Sam68 promotes osteogenic differentiation of aortic valvular interstitial cells by TNF-α/STAT3/autophagy axis

Abstract

Calcified aortic valve disease (CAVD) is a major non‐rheumatic heart valve disease in the world, with a high mortality rate and without suitable pharmaceutical therapy due to its complex mechanisms. Src‐associated in mitosis 68‐KD (Sam68), an RNA binding protein, has been reported as a signaling adaptor in numerous signaling pathways (Huot in Mol Cell Biol, 29(7), 1933‐1943, 2009), particularly in inflammatory signaling pathways. The effects of Sam68 on the osteogenic differentiation process of hVICs and its regulation on signal transducer and activator of transcription 3 (STAT3) signaling pathway have been investigated in this study. Human aortic valve samples detection found that Sam68 expression was up‐regulated in human calcific aortic valves. We used tumor necrosis factor α (TNF‐α) as an activator for osteogenic differentiation in vitro and the result indicated that Sam68 was highly expressed after TNF‐α stimulation. Overexpression of Sam68 promoted osteogenic differentiation of hVICs while Sam68 knockdown reversed this effect. Sam68 interaction with STAT3 was predicted by using String database and was verified in this study. Sam68 knockdown reduced phosphorylation of STAT3 activated by TNF‐α and the downstream gene expression, which further influenced autophagy flux in hVICs. STAT3 knockdown alleviated the osteogenic differentiation and calcium deposition promoted by Sam68 overexpression. In conclusion, Sam68 interacts with STAT3 and participates in its phosphorylation to promote osteogenic differentiation of hVICs to induce valve calcification. Thus, Sam68 may be a new therapeutic target for CAVD.

Investigation of autophagy‑related genes and immune infiltration in calcific aortic valve disease: A bioinformatics analysis and experimental validation

“…Although numerous of the factors contributing to valve calcification are understood, the role of autophagy within this process remains elusive ( 18 , 34 ). This significant research gap warrants further investigation.…”

“…Interestingly, previous studies have highlighted the key role of the RNA-binding protein Sam68 in driving human valve interstitial cell osteogenic differentiation via the STAT3 signaling pathway and autophagic flux regulation ( 18 ). In addition, autophagy upregulation has been observed in the calcified tissues of patients, showing that autophagy plays compensatory and pro-survival roles in this disease ( 19 ).…”

Predicting key gene related to immune infiltration and myofibroblast-like valve interstitial cells in patients with calcified aortic valve disease based on bioinformatics analysis

“…The initial stage of is CAVD pathological process characterized by lesion development which is similar to that of atherosclerosis, such as endothelial injury, lipid infiltration, and inflammatory response ( 72 ). Nordquist et al showed that in the mouse model of heart valve endothelial cell injury, positive injury response was associated with an acute increase in TGF-β1 enriched within the endothelial compartment and upregulation of CTHRC1 within the interstitium.…”

Osteopontin/SPP1: a potential mediator between immune cells and vascular calcification

“…Consequently, changes in these genes led to osteogenic calcification ( 82 ). Additionally, upregulated Src-associated in mitosis 68-KD (Sam68) expression was found in human CAV, which coordinated with STAT3, resulting in mineral deposition and osteogenic differentiation ( 85 ) ( Figure 2A ). These results showed that SPP1-Sam68-STAT3 signaling could mediate macrophages in CAVD.…”