Periodic Reporting for period 4 - REJUVENATION (Repair of Junctional Atrioventricular Conduction and Impulse Formation)
Période du rapport: 2021-10-01 au 2022-09-30
Background and importance for society
Every year around 300.000 European citizens receive electronic pacemaker therapies. These therapies were introduced into clinical medicine in the 1950s and 1960s and since then have gradually been improved. Regardless of these improvements, they are still not without important limitations such as inadequate sensitivity to autonomic modulation, a limited battery lifetime, which requires replacement every 5-7 years, and a non-physiological implantation site that is associated with significant adverse remodeling. Moreover, five per cent of the electronic pacemaker implantations result in serious complications that require reimplantation or other invasive procedures. In an effort to resolve the shortcomings of electronic pacemakers, extensive efforts have been put into the development of biological pacemakers using gene and cell-based therapies. Several of these developments have shown robust function in short-term animal trials and it appears only a matter of time before clinical trials will be initiated. The focus of current biological pacemaker research has been on pacing of the atrium and ventricle, thereby representing approximately 20% of the patients that now need electronic pacemaker therapies. Yet the majority of patients would benefit from repair of atrioventricular (AV) conduction, but this has been difficult to achieve biologically.
Objective
This ERC starting grant aims to develop cell-based biological pacemakers and AV bypass tracts in an effort to develop better treatments for bradyarrhythmia patients.
Every year around 300.000 European citizens receive electronic pacemaker therapies. These therapies were introduced into clinical medicine in the 1950s and 1960s and since then have gradually been improved. Regardless of these improvements, they are still not without important limitations such as inadequate sensitivity to autonomic modulation, a limited battery lifetime, which requires replacement every 5-7 years, and a non-physiological implantation site that is associated with significant adverse remodeling. Moreover, five per cent of the electronic pacemaker implantations result in serious complications that require reimplantation or other invasive procedures. In an effort to resolve the shortcomings of electronic pacemakers, extensive efforts have been put into the development of biological pacemakers using gene and cell-based therapies. Several of these developments have shown robust function in short-term animal trials and it appears only a matter of time before clinical trials will be initiated. The focus of current biological pacemaker research has been on pacing of the atrium and ventricle, thereby representing approximately 20% of the patients that now need electronic pacemaker therapies. Yet the majority of patients would benefit from repair of atrioventricular (AV) conduction, but this has been difficult to achieve biologically.
Objective
This ERC starting grant aims to develop cell-based biological pacemakers and AV bypass tracts in an effort to develop better treatments for bradyarrhythmia patients.
One of the goals of this project was to identify strategies to derive cardiomyocytes from human induced pluripotent stem cells (hiPSCs) with characteristics of the AV node. We designed two approaches to accomplish this objective. One was a functional approach, wherein properties of existing subtypes of hiPSC-derived cardiomyocytes were modulated to make them suitable for AV conduction. To this end we successfully demonstrated that we can manipulate electrophysiological properties of working myocardial cells using lentiviral gene transfer. However we were encouraged by the more holistic approach that could be obtained with phenotypic programming into the cardiac pacemaker and conduction system lineage. To this end we successfully differentiated hiPSC-derived cells towards a sinoatrial nodal (SAN) phenotype, already recapitulating important AV nodal characteristics such as pacemaker function and slow conduction. In addition we focused on identifying strategies that could steer differentiation of hiPSCs to bonafide AV nodal cell phenotype. Our work in progress demonstrates that deriving these cells is feasible and we have also made important steps towards improving the functional phenotype of such cells. The electrophysiological properties of cells generated from functional as well as phenotypic approach were extensively characterized both in 2D (single cells; will support injection) and 3D (tissue constructs; will support transplantation). Our in vitro data demonstrates that hiPSC-derived SAN and AVN cells resemble their in vivo counterparts both in their gene expression and functional characteristics. Moreover, these cells displayed pacing and conduction properties in composite in vitro models, setting the stage for in vivo testing. To be able to test the behavior of these cells in vivo, we established both small (mouse, rat) and large animal (pig) models of AV block. Our (preliminary) results are promising and further characterization is needed to establish whether they can function as surrogates for the impaired AV node.
We met important milestones in this project that lay the foundation towards realizing cell-based biological pacemakers. The knowhow we generated w.r.t molecular and functional characteristics of hiPSC-derived cardiomyocyte subtypes as well as developing new cell differentiation and tissue engineering approaches is beyond the current state of the art. Other major achievement of this project include the animal models, in particular, the porcine model of AV block we have established, that will allow us to test both cell and gene therapies directed at rejuvenating the AV node. By the end of this ERC Starting Grant project we expect to have obtained hiPSC-derived cells that can be used for in vivo delivery as well as obtaining proof-of-concept data from large animal testing.