Ca²⁺-mitochondria axis drives cell division in hematopoietic stem cells

Area of Science:

• Stem cell biology
• Mitochondrial function
• Calcium signaling

Background:

• Hematopoietic stem cells (HSCs) reside in a quiescent state in the bone marrow (BM), characterized by low mitochondrial membrane potential (ΔΨm).
• Stress hematopoiesis triggers HSC division, but the initiating mechanisms remain poorly understood.

Purpose of the Study:

• To investigate the role of mitochondria in regulating HSC cell cycle transitions during stress hematopoiesis.
• To elucidate the underlying mechanism initiating HSC division.

Main Methods:

• Analysis of mitochondrial changes in HSCs following bone marrow suppression induced by 5-fluorouracil (5-FU).
• Assessment of intracellular calcium levels and mitochondrial membrane potential (ΔΨm) in HSCs.
• Pharmacological modulation of intracellular calcium using adenosine and Nifedipine.

Main Results:

• HSCs initiate cell division following an enhancement in ΔΨm, linked to increased intracellular Ca2+.
• Overactivation of the Ca2+-mitochondria pathway results in HSC loss post-division.
• Suppression of intracellular Ca2+ using adenosine or Nifedipine prolonged HSC division intervals, enabling both division and maintenance.

Conclusions:

• The Ca2+-mitochondria pathway is a critical regulator of HSC division.
• Modulating intracellular Ca2+ levels is crucial for balancing HSC division and long-term maintenance, thereby determining HSC cell fate.