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Bone Abstracts (2016) 5 P194 | DOI: 10.1530/boneabs.5.P194

1Instituto de Investigação e Inovação em Saúde (i3S), Porto, Portugal; 2Instituto de Engenharia Biomédica (INEB), Porto, Portugal; 3Neuroscience Division, Garvan Institute of Medical Research, Sydney, Australia.

Neuropeptide Y Y1 receptor (Y1R) signalling has been shown to play a key role in bone homeostasis, emerging as a novel therapeutic target in bone diseases. Y1R knockout mice (Y1−/−) display a high-bone mass phenotype that has been mainly attributed to increased osteoblast activity. Nevertheless, the Y1R regulatory role on osteoclastogenesis and matrix resorption remains largely unknown. To clarify this, we proposed to investigate the effects of Y1R in osteoclast function and matrix demineralization/resorption, using bone marrow-derived osteoclasts retrieved from Y1−/− mice and compared to their wild-type (WT) counterparts (n=6 per genotype).

The number of TRAP-positive multinucleated cells was significantly elevated in Y1−/− cultures, when compared to WT (P<0.001). Moreover, Y1−/− osteoclasts surface area and number of nuclei (N>8) were also significantly increased (P<0.01), suggesting enhanced formation and osteoclast fusion, possibly due to an overexpression of monocyte chemoattractant protein-1 (MCP-1) in Y1-/- cultures (P<0.01). Moreover, osteoblast/osteoclast direct co-cultures demonstrated that Y1−/− osteoblasts expressed higher-levels of RANKL (P<0.01), leading to increased RANKL/OPG ratio (P<0.001).

Paradoxically, functional studies using dentine discs demonstrated that in Y1−/− cultures there is an inhibition in matrix demineralization. Scanning-electron-microscopy images revealed that Y1−/− osteoclasts produce poorly demineralized resorption pits. To quantify these differences we have developed a novel computational tool (BonePit program), which allowed us to generate tridimensional (3D) reconstructions of resorption pits and to analyse pits morphological features. 3D analyses showed that Y1−/− resorption pits displayed a marked reduction in area, volume and depth (P<0.001), when compared to WT. In fact, the gene expression of matrix resorption markers, matrix metalloproteinase-9 and cathepsin K, was downregulated in Y1−/− cultures, suggesting the presence of non-resorbing osteoclasts in Y1−/− mice.

Together, these data disclosed an important role for Y1R in osteoclastogenesis, essentially in bone matrix resorption, which may unravel new potential therapies for the treatment of osteoclastic bone diseases.

Volume 5

43rd Annual European Calcified Tissue Society Congress

Rome, Italy
14 May 2016 - 17 May 2016

European Calcified Tissue Society 

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