ROLE AND EXPRESSION OF COLONY-STIMULATING FACTOR-I AND STEEL FACTOR RECEPTORS AND THEIR LIGANDS DURING PREGNANCY IN THE MOUSE

It is becoming apparent that the effects of female sex steroid hormone s can be mediated by locally synthesized polypeptide growth factors in the uterus. In this paper we describe the patterns of expression of t wo such growth factors, steel factor and colony stimulating factor-1 ( CSF-1), and their transmembrane tyrosine kinase receptors, the product s of the c-kit and c-fms proto-oncogenes respectively. Both these uter ine synthesized cytokines are directed to uterine hematopoietic cells, the preimplantation embryo and to the extra-embryonic tissues during the postimplantation period. Studies with the CSF-1-deficient osteopet rotic (op/op) mouse show that CSF-1 has important roles during embryon ic development and in the regulation of uterine macrophages. These stu dies establish that CSF-1, whose sex steroid hormone-induced synthesis is restricted to the uterine epithelium, has a paracrine action on em bryos as well as being a mediator of epithelial-mesenchymal interactio ns.