BMAL1 regulates osteoblast differentiation through mTOR/GSK3β/β-catenin pathway

Area of Science:

• * Molecular Biology
• * Chronobiology
• * Bone Biology

Background:

• * Bone mass maintenance relies on osteoblasts, and aging leads to bone loss.
• * Circadian clock disruption is linked to aging pathologies, but its role in bone regulation is unclear.
• * Bmal1 is a key activator of the peripheral circadian clock.

Purpose of the Study:

• * To investigate the impact of Bmal1 knockdown on osteoblast differentiation and underlying mechanisms.

Main Methods:

• * Lentivirus-mediated shRNA used for Bmal1 knockdown in osteoblasts.
• * Assessed osteogenic markers, alkaline phosphatase activity, mineralization, and apoptosis.
• * Investigated signaling pathways including ERK, JNK, mTOR, and GSK3β/β-catenin.
• * Utilized inhibitors like rapamycin, TDZD-8, WNT3a, and SKL2001.

Main Results:

• * Bmal1 knockdown decreased osteogenic markers, alkaline phosphatase activity, and mineralization.
• * Bmal1 knockdown increased osteoblast apoptosis and inflammatory response.
• * Bmal1 knockdown promoted ERK/JNK phosphorylation and mTOR activity.
• * Bmal1 knockdown inhibited GSK3β/β-catenin signaling, reducing β-catenin and GSK-3β phosphorylation.
• * mTOR inhibition (rapamycin) and GSK3β inhibition (TDZD-8) partially rescued Bmal1 knockdown effects.

Conclusions:

• * Circadian gene Bmal1 regulates osteoblast differentiation and inflammation.
• * Bmal1 acts through mTOR/GSK3β/β-catenin signaling pathways.
• * Bmal1 plays a role in bone mineralization and remodeling processes.