Showing papers by "Masamichi Takami published in 2013"
TL;DR: Results indicate that OCP suppresses the chondrogenic differentiation of ATDC5 cells, at least in part, at the Sox6 transcription level.
Abstract: Implantation of octacalcium phosphate (OCP), a hydroxyapatite precursor, has been reported to induce chondrogenesis in vivo. In this study, we examined the effects of OCP on the chondrogenic differentiation of mouse chondroblastic ATDC5 cells in vitro. Contrary to our expectation, chondrogenic differentiation of ATDC5 cells evaluated by the mRNA expression of Col2a1, Acan and Col10a1 was suppressed by OCP. Among Sox9, Sox5 and Sox6, essential transcription factors for chondrogenesis, the expression of Sox6 mRNA was markedly lowered by OCP. Whereas ATDC5 cells dissolved OCP to liberate calcium and inorganic phosphorus, increased calcium or phosphate in the medium had little effect on the differentiation of these cells. Direct contact of ATDC5 cells with OCP was required to suppress the expression of Col2a1 and Sox6 mRNAs, whereas the introduction of Sox6 short interfering RNA lowered the expression of Col2a1 mRNA. On the other hand, the forced expression of Sox6 protein partially but significantly, restored the expression of Col2a1 mRNA suppressed by OCP. These results indicate that OCP suppresses the chondrogenic differentiation of ATDC5 cells, at least in part, at the Sox6 transcription level.
15 citations
TL;DR: It is found that Car9 mRNA and CA IX were expressed in proliferating but not hypertrophic chondrocytes, suggesting a possible involvement of cAMP-dependent pathway, at least in part, in induction of Col10a1 expression by down-regulation of Car9.
Abstract: Carbonic anhydrase (CA) IX is a transmembrane isozyme of CAs that catalyzes reversible hydration of CO2. While it is known that CA IX is distributed in human embryonic chondrocytes, its role in chondrocyte differentiation has not been reported. In the present study, we found that Car9 mRNA and CA IX were expressed in proliferating but not hypertrophic chondrocytes. Next, we examined the role of CA IX in the expression of marker genes of chondrocyte differentiation in vitro. Introduction of Car9 siRNA to mouse primary chondrocytes obtained from costal cartilage induced the mRNA expressions of Col10a1, the gene for type X collagen α-1 chain, and Epas1, the gene for hypoxia-responsible factor-2α (HIF-2α), both of which are known to be characteristically expressed in hypertrophic chondrocytes. On the other hand, forced expression of CA IX had no effect of the proliferation of chondrocytes or the transcription of Col10a1 and Epas1, while the transcription of Col2a1 and Acan were up-regulated. Although HIF-2α has been reported to be a potent activator of Col10a1 transcription, Epas1 siRNA did not suppress Car9 siRNA-induced increment in Col10a1 expression, indicating that down-regulation of CA IX induces the expression of Col10a1 in chondrocytes in a HIF-2α-independent manner. On the other hand, cellular cAMP content was lowered by Car9 siRNA. Furthermore, the expression of Col10a1 mRNA after Car9 silencing was augmented by an inhibitor of protein kinase A, and suppressed by an inhibitor for phosphodiesterase as well as a brominated analog of cAMP. While these results suggest a possible involvement of cAMP-dependent pathway, at least in part, in induction of Col10a1 expression by down-regulation of Car9, more detailed study is required to clarify the role of CA IX in regulation of Col10a1 expression in chondrocytes.
7 citations
TL;DR: Because of its long half-life in the body, subcutaneous denosumab administrations every 6 months are sufficient to obtain inhibitory effects on bone resorption, suggesting that this agent is more efficacious than bisphosphonates, which are presently used as anti-bone resorptive drugs.
Abstract: Denosumab (called RANMARK(®) in Japan), an anti-bone resorptive drug, is a complete human type monoclonal antibody that targets the osteoclast differentiation factor receptor activator of NF-κB ligand (RANKL). Using advanced gene-engineering techniques, Amgen Inc. (USA) has developed the drug, and it is now utilized in Japan for treatment of cancerous bone lesions associated with multiple myeloma and bone metastasis. On the other hand, denosumab has also shown inhibitory effects on bone resorption seen in patients with osteoporosis, rheumatoid arthritis, and Paget's disease, thus its range of use for medical treatment is expected to widen. Because of its long half-life in the body, subcutaneous denosumab administrations every 6 months are sufficient to obtain inhibitory effects on bone resorption, suggesting that this agent is more efficacious than bisphosphonates, which are presently used as anti-bone resorptive drugs. However, hypocalcemia might develop in patients with massive renal dysfunction. Denosumab binds to a specific loop structure of the RANKL molecule and inhibits its interaction with its receptor RANK. When labeled with radioactivity, denosumab was detected in lymph nodes and the spleen after subcutaneous administration, indicating its binding to RANKL expressed in those tissues. Thus, many medical doctors and investigators are interested in the inhibitory effects of denosumab on bone resorption as well as its mode of action.
1 citations