Successful Treatment of an Adynamic Bone Disorder with Bone Morphogenetic Protein-7 in a Renal Ablation Model

An adynamic bone disorder (ABD) is an important complication of chronic kidney disease (CKD) of unknown etiology for which there is no adequate treatment. Reported is an animal model of ablative CKD complicated by an ABD characterized by the absence of secondary hyperparathyroidism and its successful treatment with a skeletal anabolic factor, bone morphogenetic protein-7 (BMP-7). Adult mice were subjected to electrocautery of the right kidney followed by left nephrectomy. Animals were randomized into groups fed normal chow or fed low-phosphate chow supplemented with calcitriol to maintain normophosphatemia in CKD. All groups were maintained on the regimens for 12 wk. Hyperphosphatemia, secondary hyperparathyroidism, and a mild osteodystrophy developed in the CKD/chow-fed group, as expected. When dietary phosphorus was restricted and calcitriol was administered in the CKD low-phosphate/calcitriol group (ABD), Ca, PO₄, and parathyroid hormone levels were maintained normal. A significant ABD developed in the ABD group characterized by significant depressions in osteoblast number, perimeters, bone formation rates, and mineral apposition rates when compared with the sham-operated, chow-fed group. The abnormal skeletal histomorphometry was reversed by BMP-7 therapy to normal values and significantly improved from the ABD group (P < 0.05). The sham-operated low-phosphate/calcitriol-fed control group and the CKD low-phosphate/calcitriol/BMP-7 groups had reduced phosphate levels compared with the other groups (P < 0.05). ABD produced in mice with CKD in the absence of hyperparathyroidism was successfully reversed with a bone anabolic, BMP-7, associated with a reduction in plasma phosphorus.