The distinct nature of hematopoietic stem cell subpopulations studied in long-term stroma-associated culture in the mouse

Abstract

In this thesis a number of experiments is described which give evidence for the notion\nof a distinct nature of CFU-S and cells with LTRA in the mouse. The distinct nature is\nillustrated by the difference in growth characteristics of CFU-S and LTRA cells on preestablished\nbone marrow-derived stromal cell layers. We have exploited the culture of\nstem cells on stromal layers for the development of an in vitro assay for the\nquantification of long-term repopulating stem cells, marrow repopulating stem cells, and\nspleen colony forming stem cells. The basic principle for this assay is the presence of a\nfunctional hematopoietic micro-environment in vitro, formed by the marrow-derived\nstromal layer. Stromal layers of long-term bone marrow cultures were studied on their\nability to maintain stem cells with L TRA. For the measurement of L TRA we adapted a\nsyngeneic sex-mismatched bone marrow transplantation model. In addition, the\ninteraction of hematopoietic stem cells with fibronectin, a constituent of the hematopoietic rnicro~environment, was studied.\nThe thesis starts with a description of the current definitions of hematopoietic stem cells\n(Chapter 2). This is followed by an outline of the in vivo and in vitro hematopoietic\nmicro-environment of the bone marrow (Chapter 3). These two chapters precede the\nexperimental work, which is described and discussed throughout the Chapters 4-8. An\noverview of the present state of research on the cell adhesion properties of fibronectin,\nfocused on the hematopoietic cells, is part of Chapter 8. Finally, the most important\nresults are discussed in Chapter 9