COLONY-STIMULATING FACTOR-I EXPRESSION IN THE HUMAN FETUS AND NEWBORN

Colony-stimulating factor-1 (CSF-1) is a hematopoietic growth factor t hat regulates the survival, proliferation, and differentiation of mono nuclear phagocytes. Because this cellular compartment undergoes major changes during fetal and neonatal Life, we examined concurrent CSF-1 e xpression during human development. While levels increased dramaticall y after full-term birth, CSF-1 concentrations steadily declined in the preterm circulation from 2.7 to 1.9 times adult values as gestational age increased. CSF-1 was already detectable at 10 weeks gestation in spleen, intestine, lung, kidney, heart, and liver in order of decreasi ng concentration, but a positive correlation with gestational age was seen only in lung and intestine. Although a 4.4-kb CSF-1 mRNA was dete ctable in all tissues at all gestational ages, increased expression wi th advancing gestational age was observed in lung and kidney, whereas a rise and fall was observed in spleen. We conclude that CSF-1 concent ration in the human circulation is developmentally regulated and that its expression in fetal tissues is compatible with its role in regulat ing the development of tissue mononuclear phagocytes.