Interferon-γ Released by Activated CD8 + T Lymphocytes Impairs the Calcium Resorption Potential of Osteoclasts in Calcified Human Aortic Valves

In calcific aortic valve disease (CAVD), activated T lymphocytes localize with osteoclast regions; however, the functional consequences of this association remain unknown. We hypothesized that CD8(+) T cells modulate calcification in CAVD. CAVD valves (n = 52) dissected into noncalcified and calcified portions were subjected to mRNA extraction, real-time quantitative PCR, enzyme-linked immunosorbent assay, and immunohistochemical analyses. Compared with noncalcified portions, calcified regions exhibited elevated transcripts for CD8, interferon (IFN)-gamma, CXCL9, Perforin 1, Granzyme B, and heat shock protein 60. Osteoclast-associated receptor activator of NK-kappa B Ligand (RANKL), tartrate-resistant acid phosphatase (TRAP), and osteoclast-associated receptor increased significantly. The stimulation of tissue with phorbol-12-myristate-13-acetate and ionomycin, recapitulating CAVD microenvironment, resulted in IFN-gamma release. Real-time quantitative PCR detected mRNAs for CD8(+) T-cell activation (Perforin 1, Granzyme B). In stimulated versus unstimulated organoid cultures, elevated IFN-gamma reduced the mRNAs encoding for RANKL, TRAP, and Cathepsin K. Molecular imaging showed increased calcium signal intensity in stimulated versus unstimulated parts. CD14(+) monocytes treated either with recombinant human IFN-gamma or with conditioned media-derived IFN-gamma exhibited low levels of Cathepsin K, TRAP, RANK, and tumor necrosis factor receptor-associated factor 6 mRNAs, whereas concentrations of the T-cell co-activators CD80 and CD86 increased in parallel with reduced osteoclast resorptive function, effects abrogated by neutralizing anti-IFN-gamma antibodies. CD8(+) cell-derived IFN-gamma suppresses osteoclast function and may thus favor calcification in CAVD.