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Regulation of human factor IX expression using doxycycline-inducible gene expression system
Mahmoud A Srour1, Henry Fechner, Xiaomin Wang
1Institute for Experimental Hematology and Transfusion Medicine, University Clinics Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany.
Thrombosis and Haemostasis
|September 6, 2003
Summary
Gene therapy for hemophilia B using adenovectors offers an alternative to factor IX (hFIX) concentrate. This study developed a Tet-On system for controlled hFIX expression, demonstrating safe therapeutic levels in mice.
Area of Science:
- Gene therapy
- Molecular biology
- Hematology
Background:
- Hemophilia B is currently treated with factor IX (hFIX) concentrate substitution therapy.
- Viral gene transfer is an emerging alternative, but high hFIX expression may cause thrombosis.
- Controlling transgene expression within a therapeutic range is crucial for safety.
Purpose of the Study:
- To develop a tetracycline (Tet)-inducible gene regulatory system for controlled hFIX expression.
- To evaluate the efficacy and safety of this system in vitro and in vivo.
Main Methods:
- Constructed two adenovectors: Ad5.TRE.hFIX (hFIX expression) and Ad5.CMV.rtTA or Ad5.hAAT.rtTA (regulator).
- Tested expression in human cell lines and in SCID-mice.
- Administered doxycycline to modulate hFIX expression.
Main Results:
- The Ad5.TRE.hFIX/Ad5.CMV.rtTA combination showed high hFIX expression in vitro and in vivo.
- Doxycycline successfully regulated hFIX expression up and down in vitro and in vivo for at least two months.
- hFIX expression remained within the therapeutic range in mice, despite a gradual decrease over time.
Conclusions:
- A Tet-On system using adenovectors enables controllable hFIX expression for hemophilia B gene therapy.
- This system allows for safe therapeutic hFIX levels, avoiding risks associated with supra-physiological expression.
- This represents a novel method for regulating hFIX expression in gene therapy applications.