Osteocytes contribute to bone pathology in Gaucher disease

MUCCI, JUAN MARCOS; CECI, ROMINA; ROZENFELD, PAULA; BONDAR, CONSTANZA; ORMAZABAL, MAXIMILIANO; DELPINO, VICTORIA; CRIVARO, ANDREA; FERREYRA, MALENA

Simposio; World Symposium 2017; 2017

Gaucher Disease (GD) is caused by adeficiency of the lysosomal enzyme glucocerebrosidase leading to theaccumulation of glucosylceramide. Bone pathology in GD is a complex processwhich may include an increment in bone resorption by osteoclasts. This could bedue to an increment in the number of osteoclasts, induced by RANKL and cytokines.Osteocytes can also regulate osteoclastogenesis by the release of solublefactors or by apoptosis. It is known that connexin43 (Cx43) is expressed inbone cells and its function is essential for survival. The aim of our work wasto study the involvement of osteocytes in bone pathology of GD. The study was performedusing the MLO-Y4 osteocyte cell line treated with CBE (an inhibitor of glucocerebrosidase)at different time points. The osteoclastogenic potential of conditioned media(CM) from CBE treated osteocytes was evaluated by osteoclast differentiation assays. RANKL levels were evaluated by immunofluorescence, Cx43 expression was assessedby qPCR and apoptosis was studied by Annexin-V and TUNEL staining. To study the mechanism on osteoclastdifferentiation, the apoptotic body fraction of the CM and its supernatant wereobtained by centrifugation. Both fractions were used in osteoclastogenesisassays with or without OPG. CM from CBE treated osteocytes induced higherlevels of osteoclast differentiation compared to control CM (p<0,01) andhigher surface RANKL levels were observed in treated cells (p<0,05). Cx43expression diminished with CBE treatment (p<0,01) and osteocyte apoptosiswas increased (p<0,05). Induction of osteoclast differentiation by apoptoticbodies and by supernatant was observed in CM from CBE treated cells (p<0,01). OPG treatment reduced osteoclast levels in both fractions (p<0,001). Inconclusion, we showed that GCase deficiency in osteocytes leads to an increasein osteoclast differentiation through a mechanism involving osteocyte apoptosisand soluble molecules. This process could certainly contribute to bonepathogenesis in Gaucher disease.