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 hormones can be mediated by locally synthesized polypeptide growth factors in the uterus. In this paper we describe the patterns of expression of two such growth factors, steel factor and colony stimulating factor-1 (CSF-1), and their transmembrane tyrosine kinase receptors, the products of the c-kit and c-fms proto-oncogenes respectively. Both these uterine 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 osteopetrotic (op/op) mouse show that CSF-1 has important roles during embryonic development and in the regulation of uterine macrophages. These studies establish that CSF-1, whose sex steroid hormone-induced synthesis is restricted to the uterine epithelium, has a paracrine action on embryos as well as being a mediator of epithelial-mesenchymal interactions.