Mechanically induced changes in trabecular bone architecture

Bone adapts its structure to accommodate altered mechanical environments. We have previously demonstrated that adult female BALB/cByJ mice subjected to hindlimb suspension lost 58% of the fractional trabecular bone volume (BV/TV) in the distal femur. To determine sex-related differences in bone's response to the loss of mechanical stimuli, we tested the effects of hindlimb suspension on male BALB/cByJ mice. Sixteen-week old male BALB/cByJ mice were randomly assigned to age matched control and disuse groups (n=10 each). After 3 weeks, micro-computed tomography (μCT) scanning determined indices of trabecular bone quantity and architecture in the metaphyseal and subchondral regions. Hindlimb suspension significantly decreased BV/TV in the subchondral region (-23%) and showed a trend towards decreases BV/TV in the metaphyseal region (-12%). Each region showed trends towards decreased trabecular number and connectivity density and increased trabecular spacing. These results showed that though hindlimb suspension reduced trabecular bone in both regions, only the subchondral region was affected significantly. Preliminary comparisons between male and female BALB/cByJ mice suggested that hindlimb suspension had a greater effect on trabecular bone volume in female than in male mice. Future work will determine if sex-linked characteristics influence the adaptation of bone to altered mechanical loading environments.