Cripto regulates hematopoietic stem cells as a hypoxic-niche-related factor through cell surface receptor GRP78

Area of Science:

• Hematology
• Stem Cell Biology
• Molecular Biology

Background:

• Hematopoietic stem cells (HSCs) reside in specialized hypoxic niches within the bone marrow endosteum.
• Maintaining HSC quiescence and function is critical for lifelong blood cell production.

Purpose of the Study:

• To investigate the role of Cripto and its receptor GRP78 in regulating HSCs within their native niche.
• To elucidate the molecular mechanisms by which Cripto/GRP78 signaling influences HSC behavior and localization.

Main Methods:

• Flow cytometry to identify HSC subpopulations based on GRP78 expression.
• In vitro assays to assess HSC capacity and glycolytic activity.
• In vivo studies using HIF-1α knockout mice and GRP78 blocking agents.

Main Results:

• Two distinct CD34(-)KSL cell subpopulations were identified based on GRP78 expression, with differing reconstitution potentials.
• GRP78(+)HSCs, found in endosteal regions, are more hypoxic and maintain their capacity via Cripto-induced glycolysis.
• HIF-1α deficiency reduced GRP78(+)HSCs and Cripto expression; GRP78 blockade caused HSCs to migrate from the endosteum.

Conclusions:

• Cripto/GRP78 signaling is a key regulator of HSC quiescence and hypoxic niche maintenance.
• This pathway acts as an intermediary for HIF-1α in controlling HSC localization and function.
• Targeting Cripto/GRP78 may offer new strategies for modulating HSC behavior in therapeutic applications.