Intricacies of Pluripotency

Area of Science:

• Stem cell biology
• Regenerative medicine
• Developmental biology

Background:

• Pluripotent stem cells, including embryonic stem (ES) cells, induced pluripotent stem (iPS) cells, and very small embryonic-like stem cells (VSELs), can differentiate into numerous cell types.
• VSELs are found in adult organs, unlike ES/iPS cells cultured in vitro, and possess distinct epigenetic properties.
• Nuclear OCT-4 is a key factor in maintaining pluripotency.

Purpose of the Study:

• To highlight the potential of VSELs for regenerative medicine.
• To discuss the unique characteristics of VSELs, including their epigenetic status and in vivo behavior.
• To propose a reconsideration of the definition of pluripotency based on VSELs' properties.

Main Methods:

• Comparative analysis of VSELs, ES cells, and iPS cells.
• Discussion of VSELs' epigenetic status and origin.
• Review of VSELs' behavior in adult organs and response to stress.

Main Results:

• VSELs exist in adult organs and may regenerate them, showing greater potential than in vitro-derived stem cells.
• VSELs' epigenetic status is closer to primordial germ cells than the inner cell mass from which ES cells are derived.
• VSELs mobilize under stress, divide asymmetrically, and generate tissue-specific progenitors without tumor formation or immune rejection risks.

Conclusions:

• VSELs are promising candidates for regenerative medicine due to their in vivo regenerative capacity and safety profile.
• VSELs might represent 'embryonic remnants' in adult organs and could be involved in cancer initiation.
• The scientific community should consider revising the definition of pluripotency to encompass VSELs' characteristics, as they differ from traditional ES/iPS cell models.