| The eruption of teeth and the replacement of deciduous teeth are normal physiological phenomenon in children oral cavity. The formation of erupt pathway and resorption of deciduous teeth roots are the prerequisite of teeth eruption and replacement. Osteoclasts take part in these process and play an important role, experiments in vivo have established that tooth eruption fails in the absence of parathyroid hormone -related protein action in the microenvironment of the tooth because of the failure of osteoclastic bone resorption on the coronal tooth surface to form an eruption pathway. So it is significant to study the activation and differentiation of osteoclasts for understanding and control of teeth eruption and replacement.1. The research of various kinds osteotropic hormones in vitroOsteoclasts are the multinucleated giant cells that locate at bone-resorbing sites, which develop from hematopoietic cells of monocyte/macrophage lineage. Under suitable stimulation, the stem cells in hematopoietic tissues can different into mononuclear precursors and fuse into the multinucleated osteoclasts. But the mechanism of activation and differentiation of osteoclasts has not been understanded5completely, the main method to research the mechanism is cell culture. Several lines of evidence have suggested that many cytokine such as 1,25 (OH) 2Ds ,IL, M-CSF, PTH, PGEa can induce the differentiation of osteoclasts, osteoclast different factor(ODF) is also needed in these process. At present, the culture of osteoclasts in vitro is fairly difficult, and cell quantity obtained is few, the osteoclasts purity is low(<10%), all these make it difficult to study the biological characteristics of osteoclasts. So it is important to look for a better method to induce osteoclasts formation in vitro. In our study, we developed a co-culture system with rat spleen cells and osteoblastic cells, to investigate and compare the effect of different cytokine on the formation of osteoclasts in vitro. We also investigated the effect of compound cytokine in this study. The main results of our researches are below:1.1 The formation of rat osteoclasts needs the regulation of osteotropic hormones, the effect of 1,25 (OH) 203 is most powerful.1.2 The effect of compound cytokine is more powerful than single cytokine, the results used by 1,25 (OH) 2D3 and M-CSF combined or 1,25 (OH) 2D3 and PTH combined are best, cell purity reached 20%.2. The expression and role of integrins in osteoclasts.Integrins are a large family of cell surface receptors composed of non-covalently bound alpha and beta subunits which interact with extracellular matrix molecules. They have many isoforms and express in various cells, mediate recognition and adhesiveness between cells, or cells and extracellular matrix, and associate with transmission of signals across the plasma membrane. It was shown that there are integrins expression in osteoclasts, they play an important role in osteoclasts move and differentiation. Several signaling and adaptor molecules were6found to be involved in integrin-dependent signaling pathways, integrins link the adhesion of osteoclasts to the bone matrix too. The expression level of integrins is key to osteoclast function, integrin a v P 3, a v P i > a 5 P i - a 2 P i have been identified in osteoclasts, and the alpha(v)beta(3) integrin is highly expressed in osteoclasts. The present study is to investigate the expression of alpha v beta 3 integrin in osteoclast of various period in vitro by using in situ hybridization technique. Results are below:2.1 After cultured for 3 days the mRNA of alpha v beta 3 integrin in mononucleated osteoclast precursors were observed, on the fifth day multinucleated and TRAP positive cells were found. This result suggested alpha v beta 3 integrin appears in early peroid of osteoclasts formation and can be used to identify the osteoclasts as a sensitive measure.2.2 On the eighth day of culture, the expression level of alpha v beta 3 integrin was highest, fo... |
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