skeletal myoblasts after myocardial infarction and inducibility of ventricular arrhythmias
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DESCRIPTIONSkeletal myoblasts after myocardial infarction and inducibility of ventricular arrhythmias. Patricia Lemarchand. Siminiak. Amiodarone. (POZNAN trial). for some Pt. Ménasché. (MAGIC trial). Clinical trials with autologous myoblasts. Study. Year. LVEF. Patient number. Arrhythmia. - PowerPoint PPT Presentation
Skeletal myoblasts after myocardial infarction and inducibility of ventricular arrhythmiasPatricia Lemarchand
Mnasch200324+/-4%104 VTSmits200336+/-11%134 VT (2 death)Pagani20035?Herreros200336+/-8%12Amiodarone20042540%104 VTChachques200428+/-3%20AmiodaroneDib200528%242 VT?61 VT?200515 to 35 %636 VTAmiodarone ICDStudyYearLVEFPatient numberArrhythmiaClinical trials with autologous myoblasts
Related toThe history of the heart failure ?The injection procedure ?The myoblast itself ?Ventricular arrhythmiasLife threatening adverse events
Myoblasts24h after injectionBone marrow cells
No spontaneous sustained ventricular tachycardiaOccurrence of extrasystoles- rare- similar in both groups
D8 - D35Vehicle (557 hrs) Myoblasts(573 hrs)Free moving animals Spontaneous arrhythmias
Myoblasts increased ventricular electrical excitability +++
Intramural monophasic action potential (1)myoblasts No electrical coupling
Electrical coupling and arrhythmiasWhy no electrical coupling?
Intramural monophasic action potential (2)Cx43 promotes electrical coupling
Small scale clinical trials of autologous myoblast transplantation suggested the feasibility of such therapy. However, these clinical trials were hampered by unexpected episodes of ventricular tachyarrhythmias within weeks following cell transfer.
Importantly, these trials were performed with patients having severe heart failure, and one knows that these patients are prone to ventricular arrhythmias. Since ventricular arrhythmias are life-threatening adverse events, it will be important to know if the arrhythmias are related to The natural history of heart failure, the injection procedure to deliver myoblasts into the myocardium, or the myoblast itself. To answer these questions, we set up an animal model to investigate arrhythmias related to myoblast transplantationThis model was the usual one for cardiac cell therapy studies with myoblasts: in rats, myocardial infarction was induced by coronary ligation and an electrode was tied to the left ventricle for electrophysiological studies. At the same time a sample of squeletal muscle was harvested to culture myoblasts, or bone marrow was harvested at day 7.
At day 7, rats with myocardial infarction were randomized in 4 groups: a control group with MI only, a second control group with MI and intramyocardial injection of vehicle, the medium in which cells were cultured, rats with MI and intramyocardial injection of autologous myoblasts, rats with MI and intramyocardial injection of autologous bone marrow cells
Following cell injection, at day 14 to 35 after MI induction, electrophysiological studies were performed, including ECG recordings and programmed electrical stimulations.
Slides of ventricular myocardium with fluorescent myoblasts or fluorescent bone marrow cells 24 hr after injection in the left ventricleAmbulatory Telemetric recordings were performed from day 8 to day 35 in free moving rats to record spontaneaous arrhythmias, in rats injected with vehicle or autologous myoblasts, for very long periods of time (more than 500 hours of recording in each group).
Here is an example of recordings, and we were looking for sustained VT, defined as a fast ventricular rhythm of 15 or more beats.
No spontaneous sustained ventricular tachycardia was observed Only ventricular premature beats, couplets, and triplets were observed, and they were rare and similar in both groupsWe then performed electrophysiological studies using non-invasive programmed electrical stimulation.
The protocol was similar to that in human clinical evaluations/procedures, with repeated 1 ms pulse pacings .
In this case a train of 9 stimuli did not trigger any arrhythmia.
In this case 3 sitmuli striggered a non-sustained ventricular tachycardia with spontaneous termination
And in this rat, 3stimuli trigerred a sustained ventricular tachycardia degenerating into ventricular fibrillation, and here a blow in the chest stopped the ventricular fibrillation. This animal had received autologous myoblasts.Here are the results for all groups with the % of rats experiencing at least one episode of sustained ventricular tachycardia in The 4 groups. The results were similar in the control and vehicle groups. In marked contrast, the number of rats experiencing sustained VT was significantly increased in rats with myoblasts but not in rat with bone marrow
Showing that Myoblasts increased ventricular electrical excitability.
If we look overtime, the number of newly inducible rats remained stable overtime in rats from both control groups and in rats with bone marrow cells. In contrast, the first episode of sustained VT occurred at day 14 and 21 in most of the rats with myoblasts, suggesting that increased excitability was transient, as described in human clinical trialsTo evaluate electrical coupling between transplanted myoblasts and host cardiomyocytes, we also measured intramural monophasic action potentials, using the same protocol, on langendorff-perfused hearts.
Recording electrodes were placed within the infarcted area and remote from the infarcted area.
Here is the typical monophasic action potential from the skeletal muscle, showing a very short spike.
Here in the recording from the infarcted area, showing both large ventricular signals from the cardiac muscle and short spikes from the transplanted myoblasts. Obviously short spikes and ventricular signals were independent,
showing no electrical coupling between host cadiomyocytes and transplanted myoblasts.And we know that the absence of such electrical coupling will favor reentry and increase ventricular excitability.
Regarding Electrical coupling and arrhythmias,
we know that the absence of electrical coupling favors reentry and may explain ventricular excitability
An hypothesis to explain such lack in electrical coupling is that mature muscle cells do not form gap junctions with cardiomyocytes, because mature muscle cells do not express CX43, the main ventricle gap junction protein.
Then we hypothesised that in vivo Cx43 overexpression in myoblasts will increase electrical coupling and I am going to show you preliminary results on that hypothesis.To evaluate this hypothesis, we overexpressed CX43, using a CX43 lentivirus vector to transduce and overexpress CX43 in myoblasts prior to transplantation.
Here is the recording from myocardium injected with myoblasts transduced with a control empty lentivirus.
Here is the recording from myocardium injected with myoblasts overexpressing connexin43, showing a synchrony between short spikes from myoblasts and ventricular signals,
suggesting that in vivo overexrpession of Cx43 promotes electrical coupling
In contrast with bone marrow cells, Myoblast transplantation induced a specific substrate for arrhythmias
Electrophysiological studies are feasible to identify potential arrhythmogeneic risk in cardiac cell therapy protocols and may be used for any cell of potential interest.