Introduction

Pluripotent stem cells are a fascinating type of stem cell with the remarkable ability to differentiate into any cell type in the body. Researchers and clinicians are particularly interested in these cells due to their potential applications in both research and therapeutic contexts. In this study note, we’ll delve into pluripotent stem cells found in the mammalian inner cell mass (ICM).

Structure of the Inner Cell Mass

• The inner cell mass resides within the blastocyst, a stage of early embryonic development.
• Blastocyst Formation:
  • The blastocyst forms through successive cleavages of the zygote.
  • Cavitation occurs, creating a fluid-filled cavity called the blastocoel.
  • The ICM clusters together within the blastocyst.
• ICM Fate:
  • The ICM will later differentiate into the epiblast.
  • The epiblast gives rise to all cell types in the adult body, including primordial germ cells.

Promoting Pluripotency of the ICM

• Transcription Factors:
  • Key regulatory factors maintain the transient pluripotency of the ICM:
    • Oct4
    • Nanog
    • Sox2
  • These factors keep the stem cells in an uncommitted, stem cell-like state.
  • As differentiation proceeds, they are gradually lost.
• Contrasting Factor:
  • Cdx2:
    • Upregulated in the outer cells of the morula (an earlier stage).
    • Promotes trophectoderm differentiation.
    • Represses epiblast development.

Mechanisms Controlling Gene Expression

• Cell-to-Cell Interactions:
  • Crucial for specifying ICM and trophectoderm architecture.
  • Factors include:
    • Cellular Polarity along the apicobasal axis.
    • Symmetrical or Asymmetrical Divisions.
    • Localization of Partitioning Proteins.
    • E-cadherin, a cell adhesion molecule.
• Hippo Pathway Activation:
  • E-cadherin activates the Hippo pathway specifically in the ICM.
  • This pathway represses the Yap-Taz-Tead transcriptional complex.

Conclusion

Pluripotent stem cells within the inner cell mass play a critical role in early embryonic development. Understanding the intricate mechanisms controlling gene expression in the ICM and trophectoderm holds promise for advancing stem cell-based therapies across a wide range of diseases.