Circulating monocytes from patients promote calcific aortic valve disease development
Calcific Aortic Valve Disease (CAVD) is the most frequent valvular heart disease in developed countries. It is characterized by a progressive calcification of aortic valve leaflets mediated by myeloid cells, such as monocytes and macrophages. However, the molecular mechanisms involved in their recruitment and activity are still poorly understood and limit the development of a pharmacological treatments. Previous studies have already demonstrated the role of macrophages in CAVD development. However, little is known about the implication of their precursors, monocytes. Thus, we hypothesized that circulating monocytes from CAVD patients have higher pro-calcific and pro-inflammatory capacities. We aimed first to assess the pro-calcifying potential of circulating monocytes from patients with CAVD and second to better understand the molecular mechanisms of this pro-calcific effect through a whole transcriptomic study.  Methods : We first characterized monocytes sub-population, from PBMCs isolated from peripheral blood of healthy volunteers (Vol) and patients with CAVD or without CAVD (NCAVD), with flow cytometry. Then we analyzed the whole transcriptome of these monocytes by RNA sequencing (RNAseq) to identify dysregulated genes expression, further confirmed by RT-qPCR. Finally, after evaluation of monocytes secretome with multiplex analysis, we evaluated CAVD monocytes capacities to induce myofibroblastic transdifferenciation and osteoblastic differencitation of human valvular interstitial cells (hVIC) with immunocytochemistry (ICC) and O-cresolphtalein assay.  Results : In CAVD (calcific aortic valve disease) monocytes, we observe a shift in their sub-populations, with an increased frequency of classical monocytes (CD14+CD16-) and a decreased frequency of non-classical monocytes (CD14+CD16++). Interestingly, we found specific upregulation of genes linked to both inflammation (PDK4) and calcification (ATP2B1), alongside the downregulation of immunomodulatory genes (DDR1, IKBKE) in monocytes from CAVD patients. Additionally, CAVD monocytes produce lower levels of immunomodulatory and anti-osteoblastogenic cytokines (IL3, CCL3), which promote myofibroblastic transdifferentiation (TIMP1, TNC) and osteoblastic differentiation (ALPL, OPG). This correlates with an increase in asma+ and opn+ cells and a doubling of hVIC calcifications.  Conclusions : We demonstrated for the first time that circulating monocytes from CAVD patients have higher pro-inflammatory and pro-calcific capacities that might promote CAVD development. Likewise, we identify dysregulated genes, which could be used as new therapeutic targets. Overall design: used total RNA extracted from healthy volunteer (n=5), NCAVD (n=5) and CAVD (n=5) human patient monocytes. Poly-A mRNA-seq, sequencing length of 150 nt paired end (PE150) with the Illumina NovaSeq 6000 was performed.