Antagonism of the Met5-enkephalin-opioid growth factor receptor-signaling axis promotes MSC to differentiate into osteoblasts

ABSTRACT Chronic opioid therapy is associated with bone loss. This led us to hypothesize that the opioid antagonists, that include naloxone, would stimulate bone formation by regulating MSC differentiation. The opioid growth factor receptor (OGFR) is a non‐canonical opioid receptor that binds naloxo...

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Published inJournal of orthopaedic research Vol. 34; no. 7; pp. 1195 - 1205
Main Authors Thakur, Nikhil A., DeBoyace, Sean D., Margulies, Bryan S.
Format Journal Article
LanguageEnglish
Published United States Blackwell Publishing Ltd 01.07.2016
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Summary:ABSTRACT Chronic opioid therapy is associated with bone loss. This led us to hypothesize that the opioid antagonists, that include naloxone, would stimulate bone formation by regulating MSC differentiation. The opioid growth factor receptor (OGFR) is a non‐canonical opioid receptor that binds naloxone with high affinity whereas the native opioid growth factor, met5‐enkephalin (met5), binds both the OGFR and the canonical delta opioid receptor (OPRD). Naloxone and an shRNA OGFR lentivirus were employed to disrupt the OGFR‐signaling axis in cultured MSC. In parallel, naloxone was administered to bone marrow using a mouse unicortical defect model. OPRD, OGFR, and the met5‐ligand were highly expressed in MSC and osteoblasts. A pulse‐dose of naloxone increased mineral formation in MSC cultures in contrast to MSC treated with continuous naloxone or OGFR deficient MSC. Importantly, SMAD1 and SMAD8/9 expression increased after a pulse dose of naloxone whereas SMAD1, SMAD7, and ID1 were increased in the OGFR deficient MSC. Inhibited OGFR signaling decreased proliferation and increased p21 expression. The addition of naloxone to the unicortical defect resulted in increased bone formation within the defect. Our data suggest that novel mechanism through which signaling through the OGFR regulates osteogenesis via negative regulation of SMAD1 and p21. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1195–1205, 2016.
Bibliography:istex:6C8CD146ECD6C2B51815C812386F3166473A3CEF
SUNY Upstate Medical University Department of Orthopedic Surgery New Faculty Start-up Funds
ArticleID:JOR23135
ark:/67375/WNG-LTS36TMJ-K
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0736-0266
1554-527X
DOI:10.1002/jor.23135