Tesi etd-03302023-173049
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Tipo di tesi
Dottorato
Autore
BURJANADZE, GIA
URN
etd-03302023-173049
Titolo
Delayed administration of pro-regenerative miR-199a after myocardial infarction: efficacy versus untoward effects
Settore scientifico disciplinare
MED/11
Corso di studi
Istituto di Scienze della Vita - PHD IN MEDICINA TRASLAZIONALE
Commissione
relatore Prof. RECCHIA, FABIO ANASTASIO
Parole chiave
- cardiomyocyte proliferation
- gene therapy
- miRNA-199a
- myocardial infarction
Data inizio appello
27/11/2023;
Disponibilità
completa
Riassunto analitico
Acute loss of a major amount of cardiac tissue following myocardial infarction frequently leads to heart failure, an illness with a low quality of life and a high death rate. Because the prevalence of heart failure is rising, the development of an effective and safe cardio-reparative therapy could mark a significant milestone in cardiovascular medicine. Our team recently demonstrated in a pig model that intramyocardial injection of miRNA-199a genes delivered by adeno-associated viral vectors (AAV) shortly after the induction of acute myocardial infarction (MI) resulted in nearly complete recovery of cardiac morpho-functional parameters. However, 6-7 weeks following miRNA-199a delivery, the majority of the animals died suddenly, most likely due to lethal arrhythmias.
The overarching goal of this study was to investigate the hypothesis that delaying AAV6-miR199a treatment during the healing phase of MI had therapeutic effects without inducing long-term lethal arrhythmias.
The first goal was to investigate whether the therapeutic efficacy of AAV6-miR-199a delivery is time-dependent. MI was caused by placing a balloon-tipped catheter into the left anterior descending coronary artery and occluding it for 90 minutes under X-ray fluoroscopic monitoring. To evaluate baseline cardiac morpho-functional features and scar diameters, all pigs underwent baseline cardiac MRI evaluation on day 5 (Protocol 1) or day 12 (Protocol 2) post-MI. Two days after MRI, animals underwent open-chest surgery and were randomly assigned to receive 2 x 1013 of AAV6-miR-199a or empty AAV6 (AAV-control) injected in multiple places along the infarct border zone. The animals had a second cardiac MRI one month after receiving AAV. Scar mass and global and regional contractile performance parameters were not significantly different between AAV6-miR-199a and AAV-control MI in either of the Protocols.
Despite the lack of significant morpho-functional changes, the majority of pigs in both protocols died of abrupt cardiac death 6-8 weeks after AAV6-miR-199a administration. We were able to record ECG tracings in several cases that indicated ventricular fibrillation as the cause of death.
Our second goal was to see if infarcted hearts treated with miR-199a have a decreased threshold for ventricular arrhythmias in response to aberrant electrical stimuli. In infarcted hearts, electrophysiology tests were performed six weeks following AAV6-miR-199a or AAV6-control administration. While all AAV6-control animals developed ventricular arrhythmias, AAV6-miR-199a-treated pigs exhibited unexpected resistance to external extra stimuli, even with the most intense stimulation pattern.
In conclusion, our findings suggest that gene therapy using miR-199a for cardiac repair loses efficacy when delivered 7 or more days after MI, while the propensity for deadly arrhythmias remains in treated hearts. Surprisingly, the infarcted hearts treated with miR-199a, have a higher threshold for ventricular arrhythmias in response to aberrant electrical stimuli. These data provide support for the idea that delivering miR-199a via AAV vectors, which results in long-term expression, is not the best approach. Future studies will examine different types of vectors for short-term expression of miR-199a, such as synthetic nanoparticles that can only be administered during the acute phase of MI.
The overarching goal of this study was to investigate the hypothesis that delaying AAV6-miR199a treatment during the healing phase of MI had therapeutic effects without inducing long-term lethal arrhythmias.
The first goal was to investigate whether the therapeutic efficacy of AAV6-miR-199a delivery is time-dependent. MI was caused by placing a balloon-tipped catheter into the left anterior descending coronary artery and occluding it for 90 minutes under X-ray fluoroscopic monitoring. To evaluate baseline cardiac morpho-functional features and scar diameters, all pigs underwent baseline cardiac MRI evaluation on day 5 (Protocol 1) or day 12 (Protocol 2) post-MI. Two days after MRI, animals underwent open-chest surgery and were randomly assigned to receive 2 x 1013 of AAV6-miR-199a or empty AAV6 (AAV-control) injected in multiple places along the infarct border zone. The animals had a second cardiac MRI one month after receiving AAV. Scar mass and global and regional contractile performance parameters were not significantly different between AAV6-miR-199a and AAV-control MI in either of the Protocols.
Despite the lack of significant morpho-functional changes, the majority of pigs in both protocols died of abrupt cardiac death 6-8 weeks after AAV6-miR-199a administration. We were able to record ECG tracings in several cases that indicated ventricular fibrillation as the cause of death.
Our second goal was to see if infarcted hearts treated with miR-199a have a decreased threshold for ventricular arrhythmias in response to aberrant electrical stimuli. In infarcted hearts, electrophysiology tests were performed six weeks following AAV6-miR-199a or AAV6-control administration. While all AAV6-control animals developed ventricular arrhythmias, AAV6-miR-199a-treated pigs exhibited unexpected resistance to external extra stimuli, even with the most intense stimulation pattern.
In conclusion, our findings suggest that gene therapy using miR-199a for cardiac repair loses efficacy when delivered 7 or more days after MI, while the propensity for deadly arrhythmias remains in treated hearts. Surprisingly, the infarcted hearts treated with miR-199a, have a higher threshold for ventricular arrhythmias in response to aberrant electrical stimuli. These data provide support for the idea that delivering miR-199a via AAV vectors, which results in long-term expression, is not the best approach. Future studies will examine different types of vectors for short-term expression of miR-199a, such as synthetic nanoparticles that can only be administered during the acute phase of MI.
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