A role of cPLA_2 in the process when extraction socket is repaired.

造骨被认为是拔牙窝修复所必需的，cPLA_2代谢产物PGE_2对造骨功能有负调节作用。然而，cPLA_2本身是否参与骨细胞活性的调节尚不确定。在这项研究中，我们测试的可能性，cPLA_2活性是必要的破骨细胞的形成。在此基础上，我们进一步研究了cPLA_2在破骨细胞和肌细胞多核细胞形成过程中细胞融合机制的作用。cPLA_2和actin在未处理的RAW264.7细胞中分布于整个细胞质中。本实验通过应用cPLA_2特异性抑制剂或cPLA_2 siRNA，观察cPLA_2在RANKL处理的RAW264.7细胞中对多核细胞形成和骨吸收能力的调节作用。我们发现cPLA_2抑制剂C2C12多核细胞的形成也受到cPLA_2抑制剂或RNA干扰的抑制。提示cPLA_2可能参与破骨细胞的形成和成肌过程。在第47届日本口腔颌面放射学会大会（2006年5月，东京）上报告了上述结果的一部分。

Osteocasts are believed necessary for the repair of extraction socket.A cPLA_2, metabolite PGE2 has been repoted to be negative regulation of osteoclastic function. However, it is not still uncertain whether cPLA_2 per se is involved in the regulation of osteoclastic activity. In this study, we tested the possibility that cPLA_2 activity is necessary for osteoclastogenesis. Further, we investigated the role of cPLA_2 in the cell-fusion mechanism in multinucleated cell formation of osteoclasts and myocytesChanges in subcellular distributions of cPLA_2 and actin after initiation of multinucleated cell formation.Subcellular localizations of cPLA_2 and actin were analyzed by using a confocal laser scanning microscope. The cPLA_2 and actin were distributed throughout the cytoplasm of non-treated RAW264.7 cells. However, there proteins were predominantly distributed at the periphery of the RANKL-treated RAW264.7 cells.Effects of cPLA_2 inhibition in multinucleated cell formation.Next, we assessed the role of cPLA_2 in the multinucleated cell formation and in the regulation of bone resorption ability of RANKL-treated RAW264.7 cells by using the specific cPLA_2, inhibitors or the cPLA_2 siRNA. We found that the cPLA_2 inhibitors (AACOCF3 and MAFP) or cPLA_2 siRNA significantly inhibited multinucleated cell formation and in vitro bone resorption ability of RAW264.7 cells.cPLA_2 involvement in multinucleated myocyte formation of C2C12 cells.We found that multinucleated myocyte formation in C2C12 was also inhibited by the cPLA_2 inhibitors or RNA interference.Together, these results suggest that cPLA_2 may be deeply involved in osteoclastogenesis and myogenesis. A part of the above results was reported at the 47th Congress on Japanese Society for Oral and Maxillofacial Radiology (May, 2006, Tokyo).