| dc.description.abstracteng | Atrial fibrillation is the most common supraventricular arrhythmia and is associated with molecular remodelling that promotes the maintenance and worsening of the disease. Although extensive research has been performed to develop treatments to hamper the progression of atrial fibrillation, many attempts showed disappointing results when transferred to clinics. One reason could be that the results obtained in the study models do not cross the transferability gap and the observed results could not be applicable to human pathophysiology. However, the exclusive utilisation of human tissue comes with a certain number of limitations, including the poor availability of the material. One solution could come from the huge progress made in the development of induced pluripotent stem cells (iPSC), and their utilisation for 3D in vitro modelling. Unlike human materials, they are readily available, and unlike animal models, the results obtained can better be transferred to human pathophysiology. Therefore, we hypothesised that atrial cardiomyocytes derived from iPSC could be used to study mechanisms associated with acute and long-term electrical remodelling in atrial fibrillation.
In the first part, we investigated whether atrial cardiomyocytes derived from induced pluripotent stem cells (atrial iPSC) could be a suitable model for studying acute (24 hours) electrical remodelling associated with atrial fibrillation. Results showed that 3 Hz electrically paced (tachypaced) atrial iPSC showed electrical remodelling characterised by a reduction of the action potential duration at 90% repolarisation (APD90), a decreased L-type Ca2+ current (ICa,L), an impaired activation of the acetylcholine-activated inward-rectifier K+ current (IK,ACh) and the development of a constitutively active and agonist independent IK,ACh. The IK,ACh impairment was associated with a significantly reduced expression of Kir3.4.
In the second part, we evaluated the effects of acute electrical tachypacing on atrial engineered human myocardium (EHM). We showed that electrical tachypacing for 24 hours was associated with a significant reduction of the APD90 and an impaired response to the M2-receptor agonist, carbachol.
In the last part, we investigated the effects of long-term optical tachypacing on atrial EHM. This was permitted by the utilisation of an atrial iPSC line expressing the fast variant of the channelrhodopsin chrimson. The acute optical tachypacing of chrimson atrial EHM showed the same electrical remodelling observed in the electrically tachypaced atrial EHM, characterised by a significant reduction of the APD90 and an altered response to the M2-receptor agonist carbachol. Additionally, long-term optical tachypacing (7 days) of chrimson atrial EHM resulted in a hyperpolarisation of the resting membrane potential, an increase in the action potential amplitude, and the maximum upstroke velocity.
Altogether, this thesis shows that atrial iPSC and atrial EHM models can be used as experimental tools to investigate the electrical remodelling associated with acute and long-term atrial fibrillation, thus giving an outlook on the possibilities of using novel genome editing technologies for the elaboration of study models. | de |