Encapsulated human primary myoblasts deliver functional hFIX in hemophilic mice Journal Articles uri icon

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abstract

  • AbstractBackgroundHemophilia B is a bleeding disorder caused by defective factor IX (FIX), currently treated by regular infusions of plasma‐derived or recombinant FIX. We propose a gene therapy strategy based on the implantation of cells secreting FIX enclosed in alginate microcapsules as a highly desirable alternative treatment. We have reported sustained delivery of human factor IX (hFIX) in immunocompetent mice implanted with encapsulated primary mouse myoblasts engineered to secrete hFIX. As a step towards the treatment of human patients, in this study we report the implantation of encapsulated human primary myoblasts secreting hFIX in hemophilia B mice.MethodsHuman primary myoblasts were transfected with plasmids pKL4M‐hFIX, pLNM‐βIXL, pMFG‐hFIX, and transduced with retrovirus MFG‐hFIX. Two human primary myoblast clones secreting ∼1 µg hFIX/106 cells/day were enclosed in biocompatible alginate microcapsules and implanted intraperitoneally into SCID and hemophilic mice.ResultsCirculating hFIX (peak of ∼120 ng/ml) was detected in hemophilia B mice on day 1 after implantation. Human FIX delivery was transient, however, becoming undetectable on day 14. Concurrently, anti‐hFIX antibodies were detected. At the same time, activated partial thromboplastin time (APTT) was reduced from 94 s before treatment to 78–80 s. Tail bleeding time decreased from 15 min to 1.5–7 min after treatment, some mice being normalised. These findings indicate that the delivered hFIX is biologically active. Similarly treated NOD/SCID mice had circulating hFIX levels of 170 ng/ml on day 1 that remained detectable for 1 month, albeit at low levels. Cell viability of microcapsules retrieved on day 60 was below 5%.ConclusionsOur findings indicate that encapsulated human primary myoblasts secrete functional hFIX. Furthermore, implantation of encapsulated human primary myoblasts can partially correct the phenotype of hemophilia B mice, supporting the feasibility of this gene therapy approach for hemophilia B. However, the long‐term viability of the encapsulated human myoblasts must first be improved. Copyright © 2007 John Wiley & Sons, Ltd.

publication date

  • November 2007