[Effects of mechanical tensile stress on the expression of ICAM-1 mRNA in osteoblasts differentiated from rBMSCs]

To investigate the correlation between mechanical tensile stress and the expression of ICAM-1 mRNA in osteoblasts differentiatd from rBMSCs and elucidate the mechanism for osteoclastogenesis regulated by osteoblasts in bone modeling and remodeling during the process of orthodontic tooth movement.

rBMSCs-derived osteoblasts were isolated and cultured in vitro, and were subjected to static mechanical tensile stress of 1,3,5 kPa or dynamic tensile stress of 3, 5 kPa at 0.017 Hz with the use of cellular tension-stress system for 24 h. Controls were without any stress. Cells were collected at 0 h, 3 h, 6 h, 9 h, 12 h, 24 h and 48 h after stress loading. The expression patterns of ICAM-1 mRNA were examined by semiquantitative RT-PCR assay.

ICAM-1 mRNA level significantly decreased after mechanical tensile stress loading, either dysamic or static, compared with controls; the effects of inhibition positively correlated with the magnitude of stress (5 kPa>3 kPa>1 kPa). The inhibition effects of dynamic tensile stress groups exceeded the corresponding static stress (3,5 kPa dynamic stress>3,5 kPa static stress respectively). The expression of ICAM-1 mRNA significantly decreased at 3 h, reached the minimun transcription, as low as 23% of that of control, at 12 h, and then slightly rebounded and stayed at a considerably lower and stable level.

Mechanical tensile stress can regulate osteoclastogenesis by inhibiting the expression of ICAM-1 in osteoblasts derived from rBMSCs, it can lead to a better understanding of the molecular basis for osteoblast-osteoclast communication in bone resorption induced by application of mechanical tensile stress during orthodontic tooth movement.