Converse modulation of Wnt/β-catenin signaling during expansion and differentiation phases of Infrapatellar fat pad-derived MSCs for improved engineering of hyaline cartilage.

Mesenchymal stem cells (MSCs) are potential candidates in cell-based therapy for cartilage repair and regeneration. However, during chondrogenic differentiation, MSCs undergo undesirable hypertrophic maturation. This poses a risk of ossification in the neo-tissue formed that eventually impedes the clinical use of MSCs for cartilage repair. TGF-β is a potent growth factor used for chondrogenic differentiation of MSCs, however, its role in hypertrophy remains ambiguous. In the present work, we decipher that TGF-β activates Wnt/β-catenin signaling through SMAD3 and increases the propensity of Infrapatellar fat pad derived MSCs (IFP-MSCs) towards hypertrophy. Notably, inhibiting TGF-β induced Wnt/β-catenin signaling suppresses hypertrophic progression and enhances chondrogenic ability of IFP-MSCs in plasma hydrogels. Additionally, we demonstrate that activating Wnt signaling during expansion phase, promotes proliferation and reduces senescence, while improving stemness of IFP-MSCs. Thus, conversely modulating Wnt signaling in vitro during expansion and differentiation phases generates hyaline-like cartilage with minimal hypertrophy. Importantly, pre-treatment of IFP-MSCs encapsulated in plasma hydrogel with Wnt modulators followed by subcutaneous implantation in nude mice resulted in formation of a cartilage tissue with negligible calcification. Overall, this study provides technological advancement on targeting Wnt/β-catenin pathway in a 3D scaffold, while maintaining the standard chondro-induction protocol to overcome the challenges associated with the clinical use of MSCs to engineer hyaline cartilage.