Tenascin-C expression and distribution in cultured human chondrocytes and chondrosarcoma cells

Gene expression profile in human induced pluripotent stem cells: Chondrogenic differentiation in vitro, part A

Human induced pluripotent stem cells (hiPSCs) offer promise in regenerative medicine, however more data are required to improve understanding of key aspects of the cell differentiation process, including how specific chondrogenic processes affect the gene expression profile of chondrocyte-like cells and the relative value of cell differentiation markers. The main aims of the present study were as follows: To determine the gene expression profile of chondrogenic-like cells derived from hiPSCs cultured in mediums conditioned with HC-402-05a cells or supplemented with transforming growth factor β3 (TGF-β3), and to assess the relative utility of the most commonly used chondrogenic markers as indicators of cell differentiation. These issues are relevant with regard to the use of human fibroblasts in the reprogramming process to obtain hiPSCs. Human fibroblasts are derived from the mesoderm and thus share a wide range of properties with chondrocytes, which also originate from the mesenchyme. Thus, the exclusion of dedifferentiation instead of chondrogenic differentiation is crucial. The hiPSCs were obtained from human primary dermal fibroblasts during a reprogramming process. Two methods, both involving embryoid bodies (EB), were used to obtain chondrocytes from the hiPSCs: EBs formed in a chondrogenic medium supplemented with TGF-β3 (10 ng/ml) and EBs formed in a medium conditioned with growth factors from HC-402-05a cells. Based on immunofluorescence and reverse transcription-quantiative polymerase chain reaction analysis, the results indicated that hiPSCs have the capacity for effective chondrogenic differentiation, in particular cells differentiated in the HC-402-05a-conditioned medium, which present morphological features and markers that are characteristic of mature human chondrocytes. By contrast, cells differentiated in the presence of TGF-β3 may demonstrate hypertrophic characteristics. Several genes [paired box 9, sex determining region Y-box (SOX) 5, SOX6, SOX9 and cartilage oligomeric matrix protein] were demonstrated to be good markers of early hiPSC chondrogenic differentiation: Insulin-like growth factor 1, Tenascin-C, and β-catenin were less valuable. These observations provide valuable data on the use of hiPSCs in cartilage tissue regeneration.

BMP-7 enhances cell migration and αvβ3 integrin expression via a c-Src-dependent pathway in human chondrosarcoma cells

Bone morphogenic protein (BMP)-7 is a member of the transforming growth factor (TGF)-beta superfamily, which is originally identified based on its ability to induce cartilage and bone formation. In recent years, BMP-7 is also defined as a potent promoter of cell motility, invasion, and metastasis. However, there is little knowledge of the role of BMP-7 and its cellular function in chondrosarcoma cells. In the present study, we investigated the biological impact of BMP-7 on cell motility using transwell assay. In addition, the intracellular signaling pathways were also investigated by pharmacological and genetic approaches. Our results demonstrated that treatment with exogenous BMP-7 markedly increased cell migration by activating c-Src/PI3K/Akt/IKK/NF-κB signaling pathway, resulting in the transactivation of αvβ3 integrin expression. Indeed, abrogation of signaling activation, by chemical inhibition or expression of a kinase dead form of the protein attenuated BMP-7-induced expression of integrin αvβ3 and cell migration. These findings may provide a useful tool for diagnostic/prognostic purposes and even therapeutically in late-stage chondrosarcoma as an anti-metastatic agent.

Revisiting the matricellular concept

The concept of a matricellular protein was first proposed by Paul Bornstein in the mid-1990s to account for the non-lethal phenotypes of mice with inactivated genes encoding thrombospondin-1, tenascin-C, or SPARC. It was also recognized that these extracellular matrix proteins were primarily counter or de-adhesive. This review reappraises the matricellular concept after nearly two decades of continuous investigation. The expanded matricellular family as well as the diverse and often unexpected functions, cellular location, and interacting partners/receptors of matricellular proteins are considered. Development of therapeutic strategies that target matricellular proteins are discussed in the context of pathology and regenerative medicine.

Changes in biochemical markers and prediction of effectiveness of intra-articular hyaluronan in patients with knee osteoarthritis

OBJECTIVE

Intra-articular injection of hyaluronan (HA) is frequently used to treat knee osteoarthritis (OA). We studied whether HA injections induced significant changes in levels of biochemical markers in synovial fluid (SF). In addition, we investigated the possibility of predicting the effectiveness of HA based on these biochemical markers.

METHODS

Twenty-eight patients with knee OA underwent five weekly intra-articular injections of HA. Knee pain was measured on visual analog scale (VAS) before and after the five injections. Levels of biochemical markers, including chondroitin 6-sulfate (C6S), chondroitin 4-sulfate (C4S), keratan sulfate (KS), and tenascin-C (TN-C), were determined before and after the five injections. Correlations between the biochemical markers before HA injection and the improvement of VAS after the five injections were evaluated.

RESULTS

After HA injections, levels of C6S, C4S, and KS decreased significantly. Inverse correlations were observed between the levels of TN-C and C4S before HA injection and improvement of VAS after the five injections. In contrast, no significant correlation was seen between levels of C6S and KS before injections and improvement of VAS after the five injections.

CONCLUSION

The reduction in C6S, C4S, and KS levels after HA injections reflects that HA could help maintain normal cartilage metabolism. Our findings suggest that HA injections are effective in patients whose knees contain low levels of TN-C and C4S, reflecting an early stage of OA and limited synovitis.

Expression of large tenascin-C splice variants in synovial fluid of patients with rheumatoid arthritis

Tenascin-C (TN-C) is a hexameric glycoprotein component of extracellular matrix, and alternative RNA splicing creates two major TN-C size variants (the small and large variants). The large TN-C variants play key roles in many pathologic conditions in adults, including tumorigenesis, regeneration, and inflammation. This cross-sectional study compared levels of large TN-C variants in synovial fluid of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Synovial fluid samples were obtained from knees of 26 patients with advanced RA and 79 with advanced OA. Expression of TN-C splice variants was examined using Western blotting. The levels of large TN-C variants in synovial fluid were determined by an enzyme-linked immunosorbent assay. Synovium were analyzed for TN-C by immunohistochemistry. Immunoblotting showed the presence of large TN-C variants in synovial fluid from patients with RA and OA. However, levels of large TN-C variants were fourfold higher in RA samples compared with OA samples (p < 0.01). Synovial fluid levels of TN-C in RA did not correlate with C-reactive protein levels. Immunohistochemistry of the synovium showed stronger reactivity in RA samples than in OA samples. These results indicate that local synthesis of TN-C is increased during rheumatic disease.

Differential regulation of cytokine-induced MMP-1 and MMP-13 expression by p38 kinase inhibitors in human chondrosarcoma cells: potential role of Runx2 in mediating p38 effects

OBJECTIVE

To investigate mitogen activated protein (MAP) kinase pathways for their ability to differentially regulate the expression of matrix metalloprotease (MMP)-1 and -13 in human chondrosarcoma cells using pathway-selective inhibitors.

DESIGN

Human chondrosarcoma cell lines (SW1353 and JJ012) and human articular chondrocytes (HACs) were treated with cytokines (IL-1beta and TNFalpha) and the expression of MMP-1 and -13 was analyzed. The effects of MAP kinase inhibitors on cytokine-induced expression of MMP-1 and -13 were evaluated using ELISA and Western blot analyses. The possible involvement of the Runx2 pathway in mediating p38 effects on MMP-13 expression was analyzed using promoter-reporter assays, ELISA and immunoprecipitation analyses.

RESULTS

IL-1beta and TNFalpha strongly induced the expression of MMP-1 and -13 in SW1353 cells and HACs, whereas only TNFalpha was found to induce the expression of these two MMPs in JJ012 cells. Cytokine treatment did not result in a significant increase in the activity of MMPs because of the excess production of endogenous tissue inhibitors of metalloproteases (TIMPs). Treatment with p38 kinase inhibitors (SB203580 and SB242235) strongly inhibited cytokine-induced MMP-13 expression in a dose-dependent fashion while having a somewhat weaker inhibitory effect on MMP-1 expression. In contrast, inhibitors of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) pathways did not inhibit the expression of either MMP. Overexpression of Runx2 robustly stimulated the transcriptional activation of MMP-13 but had no effect on MMP-1 expression. Furthermore, IL-1beta induced the phosphorylation of Runx2, and this effect was blocked by a p38 kinase inhibitor. Our data suggest that Runx2 is likely to be a key downstream mediator of p38 effects in the differential regulation of IL-1beta induced MMP-13 expression.

CONCLUSIONS

These studies demonstrate the differential inhibition of cytokine-induced MMP-1 and -13 expression by p38 kinase inhibitors in human chondrosarcoma cells. Our studies also suggest the involvement of Runx2, at least in part, in mediating the effects of p38 on MMP-13 expression.

Gene expression during redifferentiation of human articular chondrocytes

OBJECTIVE

The aim of the present study was to investigate gene expression during the in vitro redifferentiation process of human articular chondrocytes isolated from clinical samples from patient undergoing an autologous chondrocyte transplantation therapy (ACT).

METHOD

Monolayer (ML) expanded human articular chondrocytes from four donors were cultured in a 3D pellet model and the redifferentiation was investigated by biochemistry, histology, immunohistochemistry and microarray analysis.

RESULTS

The culture expanded chondrocytes redifferentiated in the pellet model as seen by an increase in collagen type II immunoreactivity between day 7 and 14. The gene expression from ML to pellet at day 7 included an increase in cartilage matrix proteins like collagen type XI, tenascin C, dermatopontin, COMP and fibronectin. The late phase consisted of a strong downregulation of extracellular signal-regulated protein kinase (ERK-1) and an upregulation of p38 kinase and SOX-9, suggesting that the late phase mimicked parts of the signaling processes involved in the early chondrogenesis in limb bud cells. Other genes, which indicated a transition from proliferation to tissue formation, were the downregulated cell cycle genes GSPT1 and the upregulated growth-arrest-specific protein (gas). The maturation of the pellets included no signs of hypertrophy or apoptosis as seen by downregulation of collagen type X, Matrix Gla protein and increased expression of caspase 3.

CONCLUSION

Our data show that human articular chondrocytes taken from surplus cells of patient undergoing ACT treatment and expanded in ML, redifferentiate and form cartilage like matrix in vitro and that this dynamic process involves genes known to be expressed in early chondrogenesis.

siRNA mediated inhibition of MMP-1 reduces invasive potential of a human chondrosarcoma cell line

Matrix metalloproteinases (MMPs) play a crucial role in tumor cell invasion and metastasis. Expression of MMP-1 has been reported as a prognostic predictor of recurrence in human chondrosarcoma, and studies using human chondrosarcoma cell lines indicate that MMP-1 expression levels correlate with in vitro invasiveness. These observations suggest that MMP-1 activity has a central role in cell egress from the primary tumor at an early step in the metastatic cascade. In this study, siRNA was used to investigate whether knock down of the MMP-1 gene could be used to inhibit invasiveness in a human chondrosarcoma cell line. The inhibitory effect of siRNA on endogenous MMP-1 gene expression and protein synthesis was demonstrated via RT-PCR, Northern blotting, Western blotting, collagenase activity assay, and an in vitro cell migration assay. The siRNA inhibited MMP-1 expression specifically, since it did not affect the expression of endogenous glyceraldehyde phosphate dehydrogenase (GAPDH) nor other collagenases. Most importantly, the siRNA mediated reduction in MMP-1 expression correlated with a decreased ability of chondrosarcoma cells to invade a Type I collagen matrix. The reduction of invasive behavior demonstrated by human chondrosarcoma cells transfected with MMP-1 siRNA and the specificity of this inhibition supports the hypothesis that this metalloproteinase molecule is involved in initiation of chondrosarcoma metastasis.

Chondrosarcoma cell differentiation

A mixed population of lymphocytes from a healthy donor co-existed with an established culture of allogeneic chondrosarcoma cells, during which time the tumor cells changed from malignantly transformed to benign fibroblast-like morphology; from multilayered to a monolayered growth pattern; lost their potency to grow in colonies in soft agar; and showed signs of senescence. A discussion of possible molecular mechanisms for this event is offered. If there are as yet undiscovered lymphokines that can induce reversal of the malignant geno/phenotype, the cognate gene(s) should be cloned for genetic engineering and for the mass production of the corresponding molecular mediators for clinical trials.