EXPERIMENTAL-ANALYSIS OF CELL-INTERACTIONS DURING HEMATOPOIESIS

The principal approach was to study hemopoiesis on different stromal c ell underlayers (fibroblasts or fibroblast-like cells covering a forei gn body implanted into the peritoneal cavity of mice or other rodents) after intraperitoneal transplantation of syngeneic, allogeneic, and x enogeneic hemopoietic cells. The data obtained are compared with the r esults of experiments on repopulation of ectopic hemopoietic territori es (under the mouse kidney capsule) by syngeneic and xenogeneic hemopo ietic cells. Competitive cell interactions are described that occur du ring repopulation of the hemopoietic stroma or formation of the hemopo ietic foci on cellulose acetate membranes (CAMs) in the peritoneal cav ity of irradiated mice by genetically different hemopoietic cells tran splanted to these animals (multicomponent radiation chimeras). The mod el of xenogeneic and multicomponent radiation chimeras was reproduced in long-term bone marrow cultures, where hemopoietic cells of differen t genotypes coexisted, without any competitive cell elimination. The s econd part of this review deals with hemopoiesis on stromal cell under layers, formed by cells of different origin, different stages of devel opment, and obtained from other sources. These underlayers were formed on CAMs in vitro and then transferred into the peritoneal cavity of i rradiated mice, which subsequently received intraperitoneal injections of donor hemopoietic cells. Specific features of hemopoiesis on strom al underlayers formed by the following cell types are described: (1) f ibroblasts from mouse embryos at different developmental stages; (2) f ibroblasts from the skin, liver, and bone marrow of 17-day mouse fetus es and newborn mice; (3) fibroblasts from the monolayer cultures of mo use and rat bone marrow; (4) 3T3 cell line; (5) hepatocytes of 17-day mouse fetuses or sexually mature rats; (6) newborn mouse kidney cells; and (7) cells transgenic for the erythropoietin gene. The phenomena o bserved in these experiments and their probable mechanisms are discuss ed.