Model Introduction
Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammatory synovitis. It primarily affects the joints, leading to the destruction of articular cartilage and bone, ultimately causing functional impairment or even disability. Approximately 35 million people worldwide are affected, with a higher incidence in females than males, typically peaking during middle age. The pathogenesis of RA is complex, involving multiple mechanisms such as genetic factors, environmental factors, and immune system abnormalities. To study its pathological processes and develop novel therapeutic strategies, animal models have become indispensable research tools. Currently, key pathological features of RA—including synovial hyperplasia, inflammatory cell infiltration, and bone erosion—have been successfully simulated through adjuvant induction, collagen immunization, genetic engineering, and comprehensive modeling, providing vital platforms for basic mechanistic research and drug development.
Research Applications
RA animal models are widely used to:
- Study the mechanism of inflammatory cytokines (e.g., IL-6, TNF-α) in the disease.
- Analyze the relationship between immune system abnormalities and the development of synovitis.
- Evaluate the efficacy of biological agents and small-molecule targeted drugs.
- Explore the association between gut microbiota and RA pathogenesis. Different models have distinct characteristics regarding inflammation severity, chronicity, and immunological mechanisms, allowing for selection based on specific research goals.
Key Points of Experimental Design
1) Adjuvant-Induced Arthritis (AIA) Model The adjuvant-induced model is one of the most commonly used RA models.
- Induction: Typically induced using Freund’s Complete Adjuvant (FCA) or Freund’s Incomplete Adjuvant (IFA).
- Example Method: Subcutaneous injection of FCA (1 mg / 0.1 ml paraffin oil) into Sprague-Dawley rats on days 0, 30, and 40.
- Model Characteristics:
- Simulates joint inflammatory responses.
- Presents symptoms such as joint swelling, pain, and erythema. 2) Collagen-Induced Arthritis (CIA) Model The CIA model is highly similar to human RA in its immunological and pathological features.
- Method: Emulsify Type II collagen with an adjuvant and inject it into the tail base and dorsal paravertebral region of rats or mice.
- Characteristics:
- Obvious clinical manifestations.
- Suitable for studying the early stages of RA. 3) Genetic Models Constructed through transgenic or gene-editing technologies.
- Example: Tg197 Mouse Model Induces arthritis through the expression of human tumor necrosis factor (hTNF).
- Characteristics:
- Simulates chronic inflammation.
- Presents joint destruction.
- Suitable for mechanistic research and drug efficacy evaluation. 4) Combined Syndrome and Disease Model Constructed by combining Traditional Chinese Medicine (TCM) syndromes with modern disease characteristics, such as simulating “Deficiency Syndrome” or “Excess Syndrome” on the basis of drug-induced arthritis.
- Characteristics:
- Valuable in TCM research.
- The direct causal relationship with RA requires further validation. 5) Other Models
- CAIA Model: Induces arthritis by injecting collagen antibodies; suitable for studying early inflammatory responses.
- Streptococcal Cell Wall-Induced Model: Intraperitoneal injection of Group A streptococci mixed with other bacterial peptidoglycan-polysaccharide complexes into rats; acute arthritis symptoms appear within 24 hours and can progress to long-term chronic arthritis.
Key Detection Indicators
1) Inflammatory and Immunological Indicators
- Elevated levels of IL-6 and TNF-α.
- Changes in the spleen weight/body weight ratio.
- Inflammatory cytokine levels are used to assess disease severity and therapeutic effect. 2) Histopathological Features
- Synovial hyperplasia.
- Inflammatory cell infiltration.
- Bone erosion. 3) Gut Microbiota and Metabolite Changes
- Changes in the abundance of specific bacterial genera.
- Alterations in gut metabolite profiles.
- Potentially related to RA pathogenesis.
