Hypertension CRISPR Cell Models for Drug Discovery Research

Hypertension, or high blood pressure, is a leading cause of premature death worldwide. According to the World Health Organization (WHO), an estimated 1.28 billion adults aged 30-79 years have hypertension, with two-thirds living in low- and middle-income countries. The condition is a major risk factor for cardiovascular diseases, including heart attack, stroke, and kidney failure. The National Cancer Institute (NCI) does not track hypertension directly, but the WHO reports that hypertension contributes to nearly 10.8 million deaths annually. Key risk factors include unhealthy diet (high salt intake), physical inactivity, obesity, tobacco use, and genetic predisposition. Blood pressure control rates remain low globally, with only about 20% of hypertensive adults having it under control.

Hypertension is an ideal disease for mechanistic studies due to its complex, multifactorial nature involving genetic, environmental, and lifestyle factors. The availability of large public datasets, such as the UK Biobank and the International Consortium for Blood Pressure (ICBP), provides rich genetic association data. Open questions include the precise mechanisms of salt sensitivity, the role of the renin-angiotensin-aldosterone system (RAAS) in vascular remodeling, and the identification of novel drug targets for resistant hypertension. Gene-edited cell models enable precise dissection of these pathways in human cells, offering a controlled environment to study gene function and drug response.

Hypertension pathogenesis involves several interconnected pathways:

1. Renin-Angiotensin-Aldosterone System (RAAS):

• • Renin cleaves angiotensinogen to angiotensin I.
• • ACE converts angiotensin I to angiotensin II.
• • Angiotensin II binds AT1 receptors, causing vasoconstriction and aldosterone release.
• • Aldosterone increases sodium reabsorption, raising blood volume and pressure.

2. Sympathetic Nervous System (SNS) Overactivity:

• • Increased sympathetic outflow raises heart rate and vascular resistance.
• • Norepinephrine release activates alpha-adrenergic receptors.

3. Endothelial Dysfunction:

• • Reduced nitric oxide (NO) bioavailability impairs vasodilation.
• • Increased oxidative stress from NADPH oxidases (NOX) damages endothelium.

4. Renal Sodium Handling:

• • Mutations in genes like SLC12A3 (NCCT) or SCNN1B (ENaC) alter sodium reabsorption.
• • Pressure-natriuresis relationship is shifted.

Data from ClinVar and NCBI Gene. Note: Hypertension is polygenic; these are common variants with modest effect sizes.

Key signaling networks in hypertension:

• • RAAS Pathway:
• • Angiotensin II -> AT1R -> Gq/PLC -> IP3/DAG -> Ca2+ release -> vasoconstriction.
• • AT1R -> MAPK/ERK pathway -> vascular smooth muscle cell proliferation.
• • Endothelial NO Pathway:
• • Shear stress -> eNOS activation -> NO -> cGMP -> vasodilation.
• • Oxidative stress (ROS) -> NO scavenging -> endothelial dysfunction.
• • Sympathetic Signaling:
• • Norepinephrine -> beta-1 adrenergic receptors -> cAMP -> increased heart rate.
• • Alpha-1 adrenergic receptors -> vasoconstriction.
• • Renal Sodium Transport:
• • WNK kinases (WNK1, WNK4) regulate NCC and NKCC2.
• • Mutations in WNK1/WNK4 cause pseudohypoaldosteronism type II (PHAII) with hypertension.

Organoids: Kidney organoids derived from iPSCs can model renal sodium handling and RAAS interactions. They provide a 3D architecture that recapitulates nephron segments, enabling study of cell-cell interactions in hypertension.

Common animal models for hypertension:

• • Spontaneously Hypertensive Rat (SHR): Genetic model of essential hypertension.
• • Dahl Salt-Sensitive Rat: Develops hypertension on high-salt diet.
• • Angiotensin II Infusion Model: Induced hypertension via osmotic minipumps.
• • Two-Kidney, One-Clip (2K1C) Model: Renovascular hypertension.
• • Genetically Engineered Mouse Models (GEMM):
• • Renin overexpression (RenTg) mice.
• • ACE knockout mice.
• • AT1a receptor knockout mice.
• • Patient-Derived Xenograft (PDX): Not common for hypertension; more used for cancer.

CRISPR-Cas9 gene editing enables the creation of isogenic cell lines with precise genetic modifications relevant to hypertension. Examples include:

• • ACE knockout cell lines: To study the role of ACE in angiotensin II production.
• • AGT knockout cell lines: To model angiotensinogen deficiency.
• • NOS3 (eNOS) knockout cell lines: To investigate endothelial dysfunction.
• • SCNN1B (ENaC) knockout cell lines: To study renal sodium handling.
• • WNK1 or WNK4 knock-in cell lines: To model PHAII mutations.

Commercially available, sequence-verified gene-edited cell models accelerate research by providing reproducible, isogenic backgrounds. These models eliminate the confounding effects of genetic variability, enabling precise functional studies and drug screening. They are available from commercial sources and can be customized for specific mutations.

CRISPR knockout and knock-in cell lines are used to validate genes implicated in hypertension from GWAS studies. For example:

• • Knockout of UMOD (uromodulin) in kidney cells to study its role in salt-sensitive hypertension.
• • Knock-in of the ADD1 G460W variant in vascular smooth muscle cells to assess effects on sodium transport and cell contraction.
• • Knockout of NOS3 in endothelial cells to confirm its role in NO production and vasodilation.

These models allow researchers to directly link genotype to phenotype in human cells.

Isogenic cell pairs (wild-type vs. gene-edited) enable high-throughput drug screening to identify compounds that target specific pathways. For example:

• • Screening for compounds that lower angiotensin II production in ACE knockout vs. wild-type cells.
• • Testing new antihypertensive drugs in ENaC knockout cells to assess off-target effects.
• • Modeling drug resistance: For example, studying why some patients develop resistance to ACE inhibitors by examining ACE variant knock-in lines.

These approaches reduce false positives and improve translational relevance.

CRISPR-based screens can identify synthetic lethal partners or biomarkers for hypertension. For example:

• • Genome-wide CRISPR knockout screens in endothelial cells under shear stress to identify genes that regulate NO production.
• • Synthetic lethality screens in renal cells with WNK1 mutations to find targets that selectively kill cells with abnormal sodium transport.
• • Identifying secreted proteins (e.g., renin, aldosterone) as biomarkers using knockout lines to validate specificity.