B. abortus infection modulates osteocyte function

PESCE VIGLIETTI A. I., GENTILINI M. V., ARRIOLA BENÍTEZ P. C., VELÁSQUEZ L. N., GIAMBARTOLOMEI G. H., DELPINO M. V

Congreso; LXII Reunión Científica de la Sociedad Argentina de Inmunología; 2014

Osteoarticular brucellosis is the most common localization of human active disease. Osteocytes, are the most abundant cells of bone. They secrete factors that regulate osteoclast differentiation (cells involved in bone resorption). The aim is to determine if Brucella abortus (Ba) infection modifies osteocyte (MLO-Y4) function. Cytokine and chemokine production was determined by ELISA, osteoclast differentiation was determined by microscopy as the number of multinucleated cells that express tartrate-resistant acid phosphatase (TRAP). Conexin 43, E11/gp38, integrin-α and -β, tubulin-α, CD44 expression was determined by qRT-PCR. Apoptosis was determined by Hoechst dye 33342 (microscopy) and by Annexin V-FITC/Propidium Iodide (PI) (cytometry). Ba infection induced the secretion of pro-inflammatory cytokines (IL-6 and TNF-α, but not IL-1β), KC and RANKL (the main regulator of osteoclastogenesis) by osteocytes. In inflammatory condition TNF-α could be also involved in osteoclastogenesis. Our results indicated that supernatants from Ba infected osteocytes could induce osteoclast differentiation of monocytes in the presence of M-CSF (p<0.001). Using a neutralizing antibody against TNF-α or osteoprotegerin (OPG), RANKL?s decoy receptor, we determined that TNF-α and RANKL are involved in osteoclastogenesis induced by supernatants from Ba- infected osteocytes, since the number of TRAP+ multinucleated cells were significantly reduced (p<0.01). Conexin 43 and accessory molecules such as E11/gp38, integrin-α and -β, tubulin-α and CD44 are involved in cell-cell interaction necessary for osteocyte survival. Ba infection inhibits the expression of all molecules studied (p<0.05). This indicated that Ba-infection could alter osteocyte survival. We found that Ba infection induced osteocyte apoptosis, Hoechst dye 33342 (p<0.01) and Annexin V-FITC/ PI (p<0.01). Taking together our results indicated that Ba-infection could alter osteocyte function contributing to bone damage.