Pinealectomy affects bone mineral density and structure - an experimental study in sheep

Female sheep were arranged into four groups: Control, surgically ovariectomized (Ovx), surgically pinealectomized (Px) and Ovx+Px. Before and 6 months after surgery, iliac crest biopsies were harvested and structural parameters were measured using μCT. Markers of bone formation and resorption were determined. To evaluate long term changes after pinealectomy, bone mineral density (BMD) was analyzed at the distal radius at 0, 3, 9, 18 and 30 months.Cancellous bone volume (BV/TV) declined after 6 months by -13.3% Px and -21.5% OvxPx. The bone loss was due to increased trabecular separation as well as decreased thickness. The histomorphometric quantification and determination of collagen degradation products showed increased bone resorption following pinealectomy. Ovariectomy alone results in a transient bone loss at the distal radius followed by continuous increase to baseline levels. The bone resorption activity after pinealectomy causes a bone loss which was not transient, since a continuous decrease in BMD was observed until 30 months.The changes after pinealectomy in sheep are indicative of bone loss. Overall, these findings suggest that the pineal gland may influence bone metabolism and that pinealectomy can be used to induce bone loss in sheep.Treatment of osteoporotic fractures remains generally an unsolved problem[1]. The application of conventional implants for fracture fixation in osteoporotic bone is limited mostly because of the weakened bone structure[2]. Prior to the implementation of new treatment options into the clinical situation, in-vivo testing of new treatments or devices is required to prove efficiency and safety. Hence, an animal model is indispensable for demonstrating the benefit of any new modality sufficiently different from the standard treatment. The FDA Guideline recommend that agents should be evaluated in two different animal species including ovariectomized rats and a second non-rodent large animal model which possesses Haversian system