Cardiovascular Disease Cell Models for Research

Cardiovascular diseases (CVDs) remain the leading cause of global mortality, accounting for approximately 17.9 million deaths each year (WHO, 2021). This represents about 32% of all global deaths. The primary contributors are ischemic heart disease and stroke, which together cause over 85% of CVD deaths. Key risk factors include hypertension, dyslipidemia, diabetes, smoking, and physical inactivity. The economic burden is substantial, with direct and indirect costs estimated in the hundreds of billions annually in the US alone (NCI). While survival rates for acute events have improved, the chronic nature of heart failure and other CVDs imposes a significant long-term burden. Five-year survival varies widely by condition; for example, heart failure has a 5-year survival of approximately 50% (NCI).

CVD encompasses a diverse range of pathologies, including atherosclerosis, cardiomyopathy, arrhythmias, and heart failure. This heterogeneity makes it an ideal subject for mechanistic studies. The availability of well-characterized cell lines (e.g., AC16, H9c2, iPSC-derived cardiomyocytes) and public datasets (e.g., GTEx, GEO) facilitates research. Open questions include the molecular basis of disease susceptibility, the role of genetic variants in drug response, and the development of resistance to therapies. Gene-edited cell models provide a powerful tool to dissect these mechanisms and validate novel therapeutic targets.

Several pathways are central to CVD pathogenesis:

• • Lipid Metabolism and Atherosclerosis: Dysregulation of LDL cholesterol uptake via LDLR, PCSK9-mediated degradation, and cholesterol efflux via ABCA1/ABCG1.
• • Inflammation and Immune Response: Activation of NF-κB, NLRP3 inflammasome, and cytokine signaling (IL-6, TNF-α) in endothelial cells and macrophages.
• • Renin-Angiotensin-Aldosterone System (RAAS): Overactivation leads to vasoconstriction, fibrosis, and hypertrophy.
• • Calcium Handling and Excitation-Contraction Coupling: Mutations in ion channels (e.g., SCN5A, KCNQ1) and calcium regulators (RYR2, SERCA) cause arrhythmias and cardiomyopathy.

Data from ClinVar and COSMIC.

Key signaling networks in CVD include:

• • MAPK/ERK Pathway: Involved in cardiomyocyte hypertrophy and fibrosis. Key nodes: RAS, RAF, MEK, ERK.
• • PI3K/AKT Pathway: Regulates cell survival, growth, and metabolism. Key nodes: PI3K, AKT, mTOR.
• • Wnt/β-Catenin Pathway: Plays a role in cardiac development and remodeling. Key nodes: Wnt, LRP5/6, β-catenin.
• • TGF-β/SMAD Pathway: Mediates fibrosis and inflammation. Key nodes: TGF-β, SMAD2/3, SMAD4.
• • Calcium/Calcineurin/NFAT Pathway: Critical for cardiac hypertrophy. Key nodes: Ca2+, calcineurin, NFAT.

Organoids, such as cardiac organoids derived from iPSCs, offer a more physiologically relevant 3D model that recapitulates cell-cell interactions and tissue-level functions.

• • PDX (Patient-Derived Xenograft): Not commonly used for CVD, but can be used for cardiac tumors.
• • GEMM (Genetically Engineered Mouse Models): Examples include ApoE-/- and LDLR-/- mice for atherosclerosis, and MYH7 mutant mice for cardiomyopathy.
• • Induced Models: Surgical models like transverse aortic constriction (TAC) for heart failure, and ischemia-reperfusion injury models.

CRISPR-Cas9 technology enables the creation of isogenic cell lines with precise genetic modifications, such as knockouts (KO) of disease-associated genes or knock-ins (KI) of specific mutations. For example, a PCSK9 knockout in HepG2 cells can be used to study LDL receptor regulation, while a MYH7 R403Q knock-in in iPSC-CMs can model hypertrophic cardiomyopathy. These gene-edited cell models are commercially available from several vendors, providing sequence-verified, quality-controlled cells that accelerate research. They are essential for validating drug targets and understanding disease mechanisms.

Gene-edited cells are used to validate the function of genes identified in GWAS or sequencing studies. For example, knocking out the LDLR gene in hepatocytes confirms its role in cholesterol uptake. Similarly, introducing a specific SCN5A mutation into cardiomyocytes can elucidate its effect on sodium current and arrhythmia susceptibility.

Isogenic pairs (wild-type vs. gene-edited) are used in high-throughput screens to identify compounds that selectively target mutant cells. For instance, a PCSK9 knockout cell line can be used to test the efficacy of PCSK9 inhibitors. Resistance mechanisms can be studied by exposing cells to drugs and selecting for resistant clones, then identifying the genetic changes.

CRISPR screens can identify genes that, when knocked out, confer resistance or sensitivity to certain treatments. Synthetic lethality screens in cardiovascular cells can reveal novel therapeutic targets. For example, knocking out a gene that is essential for the survival of cells with a specific mutation may identify a vulnerability that can be exploited therapeutically.