Biochemical and immunohistochemical investigations on bone formation and remodelling in ovariectomised rats with tamoxifen citrate administration

Background: Osteoporosis results with the imbalance between osteoblastic formation and osteoclastic resorption, resulting in susceptibility to bone fractures. Ovariectomy leads to osteoporosis by triggering alterations in bone formation and structure. Tamoxifen as an anti-oestrogen is used for adjuvant therapy especially in metastatic diseases and known to have a bone mass protective effect after ovariectomy. Materials and methods: An animal model of ovariectomy induced osteoporosis after tamoxifen citrate administration was studied via biochemical and immunohistochemical methods. Female Wistar albino rats (n = 45), selected according to their oestrous cycle, were divided into three groups; I - control, II - ovariectomy, III - ovariectomy + tamoxifen. Following ovariectomy, tamoxifen citrate (10 mg/kg) was given intraperitoneally daily for 8 weeks. At the end of the period, animals were sacrificed under anaesthesia, blood samples were taken to measure oestrogen, calcium, and alkaline phosphate. Tibia bone samples were fixed in formalin solution and decalcified with 5% ethylene-diamine tetra acetic acid. After the routine histological follow up, samples were embedded in paraffin and cut with a microtome for semi-thin sections. Primary antibodies osteonectin and osteopontin were applied to sections and examined under light microscope. Results: As a consequence, when oestrogen and calcium data were compared there was a decrease in ovariectomy group with an increase in alkaline phosphatase. In ovariectomy + tamoxifen group, these values were close to the control group. Osteonectin was observed to promote bone formation by influencing collagen fibre formation, extracellular matrix development, osteoblast differentiation and the capacity to affect osteoclast activity. Conclusions: It has been suggested that osteopontin, the cytokine and cell binding protein, stimulates cellular signalling pathways, induces bone remodelling and acts in osteoporosis.