Fetal hematopoietic stem cells express MFG-E8 during mouse embryogenesis.

Area of Science:

• Developmental Biology
• Hematology
• Cell Biology

Background:

• Milk fat globule-EGF-factor 8 protein (MFG-E8) is known for roles in cell interactions and tissue repair.
• MFG-E8 expression has been observed in various tissues, but its presence in hematopoietic stem cells (HSCs) during hematopoiesis was previously unreported.

Purpose of the Study:

• To investigate the expression of MFG-E8 in hematopoietic tissues during mouse embryogenesis.
• To determine if MFG-E8 is present in fetal HSCs and explore its potential role in embryonic hematopoiesis.

Main Methods:

• Immunohistochemistry was used to detect MFG-E8 expression in embryonic hematopoietic sites.
• Fluorescence-activated cell sorting (FACS) and polymerase chain reaction (PCR) were employed to analyze MFG-E8 expression in purified HSC populations.

Main Results:

• MFG-E8 was specifically expressed in CD34(+) HSCs across all embryonic hematopoietic sites (yolk sac, aorta-gonad-mesonephros, placenta, fetal liver).
• Purified fetal liver CD34(+) cells, expressing c-Kit and Sca-1, showed high MFG-E8 expression, unlike CD34(-) cells.
• MFG-E8 was absent in adult mouse bone marrow HSCs, being confined to F4/80(+) macrophages.

Conclusions:

• This study provides the first evidence of MFG-E8 expression in fetal HSC populations.
• MFG-E8 likely plays a significant role in embryonic hematopoiesis.