Existing sheep osteoporosis models exhibit disadvantages, due to failure of reliable induction of substantial bone loss, lack of comparability to the human condition, challenging surgical procedures or serious ethical concerns. This study aimed to evaluate the suitability of the old sheep as a model for senile osteopenia.
Lumbar vertebral bodies (L3-L5) of old (6-10 years; n=41 vertebrae) and young (2-4 years; n=30 vertebrae) female merino sheep were analyzed by bone densitometry, quantitative histomorphometry, and biomechanical testing of the central spongious region.
Old animals showed similar bone mineral density of the vertebral bodies, but significantly decreased structural (BV/TV ratio, 40.2 ± 0.6% versus 44.8 ± 0.7% for young sheep, 10.4% decrease) and bone formation parameters (OV/TV, 0.2 ± 0.1% versus 0.3 ± 0.1% for young sheep, 24.2% decrease; OS/BS, 3.1 ± 1.2% versus 3.3 ± 0.7% for young sheep, 5.5% decrease), as well as significantly increased bone erosion (Oc.S/BS; 0.3 ± 0.1% versus 0.1 ± 0.1 % for young sheep, 2.2-fold increase). This resulted in significantly decreased biomechanical properties (compression strength, 23.7 ± 1.0 MPa versus 26.7 ± 1.1 MPa for young sheep, 11.4% decrease).
The old sheep may provide a suitable model of senile osteopenia with thinned bone structure, diminished bone formation, and augmented bone erosion. In addition, the underlying physiological aging concept eliminates challenging surgical procedures or ethical concerns and may be well representative of the human condition.