Human heart-forming organoids recapitulate early heart and foregut development

Abstract

Organoid models of early tissue development have been produced for the intestine, brain, kidney and other organs, but similar approaches for the heart have been lacking. Here we generate complex, highly structured, three-dimensional heart-forming organoids (HFOs) by embedding human pluripotent stem cell aggregates in Matrigel followed by directed cardiac differentiation via biphasic WNT pathway modulation with small molecules. HFOs are composed of a myocardial layer lined by endocardial-like cells and surrounded by septum-transversum-like anlagen; they further contain spatially and molecularly distinct anterior versus posterior foregut endoderm tissues and a vascular network. The architecture of HFOs closely resembles aspects of early native heart anlagen before heart tube formation, which is known to require an interplay with foregut endoderm development. We apply HFOs to study genetic defects in vitro by demonstrating that NKX2.5-knockout HFOs show a phenotype reminiscent of cardiac malformations previously observed in transgenic mice.

Cardioids reveal self-organizing principles of human cardiogenesis

“…Interestingly, the same range of lower WNT and ACTIVIN signaling dosages stimulated ventricular specification and EC lining formation suggesting a potential coordination between these processes. Inner lining of a cardiac chamber-like structure has not been observed before in neither cardiac microtissues (Giacomelli et al, 2017) nor more complex foregut-heart organoids and gastruloids (Drakhlis et al, 2021;Rossi et al, 2021). Generation of a separate EC layer/lining in the context of a chamber cavity is crucial for activation of mechanosensing in vivo.…”

“…This approach allows dissecting, with high statistical power, when and where the functions of specific factors are required. The simplicity and modularity of the system that can contain either one, two, or three cardiac lineages, without interference of non-cardiac tissues as in more complex embryoid models (Drakhlis et al, 2021;Rossi et al, 2021), makes it possible to reduce self-organization and its underlying molecular and cell biological mechanisms to its bare essentials. Complexity in cardioids can therefore be tailored to the biological question asked.…”

“…However, as heart development progresses, additional lineages (second heart field, cardiac neural crest), cell types (pacemakers, immune cells), and structures (atria, right ventricle, outflow/inflow tracts) become integrated into the heart, and most congenital diseases arise during these later stages (Kelly et al, 2014;Meilhac and Buckingham, 2018). Certain aspects of cardiogenesis also depend on interactions with other germ layers, which can be specifically studied with other models (Drakhlis et al, 2021;Rossi et al, 2021;Silva et al, 2020). Cardioids therefore provide a foundation for incorporation of additional cardiac lineages and structures by signaling controlled self-organization but in the present form, are unlikely yet to faithfully recapitulate most cardiac defects.…”

“…Similarly, mouse and human PSC-derived 3D cardiac models including spherical aggregates (microtissues) of CMs and other (cardiac) cell types (Giacomelli et al, 2017(Giacomelli et al, , 2020Richards et al, 2020) have been established as promising high throughput tools for drug discovery. Moreover, recent embryoid models (Drakhlis et al, 2021;Rossi et al, 2021;Silva et al, 2020) rely on complex self-organization of non-cardiac (e.g., foregut endoderm) and cardiac lineages and thus provide further insights into germ layer interactions during early organogenesis. However, existing models do not recapitulate cardiac-specific self-organization to acquire in vivo-like architecture such as a CM chamber with inner endocardial cavity lining and are therefore limited as models of human cardiogenesis and heart disease.…”

Genetic Cardiomyopathies: The Lesson Learned from hiPSCs

“…Defined and widely available culture methods able to improve the electrophysiological, mechanical, and metabolic maturity of iPSC-CMs will constitute a turning point in the field [7], since maturity strongly affects predictiveness and consequently reproducibility of the experimental findings. Research is currently focusing on paracrine signaling, modulating effects of non-CMs cells and extracellular matrix [97,98], substrate stiffness, and metabolism [6,7], and several developmental-based protocols are being developed that direct differentiation of distinct cardiomyocyte subtypes [99][100][101] and generate 3D microtissues and organoids that closely resemble aspects of early native heart [96,97,102] (Table 1).…”