Systemic lupus erythematosus Cell Models for Research

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a global prevalence estimated at 3.41 million cases (WHO, 2023). Incidence ranges from 0.3 to 23.2 per 100,000 person-years, with a female-to-male ratio of 9:1. The 5-year survival rate exceeds 95% in developed countries, but morbidity remains high due to organ damage and infections (NCI). Risk factors include genetic predisposition, hormonal influences, and environmental triggers such as UV light and infections.

SLE is ideal for mechanistic studies due to its complex autoimmune pathogenesis involving dysregulated innate and adaptive immunity. Public datasets such as GEO and ImmPort provide extensive transcriptomic and epigenetic data from patient samples. Open questions include the role of specific genetic variants in disease susceptibility and the molecular mechanisms driving flares. Gene-edited cell models enable functional validation of these variants and identification of novel therapeutic targets.

• • SLE pathogenesis involves several key pathways:
• • Type I Interferon (IFN) Pathway: Overproduction of IFN-α by plasmacytoid dendritic cells drives immune dysregulation.
• • B Cell Signaling: Enhanced B cell receptor signaling and defective tolerance lead to autoantibody production.
• • T Cell Dysregulation: Abnormal T cell subsets, including Th17 and Tfh, promote inflammation.
• • Neutrophil Extracellular Traps (NETs): Excessive NET formation exposes self-antigens and activates innate immunity.

Data from TCGA and COSMIC.

• • Key signaling networks in SLE include:
• • Type I IFN Signaling: Activation of JAK-STAT pathway leads to expression of interferon-stimulated genes (ISGs).
• • NF-κB Pathway: Involved in inflammatory cytokine production.
• • PI3K/AKT/mTOR: Regulates lymphocyte survival and proliferation.
• • MAPK Pathway: Modulates cytokine responses in immune cells.

Key nodes: IRF5, STAT4, TLR7, MyD88, TRAF6, and IKKα/β.

Organoids derived from patient tissues are emerging as more physiologically relevant models, but they are limited by complexity and cost.

• • MRL/lpr mice: Spontaneous lupus-like disease with lymphoproliferation.
• • NZB/W F1 mice: Spontaneous autoimmune disease resembling SLE.
• • Induced models: Pristane-induced lupus in BALB/c mice.
• • PDX models: Patient-derived xenografts are less common for SLE due to the immune component.

CRISPR-based gene editing enables the creation of isogenic cell lines with specific genetic modifications, such as knockouts of susceptibility genes (e.g., IRF5) or knock-ins of disease-associated variants (e.g., TLR7 gain-of-function). These models are commercially available and sequence-verified, providing reproducible tools for mechanistic studies and drug screening. For example, an IRF5 knockout THP-1 line can be used to study IFN pathway regulation, while a TLR7 knock-in HEK293 line can be used for high-throughput screening of TLR7 inhibitors.

Knockout and knock-in lines are used to validate the role of specific genes in SLE pathogenesis. For instance, knocking out IRF5 in THP-1 cells reduces IFN-α production, confirming its role in the pathway. Similarly, introducing a TLR7 gain-of-function mutation into HEK293 cells recapitulates enhanced signaling, enabling study of downstream effects.

Isogenic pairs (wild-type vs. knockout) are used in drug screening to identify compounds that specifically target the mutated pathway. For example, screening a library of kinase inhibitors against a STAT4 knockout line can reveal selective inhibitors. Resistance mechanisms can be studied by exposing cells to increasing drug concentrations and identifying genetic changes.

CRISPR synthetic lethality screens can identify genes that are essential only in the context of a specific mutation. For example, in a TLR7-activated cell line, knocking out genes involved in the IFN pathway may reveal novel therapeutic targets. Such screens can also identify biomarkers for patient stratification.