Disrupting Interactions Between β-Catenin and Activating TCFs Reconstitutes Ground State Pluripotency in Mouse Embryonic Stem Cells

Wnt pathway modulation generates blastomere-derived mouse embryonic stem cells with different pluripotency features

PURPOSE

This study aimed to determine the role of Wnt pathway in mouse embryonic stem cell (mESC) derivation from single blastomeres isolated from eight-cell embryos and in the pluripotency features of the mESC established.

METHODS

Wnt activator CHIR99021, Wnt inhibitor IWR-1-endo, and MEK inhibitor PD0325901 were used alone or in combination during ESC derivation and maintenance from single blastomeres biopsied from eight-cell embryos. Alkaline phosphatase activity, FGF5 levels, expression of key pluripotency genes, and chimera formation were assessed to determine the pluripotency state of the mESC lines.

RESULTS

Derivation efficiencies were highest when combining pairs of inhibitors (15-24.7%) than when using single inhibitors or none (1.4-10.1%). Full naïve pluripotency was only achieved in CHIR- and 2i-treated mESC lines, whereas IWR and PD treatments or the absence of treatment resulted in co-existence of naïve-like and primed-like pluripotency features. IWR + CHIR- and IWR + PD-treated mESC displayed features of primed pluripotency, but IWR + CHIR-treated lines were able to generate germline-competent chimeric mice, resembling the predicted properties of formative pluripotency.

CONCLUSION

Wnt and MAPK pathways have a key role in the successful derivation and pluripotency features of mESC from single precompaction blastomeres. Modulation of these pathways results in mESC lines with various degrees of naïve-like and primed-like pluripotency features.

Short-term retinoic acid treatment sustains pluripotency and suppresses differentiation of human induced pluripotent stem cells

Human pluripotent stem cells (hPSCs), including human embryonic stem cells (hESCs) derived from blastocyst and human induced pluripotent stem cells (hiPSCs) generated from somatic cells by ectopic expression of defined transcriptional factors, have both the ability to self-renew and to differentiate into all cell types. Here we explored the two antagonistic effects of retinoic acid (RA) on hiPSCs. Although RA has been widely described as a pharmacological agent with a critical role in initiating differentiation of pluripotent stem cells, we demonstrate that short-term RA exposure not only antagonizes cell differentiation and sustains pluripotency of hiPSCs, but it also boosts and improves their properties and characteristics. To shed light on the mechanistic insights involved in the resistance to differentiation of hiPSCs cultured in RA conditions, as well as their improved pluripotency state, we focused our attention on the Wnt pathway. Our findings show that RA inhibits the Wnt canonical pathway and positively modulates the Akt/mTOR signaling, explaining why such perturbations, under our experimental conditions, do not lead to hiPSCs differentiation. Altogether, these data uncover a novel role for RA in favouring the maintenance of ground-state pluripotency, supporting its bivalent role, dose- and time-dependent, for hiPSCs differentiation and self-renewal processes.