Journal of Dental Research, Vol 72, 1351-1355, Copyright © 1993 by International & American Associations for Dental Research Online Journals
Effect of centrifugal force on growth of mouse osteoblastic MC3T3-E1 cells in vitro
H. Inoue, O. Nakamura, Y. Duan, Y. Hiraki and M. Sakuda
Department of Orthodontics, Osaka University Faculty of Dentistry, Japan.
The effect of biomechanical force on growth of skeletal tissue was studied
in monolayer cultures of mouse osteoblastic MC3T3-E1 cells which were
centrifuged at 320 g for 15 min to 72 h in a CO2 incubator. Centrifugation
of the cells for 30 min in low concentrations (0.3 or 1%) of fetal bovine
serum (FBS) caused a two-fold increase of [3H]thymidine incorporation at 20
h from the start of centrifugation. However, centrifugation under 10% FBS
caused no increase in [3H]thymidine incorporation into DNA. Under 0.3% FBS,
[3H]thymidine incorporation increased in a manner dependent on the period
of centrifugation and reached a maximum when the cells were centrifuged for
3 h. Stimulation of DNA synthesis by centrifugation was abolished in the
presence of H-7, an inhibitor of protein kinase C. Moreover, conditioned
medium collected from the centrifuged cultures increased [3H]thymidine
incorporation by two-fold over the basal when added to a quiescent culture
of MC3T3-E1 cells. These results suggest that centrifugal force stimulates
growth of osteoblastic cells through autocrine secretion of some diffusible
growth-promoting activity. On the other hand, centrifugation of the cells
inhibited induction by FBS of alkaline phosphatase activity and
calcium-uptake, two indices of the differentiated phenotype of osteoblasts.
