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CULTURE IN 3D-CLINOSTAT INHIBITS TGF-beta, p38 MAPK IN DIFFERENTIATION OF HUMAN OSTEOBLASTS.  L.Yuge¹, Y. Kumei², M. Kanno¹, Y. Ikuta¹, K.Kataoka¹ and H.Kajihara^{1  1}Faculty of Medicine, Hiroshima University, Hiroshima, Japan. ²Faculty of Dentistry, Tokyo Medical and Dental University, Tokyo, Japan.

     A 3D-clinostat is a multi-directional gravity device for simulating microgravity (10^-4G).  We cultured osteoblasts in the 3D-clinostat, examining differentiation of osteoblasts in terms of cytokines, MAPK-cascade, and morphology including histological detection of minerals.  The results obtained are as follows: 1) Formation of bone nodules, alkaline phosphatase (AlPase ) activity, and calcification were detected after 21 days of culture in a normal environment but not in the 3D-clinostat. 2) Osteocalcin production is increased in the control, while it is decreased in the 3D-clinostat. 3) Phosphorylation of p38 MAPK was repressed in the 3D-clinostat, while total p38 MAPK was not changed. 4) Formation of bone nodules, AlPase activity and calcium deposits were inhibited completely by a p38 MAPK inhibitor, SB 203580, but partially by a MAPK/ERK 1/2 inhibitor, U-0126.  5) TGF-beta and IL-1 were repressed in the 3D-clinostat.  It is concluded by these results that (1) the osteogenesis is inhibited in culture in the 3D-clinostat, and (2) this inhibition is largely attributed to the suppression of p38 MAPK phosphorylation.  (3) Repression of TGF-beta and IL-1 relates to the inhibition of osteogenesis. 

      (Supported by Japan Space Forum, Space Utilization Research and the Japanese Ministry of Education)