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Collynn F. Woeller, Elisa Roztocil, Christine Hammond, Steven E. Feldon; TSHR Signaling Stimulates Proliferation Through PI3K/Akt and Induction of miR-146a and miR-155 in Thyroid Eye Disease Orbital Fibroblasts. Invest. Ophthalmol. Vis. Sci. 2019;60(13):4336-4345. doi: https://doi.org/10.1167/iovs.19-27865.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the molecular pathways that drive thyroid stimulating hormone receptor (TSHR)–induced cellular proliferation in orbital fibroblasts (OFs) from thyroid eye disease (TED) patients.
Orbital fibroblasts from TED and non-TED patients were treated with TSH and changes in gene expression and proliferation were measured. To determine the role of TSHR, TSHR-specific siRNA was used to deplete TSHR levels. Proliferation was measured by bromodeoxyuridine (BrdU) incorporation. PI3K/Akt activation was analyzed by Western blot. The PI3K inhibitor LY294002 was used to investigate PI3K/Akt signaling in OF proliferation. Expression of TSHR, inflammatory cytokines, proliferation related genes and miR-146a and miR-155 were measured by qPCR.
Orbital fibroblasts from TED patients proliferate significantly more than non-TED OFs in response to TSH. TSH-induced proliferation was dependent upon TSHR expression and required the PI3K/Akt signaling cascade. TSHR activation stimulated miR-146a and miR-155 expression. TED OFs produced significantly more miR-146a and miR-155 than non-TED OFs. MiR-146a and miR-155 targets, ZNRF3 and PTEN, which both limit cell proliferation, were decreased in TSH treated OFs.
These data reveal that TSHR signaling in TED OFs stimulates proliferation directly through PI3K/Akt signaling and indirectly through induction of miR-146a and miR-155. MiR-146a and miR-155 enhance TED OF proliferation by reducing expression of target genes that normally block cell proliferation. TSHR-dependent expression of miR-146a and miR-155 may explain part of the fibroproliferative pathology observed in TED.
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