Regulatory T cells improve nephrocalcinosis but not dystrophic cardiac calcinosis in DBA/2 mice

Nephrocalcinosis is characterized by aberrant deposition of calcium in the kidneys and is seen in phosphate nephropathy, primary hyperparathyroidism, and distal renal tubular acidosis. To further evaluate the specific pathophysiologic role of T cells in ectopic calcification, we used DBA/2 mice that are prone to develop nephrocalcinosis and dystrophic cardiac calcinosis. Female DBA/2 mice were depleted of T cells (n = 10) or regulatory T cells (Tregs) (n = 15) using either an anti-CD3ɛ or an anti-CD25 monoclonal antibody and compared with isotype-treated controls (n = 9; n = 15), respectively. After this immunomodulation, the DBA/2 mice were given a high-phosphate diet for 9 days and the degree of calcification was assessed by microcomputed tomography. Successful depletion was confirmed by flow cytometry of splenocytes. In DBA/2 mice, the high-phosphate diet induced a phenotype of nephrocalcinosis and dystrophic cardiac calcinosis. T-cell depletion significantly increased renal calcification in microcomputed tomography (P = 0.022). Concordantly, Treg depletion significantly deteriorated acute phosphate nephropathy (P = 0.039) and was associated with a significantly increased mortality rate (P = 0.004). Immunomodulation had no impact on the amount of cardiac calcification. Semiquantitative histopathologic evaluations with Alizarin Red staining independently confirmed the respective radiologic measurements. In summary, our data suggest a pivotal role of T cells, particularly Tregs, in the progression of nephrocalcinosis and emphasize the fact that inflammation deteriorates the outcome in acute phosphate nephropathy.