Bone Abstracts

FDA guidelines recommend the sheep as large animal model for osteoporosis. Studies of osteoporosis induction use dual energy x-ray absorptiometry (DEXA) to evaluate bone status. Experimentally, the T-score is calculated based on reference bone mineral density (BMD) values of animals before treatment (0 M). Whereas clinically the reference BMD represents values of an independent group of patients around 30 years old. The study hypothesize that the use of additional independent reference group will increase stringency of the acquired T-score.

Thirty-one female merino land sheep with an average age of 5.5 years were used for osteoporosis induction. Following groups were compared: (i) control-group (C; n=8); (ii) ovariectomized group (OVX; n=7); (iii) OVX combined with a deficient diet (OVXD; n=8); (iv) OVXD combined with methylprednisolone administration (OVXDS; n=8). Further, an independent group of 32 healthy sheep (4–6 years old) were taken as a reference group. BMD was measured at 0 M, 3 M and 8 M. BMD of clinically relevant regions; femur head and lumbar vertebrae (LV) were calculated.

Initially peak bone mass was tested for all animals pre-treatment. Fluctuation in BMD values peaked twice at 5 years and at 9 years of age. However, the BMD drop was dramatic after 9 years. The T score depending on the 0 M as reference reflected a lower score in the OVXDS at 3 M and 8 M (−3 and −4.2, respectively). However, utilizing the independent reference group, the T-score of the OVXD declined into −1.8 at 3 M and −2.8 at 8 M.

Triple therapy has successfully reduced the BMD of sheep model. The use of an independent reference group changed the interpretation of the data; thusly calculated osteoporotic bone status at 3M in OVXDS group became osteopenic. Internal reference might falsify T-score results, and is more suitable for Z-score calculation. Therefore, a collective online database can enhance experimental T-score calculation.