Osteocytes and IL-6 contribute to bone pathology in gaucher disease.

ANDREA CRIVARO; JUAN M MUCCI; MALENA FERREYRA; CONSTANZA BONDAR; MAXIMILIANO ORMAZABAL; MARIA VICTORIA DELPINO; PAULA ROZENFELD

Congreso; 66. LXIV Reunión Anual de la Sociedad Argentina de Inmunología (SAI). 15-19 Noviembre 2016; 2016

Gaucher Disease (GD) is caused by deficiency of the lysosomalenzyme glucocerebrosidase leading to the accumulationof glucosylceramide. In spite of treatment, bone alterations inGaucher patients persist. This could rely on the increment of thenumber of osteoclasts (induced by RANKL and/or citoquines) orthe augmented apoptosis of osteocytes. Connexin43 (Cx43) isexpressed in bone cells and its function seems to be essentialfor survival. The aim of our work was to study the involvement ofosteocytes in bone pathology of GD. The study was performed usingthe MLO-Y4 osteocyte cell line treated with CBE (an inhibitor ofglyucocerebrosidase) at different time points. The osteoclastogenicpotential of conditioned media (CM) from CBE treated osteocyteswas evaluated by osteoclast differentiation assays; and RANKLlevels in osteocytes were evaluated by immunofluorescence. Cx43expression was measured by qPCR and apoptosis was studied byAnnexin-V and TUNEL staining. On the other hand, osteoclastogenesisassays were performed with the apoptotic body fraction ofCM and the supernatant fraction of the CM both in the presence (orabsence) of OPG. The CM from CBE treated osteocytes inducedhigher levels of osteoclast differentiation compared to control CMand higher surface RANKL levels were observed in treated cells.Cx43 expression diminished with CBE treatment and osteocyteapoptosis was increased. The induction of osteoclast differentiationby apoptotic bodies and supernatant was higher in CBE treatedCM by both fractions and OPG treatment reduced osteoclast levelsin both cases. Levels of IL-6, TNF-á and IL-1â were evaluated byELISA in supernatant. Only IL-6 levels presented an incrementin CBE supernatant. In conclusion, we have shown the possibleinvolvement of osteocytes in bone pathology of GD through aninduction of osteoclast differentiation. This induction would berelated to a higher apoptotic state of osteocytes that could involveCx43 as well as RANKL and IL-6.