some promising results but joint replacement surgery is by far the most common therapeutic approach. The difficulty lies on the limited regeneration capacity of the articular cartilage, poor blood supply and the paucity of resident progenitor stem cells. In addition, our poor understanding of the molecular signalling pathways involved in the senescence and apoptosis of chondrocytes is a major factor restricting further progress in the area. This review focuses on molecules and approaches that can be implemented to delay or even rescue chondrocyte apoptosis. Ways of modulating the physiologic response to trauma preventing chondrocyte death are proposed. The use of several cytokines, growth factors and advances made in altering several of the degenerative genetic pathways involved in chondrocyte apoptosis and degradation are also presented. The suggested approaches can help clinicians to improve cartilage tissue regeneration.

Ovarian cancer G protein-coupled receptor 1 is involved in acid-induced apoptosis of endplate chondrocytes in intervertebral discs

Ovarian cancer G protein-coupled receptor 1 (OGR1) has been shown to be a receptor for protons. We investigated the role of proton-sensing G protein-coupled receptors in the apoptosis of endplate chondrocytes induced by extracellular acid. The expression of proton-sensing G protein-coupled receptors was examined in rat lumbar endplate chondrocytes. Knockdown of OGR1 was achieved by transfecting chondrocytes with specific short hairpin RNA (shRNA) for OGR1. Apoptotic changes were evaluated by DNA fragmentation ELISA, electron microscopy, and flow cytometry. Intracellular calcium ([Ca(2+) ]i) was analyzed with laser scanning confocal microscopy. The mechanism of OGR1 in acid-induced apoptosis of endplate chondrocytes was also investigated. We found that OGR1 was predominantly expressed in rat endplate chondrocytes, and its expression was highly upregulated in response to acidosis. Knocking down OGR1 with shRNAs effectively attenuated acid-induced apoptosis of endplate chondrocytes and increased [Ca(2+) ]i. Blocking OGR1-mediated [Ca(2+) ]i elevation inhibited acid-induced calcium-sensitive proteases such as calpain and calcineurin, and also inhibited the activation of Bid, Bad, and Caspase 3 and cleavage of poly (ADP-ribose) polymerase (PARP). OGR1-mediated [Ca(2+) ]i elevation has a crucial role in apoptosis of endplate chondrocytes by regulating activation of calcium-sensitive proteases and their downstream signaling.

Multi-target lentivirus specific to hepatocellular carcinoma: in vitro and in vivo studies

BACKGROUND & AIMS

We aimed at investigating the effects of the targeted transduction of the Wtp53-pPRIME-miR30-shRNA gene into liver cancer cells, under the mediation of anti-alpha fetoprotein scFv-directed lentivirus, and the inhibitory effect of this system on liver cancer cells.

METHODS

The result of infection was observed by fluorescence microscopy. Polymerase chain reaction and Western blotting were used to demonstrate the successful transduction and transcription of the Wtp53-pPRIME-miR30-shRNA-IGF1R gene. Cell growth was observed via the Cell-Counting Kit-8 Method, and cell apoptosis was detected by terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling. To observe further the effects of AFP-Wtp53-pPRIME-miR30-shRNA-IGF1R therapy in animals, models of BALB-C nude mice bearing subcutaneous human hepatocellular carcinoma were established. The influence of the growth of subcutaneously transplanted tumor, expression of Wtp53 protein, apoptosis, and microvessel formation on the overall level of AFP-Wtp53 pPRIME-miR30-shRNA-IGF1R were also evaluated.

RESULTS

Recombinant lentivirus was successfully constructed, and its functional plaque-forming unit titer was determined as 4.58 × 10(9)plaque-forming units/ml. A positive strand was detected by polymerase chain reaction and Western blotting. Lentiviral construction worked effectively in AFP-positive liver cancer cells. In vitro and in vivo experiments showed that the recombinant lentivirus was more efficacious in inhibiting the proliferation of Hep3B cells.

CONCLUSIONS

The Wtp53-pPRIME-miR30-shRNA gene can be subjected to targeted transduction into liver cancer cells under the mediation of anti-alpha fetoprotein scFv-directed lentivirus. The Wtp53-pPRIME-miR30-shRNA system has targeting ability and lethal effects on liver cancer cells.

Both endoplasmic reticulum and mitochondria are involved in disc cell apoptosis and intervertebral disc degeneration in rats

Intervertebral disc cell apoptosis occurs through either death receptor or mitochondrial pathway, but whether disc cell apoptosis is also mediated by the endoplasmic reticulum (ER) pathway remains unclear. The objective of this study was to investigate whether ER and mitochondria are co-involved in disc cell apoptosis and intervertebral disc degeneration (IVDD) in rats. Forty-eight rats were used for in vivo experiments. IVDD was characterized by X-ray and histomorphology examination, disc cell apoptosis was detected by TUNEL staining, and the co-involvement of ER and mitochondria in apoptosis was determined by immunohistochemical staining for GRP78, GADD153, caspase-12, and cytochrome C. Additional eight rats were used for annular cell isolation and culture. After sodium nitroprusside treatment, annular cell apoptosis was observed morphologically and quantified by flow cytometry; the expression of biomarkers of ER stress and mitochondrial dysfunction were analyzed by reverse transcriptase PCR (RT-PCR), fluorescence double labeling, and Western blot; and mitochondrial membrane potential was detected by 5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbo cyanine iodide (JC-1) staining. Finally, NS3694 and Z-ATAD-FMK were employed to inhibit the formation of apoptosome complex and the activation of caspase-12, respectively, and apoptotic incidence and caspase-9 activity were assayed. We found that IVDD, induced by unbalanced dynamic and static forces in the rats, was accompanied by increased disc cell apoptosis and enhanced expression of GRP78, GADD153, caspase-12, and cytochrome C. Annular cell apoptosis induced by sodium nitroprusside was confirmed by morphologic observation and flow cytometry. With increased apoptosis, the expression of GRP78, GADD153, and caspase-12 upregulated, mitochondrial membrane potential decreased, and accumulation of cytochrome C in the cytosol manifested. Furthermore, NS3694 and Z-ATAD-FMK dramatically suppress annular cell apoptosis and caspase-9 activity. In conclusion, disc cell apoptosis mediated simultaneously by ER and mitochondria plays a potent role in IVDD.

IGF-1 regulation of type II collagen and MMP-13 expression in rat endplate chondrocytes via distinct signaling pathways

OBJECTIVE

Abnormal maturation and ossification of the endplate chondrocytes play a central role in the pathogenesis of degenerative disorders of the cervical spine. It is widely held that insulin like growth factor-1 (IGF-1) stimulates chondrocyte proliferation and inhibits chondrocyte terminal differentiation both in vitro and in vivo. However, the mechanism underlying such regulation is not fully understood. The present study aimed to determine the role of IGF-1 on the mRNA expression of collagen type II, alpha 1 (Col2a1) and matrix metallopeptidase 13 (MMP-13) in rat endplate chondrocytes. The possible pathways that transduce IGF-1 effects such as phosphatidylinositol-3 (PI-3)-kinase (PI3K) and mitogen activated protein kinase (MAPK) were also investigated in these cells.

METHODS

Cultured endplate chondrocytes harvested from rat cervical spines were treated with IGF-1 (100ng/ml), and the changes in Col2a1 and MMP-13 mRNA were monitored with real-time polymerase chain reaction (PCR). MMP-13 activity was also assayed. Activation of signaling proteins was evaluated by western blot analysis. Cells were also treated with pharmacological agents that block PI3K and MAPK signaling pathways.

RESULTS

IGF-1 increased Col2a1 mRNA expression in rat endplate chondrocytes in a time- and dose-dependent manner. IGF-1 treatment resulted in a fourfold increase of Col2a1 mRNA with the effect maximizing at 24h. In contrast, IGF-1 treatment for 24h caused a roughly 50% reduction in MMP-13 mRNA. Similar effects were seen on the protein levels of type II collagen (col2) and MMP-13. Consistent with these results, IGF-1 also repressed MMP-13 activity. IGF-1 activated both the PI3K and the extracellular signal-regulated kinase (ERK) pathways as evidenced by phosphorylation of either Akt or ERK1/2 (respectively). The PI3K inhibitor Wartmannin significantly inhibited the IGF-1 effect on Col2a1 mRNA expression but did not affect IGF-1-induced repression of MMP-13 expression. In contrast, the ERK/MAPK inhibitor PD98059 significantly inhibited the effect of IGF-1 on MMP-13 mRNA repression and enhanced IGF-1-induced Col2a1 mRNA expression.

CONCLUSIONS

In rat endplate chondrocytes the PI3K pathway mainly transduces IGF-1 effect on col2 expression while the ERK pathway mediates IGF-1 effect on MMP-13 expression.

IGF2-driven PI3 kinase and TGFbeta signaling pathways in chondrogenesis

Insulin-like growth factor-2 (IGF2) is essential for fetal development as well as maintenance of adult organs such as brain and liver. Although genetic polymorphisms of IGF2 are linked to cytoskeletal variations little is known about the mechanisms of IGF2 action in proliferation and differentiation of chondrocytes for skeletal growth. A genome-wide mRNA expression analysis using C28/I2 chondrocyte cells studied potential signaling pathways underlying the responses to IGF2. Microarray data predicted involvement of the phosphatidylinositol 3-kinase (PI3K) and transforming growth factor beta (TGFbeta) signaling pathways. Protein analyses revealed IGF2 administration activated phosphorylation of Akt and GSK3beta in the PI3K pathway. LY294002 (selective inhibitor of PI3K) blocked Akt phosphorylation and abolished IGF2-driven elevation of the mRNA levels of the proteoglycans, Aggrecan and Versican. LY294002 did not suppress upregulation of TGFbeta mRNA induced by IGF2, so IGF2 activates PI3K and TGFbeta pathways. IGF2-driven transcriptional activation of proteoglycan genes such as Aggrecan and Versican is mediated by the PI3K pathway.

Association of a single nucleotide polymorphism in the insulin-like growth factor-1 receptor gene with spinal disc degeneration in postmenopausal Japanese women

STUDY DESIGN

An association study investigating the genetic etiology for spinal disc degeneration.

OBJECTIVE

To determine the association of single-nucleotide polymorphism (SNP) in the insulin-like growth factor-1 receptor (IGF1R) with spinal disc degeneration.

SUMMARY OF BACKGROUND DATA

Insulin-like growth factor-1 (IGF-1) signaling pathway is involved in cartilage development and homeostasis, suggesting that genetic variations of genes involved in this pathway may affect the pathogenesis of cartilage-related diseases, such as disc degeneration.

METHODS

We evaluated the presence of endplate sclerosis, osteophytes, and narrowing of disc spaces in 434 Japanese postmenopausal women. A SNP in the IGF1R gene at intron 1 was determined using TaqMan polymerase chain reaction method.

RESULTS

We compared those who carried the G allele (GG or GC, n = 290) with those who did not (CC, n = 144). We found that the subjects with the G allele (GG or GC) were significantly over-represented in the subjects having higher disc narrowing score (P = 0.0033; odds ratio, 2.04; 95% confidence interval, 1.27-3.29 by logistic regression analysis).

CONCLUSION

We suggest that a genetic variation at the IGF1R gene locus is associated with spinal disc degeneration, in line with the involvement of the IGF1R gene in the cartilage metabolism.

Interleukin-1β enhances the effect of serum deprivation on rat annular cell apoptosis

Excessive apoptosis of disc cells is believed to play an important role in intervertebral disc (IVD) degeneration. It has been shown that interleukin-1beta (IL-1beta) is involved in the failure of disc matrix by suppressing the synthesis of matrix components and stimulating the expression of matrix metalloproteinases. However, whether IL-1beta induces disc cell apoptosis is still unclear. The objective of this study was to investigate the effect of IL-1beta on the apoptosis of rat annular cells cultured with or without serum supplement. First-passage rat annular cells were cultured with 0% or 10% fetal bovine serum (FBS) supplement and stimulated with 0, 10, 20 or 50 ng/ml IL-1beta for 12, 24 or 48 h. Apoptotic incidences were quantified by flow cytometry, morphologic changes in apoptotic cells were visualized by Hoechst 33258 staining and phase-contrast microscopy, and caspase-3 activity was also determined. When rat annular cells were cultured with 10% FBS supplement, no significant changes in apoptotic incidences, apoptotic morphology and caspase-3 activity were observed even when cells were stimulated with 50 ng/ml IL-1beta for 48 h. In contrast, serum deprivation for 24 h led to an increase in apoptotic incidences, the number of apoptotic nuclei and caspase-3 activity, and IL-1beta significantly increased the effects of serum deprivation in a dose-dependent manner. Our results indicate that IL-1beta alone is not a sufficient stimulus to induce disc cell apoptosis and that in order to suppress disc cell apoptosis, improving the nutrient supply to the disc may be more effective than antagonizing the adverse effects of IL-1beta.

The cell biology of intervertebral disc aging and degeneration

Intervertebral disc degeneration, which mimics disc aging but occurs at an accelerated rate, is considered to be related to neck or low back pain and disc herniation. Degenerated discs show breakdown of the extracellular matrix and thus fail to bear the daily loadings exerted on the spine. Rather than a passive process of wear and tear, disc degeneration is an aberrant, cell-mediated response to progressive structural failure due to aging and other environmental factors such as abnormal mechanical stress. With aging and degeneration, disc cells undergo substantially biologic changes, including alternation of cell type in the nucleus pulposus, increased cell density but decreased number of viable cells as a result of increased cell death and increased cell proliferation, increased cell senescence, and altered cell phenotype which is characterized by compromised capability of synthesizing correct matrix components and by enhanced catabolic metabolism. These changes are involved in the process of disc degeneration through the complicated interactions among them. To retard or reverse disc degeneration, the abnormal conditions of the decreased viable cell population and the altered cell phenotype should be corrected. As potential therapies for disc degeneration, intradiscal protein injection, gene transfer and cell implantation are being understudied in vivo. Suppression of excessive apoptosis and accelerated senescence of disc cells may be other choices for treating disc degeneration. When performing a biologic therapy in order to repair or regenerate the degenerated disc, nutrient and biomechanical factors should also be incorporated, because they are the major causes of the biologic changes experienced by disc cells. Moreover, a very early intervention is indicated by the finding that the onset of human disc degeneration occurs as early as by adolescence.

[Study of Yiqi Huayu Bushen recipe and its decomposed formulas in regulating gene expressions in degenerated cervical intervertebral discs of rats]

OBJECTIVE

To investigate the gene expression changes in the degenerated cervical intervertebral discs of rats, and to study the function of Yiqi Huayu Bushen Recipe, a compound Chinese herbal medicine, and its discomposed formulas in regulating gene expressions in the degenerated cervical intervertebral discs.

METHODS

The rat model with degenerated cervical intervertebral discs caused by imbalance between the dynamic and static forces was established. The mRNA was extracted from the cervical intervertebral discs of rats in the normal control and experiment groups, and the cDNA probes were obtained by inverse transcript. The cDNA probes were hybridized with the gene chips. The gene expression pattern was gained with a laser scanner. Image analysis, standardized ratio value and cluster analysis were used to investigate the differential of gene expressions between the control and experiment groups.

RESULTS

Cluster analysis showed that the gene chips of No.1 (Yiqi Huayu group), No.2 (Yiqi Bushen group) and No.3 (Huayu Bushen group) were in one class, while the gene chips of No.4 (untreated group) and No.5 (Yiqi Huayu Bushen group) were in the other. The gene expression of No.4 was different from the others mostly, and the gene expressions of No.2 and No.3 were similar. There were 96 genes expressed differently in three cases and among them 77 genes were already known and the expression of 48 genes were up-regulated (ratio>1.0), and 29 down-regulated (ratio<0.5). There were 25 genes expressed differently between the untreated group and the herb-treated groups.

CONCLUSIONS

The gene expressions of the degenerated rat intervertebral discs are changed. Yiqi Huayu Bushen Recipe and its discomposed formulas have the effect of regulating the expressions of related genes, such as PI(3)K, PTK, ERK3, and PH1B1.

Programmed cell death in intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is largely a process of destruction and failure of the extracellular matrix (ECM), and symptomatic IVD degeneration is thought to be one of the leading causes of morbidity or life quality deterioration in the elderly. To date, however, the mechanism of IVD degeneration is still not fully understood. Cellular loss from cell death in the process of IVD degeneration has long been confirmed and considered to contribute to ECM degradation, but the causes and the manners of IVD cell death remain unclear. Programmed cell death (PCD) is executed by an active cellular process and is extensively involved in many physiological and pathological processes, including embryonic development and human degenerative diseases. Thus, the relationship between PCD and IVD degeneration has become a new research focus of interest in recent years. By reviewing the available literature concentrated on PCD in IVD and discussing the methodology of detecting PCD in IVD cells, its inducing factors, the relationship of cell death to ECM degradation, and the potential therapy for IVD degeneration by modulation of PCD, we conclude that IVD cells undergo PCD via different signal transduction pathways in response to different stimuli, that PCD may play a role in the process of IVD degeneration, and that modulation of PCD might be a potential therapeutic strategy for IVD degeneration.