Multi-lineage 'stem' cells in the mammalian embryo.

Area of Science:

• Developmental biology
• Cell biology
• Mammalian embryology

Background:

• The definition of 'stem cell' varies between cell biology and embryology.
• Studies on tissue renewal kinetics in mature organisms have refined the term 'stem cell' in cell biology.
• In embryology, 'stem cell' is often synonymous with 'progenitor cell'.

Purpose of the Study:

• To review methods for identifying multi-lineage progenitor cells in mammals.
• To discuss the occurrence and properties of progenitor cells in embryonic and extra-embryonic tissues of the mouse conceptus.
• To examine attributes of stem cells derived from in vitro blastocyst outgrowths.

Main Methods:

• Examination of established methods for identifying multi-lineage progenitor cells.
• Review of literature on progenitor cell occurrence and properties in mouse conceptus tissues.
• Discussion of stem cell characteristics from in vitro blastocyst outgrowths.

Main Results:

• Progenitor cells are key to tissue renewal and have distinct properties in embryonic and extra-embryonic contexts.
• Mammalian progenitor cell identification methods are established.
• Stem cells from in vitro blastocyst outgrowths exhibit specific attributes.

Conclusions:

• The distinction between 'stem cell' and 'progenitor cell' is context-dependent.
• Understanding progenitor cells in mammalian development is critical for developmental biology.
• In vitro culture systems provide insights into stem cell potential.