Apoptotic dysregulation mediates stem cell competition and tissue regeneration

Area of Science:

• Stem cell biology
• Cellular mechanisms
• Tissue regeneration

Background:

• Adult stem cells are crucial for lifelong tissue repair and regeneration.
• Understanding stem cell behavior, particularly resistance to apoptosis, is vital for regenerative medicine.
• Dysregulated apoptosis in stem cells can impact tissue homeostasis and disease.

Purpose of the Study:

• To investigate the role of the pro-apoptotic protein Bax in hair follicle stem cell competition.
• To elucidate the molecular mechanisms by which Bax-deficient stem cells influence neighboring cells.
• To explore the therapeutic potential of modulating Bax in stem cell-driven tissue repair.

Main Methods:

• Utilized genetic manipulation to deplete the pro-apoptotic Bax protein in hair follicle stem cells.
• Investigated cell-cell interactions and the role of Tumor Necrosis Factor alpha (TNFα) in stem cell competition.
• Analyzed the activation of the NFκB pathway and the expression of TNF receptor 2 (TNFR2) in stem cells.
• Assessed the impact of Bax depletion on stem cell pool size and wound healing in vivo.

Main Results:

• Bax-deficient hair follicle stem cells eliminate viable neighbors through membrane-bound TNFα, inducing apoptosis in 'loser' cells via contact-dependent mechanisms.
• This competitive phenotype is mediated by intrinsic Nuclear Factor kappa B (NFκB) activation.
• Winner stem cells exhibit enhanced responsiveness to TNFα due to elevated TNFR2 expression.
• In vivo Bax depletion increases the stem cell pool, accelerating wound repair and hair follicle regeneration.

Conclusions:

• Established a novel mechanism of mammalian cell competition involving Bax-deficient stem cells and TNFα signaling.
• Demonstrated that Bax loss confers a competitive advantage to stem cells, promoting tissue regeneration.
• Highlighted the therapeutic implications of this cell competition mechanism for regenerative medicine and cancer research.