β-Catenin Limits Osteogenesis on Regenerative Materials in a Stiffness-Dependent Manner

Area of Science:

• Biomaterials Science
• Regenerative Medicine
• Cell Biology

Background:

• Targeted refinement of regenerative materials necessitates understanding cell-material interactions.
• Mineralized collagen-glycosaminoglycan (MC-GAG) scaffolds promote skull regeneration in vivo.
• The role of scaffold stiffness in MC-GAG mediated osteogenesis is not fully understood.

Purpose of the Study:

• To evaluate the impact of MC-GAG scaffold stiffness on canonical Wnt (cWnt) signaling.
• To investigate the interplay between Wnt signaling, mechanotransduction, and osteogenic differentiation.
• To identify potential targets for optimizing skeletal regenerative materials.

Main Methods:

• Primary human bone marrow-derived mesenchymal stem cells (hMSCs) were cultured on MC-GAG scaffolds with varying stiffness (0.3 kPa vs 3.9 kPa).
• Expression of activated β-catenin and YAP protein was assessed.
• Wnt pathway inhibition and β-catenin knockdown were performed to study their effects on osteogenic differentiation and signaling pathways.

Main Results:

• Stiffer MC-GAG scaffolds (3.9 kPa) significantly increased activated β-catenin and YAP expression in hMSCs.
• Overall Wnt pathway inhibition reduced osteogenic differentiation and increased BMP4/p-Smad1/5 on stiffer scaffolds.
• β-catenin knockdown on stiffer scaffolds enhanced osteogenic differentiation and mineralization, increasing BMP4, p-Smad1/5, and Runx2 expression.

Conclusions:

• Scaffold stiffness modulates Wnt and mechanotransduction pathways, promoting osteogenesis on MC-GAG.
• Activated β-catenin acts as a limiting factor in stiffness-induced osteogenesis on MC-GAG.
• Modulating β-catenin levels may be a strategy to optimize stiffness for skeletal regenerative materials.