The inherent differentiation program of short-term hematopoietic repopulating cells changes during human ontogeny

Area of Science:

• Hematology
• Developmental Biology
• Stem Cell Biology

Background:

• Human umbilical cord blood (CB) is a promising source for hematopoietic stem cell therapy due to accessibility and low immunogenicity.
• However, CB transplantation is associated with significantly delayed and deficient platelet recovery in recipients, a phenomenon with an unknown underlying cause.

Purpose of the Study:

• To investigate the intrinsic differentiation capacity of human short-term repopulating cells (STRCs) from CB.
• To elucidate the reasons for impaired megakaryopoiesis and subsequent thrombopoiesis in CB transplantation.

Main Methods:

• Quantitative xenotransplantation of human STRCs into NOD/SCID-beta2m(-/-) mice.
• Assessment of myeloid-restricted STRC-M cell output, focusing on megakaryocytic and erythroid differentiation.
• In vitro pre-treatment of CB cells with growth factors and in vivo administration of granulocyte colony-stimulating factor.

Main Results:

• CB-derived myeloid-restricted STRC-M exhibited significantly reduced megakaryocytic and erythroid cell output compared to adult sources.
• In vitro growth factor stimulation did not enhance megakaryocytopoiesis in vivo.
• In vivo administration of granulocyte colony-stimulating factor did not alter human STRC differentiation.

Conclusions:

• Human STRC differentiation capacity is developmentally regulated by intrinsic mechanisms.
• These mechanisms are not influenced by currently available hematopoietic growth factors.
• The findings explain the observed deficiency in thrombopoiesis following clinical CB transplantation.