β-Catenin Regulation During Tgf-β2-Induced Tenogenesis of Mesenchymal Stem Cells and Impacts on Cadherin Cell-Cell Junctions

Regenerative strategies for tendon injuries are needed, but are challenged by limited information on the protein regulators of stem cell differentiation toward the tendon lineage (tenogenesis). Prior work shows that transforming growth factor (TGF)-β2 may induce tenogenesis in mesenchymal stem cells (MSC)s and impact levels of cadherin cell-cell junction proteins, including N-cadherin and Cadherin-11. However, the interactions between cadherins and intracellular signaling proteins during TGF-β2-induced tenogenesis are unknown. One such protein, β-catenin, is of interest due to its role in actin-cadherin coupling and the canonical Wnt pathway. We evaluated the role of β-catenin in TGF-β2-induced tenogenesis of MSCs and the impact on N-cadherin and Cadherin-11 levels. Mouse MSCs were supplemented with TGF-β2 to induce tenogenic differentiation, and a chemical inhibitor to inactivate GSK3β-mediated degradation of β-catenin and allow accumulation of cytosolic β-catenin. Total β-catenin levels, N-cadherin, and Cadherin-11 decreased with TGF-β2 treatment. Increasing cytosolic β-catenin via GSK3β inactivation also disrupted fibroblastic cell morphology. A tendon differentiation marker, tenomodulin, was not impacted. These results suggest that β-catenin may play a role in early tenogenesis, but that regulation of N-cadherin and Cadherin-11 occurs independently of β-catenin.