Yes-associated protein 1 regulates proliferation of mesenchymal stem cells by regulating the β-catenin signaling pathway

Abstract Objectives: The placenta and umbilical cord are preeminent candidate sources of mesenchymal stem cells (MSCs). However, placenta-derived MSCs (P-MSCs) showed greater proliferation capacity than umbilical cord-derived MSCs (UC-MSCs) in our study. We investigated the drivers of this proliferation difference and elucidated the mechanisms of proliferation regulation. Materials and Methods: Proteomic profiling and Gene Ontology (GO) functional enrichment were conducted to identify candidate proteins that may influence proliferation. Using lentiviral or small interfering RNA infection, we established overexpression and knockdown models and observed changes in cell proliferation to examine whether a relationship exists between the candidate proteins and proliferation capacity. Real-time quantitative polymerase chain reaction, western blotting, and immunofluorescence assays were conducted to elucidate the mechanisms underlying proliferation. Results: Six candidate proteins were selected based on the results of proteomic profiling and GO functional enrichment. Through further validation, Yes-associated protein 1 (YAP1) and β-catenin were confirmed to affect MSC proliferation rates. YAP1 and β-catenin showed increased nuclear co-localization during cell expansion. YAP1 overexpression significantly enhanced proliferation capacity and upregulated the expression of both β-catenin and the transcriptional targets of Wnt signaling, CCND1 and c-MYC, whereas silencing β-catenin attenuated this effect. We found that YAP1 directly interacts with β-catenin in the nucleus to form a transcriptional YAP/β-catenin/TCF4 complex. Conclusions: Our study revealed that YAP1 and β-catenin cause the different proliferation capacities of P-MSCs and UC-MSCs. Mechanism analysis showed that YAP1 stabilized the nuclear β-catenin protein, and also triggered the Wnt/β-catenin pathway, promoting proliferation.