MiR-33a Controls hMSCS Osteoblast Commitment Modulating the Yap/Taz Expression Through EGFR Signaling Regulation

Area of Science:

• Biomedical Sciences
• Regenerative Medicine
• Molecular Biology

Background:

• Mesenchymal stromal cells (hMSCs) are crucial for bone regeneration, but underlying signaling pathways for osteoblast commitment remain unclear, hindering therapeutic success.
• Previous research identified microRNAs (miRNAs) regulating hMSC osteoblast differentiation via hypoxia and cytoskeletal changes.
• Epithelial to mesenchymal transition (EMT) and epidermal growth factor receptor (EGFR) signaling, impacting Yes-associated protein (YAP)/PDZ-binding motif (TAZ) expression, are also implicated.

Purpose of the Study:

• To investigate the role of the miR-33a family in modulating YAP/TAZ expression and regulating EGFR signaling during osteoblast commitment.
• To elucidate the specific functions of miR-33a-5p and miR-33a-3p in maintaining hMSC and osteoblast phenotypes, respectively.

Main Methods:

• Utilized gain and loss of function studies with miR-33a-5p and miR-33a-3p in hMSCs and primary osteoblast (Nh-Ost) cell lines.
• Assessed gene expression changes using qRT-PCR and Western blot, and evaluated osteoblast differentiation with Osteoimage assays.
• Investigated YAP as a miR-33a-3p target and analyzed EGFR signaling's role in miR-33a-3p-mediated YAP/TAZ modulation through EGF and EGFR inhibitor treatments.

Main Results:

• A balance between miR-33a-5p and miR-33a-3p expression was observed during hMSC osteoblast differentiation.
• miR-33a-5p maintained the hMSC phenotype, while miR-33a-3p promoted osteoblast phenotype maintenance by regulating YAP/TAZ via EGFR signaling.
• EGFR inhibition counteracted miR-33a-3p's effects on YAP/TAZ, preserving the hMSC committed phenotype.

Conclusions:

• miR-33a-3p plays a critical role in osteoblast commitment by regulating YAP/TAZ through EGFR signaling.
• A potential personalized therapeutic strategy for bone regeneration involves miR-33a delivery to simultaneously target EGFR and YAP signaling.