Résumé
Raw264.7 cells were incubated with receptor activator of NF-kappa B ligand (RANKL) and α-melanocyte stimulating hormone(α-MSH) for6 d.The amount of osteoclast cells were counted by tartrate resistant acid phosphatase staining and the acid phosphatase activity was assayed.The expressions of 5 melanocortin receptors (MCR) in Raw264.7 cells were determined by RT-PCR.The results showed that the number of osteoclasts in RANKL +α-MSH group was significantly increased compared with RANKL group (P ＜ 0.05),but there was no osteoclast formation in α-MSH group.Compared with control group and α-MSH group,the acid phosphatase activities were significantly increased in RANKL group and α-MSH+RANKL group (P＜0.05).All five MCRs were expressed in the Raw264.7 cells shown by RT-PCR.These results suggest that α-MSH may promote osteoclasts formation through RANK signaling pathway.
Résumé
Objective To determine the role of epidermal growth factor receptor(EGFR) signaling in endochondral ossification.Methods Long bones,from EGFR knockout mice(EGFR-/-),wild type(EGFR+/+) and(or) heterozygous mice(EGFR+/-) were collected and Trichrome Masson staining,in situ hybridization and tartrate-resistant acid phosphatase(TRAP) staining were used to observe endochondral ossification and recruitment of osteoclasts;Osteoclast formation was observed by addition of EGFR tyrosine kinase inhibitor AG1478 to the cultured osteoclasts from bone marrow cells.Results Due to the same phenotype of EGFR+/+ and EGFR+/-,they were regarded as EGFR+/+ in our study.EGFR deficiency caused delayed primary endochondral ossification of cartilage anlage and delayed osteoclast recruitment.The hypertrophic cartilage area in EGFR-/-mice was about 5 times longer than that in EGFR+/+ mice.There was different distribution of MMP-9 between EGFR+/+ and EGFR-/-in E16.5,but there was no difference about the quantity of MMP-9 in osteoclasts between EGFR-/-and EGFR+/+.However,inhibition of EGFR signaling with AG1478 significantly decreased osteoclast formation compared with control group with DMSO(P
Résumé
Bone is a complex tissue in which resorption and formation continue throughout life. The bone tissue contains various types of cells, of which the bone forming osteoblasts and bone resorbing osteoclasts are mainly responsible for bone remodeling. Periodontal disease represents example of abnormal bone remodeling. Osteoclasts are multinucleated cells present only in bone. It is believed that osteoclast progenitors are hematopoietic origin, and they are recruited from hematopoietic tissues such as bone marrow and circulating blood to bone. Cells present in the osteoclast microenvironment include marrow stromal cells, osteoblasts, macrophages, T-lymphocytes, and marrow cells. These cells produce cytokines that can affect osteoclast formation. In vitro model systems using bone marrow cultures have demonstrated that IL-1 beta, IL-3, TNF-alpha, bFGF can stimulate the formation of osteoclasts. In contrast, IL-4 inhibits osteoclast formation. Knowledge of cytokines and bFGF that affect osteoclast formation and their capacity to modulate the bone-resorbing process should provide critical insights into normal calcium homeostasis and disorders of bone turnover such as periodontal disease, osteoporosis and Paget's disease.