Abstract
Background: Hemophilia 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. Methods: Human 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. Results: Circulating 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%. Conclusions: Our 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.
Original language | English |
---|---|
Pages (from-to) | 1002-1010 |
Number of pages | 9 |
Journal | Journal of Gene Medicine |
Volume | 9 |
Issue number | 11 |
DOIs | |
Publication status | Published - Nov 2007 |
Externally published | Yes |
Keywords
- Alginate
- Factor IX
- Gene therapy
- Hemophilia B
- Microcapsules
- Myoblasts
ASJC Scopus subject areas
- Molecular Medicine
- Molecular Biology
- Genetics
- Drug Discovery
- Genetics(clinical)