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High glucose alters the secretome of mechanically stimulated osteocyte‐like cells affecting osteoclast precursor recruitment and differentiation

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Journal of Cellular Physiology

Published online on

Abstract

Diabetes mellitus (DM) induces bone deterioration, while mechanical stimulation promotes osteocyte‐driven bone formation. We aimed to evaluate the interaction of acute exposure (24 h) to high glucose (HG) with both the pro‐survival effect conferred to osteocytic MLO‐Y4 cells and osteoblastic MC3T3‐E1 cells by mechanical stimulation and the interaction of these cells with osteoclast precursor RAW264.7 cells. We found that 24 h of HG (25 mM) pre‐exposure prevented both cell survival and ERK and β‐catenin nuclear translocation upon mechanical stimulation by fluid flow (FF) (10 min) in both MLO‐Y4 and MC3T3‐E1 cells. However, migration of RAW 264.7 cells was inhibited by MLO‐Y4 cell‐conditioned medium (CM), but not by MC3T3‐E1 cell‐CM, with HG or FF. This inhibitory effect was associated with consistent changes in VEGF, RANTES, MIP‐1α, MIP‐1β MCP‐1, and GM‐CSF in MLO‐Y4 cell‐CM. RAW264.7 proliferation was inhibited by MLO‐Y4 CM under static or HG conditions, but it increased by FF‐CM with or without HG. In addition, both FF and HG abrogated the capacity of RAW 264.7 cells to differentiate into osteoclasts, but in a different manner. Thus, HG‐CM in static condition allowed formation of osteoclast‐like cells, which were unable to resorb hydroxyapatite. In contrast, FF‐CM prevented osteoclastogenesis even in HG condition. Moreover, HG did not affect basal RANKL or IL‐6 secretion or their inhibition induced by FF in MLO‐Y4 cells. In conclusion, this in vitro study demonstrates that HG exerts disparate effects on osteocyte mechanotransduction, and provides a novel mechanism by which DM disturbs skeletal metabolism through altered osteocyte‐osteoclast communication. This in vitro study demonstrates that HG exerts disparate effects on osteocyte mechanotransduction, and provides a novel mechanism by which DM disturbs skeletal metabolism through altered osteocyte‐osteoclast communication.