gms | German Medical Science

Background: Osteoporosis is a serious skeletal disorder of humans characterized by reduced bone density and deterioration of bone microarchitecture that leads to bone fragility and increased fracture risk. Osteoporosis develops with ageing, in the course of nutritional deficiency and after glucocorticoids administration due to alteration of bone remodelling. Connexin 43 (Cx43) is a gap junctional protein and plays a pivotal role in normal bone homoestasis, morphogenesis, cellular differentiation, and ossification. In the present study we investigate its distribution pattern by immunohistochemistry in a rat model with osteoporosis induced by combined ovariectomy, glucocorticoid treatment, and deficient diet. These investigations have been performed in order to elucidate the questions whether (1) cx 43 expression is altered in the osteoporotic bone, and whether different induction procedures of osteoporosis might lead to different expression pattern of cx43 in contrast to normal bone.

Methods: Female Sprague Dawley rats were grouped into Sham, OVX+Diet and OVX+Steroid. Lumbar vertebrae (L4) of 3 months and 12 months rats were dissected, demineralised, paraffin embedded and sectioned at 5 µm. Sections were processed for immunohistochemistry. Cx43 distribution was photographed, quantified and was statistically analysed using two way ANOVA.

Results: Average percentage of Cx43 positive areas covered with osteoblast were quantified. Cx 43 distribution showed significant reduction in the OVX-Diet group (P<0.05) and highly significant reduction in the OVX-steroid group (P<0.01) compared to the Sham group used as a control.

Conclusion: it could be demonstrated that Cx43 expression of osteoblasts is diminished in the rat model with osteoporosis. Therefore, it might be concluded that altered expression of Cx 43 (i.e. gap junctional communication) is associated with severe bone loss and disturbed bone mineralization observed in the course of osteoporosis.