Experimental analysis of cell interactions during hemopoiesis.

The principal approach was to study hemopoiesis on different stromal cell underlayers (fibroblasts or fibroblast-like cells covering a foreign body implanted into the peritoneal cavity of mice or other rodents) after intraperitoneal transplantation of syngeneic, allogeneic, and xenogeneic hemopoietic cells. The data obtained are compared with the results of experiments on repopulation of ectopic hemopoietic territories (under the mouse kidney capsule) by syngeneic and xenogeneic hemopoietic cells. Competitive cell interactions are described that occur during repopulation of the hemopoietic stroma or formation of the hemopoietic foci on cellulose acetate membranes (CAMs) in the peritoneal cavity of irradiated mice by genetically different hemopoietic cells transplanted to these animals (multicomponent radiation chimeras). The model of xenogeneic and multicomponent radiation chimeras was reproduced in long-term bone marrow cultures, where hemopoietic cells of different genotypes coexisted, without any competitive cell elimination. The second part of this review deals with hemopoiesis on stromal cell underlayers, formed by cells of different origin, different stages of development, and obtained from other sources. These underlayers were formed on CAMs in vitro and then transferred into the peritoneal cavity of irradiated mice, which subsequently received intraperitoneal injections of donor hemopoietic cells. Specific features of hemopoiesis on stromal underlayers formed by the following cell types are described: (1) fibroblasts from mouse embryos at different developmental stages; (2) fibroblasts from the skin, liver, and bone marrow of 17-day mouse fetuses and newborn mice; (3) fibroblasts from the monolayer cultures of mouse 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 observed in these experiments and their probable mechanisms are discussed.