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O-GlcNAcylation promotes osteoclastogenesis and dictates aggressive bone resorption by osteoclasts

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Author(s):
Thaise Mayumi Taira
Total Authors: 1
Document type: Doctoral Thesis
Press: Ribeirão Preto.
Institution: Universidade de São Paulo (USP). Faculdade de Odontologia de Ribeirão Preto (PCARP/BC)
Defense date:
Examining board members:
Sandra Yasuyo Fukada Alves; Luciane Portas Capelo; Francisco Wanderley Garcia de Paula e Silva; Pedro Manoel Mendes de Moraes Vieira
Advisor: Sandra Yasuyo Fukada Alves
Abstract

Osteoclasts play a key role in the regulation of bone mass, which to differentiate and reabsorb bone require high energy expenditure. Glucose, the main energy source for several cellular processes, is crucial for osteoclastogenesis and for the maintenance of active osteoclasts. However, the role of glucose metabolic pathways on osteoclasts has not been well elucidated. Therefore, in order to explore a branch of the glycolysis pathway, we evaluated the effect of O-GlcNAcylation, which is a post-translational modification resulting from glucose metabolism through the hexosamine pathway. This process consists of the addition of GlcNAc in serine/threonine moieties of nuclear and cytoplasmic by OGT enzyme. O-GlcNAcylation regulates several cellular processes including transcription factors, enzymatic activity, functions of nuclear and cytoplasmic proteins, among others. Therefore, the aim of our study was to evaluate the role of O-GlcNAcylation on osteoclastogenesis and osteoclast\'s activity in vitro, and on physiological and pathological bone remodeling in vivo. For osteoclast culture, we used bone marrow from C57BL/6 mice treated with GlcNAc or OGT inhibitors (OSMI-1 and 5SGlcNAc), and we also used bone marrow from Ogt genetic deletion in monocytes (LysM-Cre Ogt fl/fl ), and in osteoclasts (CtsK-Cre Ogt fl/fl ) mice, with their respective controls mice. To evaluate the osteoclasts\' resorption behavior with GlcNAc and OSMI-1 treatment we used human cells for osteoclast culture. For in vivo analysis, we used CtsK-Cre Ogt fl/fl mice and CtsK-Cre as a control group to evaluate bone parameters and to induce the periapical lesion model. First, we observed that GlcNAc addition stimulates murine osteoclast\'s differentiation and activity, while OSMI-1 and 5SGlcNAc inhibited. Together, Ogt deficiency in monocytes impaired osteoclast\'s differentiation, and their demineralization capacity, showing a decrease in NFATc1, αV Integrin, and Cathepsin K protein expression during all osteoclast\'s differentiation process. Besides this, GlcNAc stimulates human osteoclast\'s differentiation and induces osteoclasts to resorb more aggressively. This effect was also reversed in the presence of OSMI-1. Going beyond our in vitro studies, we observed that Ogt deficiency mice in osteoclasts did not present physiological bone resorption in the femur after 16-weeks old, since these mice presented higher bone volume and trabecular thickness when compared with its control group. The femur cortical bone also presented a higher bone volume and less porosity in CtsK-Cre Ogt fl/fl mice. Finally, as a possible target of O-GlcNAcylation, we have NFATc1, since it was more expressed in the nucleus in the presence of GlcNAc. These data show that O-GlcNAcylation plays an important role in murine and human osteoclastogenesis, in addition to altering the resorption behavior of osteoclasts to a more aggressive mode. Finally, our data show a possible mechanism for bone loss and fragility mediated by excessive osteoclast activity in osteolytic diseases. Therefore, the present study opens new avenues for O-GlcNAcylation on osteoclasts as a possible therapeutic intervention on osteometabolic diseases. (AU)

FAPESP's process: 17/23264-4 - Role of O-GlcNacylation in the bone loss in periapical lesion model
Grantee:Thaise Mayumi Taira
Support Opportunities: Scholarships in Brazil - Doctorate