Hemophilia B is a bleeding disorder caused by the lack of FIX in the plasma and affects 1 in 30,000 males. Patients suffer from recurrent bleeds in soft tissues leading to physical disability in addition to life threatening bleeds. Current treatment (based on FIX infusion) is transient and plagued by increased risk for blood-borne infections (HCV, HIV), high costs and limited availability. This has fueled a search for gene/cell therapy based alternatives. Gene therapy with viruses is beset with problems of safety and increased immunogenicity. Being the natural site of FIX synthesis, the liver is expected to provide immune-tolerance and easy circulatory access. Liver transplantation is a successful, long-term therapeutic option but is limited by scarcity of donor livers and chronic immunosuppression, making iPSC-based cell therapy an attractive prospect. As part of this project, we will generate iPSCs from hemophilic patients that will be genetically corrected by inserting FIX coding DNA. After correction, we will differentiate these iPSCs into liver cells which will then be transplanted into our mouse model of hemophilia that can accept human hepatocytes and allow their proliferation. These mice exhibit disease symptoms similar to human patients and we propose that by injecting our corrected liver cells they will exhibit normal clotting as measured by various biochemical and physiological assays. If successful, this will provide a long-term cure for hemophilia and will serve as a proof-of-concept for the treatment of other liver diseases.
With this long term aim, during the first year of the project, we have procured two hemophilic patient samples and two control samples from our collaborators. We have successfully generated iPSCs with no long-term genomic changes. We are currently working towards identifying the mutations in the patients that were responsible for the disease. Our efforts are presently directed towards correcting the mutations in the patient derived iPSCs so that they can now produce a functional FIX protein.