αvβ3 integrin as a linker between fibrosis and thyroid hormones crosstalk
2Sackler Faculty of Medicine, Tel Aviv University, Israel
3Research Authority, Meir Medical Center, Israel
4Department of Plastic Surgery, Meir Medical Center, Israel
5Oncogenetic Laboratory, Meir Medical Center, Israel
6Department of Internal Medicine E, Meir Medical Center, Israel
7Translational Hemato-Oncology Laboratory, Hematology Institute and Blood Bank, Meir Medical Center, Israel
Background: Systemic-sclerosis (SSc) is an autoimmune disease characterized by skin fibrosis. Key players in fibrosis are myofibroblasts (MF) that following TGFb exposure produce collagen-rich extracellular-matrix (fibrotic-ECM). Latent-TGFb is bound to the ECM and is activated by αv integrins. MF express both αvβ3 integrin, a membrane receptor for thyroid hormones (TH=T3/T4) and pro-fibrotic miRNA-21. miRNA-21 promotes deiodinase type-3 expression (DIO3) that degrades T3. T3 attenuates fibrosis. We hypothesized that avb3 through its TH binding site affects the fibrotic processes.
Methods: 1.Dermal-fibroblast (DF) cultured without/with TGFb were removed by a strong base, leaving "normal/fibrotic" ECM in wells, respectively. DF were cultured on those matrices without/with tetraiodothyroacetic-acid (tetrac-an avb3 ligand and T4 antagonist) for 48-72hr, harvested and evaluated for proliferation (cell-count,cyclin-D1), MF pro-fibrotic markers (aSMA, collagen, elastin), αvβ3, miRNA-21 and DIO3 expressions (western-blot,PCR). 2.SSc patients (n=19) were divided into high/low T3 groups and evaluated for circulating miRNA-21 levels.
Results: The "fibrotic-ECM" increased DF proliferation and expression of MF pro-fibrotic markers, avb3, miRNA-21 and DIO3 compared to "normal-ECM" (24-123%↑,p≤0.05). Addition of tetrac to MF downregulated cell proliferation to the control level and pro-fibrotic markers expression (20-47%↓,p≤0.05), compared to cells without tetrac. Furthermore, it reduced αvβ3, miRNA-21 and DIO3 levels (40-50%↓,p≤0.05). Accordingly, reduced miRNA-21 levels were found in the high T3 SSc group, compared to the low T3 group (p≤0.05).
Conclusion:Tetrac has both an anti-fibrotic and inhibitory effect on DIO3 level. This result and the inverse levels of miRNA-21 and T3 in SSc patients suggest that the αvβ3-miRNA-21-DIO3-T3 pathway link between fibrosis and thyroid hormones.