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Heparin is an essential anticoagulant used for treating and preventing thrombosis. However, the complexity of heparin has hindered the development of a recombinant source, making its supply dependent on a vulnerable animal population. In nature, heparin is produced exclusively in mast cells, which are not suitable for commercial production, but mastocytoma cells are readily grown in culture and make heparan sulfate, a closely related glycosaminoglycan that lacks anticoagulant activity. Using gene expression profiling of mast cells as a guide, a multiplex genome engineering strategy was devised to produce heparan sulfate with high anticoagulant potency and to eliminate contaminating chondroitin sulfate from mastocytoma cells. The heparan sulfate purified from engineered cells grown in chemically defined medium has anticoagulant potency that exceeds porcinederived heparin and confers anticoagulant activity to the blood of healthy mice. This work demonstrates the feasibility of producing recombinant heparin from mammalian cell culture as an alternative to animal sources.
Background: Although most biologics are produced using recombinant technologies, heparin persists as a product purified from animal tissues. A cell based system for production of heparin would eliminate risk of supply shortage and contamination. Additionally, genetic engineering could yield heparin with improved qualities such as reduced risk of heparin-induced thrombocytopenia. Aims: This work is focused on engineering mammalian cell lines and bioprocess methods to produce recombinant heparin. Methods: The heparan sulfate biosynthetic pathway of mastocytoma cells was genetically engineered to alter the expression of heparan sulfate sulfotransferases. The resulting cell lines were screened for production of anti-FXa activity. Heparan sulfate production from a candidate cell line was tested in chemically defined medium. The recombinant product was characterized structurally and in clotting, anti-protease and heparin induced thrombocytopenia assays. Results: Engineered cells produced heparan sulfate in chemically defined medium with anti-Xa and anti-IIa activity exceeding the requirement for unfractionated heparin despite having lower sulfate content. Chain length was longer than unfractionated heparin. Additionally, binding to platelet factor 4 was reduced compared to unfractionated heparin, suggesting less risk of heparin-induced thrombocytopenia. Conclusion: These results demonstrate the feasibility of producing a substitute for unfractionated heparin from recombinant cell culture. Additionally, recombinant technology may allowmore »