BONE-MARROW STROMAL CELLS INDUCE MYELOID AND LYMPHOID DEVELOPMENT OF THE SORTED HEMATOPOIETIC STEM-CELLS IN-VITRO

Regulation of development of hematopoietic stem cells was examined by culturing Lin(-) c-Kit(+) Sca1(+) stem cells sorted from bone marrow ( BM) cells by fluorescence-activated cell sorting on a layer of TBR59, a BM stromal cell line established from simian virus 40 T-antigen gene transgenic mice. The sorted stem cells did not show self-renewal, but two waves (at 7 and 13 days) of a cobblestone formation were induced by the stromal cell layer. The cobblestones were formed by finite cell division (eight divisions on average) of sorted Lin(-) c-Kit(+) Sca1( +) stem cells, and divided cells were still immature. The C-Kit(high) stem cell population was induced to form the first wave of cobblestone formation committed to myeloid lineage, whereas c-Kit(low) population was induced to form the second wave of this formation committed to ly mphoid lineage. Both cobblestone formations require c-Kit function, bu t very late activation antigen-4-vascular cell adhesion molecule-1 int eraction plays different parts in the two lineages. (C) 1995 by The Am erican Society of Hematology.