Chromatographic separation of recombinant human erythropoietin isoforms

Erythropoietin (EPO) is the main regulator of erythropoiesis. The human glycoprotein hormone is heterogeneous when analyzed by isoelectric focusing (IEF). We investigated the possibility of fractionating EPO isoforms using different chromatographic methods. A recombinant human EPO (rhEPO) was obtained from the culture supernatants of a human B-lymphoblastoid cell line transfected by the human EPO gene. Highly purified rhEPO preparations were obtained by immunoaffinity purification. More than fourteen isoforms were observed after IEF. Among the different methods developed for isoform fractionation, the most reproducible results were obtained by DEAE-Sephacel chromatography. Seven fractions of decreasing isoelectric point (pI) were obtained. The specific activity of these fractions measured by an immunoradiometric assay was not equally distributed.