Figure 3

Localization of CXCL12⁺ cells in control and myelodysplastic syndrome (MDS)/acute myelogenous leukemia with myelodysplasia-related changes (AML-MRC) bone marrow. (a–d) Double immunostaining for CXCL12 (blue) and CD34 (brown) in bone marrow samples. Black arrowheads indicate CXCL12⁺ cells. White arrowheads indicate CD34⁺ hematopoietic cells. Black arrows indicate vascular endothelial cells (also CD34⁺). Among the CD34⁺ cells, we distinguished between vascular endothelial cells and CD34⁺ hematopoietic cells as follows. The vascular endothelial cells were elongated and formed luminal spaces, whereas CD34⁺ hematopoietic cells were spherical and had a large round nucleus and scant cytoplasm (high N/C ratio). Scale bar indicates 25 μm. (a and b) Representative images of control bone marrow showing parenchymal (a) and perivascular (b) localization of CXCL12⁺ cells and their proximity to CD34⁺ hematopoietic cells. (c and d) Representative images of myelodysplastic syndrome (MDS bone marrow showing increased numbers of CD34⁺ hematopoietic cells near CXCL12⁺ cells. The clusters of CD34⁺ hematopoietic cells (abnormal localization of immature (ALIP)) also localized near CXCL12⁺ cells (d). (e) Triple immunostaining for CXCL12 (red), CD34 (brown), and c-kit (blue) in MDS bone marrow. Scale bars indicate 25 μm (left panel) and 10 μm (right panels). Black arrows indicate vascular endothelial cells identified as CD34⁺c-kit^- elongated luminal structure. White arrowheads indicate CD34⁺ hematopoietic cells identified as CD34⁺c-kit⁺ round cells with high N/C ratio. CXCL12⁺ cells (black arrowheads) were located in the perivascular area and among the hematopoietic nests. They were mostly in contact with CD34⁺c-kit⁺ hematopoietic cells.