gms | German Medical Science

Objectives: Osteoporosis is a systemic skeletal disease generating a lower bone density resulting in a higher risk of bone fracture. In Germany, about 8% of its population suffers from osteoporosis. To relief the quality-of-life loss and socio-economic impacts of osteoporosis, better understanding of disease progress at cellular and molecular level is crucial.

The aim of this study is monitoring the progression of osteoporosis induction in a sheep model. Therefore, iliac crest biopsies in merino sheep were investigated after 0, 3, and 8 months post induction. Samples from untreated and ovariectomized sheep were taken as controls for two ovariectomized treated groups (diet and diet/steroid).

Methods: 32 skeletally mature female merino sheep with an average age of 5.5 years were divided into 4 groups (n=8 each): control group (C), bilateral ovariectomized (OVX), OVX and a calcium- and vitamin-D2/3-deficient diet (OVXD), and OVX, diet and corticosteroids (OVXDS). Iliac crest biopsies were taken at 0M, 3M and 8M (M=months). Samples were stained with Movat pentachrom for descriptive and histomorphometrical analysis. Immunohistochemical and enzymohistochemical analysis was performed to visualize oteoclasts (TRAP and CD68) and osteoblasts (osteocalcin and ALP). Osteocyte number and morphology were detected using silver nitrate and Rhodamine stains. Histomorphometry was conducted in ImageJ software and statistical analysis was run in IBM SPSS software.

Results and Conclusion: Descriptive analysis showed noticeably inferior bone quality and bone mass of the animals in the OVXDS after 8M in comparison with the C group. Osteoclast size, nucleus numbers and position were not deviant between the groups. However, histomorphometrical analysis of multi-nucleated TRAP positive cells showed lower osteoclast numbers in the OVXDS at 8M. ALP positive areas were higher in the OVXDS at 8M compared to the controls. Interestingly, spindle-shaped osteocytes were lower in the OVXDS biopsies.

Solely the OVXDS group reflects structural symptoms of osteoporotic bone after 8M. The affected osteocyte network correlates to bone's biomechanical properties. Nonetheless, running characterization of bone regions (femur and spine) will determine model suitability for preclinical research especially the development of bone augmenting biomaterials. This current study emphasizes the effect of malnutrition in combination with steroid-treatment as well as the effect of estrogen depletion on bone homoeostasis.