Human erythropoietin was first purified in 1977 from 2500 liters of urine from an anemic patient. Following this event, in 1985 the human erythropoietin cDNA sequence was mapped. Today, with advances in molecular genetics engineering, it is possible to synthesize recombinant human erythropoietin in various cell types.
Recombinant human erythropoietin synthesized in Escherichia coli is unstable at high temperatures and tends to aggregate. The mammalian cell system is the only expression system that can perfectly duplicate the complex structure of biological active erythropoietin that comprises two disulfide bridges and four glycosylation sites. The recombinant human erythropoietin synthesized in mammalian cells is more stable due to its 40% carbohydrate component.