Cell cycle and differentiation of Sca-1 and Sca-1 hematopoietic stem and progenitor cells.

Hematopoietic stem and progenitor cells (HSPCs) are crucial for lifelong blood cell production. We analyzed the cell cycle and cell production rate in HSPCs in murine hematopoiesis. The labeling of DNA-synthesizing cells by two thymidine analogues, optimized for in-vivo use, enabled determination of the cell cycle flow rate into G2-phase, the duration of S-phase and the average cell cycle time in Sca-1 and Sca-1 HSPCs.

Stem Cell Defect in Ubiquitin-Green Fluorescent Protein Mice Facilitates Engraftment of Lymphoid-Primed Hematopoietic Stem Cells.

Transgenic mice expressing green fluorescent protein (GFP) are useful in transplantation experiments. When we used ubiquitin-GFP (UBC-GFP) transgenic mice to study the availability of niches for transplanted hematopoietic stem and progenitor cells, the results were strikingly different from the corresponding experiments that used congenic mice polymorphic in the CD45 antigen. Analysis of these unexpected results revealed that the hematopoiesis of UBC-GFP mice was outcompeted by the hematopoiesis of wild-type (WT) mice.

Low c-Kit Expression Level Induced by Stem Cell Factor Does Not Compromise Transplantation of Hematopoietic Stem Cells.

The c-Kit expression level is decreased in regenerating bone marrow, and such bone marrow performs poorly when co-transplanted with normal bone marrow. We asked whether diminished numbers of c-Kit receptors on hematopoietic stem and progenitor cells (HSPCs) after their internalization induced by the binding of the cytokine stem cell factor (SCF) would jeopardize transplantability of HSPCs. We used a battery of functional assays to evaluate the capacity of HSPCs with markedly different c-Kit expression levels to be transplanted.