Zetos: a culture loading system for trabecular bone. Investigation of different loading signal intensities on bovine bone cylinders.

The objective of this investigation was to test the effects of different intensities (1000, 1500, 2000, 3000, and 4000 microstrain) of a physiological loading signal (jumping) on trabecular bone stiffness and osteoid thickness using the ZETOS culture and loading system. Fourty eight bovine bone samples were randomised equally across 6 groups: 5 loading groups and 1 control group. The bone samples were cultured for 26 days (DMEM high glucose medium) and subjected to mechanical stress on 23 days. The stiffness of the samples was determined each day before loading in the loading groups and every 3rd day in the control group. The stiffness measurements in the loaded groups were significantly higher than in the control group. The degree of stiffness increased continuously throughout the observation period in the 1500, 2000, and 3000 microstrain groups. Maximum stiffness was achieved in the 4000 microstrain after a very short time (8th loading day) and then remained constant to the end of the investigation. The osteoid thickness in this group was, however, not higher than in the 2000 and 3000 microstrain groups. The 2000 microstrain group showed the highest proportion of newly formed osteoid. The amounts of osteoid deposited in the 2000, 3000 and 4000 microstrain groups were significantly greater than in the control group. Moreover, a correlation between increasing intensity of the signal and increase in osteoid deposition was observed. Histological investigations were conducted on non-decalcified bone and showed a well-preserved trabecular architecture and cell morphology.