SHOX2 Overexpression Favors Differentiation of Embryonic Stem Cells into Cardiac Pacemaker Cells, Improving Biological Pacing Ability

Abstract

SummaryWhen pluripotency factors are removed, embryonic stem cells (ESCs) undergo spontaneous differentiation, which, among other lineages, also gives rise to cardiac sublineages, including chamber cardiomyocytes and pacemaker cells. Such heterogeneity complicates the use of ESC-derived heart cells in therapeutic and diagnostic applications. We sought to direct ESCs to differentiate specifically into cardiac pacemaker cells by overexpressing a transcription factor critical for embryonic patterning of the native cardiac pacemaker (the sinoatrial node). Overexpression of SHOX2 during ESC differentiation upregulated the pacemaker gene program, resulting in enhanced automaticity in vitro and induced biological pacing upon transplantation in vivo. The accentuated automaticity is accompanied by temporally evolving changes in the effectors and regulators of Wnt signaling. Our findings provide a strategy for enriching the cardiac pacemaker cell population from ESCs.

The formation and function of the cardiac conduction system

“…Shox2 is specifically expressed in the SV and is required for early SAN development and function (Blaschke et al, 2007;Espinoza-Lewis et al, 2009;Puskaric et al, 2010). In cultured embryonic stem cells (ESCs), Shox2 directs differentiation towards a pacemaker-like phenotype (Ionta et al, 2015). In vivo, Shox2 suppresses the working myocardial gene programme via repression of Nkx2-5 (Espinoza-Lewis et al, 2011).…”

Shox2: The Role in Differentiation and Development of Cardiac Conduction System

“…AVJ develops from the dorsal mesenchymal protrusion, cushion septum tissues and the AVC-originating myocardium, including AVN progenitor cells (Munshi 2012;Ionta et al 2015). In contrast to the previous opinion that Shox2 expression is specifically distributed in the SAN and its precursor tissues, Shox2 is also expressed in the dorsal mesenchymal protrusion tissues and AVJ during embryonic development (Sun et al 2015).…”

“…Recently, with the maturation of experimental techniques for various pluripotent stem cells (Braam et al 2009;Bernstein and Srivastava 2012;Burridge et al 2012;Priori et al 2013;Karakikes et al 2015;Broughton and Sussman 2016;Atmanli and Domian 2017;Ratajczak et al 2017), the research on induction of stem cells to directionally differentiate into pacemaker cells to form biological pacemakers has shown a breakthrough and thus should promote the CCS regeneration and in vivo transplantation therapies (Davis et al 2011;Bernstein and Srivastava 2012;Xin et al 2013;Broughton and Sussman 2016;Kishore and Khan 2016). Exogenous overexpression of human SHOX2 in mouse embryonic stem cells can enhance the expression of Cx45, Hcn4, and endogenous Shox2 and inhibit the expression of Nkx2.5 and Cx43 (Ionta et al 2015). An embryoid body (EB) overexpressing the SHOX2 gene can show higher automatic rhythmicity compared to pacemaker cells as well as the function of biological pacemakers after a transplant into the rat heart .…”

“…However, replacement of Shox2 with SHOX demonstrated a fully developed SAN and normal pacemaking function in Shox2 deficient mice . In addition, overexpression of SHOX2 during differentiation of embryonic stem cells upregulated the pacemaker gene program, enhanced automaticity and induced biological pacing upon transplantation in vivo (Ionta et al 2015). According to a study on 378 early-onset AF patients (Hoffmann et al 2016), the 3'-untranslated region (UTR) variant c*28T>C of the SHOX2 gene is related to AF and leads to pulmonary vein interval elongation during sinus rhythm in patients (Fig.…”

Tools to Keep the Clock Ticking: Molecular Approaches to Treat Sinus Node Dysfunction

“…Therefore, substantial efforts have been made to develop biological pacemakers using cell and gene therapies [17,18]. Overexpression of HCN channels in vivo, either via the direct adenoviral delivery of HCN or the injection of HCN-expressing mesenchymal stem cells (MSCs), can indeed provide biological pacemakers capable of driving ventricular activation [17,19]. However, further optimization is required to obtain a clinically relevant performance.…”