Erythropoietin and erythropoietin receptor in the developing human central nervous system

We have previously shown the presence of erythropoietin (Epo) within the spinal fluid of normal preterm and term infants, and the presence of Epo receptor (Epo-R) in the spinal cords of human fetuses. It is not known, however: 1) whether cells within the fetal central nervous system (CNS) express Epo; 2) if so, whether this expression changes with development; 3) which cells within the CNS express Epo-R; 4) whether Epo-R expression within the CNS changes with development; and 5) whether Epo-R within the fetal CNS are functional. Expression of mRNA for Epo and Epo-R was sought by reverse transcription-PCR in mixed primary cultures of fetal spinal cords as well as NT2 and hNT cells, human cell lines of neuronal precursors and mature neurons, respectively. Epo was measured by ELISA in spent media from primary cell culture, and immunohistochemistry was used to identify Epo-R on neurons and glia in cell culture, and in brain sections. Developmental changes in Epo and Epo-R expression were sought in spinal cords and brains from fetuses of 7-24 wk postconception by semiquantitative PCR. To assess Epo-R function, NT2 cells were exposed to conditions which stimulate programmed cell death, and rescue from apoptosis by the addition of recombinant Epo was evaluated by nuclear matrix protein ELISA, cell counts, and by Klenow labeling of DNA fragments. Epo and Epo-R mRNA were expressed in mixed primary cultures of neural tissues and NT2 and hNT cells. Epo was detected by ELISA in media removed from mixed cell cultures, and immunohistochemical staining confirmed the presence of Epo-R on neurons and their supporting cells. Semiquantitative PCR revealed no significant change in expression of either Epo or Epo-R in spinal cords between 7 and 16 wk of gestation, with increased expression of Epo and Epo-R in brains from 8 to 24 wk of gestation. Epo mRNA expression from neurons doubled under conditions of hypoxia. Recombinant Epo decreased apoptotic cell death of neurons under conditions of hypoxia. Protein and mRNA for Epo and its receptor are expressed by human neurons and glial cells in spinal cord and brain during fetal development. These receptors appear to have a neuroprotective effect in conditions of hypoxia.