Effects of physiologic dynamic strain on human osteoblasts

The cell activity of human bone derived cell cultures was studied after mec hanical stimulation by cyclic strain at a magnitude occurring in physiologi cally loaded bone tissue. Monolayers of subconfluently grown human bone der ived cells were stretched in rectangular silicone dishes with cyclic uniaxi al movement along their longitudinal axes. Strain was applied over two days for 30 min per day with a frequency of 1 Hz and a strain magnitude of 1000 mu strain. Cyclic stretching of the cells resulted in an increased prolife ration (10-48 %) and carboxyterminal collagen type I propeptide release (7- 49 %) of human cancellous bone derived osteoblasts while alkaline phosphata se activity and osteocalcin release were significantly reduced by 9-25 % an d 5-32 % respectively. These results demonstrate that cyclic strain at phys iologic magnitude reads to an increase of osteoblast activities related to matrix production while those activities which are characteristic for the d ifferentiated osteoblast and relevant for matrix mineralization are decreas ed.