Inhibition of transforming growth factor β signaling promotes epiblast formation in mouse embryos

Area of Science:

• Developmental Biology
• Stem Cell Biology
• Molecular Embryology

Background:

• Early embryonic development involves critical lineage segregation events, including the formation of hypoblast and epiblast from the inner cell mass.
• Pluripotency maintenance in embryonic stem cells (ESCs) is regulated by complex signaling networks.
• Small molecules offer a means to modulate these signaling pathways and study their effects on early development.

Purpose of the Study:

• To investigate the influence of small molecules and growth factors on second-lineage segregation in mouse preimplantation embryos.
• To determine the role of the transforming growth factor-beta (TGFβ) pathway in regulating epiblast and hypoblast formation.
• To assess the functional capacity of epiblast cells derived from manipulated signaling environments.

Main Methods:

• Treatment of mouse embryos at various preimplantation stages (two-cell, four-cell, morula) with specific small molecules and growth factors.
• Inhibition and activation of key signaling pathways including TGFβ, glycogen synthase kinase 3 (GSK3), bone morphogenetic protein 4 (BMP4), protein kinase A (PKA), and Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3).
• Assessment of epiblast and hypoblast cell numbers and proliferation, and evaluation of the pluripotency of derived ESCs.

Main Results:

• Inhibition of the TGFβ pathway significantly increased epiblast cell proliferation and formation, yielding functional pluripotent ESCs.
• Activation of the TGFβ pathway reduced epiblast formation.
• Inhibition of GSK3 and activation of BMP4 signaling decreased both epiblast and hypoblast formation, while PKA and JAK/STAT3 pathways showed no significant effect on lineage segregation.
• Simultaneous inhibition of TGFβ, GSK3β, and fibroblast growth factor (FGF)/extracellular signal-regulated kinases (Erk) pathways synergistically enhanced epiblast proliferation.

Conclusions:

• The TGFβ pathway plays a critical role in regulating second-lineage segregation during mouse preimplantation development.
• Modulating TGFβ signaling is a viable strategy to enhance epiblast proliferation and maintain pluripotency.
• Combined inhibition of TGFβ, GSK3β, and FGF/Erk pathways offers a potent method for promoting epiblast expansion, with implications for stem cell research and regenerative medicine.