TXNIP Suppresses the Osteochondrogenic Switch of Vascular Smooth Muscle Cells in Atherosclerosis

by Selleckchem | Sep 28 2023

Background: The osteochondrogenic switch of vascular smooth muscle cells (VSMCs) is a pivotal cellular process in atherosclerotic calcification. However, the exact molecular mechanism of the osteochondrogenic transition of VSMCs remains to be elucidated. Here, we explore the regulatory role of TXNIP (thioredoxin-interacting protein) in the phenotypical transitioning of VSMCs toward osteochondrogenic cells responsible for atherosclerotic calcification.

Methods: The atherosclerotic phenotypes of Txnip-/- mice were analyzed in combination with single-cell RNA-sequencing. The atherosclerotic phenotypes of Tagln-Cre; Txnipflox/flox mice (smooth muscle cell-specific Txnip ablation model), and the mice transplanted with the bone marrow of Txnip-/- mice were analyzed. Public single-cell RNA-sequencing dataset (GSE159677) was reanalyzed to define the gene expression of TXNIP in human calcified atherosclerotic plaques. The effect of TXNIP suppression on the osteochondrogenic phenotypic changes in primary aortic VSMCs was analyzed.

Results: Atherosclerotic lesions of Txnip-/- mice presented significantly increased calcification and deposition of collagen content. Subsequent single-cell RNA-sequencing analysis identified the modulated VSMC and osteochondrogenic clusters, which were VSMC-derived populations. The osteochondrogenic cluster was markedly expanded in Txnip-/- mice. The pathway analysis of the VSMC-derived cells revealed enrichment of bone- and cartilage-formation-related pathways and bone morphogenetic protein signaling in Txnip-/- mice. Reanalyzing public single-cell RNA-sequencing dataset revealed that TXNIP was downregulated in the modulated VSMC and osteochondrogenic clusters of human calcified atherosclerotic lesions. Tagln-Cre; Txnipflox/flox mice recapitulated the calcification and collagen-rich atherosclerotic phenotypes of Txnip-/- mice, whereas the hematopoietic deficiency of TXNIP did not affect the lesion phenotype. Suppression of TXNIP in cultured VSMCs accelerates osteodifferentiation and upregulates bone morphogenetic protein signaling. Treatment with the bone morphogenetic protein signaling inhibitor K02288 abrogated the effect of TXNIP suppression on osteodifferentiation.

Conclusions: Our results suggest that TXNIP is a novel regulator of atherosclerotic calcification by suppressing bone morphogenetic protein signaling to inhibit the transition of VSMCs toward an osteochondrogenic phenotype.

Comments:

In this study, the researchers aimed to investigate the role of TXNIP (thioredoxin-interacting protein) in the phenotypic transition of vascular smooth muscle cells (VSMCs) towards an osteochondrogenic phenotype, which is associated with atherosclerotic calcification. They conducted various experiments using mouse models, single-cell RNA-sequencing, and in vitro cell culture techniques.

First, they analyzed atherosclerotic lesions in mice lacking the Txnip gene (Txnip-/- mice). These mice exhibited increased calcification and collagen deposition in the atherosclerotic lesions compared to control mice. Single-cell RNA-sequencing analysis revealed that VSMC-derived populations, particularly the osteochondrogenic cluster, were significantly expanded in Txnip-/- mice. Pathway analysis of these VSMC-derived cells showed enrichment of pathways related to bone and cartilage formation, as well as bone morphogenetic protein (BMP) signaling.

To further confirm the role of TXNIP in atherosclerotic calcification, the researchers used a mouse model with specific deletion of Txnip in smooth muscle cells (Tagln-Cre; Txnipflox/flox mice). These mice exhibited similar calcification and collagen-rich atherosclerotic phenotypes as Txnip-/- mice, suggesting that smooth muscle cell-specific deletion of Txnip is sufficient to recapitulate the effects.

Additionally, they investigated the role of TXNIP in the hematopoietic system by transplanting bone marrow from Txnip-/- mice into wild-type mice. Interestingly, the hematopoietic deficiency of TXNIP did not affect the development of atherosclerotic lesions, indicating that the regulation of atherosclerotic calcification by TXNIP is primarily mediated through VSMCs rather than hematopoietic cells.

In vitro experiments using primary aortic VSMCs further supported the findings. Suppression of TXNIP in cultured VSMCs accelerated their differentiation towards an osteochondrogenic phenotype and upregulated BMP signaling. Treatment with a BMP signaling inhibitor reversed the effect of TXNIP suppression on osteodifferentiation, suggesting that TXNIP inhibits the transition of VSMCs towards an osteochondrogenic phenotype by suppressing BMP signaling.

In conclusion, the study suggests that TXNIP acts as a novel regulator of atherosclerotic calcification by inhibiting the transition of VSMCs towards an osteochondrogenic phenotype. It achieves this by suppressing BMP signaling, which is involved in bone and cartilage formation. These findings provide new insights into the molecular mechanisms underlying atherosclerotic calcification and identify TXNIP as a potential target for therapeutic interventions in this process.