Role of N-Cadherin in a Niche-Mimicking Microenvironment for Chondrogenesis of Mesenchymal Stem Cells <i>In Vitro</i>

Abstract

During the development of natural cartilage, mesenchymal condensation is the starting event of chondrogenesis, and mesenchymal stem cells (MSCs) experienced a microenvironment transition from primarily cell–cell interactions to a later stage, where cell–extracellular matrix (ECM) interactions dominate. Although micromass pellet culture has been developed to mimic mesenchymal condensation in vitro, the molecular mechanism remains elusive, and the transition from cell–cell to cell–ECM interactions has been poorly recapitulated. In this study, we first constructed MSC microspheres (MMs) and investigated their chondrogenic differentiation with functional blocking of N-cadherin. The results showed that early cartilage differentiation and cartilage-specific matrix deposition of MSCs in the group with the N-cadherin antibody were significantly postponed. Next, poly(l-lysine) treatment was transiently applied to promote the expression of N-cadherin gene, CDH2, and the treatment-promoted MSC chondrogenesis. Upon one-day culture in MMs with established cell–cell adhesions, collagen hydrogel-encapsulated MMs (CMMs) were constructed to simulate the cell–ECM interactions, and the collagen microenvironment compensated the inhibitory effects from N-cadherin blocking. Surprisingly, chondrogenic-differentiated cell migration, which has important implications in cartilage repair and integration, was found in the CMMs without N-cadherin blocking. In conclusion, our study demonstrated that N-cadherin plays the critical role in early mesenchymal condensation, and the collagen hydrogel provides a supportive microenvironment for late chondrogenic differentiation. Therefore, sequential presentations of cell–cell adhesion and cell–ECM interaction in an engineered microenvironment seem to be a promising strategy to facilitate MSC chondrogenic differentiation.

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