BMAL1 Promotes Valvular Interstitial Cells' Osteogenic Differentiation through NF-κ B/AKT/MAPK Pathway

Area of Science:

• Cardiovascular Biology
• Molecular Biology
• Biochemistry

Background:

• Calcific aortic valve disease (CAVD) is a prevalent condition in aging populations, lacking effective medical interventions.
• Brain and muscle ARNT-like 1 (BMAL1) has been implicated in various calcification processes, with distinct tissue-specific roles.

Purpose of the Study:

• To investigate the specific role of BMAL1 in the pathogenesis of CAVD.
• To elucidate the molecular mechanisms by which BMAL1 influences osteogenic differentiation in human valvular interstitial cells (HVICs).

Main Methods:

• Quantified BMAL1 protein levels in normal and calcified human aortic valves and isolated VICs.
• Utilized an in vitro model of HVICs cultured in osteogenic medium to assess BMAL1 expression and localization.
• Employed TGF-β and RhoA/ROCK inhibitors, RhoA-siRNA, and BMAL1 knockdown to investigate regulatory pathways.
• Performed Chromatin Immunoprecipitation (ChIP) and Western blotting to analyze protein interactions and signaling pathway activation.

Main Results:

• BMAL1 expression was significantly upregulated in calcified aortic valves and VICs.
• Osteogenic medium increased BMAL1 expression in HVICs; BMAL1 knockdown inhibited HVIC osteogenic differentiation.
• TGF-β/RhoA/ROCK signaling pathways mediate the osteogenic medium-induced increase in BMAL1.
• BMAL1 knockdown reduced levels of phosphorylated AKT, IκBα, p65, and JNK, indicating involvement in NF-κB/AKT/MAPK signaling.

Conclusions:

• BMAL1 expression in HVICs is promoted by osteogenic medium via the TGF-β/RhoA/ROCK pathway.
• BMAL1 regulates HVIC osteogenic differentiation not as a transcription factor, but through the NF-κB/AKT/MAPK pathway.