Inducing Right Ventricular-like Cardiomyocytes from hPSCs

Human pluripotent stem cell-derived cardiomyocytes are widely used for disease modeling, electrophysiology, and therapeutic research, but cardiomyocytes generated by standard protocols are not necessarily equivalent to cells from every cardiac chamber. The 2025 study by Saito and colleagues addressed this limitation by developing a method for producing right ventricular-like cardiomyocytes from human pluripotent stem cells. The work is reported in Stem Cell Research & Therapy.

Study Background and Research Question

The left and right ventricles have different developmental origins and physiological workloads. During embryogenesis, first heart field progenitors contribute primarily to the linear heart tube and left ventricle, whereas anterior second heart field progenitors migrate into the outflow tract and contribute substantially to the right ventricle. The reference study describes these populations using transcriptional distinctions that include TBX5-positive, NKX2-5-positive first heart field-like cells and TBX5-negative, NKX2-5-positive anterior second heart field-like cells.

This developmental separation creates an important experimental problem. A cardiomyocyte generated in vitro may express general cardiac markers while still lacking the chamber-specific identity needed to model a right ventricular disorder. Conditions such as arrhythmogenic right ventricular cardiomyopathy, Brugada syndrome, congenital heart disease, and right-heart failure associated with pulmonary hypertension therefore require careful interpretation when hPSC-derived cells are used. The authors asked whether cardiac differentiation could be redirected toward an anterior second heart field-like state and whether the resulting cardiomyocytes would show measurable right ventricular-like characteristics.

Key Innovation from the Reference Study

The central innovation was to modify an established sequential GSK3β inhibition followed by Wnt inhibition protocol, commonly referred to as GiWi, during the stage when mesoderm is formed. Rather than treating chamber identity as a property that appears only after cardiomyocytes have been generated, the authors manipulated an earlier developmental decision. Insulin or bone morphogenetic protein antagonists were used during mesoderm induction to reduce endogenous BMP signaling, and the consequences were assessed at both the progenitor and cardiomyocyte stages.

This design links a controllable signaling event to a developmental lineage outcome. In the unmodified GiWi condition, the cultures produced mainly first heart field-like progenitors and later left ventricular-like cardiomyocytes. Reducing BMP signaling shifted the progenitor profile away from first heart field markers and toward second heart field markers. The resulting cells displayed an RV-like gene expression pattern and functional differences from the control population. According to the reference study, this provides a practical route for generating chamber-biased hPSC-CMs rather than relying on an apparently uniform cardiomyocyte preparation.

Methods and Experimental Design Insights

The experimental logic proceeded through several linked stages. First, the researchers used the GiWi cardiac differentiation framework as a baseline. This was important because it allowed the chamber-specific effect of mesodermal signaling modulation to be evaluated against a recognized cardiac induction method rather than against an undefined differentiation condition.

Second, the investigators introduced insulin or BMP antagonists during mesoderm formation. The purpose was not simply to increase total cardiomyocyte yield, but to alter the balance between cardiac progenitor populations. The authors then examined FHF- and SHF-associated markers in progenitor cells, allowing lineage bias to be evaluated before terminal cardiomyocyte characterization.

Third, cardiomyocytes derived from the different progenitor populations were compared using chamber-associated gene expression and functional phenotyping. The reported functional measurements included spontaneous contraction rate, intracellular calcium transients, and cell size. These readouts are useful because a chamber identity claim based only on transcript markers may not reflect a meaningful cellular phenotype.

Protocol Parameters

• Baseline cardiac induction: Use the sequential GSK3β inhibition and Wnt inhibition GiWi framework described in the reference study as the control differentiation condition.
• Mesodermal signaling intervention: In the reported workflow, insulin or BMP antagonists were introduced during mesoderm formation to reduce endogenous BMP signaling and promote an SHF-like progenitor profile.
• Lineage assessment: Evaluate FHF- and SHF-associated progenitor markers before interpreting the final cardiomyocyte phenotype; this separates early lineage specification from later maturation.
• Cardiomyocyte validation: Compare chamber-associated gene expression together with spontaneous beating, Ca²⁺ transients, and cell size rather than using a single marker as evidence of RV identity.
• Replication consideration: The study establishes the signaling principle, but concentrations, exposure windows, cell-line responses, and maturation conditions should be optimized independently for each hPSC system.

Core Findings and Why They Matter

The first major finding was that the unmodified GiWi protocol predominantly generated FHF-like progenitors that gave rise to LV-like cardiomyocytes. This result provides a useful reference state: a standard cardiac differentiation protocol may be biased toward one chamber-related developmental program even when it produces large numbers of cardiomyocytes.

The second finding was that reducing BMP signaling during mesoderm induction decreased FHF marker expression and increased SHF marker expression. This places BMP pathway activity at a strategically important point in the differentiation sequence. The result does not mean that BMP signaling alone fully determines chamber identity, but it shows that early pathway modulation can alter the developmental composition of the cardiac progenitor pool.

The third finding was that cardiomyocytes derived from the SHF-like population expressed RV-like genes and differed phenotypically from control LV-like cardiomyocytes. The differences included spontaneous contraction rate, calcium-handling behavior measured through Ca²⁺ transients, and cell size. Because these features are relevant to excitation-contraction behavior, the study moves beyond a purely molecular definition of chamber identity.

These findings matter for disease modeling. If a right ventricular disease is studied in an unspecified hPSC-CM population, disease-associated effects may be diluted, misinterpreted, or attributed to generic cardiomyocyte stress. A more defined RV-like preparation may improve the biological relevance of models for disorders that preferentially affect the right ventricle. It may also help researchers determine whether a phenotype reflects disease biology or simply an inappropriate chamber identity.

Comparison with Existing Internal Articles

An internal article on UBXN2A pathways and chamber-specific cardiomyocyte studies discusses pharmacological applications alongside cardiac modeling; it can be read here. Its relationship to the reference study is contextual rather than evidentiary. Saito et al. establish a developmental method for generating RV-like cardiomyocytes, whereas the internal article addresses a broader combination of signaling and pharmacology topics and should not be treated as independent validation of the differentiation protocol.

A second internal article focused on voltage-gated sodium channel opener applications is available here. It is relevant to downstream electrophysiology and assay design, but it addresses pharmacological control of membrane excitability rather than specification of FHF- or SHF-derived cardiomyocytes. Keeping these research questions separate is important: chamber identity is established through developmental patterning and validation, while sodium-channel perturbation is a later experimental manipulation.

Limitations and Transferability

The study establishes RV-like identity, not a complete replica of an adult human right ventricle. hPSC-CMs generally require additional maturation and tissue-level context to reproduce adult electrophysiology, metabolism, force generation, and structural organization. The reported differences in contraction, calcium transients, and cell size are therefore valuable phenotypic evidence, but they should not be interpreted as proof of full functional equivalence to adult ventricular myocardium.

Another limitation is that marker-based lineage assignment can be sensitive to differentiation timing, hPSC line, culture density, and assay conditions. A protocol that produces a strong SHF-like signal in one cell line may show a different magnitude of response in another. For this reason, replication should include matched GiWi controls, early progenitor analysis, chamber-associated gene measurements, and functional testing.

The paper also does not establish that every right ventricular disease will be better modeled solely by using RV-like cardiomyocytes. Disease mechanisms may involve fibroblasts, endothelial cells, immune cells, mechanical loading, or three-dimensional tissue architecture. The method is best viewed as a way to improve the cardiac cell starting material, which can then be integrated with disease-relevant genetic backgrounds and multicellular systems.

Research Support Resources

Why this cross-domain matters, maturity, and limitations

The connection between chamber-specific cardiomyocyte differentiation and sodium-channel pharmacology is methodological rather than demonstrated by the reference study. Saito et al. did not test Veratridine, sodium-channel opening, or pharmacological induction of the reported RV-like phenotype. Accordingly, a sodium-channel reagent should not be presented as a driver of RV specification. Its relevance begins in separate downstream experiments that examine membrane excitability, calcium handling, electrical stress, or blocker responses in characterized cardiomyocytes.

For those related electrophysiology workflows, researchers can use Veratridine (SKU B7219), a voltage-gated sodium channel opener and steroidal alkaloid neurotoxin. The product information describes its use in sodium channel dynamics research, excitotoxicity studies, seizure mechanism research, and screening assays for sodium channel blockers. These applications should be designed as independent pharmacological experiments after chamber identity has been established, with appropriate untreated and channel-blocker controls.