Haematopoietic action of flt3 ligand on cord blood‐derived CD34‐positive cells expressing different levels of flt3 or c‐kit tyrosine kinase receptor: comparison with stem cell factor

Abstract

We compared the effect of human flt3 ligand (FL) and stem cell factor (SCF) on cord blood (CB)‐derived CD34+ cells expressing different levels of flt3 or c‐kit tyrosine kinase (TK) receptor in clonal cell culture. The c‐kit receptor was expressed by 58.5±16.7% of CB CD34+ cells (n = 19), in which c‐kithigh, c‐kitlow and c‐kit‐ cell populations could be identified. In contrast, the flt3 receptor (FR) was weakly expressed on 58.6±8.3% (n = 9) of CB CD34+ cells. FL+erythropoietin (Epo) failed to support erythroid burst (BFU–E) formation by any subpopulation of CD34+ cells. However, SCF+Epo supported BFU–E and erythrocyte‐containing mixed (CFU–mix) colony formation from all subpopulations. Interestingly, FL markedly augmented CFU–mix colony formation supported by interleukin (IL)‐ 3+Epo when CD34+c‐kitlow or CD34+FR+ cells were used as the target. On the other hand, SCF significantly enhanced CFU‐mix colony formation supported by IL‐3+Epo when CD34+c‐kithigh or low and CD34+FR+ cells were used. The replating potential of CFU–mix supported by IL‐3 + Epo + FL was greater when CD34+c‐kitlow or CD34+FR+ cells were used. When the CD34+c‐kitlow cells were used, the number of lineages expressed in secondary cultures of CFU–mix colonies derived from primary cultures containing IL‐3 + Epo+FL or SCF was significantly larger than when the primary cultures contained IL‐3+Epo. Furthermore, the number of long‐term culture‐initiating cells found in CD34+FR+ cells was larger than that in FR‐ cells. CB‐derived CD34+c‐kitlow cells represent a less mature population than c‐kithigh cells, as reported previously. Therefore, these results indicate that both FL and SCF can act on primitive multipotential progenitors. However, it is still uncertain whether CB‐derived CD34+FR+ cells are less mature than CD34+FR‐ cells.

Identification of Long-Term Repopulating Potential of Human Cord Blood-Derived CD34−flt3− Severe Combined Immunodeficiency-Repopulating Cells by Intra-Bone Marrow Injection

“…It is well documented that the tyrosine kinase receptors c-kit and flt3 are expressed and function in early mouse [1][2][3][4][5][6][7][8][9][10] and human hematopoiesis [1,[11][12][13][14][15][16][17][18][19][20][21]. Moreover, their respective ligands, stem cell factor (SCF) and flt3 ligand (FL), synergistically act with each other and play an important role in the regulation (generation, maintenance, proliferation, differentiation, and expansion) of early stages of murine and human candidate hematopoietic stem cells (HSCs) .…”

“…It is well documented that the tyrosine kinase receptors c‐kit and flt3 are expressed and function in early mouse [1, , , , , , , , –10] and human hematopoiesis [1, 11, , , , , , , , , –21]. Moreover, their respective ligands, stem cell factor (SCF) and flt3 ligand (FL), synergistically act with each other and play an important role in the regulation (generation, maintenance, proliferation, differentiation, and expansion) of early stages of murine and human candidate hematopoietic stem cells (HSCs) [1, , , , , , , , , , , , , , , , , , , –21]. The most primitive HSCs in mammals, including mice and humans, have long been believed to be CD34 antigen‐positive (CD34 + ) [22].…”

“…Until now, a number of studies have reported that flt3 is expressed and functioned in the human CD34 + hematopoietic progenitor cells [11, , , , , –17, 19, 20], including long‐term culture‐initiating cells (LTC‐ICs) [15, 20, 31]. However, only two reports have demonstrated, using the conventional intravenous injection method, that human CB‐ and bone marrow (BM)‐derived CD34 + HSCs capable of multilineage reconstitution in nonobese diabetic (NOD)/SCID mice express flt3 tyrosine kinase receptor [31, 32].…”

Membrane-bound human SCF/KL promotes in vivo human hematopoietic engraftment and myeloid differentiation

“…[17][18][19] For reconstitution of human myeloid and lymphoid cells, 5 ϫ 10 2 to 5.3 ϫ 10 4 FACS-purified CB Lin Ϫ CD34 ϩ CD38 Ϫ HSCs were transplanted into newborn sublethally irradiated (1.5 Gy) hSCF Tg NSG mice and into non-Tg NSG controls (Table 1). To determine the kinetics of human hematopoietic chimerism in the recipient circulation, we performed flow cytometric analysis of PB every 3 to 4 weeks starting at 4 to 6 weeks after transplantation.…”

Protective effect of Flt3L on organ structure during advanced multiorgan dysfunction syndrome in mice

“…In vitro studies have demonstrated that Flt3L promoted the differentiation of CD34 + hemopoietic stem cells from bone marrow and umbilical blood into DCs, and enhanced DC amplification resulting from GM-CSF and TNF-α induction, thereby increasing the number of DCs ( 15 ). In vivo studies have revealed that Flt3L increased the number of DCs in the spleen, bone marrow, lymph nodes and liver of mice ( 8 , 11 – 17 ).…”