Structure of rhTPO. Recombinant human TPO (rhTPO) is a fully glycosylated TPO made in Chinese hamster ovary (CHO) cells. It contains the TPO receptor binding domain (Mpl-binding domain) and the carbohydrate-rich COOH terminal domain. Red arrows indicate alpha helical areas; blue ovals denote areas of glycosylation. Illustration by Paulette Dennis.