Stimulation of chondrogenesis in ATDC5 chondroprogenitor cells and hypertrophy in mouse by Genkwadaphnin

Involvement of ADAM12 in Chondrocyte Differentiation by Regulation of TGF-β1-Induced IGF-1 and RUNX-2 Expressions

A disintegrin and metalloproteinase 12 (ADAM12) is known to be involved in chondrocyte proliferation and maturation; however, the mechanisms are not fully understood. In this study, expression and localization of ADAM12 during chondrocyte differentiation were examined in the mouse growth plate by immunohistochemistry. Adam12 expression during ATDC5 chondrogenic differentiation was examined by real-time PCR and compared with the expression pattern of type X collagen. The clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system was used to generate Adam12-knockout (KO) ATDC5 cells. Adam12-KO and Adam12 overexpressing cells were used for analyses of ADAM12 expression with or without TGF-β1 stimulation. ADAM12 was identified predominantly in chondrocytes of the proliferative zone in mouse growth plates by immunohistochemistry. Adam12 was upregulated prior to Col10a1 during chondrogenic differentiation in wild-type ATDC5 cells. In Adam12-KO ATDC5 cells, following initiation of chondrogenic differentiation, we observed a reduction in Igf-1 expression along with an upregulation of hypertrophy-associated Runx2, Col10a1, and type X collagen protein expressions. In ATDC5 wild-type cells, stimulation with TGF-β1 upregulated the expressions of Adam12 and Igf-1 and downregulated the expression of Runx2. In contrast, in Adam12-KO ATDC5 cells, these TGF-β1-induced changes were suppressed. Adam12 overexpression resulted in an upregulation of Igf-1 and downregulation of Runx2 expression in ATDC5 cells. The findings suggest that ADAM12 has important role in the regulation of chondrocyte differentiation, potentially by regulation of TGF-β1-dependent signaling and that targeting of ADAM12 may have a role in management of abnormal chondrocyte differentiation.

neo-Clerodane Diterpenoids from Salvia polystachya Stimulate the Expression of Extracellular Matrix Components in Human Dermal Fibroblasts

Eleven neo-clerodane diterpenoids (1-11) including the new analogues 1, 2, and 10, and 3',5,6,7-tetrahydroxy-4'-methoxyflavone (12) were isolated from the aerial parts of Salvia polystachya. Polystachyne G (1) and 15-epi-polystachyne G (2) were isolated as an epimeric mixture, containing a 5-hydroxyfuran-2(5H)-one unit in the side chain at C-12 of the neo-clerodane framework. Polystachyne H (10) contains a 1(10),2-diene moiety and a tertiary C-4 hydroxy group. The structures of these compounds were established by analysis of their NMR spectroscopic and MS spectrometric data. The absolute configurations of compounds 3, 4, and 10 were determined through single-crystal X-ray diffraction analysis. The antibacterial, antifungal, and phytotoxic activities of the diterpenoids were determined. In addition, the stimulatory effect of the expression of extracellular matrix components of nine of the isolates (1-8 and 11) was assayed. Compounds 1-4, 8, and 11 increased the expression of the genes codifying for type I, type III, and type V collagens and for elastin.

Aloe-Emodin Induces Chondrogenic Differentiation of ATDC5 Cells via MAP Kinases and BMP-2 Signaling Pathways

Endochondral bone formation is the process by which mesenchymal cells condense into chondrocytes, which are ultimately responsible for new bone formation. The processes of chondrogenic differentiation and hypertrophy are critical for bone formation and are therefore highly regulated. The present study was designed to investigate the effect of aloe-emodin on chondrogenic differentiation in clonal mouse chondrogenic ATDC5 cells. Aloe-emodin treatment stimulated the accumulation of cartilage nodules in a dose-dependent manner. ATDC5 cells were treated with aloe-emodin and stained with alcian blue. Compared with the control cells, the ATDC5 cells showed more intense alcian blue staining. This finding suggested that aloe-emodin induced the synthesis of matrix proteoglycans and increased the activity of alkaline phosphatase. Aloe-emodin also enhanced the expressions of chondrogenic marker genes such as collagen II, collagen X, BSP and RunX2 in a time-dependent manner. Furthermore, examination of the MAPK signaling pathway showed that aloe-emodin increased the activation of extracellular signal-regulated kinase (ERK), but had no effect on p38 and c-jun N-terminal kinase (JNK). Aloe-emodin also enhanced the protein expression of BMP-2 in a time-dependent manner. Thus, these results showed that aloe-emodin exhibited chodromodulating effects via the BMP-2 or ERK signaling pathway. Aloe-emodin may have potential future applications for the treatment of growth disorders.

Interleukin-1β induces fibroblast growth factor 2 expression and subsequently promotes endothelial progenitor cell angiogenesis in chondrocytes

Angiogenesis is an important event in the process of arthritis. Stimulating chondrocytes with IL-1β increased the expression of FGF-2, via the IL-1RI/ROS/AMPK/p38/NF-κB signalling pathway. FGF-2-neutralizing antibody abolished ATDC5-conditional medium-mediated angiogenesis both in vitro and in vivo.

Arthritis is a process of chronic inflammation that results in joint damage. IL (interleukin)-1β is an inflammatory cytokine that acts as a key mediator of cartilage degradation, and is abundantly expressed in arthritis. Neovascularization is one of the pathological characteristics of arthritis. However, the role of IL-1β in the angiogenesis of chondrocytes remains unknown. In the present study, we demonstrate that stimulating chondrocytes (ATDC5) with IL-1β increased the expression of FGF (fibroblast growth factor)-2, a potent angiogenic inducer, and then promoted EPC (endothelial progenitor cell) tube formation and migration. In addition, FGF-2-neutralizing antibody abolished ATDC5-conditional medium-mediated angiogenesis in vitro, as well as its angiogenic effects in the CAM (chick chorioallantoic membrane) assay and Matrigel plug nude mice model in vivo. IHC (immunohistochemistry) staining from a CIA (collagen-induced arthritis) mouse model also demonstrates that arthritis increased the expression of IL-1β and FGF-2, as well as EPC homing in articular cartilage. Moreover, IL-1β-induced FGF-2 expression via IL-1RI (type-1 IL-1 receptor), ROS (reactive oxygen species) generation, AMPK (AMP-activated protein kinase), p38 and NF-κB (nuclear factor κB) pathway has been demonstrated. On the basis of these findings, we conclude that IL-1β promotes FGF-2 expression in chondrocytes through the ROS/AMPK/p38/NF-κB signalling pathway and subsequently increases EPC angiogenesis. Therefore IL-1β serves as a link between inflammation and angiogenesis during arthritis.

ATDC5: an excellent in vitro model cell line for skeletal development

The ATDC5 cell line is derived from mouse teratocarcinoma cells and characterized as a chondrogenic cell line which goes through a sequential process analogy to chondrocyte differentiation. Thus, it is regarded as a promising in vitro model to study the factors that influence cell behaviors during chondrogenesis. It also provides insights in exploring signaling pathways related to skeletal development as well as interactions with innovative materials. To date, over 200 studies have utilized ATDC5 to obtain lots of significant findings. In this review, we summarized the literature of ATDC5 related studies and emphasized the application of ATDC5 in chondrogenesis. In addition, the general introduction of ATDC5 including its derivation and characterization is covered in this article.

Matrilin-3 chondrodysplasia mutations cause attenuated chondrogenesis, premature hypertrophy and aberrant response to TGF-β in chondroprogenitor cells

Studies have shown that mutations in the matrilin-3 gene (MATN3) are associated with multiple epiphyseal dysplasia (MED) and spondyloepimetaphyseal dysplasia (SEMD). We tested whether MATN3 mutations affect the differentiation of chondroprogenitor and/or mesenchymal stem cells, which are precursors to chondrocytes. ATDC5 chondroprogenitors stably expressing wild-type (WT) MATN3 underwent spontaneous chondrogenesis. Expression of chondrogenic markers collagen II and aggrecan was inhibited in chondroprogenitors carrying the MED or SEMD MATN3 mutations. Hypertrophic marker collagen X remained attenuated in WT MATN3 chondroprogenitors, whereas its expression was elevated in chondroprogenitors expressing the MED or SEMD mutant MATN3 gene suggesting that these mutations inhibit chondrogenesis but promote hypertrophy. TGF-β treatment failed to rescue chondrogenesis markers but dramatically increased collagen X mRNA expression in mutant MATN3 expressing chondroprogenitors. Synovium derived mesenchymal stem cells harboring the SEMD mutation exhibited lower glycosaminoglycan content than those of WT MATN3 in response to TGF-β. Our results suggest that the properties of progenitor cells harboring MATN3 chondrodysplasia mutations were altered, as evidenced by attenuated chondrogenesis and premature hypertrophy. TGF-β treatment failed to completely rescue chondrogenesis but instead induced hypertrophy in mutant MATN3 chondroprogenitors. Our data suggest that chondroprogenitor cells should be considered as a potential target of chondrodysplasia therapy.

Isopsoralen Induces Differentiation of Prechondrogenic ATDC5 Cells via Activation of MAP Kinases and BMP-2 Signaling Pathways

Endochondral bone formation is the process by which mesenchymal cells condense to become chondrocytes, which ultimately form new bone. The process of chondrogenic differentiation and hypertrophy is critical for bone formation and as such is regulated by many factors. In this study, we aimed to indentify novel factors that regulate chondrogenesis. We investigated the possible role of isopsoralen in induction of chondrogenic differentiation in clonal mouse chondrogenic ATDC5 cells. Isopsoralen treatment stimulated the accumulation of cartilage nodules in a dose-dependent manner. Further, ATDC5 cells treated with isopsoralen were stained more intensely with Alcian blue than control cells, suggesting that isopsoralen increases the synthesis of matrix proteoglycans. Similarly, isopsoralen markedly induced the activation of alkaline phosphatase activity compared with control cells. Isopsoralen enhanced the expressions of chondrogenic marker genes such as collagen II, collagen X, OCN, Smad4 and Sox9 in a time-dependent manner. Furthermore, isopsoralen induced the activation of extracellular signal-regulated kinase (ERK) and p38 MAP kinase, but not that of c-jun N-terminal kinase (JNK). Isopsoralen significantly enhanced the protein expression of BMP-2 in a time-dependent manner. PD98059 and SB 203580, inhibitors of ERK and p38 MAPK, respectively, decreased the number of stained cells treated with isopsoralen. Taken together, these results suggest that isopsoralen mediates a chondromodulating effect by BMP-2 or MAPK signaling pathways, and is therefore a possible therapeutic agent for bone growth disorders.