Rescue Of Ctni Null Mice By Application Of Aav-9 Encoding Ctni Gene

Background: Heart diastolic dysfunction can be caused by cardiac troponin I (cTnI) deficiencies or mutations. Our lab has created a unique cTnI gene knockout mouse model, demonstrating that homozygous cTnI null mice (-/-) die at postnatal day 18 (p18). In this study, we have applied gene therapy using adeno-associated virus serotype 9 (AAV9) carrying wild-type cTnI gene to rescue mice from a lethal cTnI knockout phenotype. Methods: The proposed gene therapy strategies involve novel approaches delivering AAV9 via intraperitoneal injection in newborn cTnI mice (-/-), employing a cardiac-specific promoter (chicken cTnT promoter) to express cTnI protein in myocardial cells. Results: Mice treated with doses ranging from 2e10 10 vg/g (vector genome per gram) to 8e10 10 vg/g at p10 displayed an increased life span compared to mice without treatment. 5e10 10 vg/g multi-injection two-dose treatment at p10 and p14 demonstrated 22 additional days of life past p18 ( Figure A) . Using echocardiography, treated mice showed significant improvement in left ventricular diastolic function compared to mice without treatment. In addition, western blotting of cardiac samples demonstrated restored cTnI proteins in treated mice. Conclusion: The in vivo gene therapy approach shows that our mouse model can survive 2-3 weeks longer than untreated cTnI null mice. These data suggest AAV-9 serotype with a cardiac-specific promoter is a promising tool in treating cardiomyopathies by restoring cardiac proteins and reversing diastolic dysfunction.