The intestinal stem cell markers Bmi1 and Lgr5 identify two functionally distinct populations

Area of Science:

• Gastroenterology and Hepatology
• Stem Cell Biology
• Regenerative Medicine

Background:

• The small intestine epithelium requires constant regeneration, maintained by intestinal stem cells (ISCs).
• Bmi1 and Lgr5 are known ISC markers, but their functional differences are unclear.

Purpose of the Study:

• To elucidate the functional distinctions between Bmi1-marked and Lgr5-marked ISCs in vivo.
• To define the roles of these ISC populations in homeostatic and injury-induced intestinal regeneration.

Main Methods:

• In vivo lineage tracing and functional assays in mice.
• Irradiation injury models to assess ISC responses.
• Clonogenic spheroid culture of isolated ISCs.

Main Results:

• Lgr5+ ISCs are mitotically active, Wnt-sensitive, and crucial for homeostatic regeneration, but sensitive to irradiation.
• Bmi1+ ISCs are quiescent, Wnt-insensitive, radiation-resistant, and serve as reserve stem cells.
• Post-irradiation, Bmi1+ ISCs proliferate to repopulate damaged crypts, demonstrating a lineage relationship with Lgr5+ cells.

Conclusions:

• Bmi1+ ISCs represent a quiescent, injury-inducible reserve population distinct from Lgr5+ ISCs.
• Distinct ISC populations orchestrate homeostatic versus injury-induced regeneration in the small intestine.