Persistence of bone and mineral disorders 2 years after successful kidney transplantation.

Background: Studies that have conducted bone biopsies after kidney transplantation are scarce, and the results are conflicting.

Methods: We evaluate the bone histomorphometry, in vitro proliferation, and alkaline phosphatase expression in osteoblasts isolated from bone biopsies from 27 kidney transplant patients. The patients had preserved renal function and were treated with the same immunosuppressive therapy, receiving a minimum dose of corticosteroids.

Results: The biochemical analysis revealed that 41% of the patients presented with hypercalcemia, 26% presented with hypophosphatemia, and hypovitaminosis D was detected in 63%. The histomorphometric analysis showed a reduced trabecular number and increased trabecular separation, mineral apposition rate, and mineralization lag time, as well as higher osteoid surface, osteoblastic surface, resorption surface, and osteoclastic surface and a lower mineralizing surface, compared with the controls. Based on the TMV classification, bone turnover was normal in 48%, high in 26%, and low in 26% of patients. Bone mineralization was delayed in 48% of the patients, and 58% of the patients with hypovitaminosis D presented with delayed bone mineralization. Bone volume was low in 37% of the patients. The osteoblasts from patients exhibited a higher degree of proliferation compared with those from controls.

Conclusion: Eight-two percent of our patients presented with alterations in at least one of the TMV parameters. Persistence of hyperparathyroidism, hypovitaminosis D, and immunosuppressive drugs may have influenced osteoblast function, which would explain many of the bone alterations found in these patients.