ERYTHROPOIETIN MESSENGER-RNA EXPRESSION IN HUMAN FETAL AND NEONATAL TISSUE

Based on animal experiments, a switch of the erythropoietin (EPO) prod uction site from the liver in the fetus to the kidneys in the adult ha s been postulated. To study the switch in humans, we have quantitated EPO mRNA expression in liver, kidney, spleen, and bone marrow of human fetuses and neonates by means of a competitive polymerase chain react ion (PCR), Tissue samples from 66 routine postmortem examinations were obtained. EPO mRNA was expressed in 97% of the tissue specimen derive d from the liver (n = 66) and in 93% of those from the kidneys (17 wee ks of gestation until 18 months after birth; n = 59). For the first ti me the EPO gene was found expressed in vivo in human spleen (96% of 64 samples) and in fetal and neonatal bone marrow (81% of 21 samples). E PO mRNA expression in the kidneys increased significantly beyond 30 we eks of gestation (P < .05). Although there was a slight decrease in EP O mRNA content per g liver tissue towards birth, the liver accounted f or about 80% of the total body EPO mRNA. The contribution of the splee n and bone marrow were minor compared with liver and kidneys. Our resu lts indicate that in humans the liver is the primary site of EPO gene expression not only in fetal, but also in neonatal life. A significant increase of renal EPO mRNA expression after 30 weeks of gestation mig ht indicate the beginning switch. (C) 1998 by The American Society of Hematology.