Transcription factor 21 accelerates vascular calcification in mice by activating the IL-6/STAT3 signaling pathway and the interplay between VSMCs and ECs.

Vascular calcification is caused by the deposition of calcium salts in the intimal or tunica media layer of the aorta, which increases the risk of cardiovascular events and all-cause mortality. However, the mechanisms underlying vascular calcification are not fully clarified. Recently it has been shown that transcription factor 21 (TCF21) is highly expressed in human and mouse atherosclerotic plaques. In this study we investigated the role of TCF21 in vascular calcification and the underlying mechanisms. In carotid artery atherosclerotic plaques collected from 6 patients, we found that TCF21 expression was upregulated in calcific areas. We further demonstrated TCF21 expression was increased in an in vitro vascular smooth muscle cell (VSMC) osteogenesis model. TCF21 overexpression promoted osteogenic differentiation of VSMC, whereas TCF21 knockdown in VSMC attenuated the calcification. Similar results were observed in ex vivo mouse thoracic aorta rings. Previous reports showed that TCF21 bound to myocardin (MYOCD) to inhibit the transcriptional activity of serum response factor (SRF)-MYOCD complex. We found that SRF overexpression significantly attenuated TCF21-induced VSMC and aortic ring calcification. Overexpression of SRF, but not MYOCD, reversed TCF21-inhibited expression of contractile genes SMA and SM22. More importantly, under high inorganic phosphate (3 mM) condition, SRF overexpression reduced TCF21-induced expression of calcification-related genes (BMP2 and RUNX2) as well as vascular calcification. Moreover, TCF21 overexpression enhanced IL-6 expression and downstream STAT3 activation to facilitate vascular calcification. Both LPS and STAT3 could induce TCF21 expression, suggesting that the inflammation and TCF21 might form a positive feedback loop to amplify the activation of IL-6/STAT3 signaling pathway. On the other hand, TCF21 induced production of inflammatory cytokines IL-1ß and IL-6 in endothelial cells (ECs) to promote VSMC osteogenesis. In EC-specific TCF21 knockout (TCF21ECKO) mice, VD3 and nicotine-induced vascular calcification was significantly reduced. Our results suggest that TCF21 aggravates vascular calcification by activating IL-6/STAT3 signaling and interplay between VSMC and EC, which provides new insights into the pathogenesis of vascular calcification. TCF21 enhances vascular calcification by activating the IL-6-STAT3 signaling pathway. TCF21 inhibition may be a new potential therapeutic strategy for the prevention and treatment of vascular calcification.

Mesenchymal stem cell transplantation worsens intestinal inflammation and microenvironment in PI3Kγ-knockout mice.

Considering the possible interaction between mesenchymal stem cells (MSCs) and PI3Kγ-associated drugs, we evaluated the efficacy and action mechanism of MSCs in the treatment of colitis in PI3Kγ-/- mice. Trinitro-benzene-sulfonic acid enema was used to create a colitis model, and MSCs were transplanted through the caudal vein to treat colitis in wild-type and PI3Kγ-/- mice. We sequenced microbial 16S rRNA genes in the colonic mucosa of PI3Kγ-/- and wild-type mice and quantified colonic IgA, IL-2, IL-10, IL-17A, occludin, and serum IgA. MSC transplantation led to a more serious reduction in the weight of trinitro-benzene-sulfonic acid-administered PI3Kγ-/- mice than that in wild-type mice. The disease activity index, pathological scoring, number of taxa in the colon, Berger-Parker index, I-index, proportion of Proteobacteria, and IgA level in the blood were higher in PI3Kγ-/- mice than in wild-type mice after MSC transplantation. The occludin and IL-10 levels in the colon tissues decreased before and after MSC transplantation in PI3Kγ-/- mice, whereas they were increased in wild-type mice The IL-17 level decreased in both wild-type and PI3Kγ-/- mice, with knockout mice showing a greater decrease. Therefore, MSC transplantation in PI3Kγ-/- mice led to increased numbers of exogenous pathogenic microorganisms and enhanced colitis that was difficult to relieve.