Effects of Simulated Microgravity on Human Osteoblast-Like Cells in Culture

Toshiyuki Kunisada, Akira Kawai, Hajime Inoue, Masayoshi Namba

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


Physiological strain plays an important role in maintaining the normal function and metabolism of bone cells. It is well known that the mineral content of astronauts' bones decreases during spaceflight. Thus, gravity is one of the important factors in the muscloskeletal system. The vector-free horizontal clinostat has been used to simulate conditions of microgravity for examining such effects on cells in culture. We analyzed the effects of simulated microgravity using a horizontal clinostat on cultured osteoblast-like cells (HuO9 cell line). Total cellular protein, which was measured as an indication of cell proliferation, was not significantly inhibited under simulated microgravity conditions. No morphological changes were detected under microgravity conditions by phase-contrast microscopy. However, the alkaline phosphatase (ALP) activity and osteocalcin production of the HuO9 cells decreased significantly under microgravity conditions. Our data indicate that simulated microgravity directly inhibits some differentiation phenotypes and some functions of osteoblasts. On the other hand, the addition of 1,25-dihydroxy-vitamin D3 (1,25-(OH)2-D3) increased ALP activity under simulated microgravity conditions, although the total activity of ALP in the cells treated with 1,25-(OH)2-D3 was still lower under simulated microgravity conditions than that in the control cells. However, the cells under simulated microgravity conditions showed a greater enhancement of ALP activity by treatment with 1,25-(OH)2-D3.

Original languageEnglish
Pages (from-to)135-140
Number of pages6
JournalActa medica Okayama
Issue number3
Publication statusPublished - Jun 1997


  • Alkaline phosphatase
  • Microgravity
  • Osteoblast
  • Osteocalcin

ASJC Scopus subject areas

  • General Biochemistry,Genetics and Molecular Biology


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