The C‐terminal fragment of parathyroid hormone‐related peptide promotes bone formation in diabetic mice with low‐turnover osteopaenia

BACKGROUND AND PURPOSE Current data suggest that parathyroid hormone (PTH)‐related peptide (PTHrP) domains other than the N‐terminal PTH‐like domain contribute to its role as an endogenous bone anabolic factor. PTHrP‐107‐139 inhibits bone resorption, a fact which has precluded an unequivocal demonstration of its possible anabolic action in vivo. We thus sought to characterize the osteogenic effects of this peptide using a mouse model of diabetic low‐turnover osteopaenia. EXPERIMENTAL APPROACH PTHrP‐107‐139 was administered to streptozotocin‐induced diabetic mice, with or without bone marrow ablation, for 13 days. Osteopaenia was confirmed by dual‐energy X‐ray absorptiometry and microcomputed tomography analysis. Histological analysis was performed on paraffin‐embedded bone tissue sections by haematoxylin/eosin and Masson's staining, and tartrate‐resistent acid phosphatase immunohistochemistry. Mouse bone marrow stromal cells and osteoblastic MC3T3‐E1 cells were cultured in normal and/or high glucose (HG) medium. Osteogenic and adipogenic markers were assessed by real‐time PCR, and PTHrP and the PTH 1 receptor protein expression by Western blot analysis. KEY RESULTS PTHrP‐107‐139 reversed the alterations in bone structure and osteoblast function, and also promoted bone healing after marrow ablation without affecting the number of osteoclast‐like cells in diabetic mice. This peptide also reversed the high‐glucose‐induced changes in osteogenic differentiation in both bone marrow stromal cells and the more differentiated MC3T3‐E1 cells. CONCLUSIONS AND IMPLICATIONS These findings demonstrate that PTHrP‐107‐139 promotes bone formation in diabetic mice. This mouse model and in vitro cell cultures allowed us to identify various anabolic effects of this peptide in this scenario.