Pulmonary fibrosis model

Pulmonary fibrosis is a chronic disease characterized by scarring and loss of function of the lung interstitium, which is common in idiopathic pulmonary fibrosis (IPF) and radiation-/drug-induced lung injury.

Apr 8th,2025 63 Views

Pulmonary Fibrosis Model Construction and Application Guide

Pulmonary fibrosis is a chronic disease characterized by interstitial scarring and loss of function, which is common in idiopathic pulmonary fibrosis (IPF) and radiation/drug-induced lung injury. The following are the main experimental models and their construction methods, evaluation indicators and application scenarios.

I. Model types and core methods

1. Chemical induction model (bleomycin-induced)

principle ： Bleomycin induces alveolar epithelial damage and activates fibroblast proliferation and collagen deposition by producing reactive oxygen species (ROS) and pro-inflammatory factors.

Build steps :

Animal selection : C57BL/6 mice (high sensitivity), SD rats (suitable for long-term studies).

Route of administration :

Intratracheal instillation (Most commonly used): After anesthesia, inject bleomycin (mice: 1-3 U/kg, rats: 5-7 U/kg, dissolved in 50 μL saline) through the endotracheal tube.

Nebulizer inhalation : Continuous 3-5 days of aerosol exposure (concentration 0.5-1 U/mL, 30 minutes per day).

Time Node :

Acute inflammatory phase : 7-14 days (mainly inflammatory cell infiltration).

Fibrosis stage : 21-28 days (peak of collagen deposition).

2. Genetically engineered mouse models

principle ：Targeted regulation of fibrosis-related pathways (TGF-β, Wnt/β-catenin, etc.) through gene editing technology. Common models :

Gene/phenotype	Features
TGF-β1 overexpression	Directly drives fibroblast activation and collagen synthesis
SP-C mutation (SFTPC mutation)	Simulates inherited interstitial lung disease (eg, IPF)
Fas ligand-induced apoptosis	Alveolar epithelial apoptosis drives fibrosis

3. Radiation-induced model

principle : Localized thoracic radiation (eg, single-fraction 10-20 Gy) causes DNA damage and chronic inflammation, simulating radiation-induced pulmonary fibrosis.

Applicable scenarios : To study the mechanism and intervention measures of pulmonary fibrosis after radiotherapy.

4. Cell transplantation model

Construction method :

Fibroblast adoptive transfer : In vitro activated fibroblasts (e.g. overexpressing α-SMA) were injected into mice via the tail vein.

Bone marrow derived cells (BMDC) : Transplantation of GFP-labeled BMDCs and tracking their differentiation in lung tissue (such as transformation into myofibroblasts).

II. Model Monitoring and Evaluation Indicators

1. Histopathological Analysis

H&E staining : Evaluate inflammatory cell infiltration and alveolar structural destruction (Ashcroft score: 0-8 points, ≥4 points indicates significant fibrosis).

Masson's trichrome stain : Quantitative analysis of collagen fibers (blue) (ImageJ software was used to calculate the collagen area ratio).

Immunohistochemistry : Detect α-SMA (myofibroblast marker), TGF-β, Vimentin, etc.

2. Molecular marker detection

qPCR/WB :

Gene/Protein	Function
Col1a1、Col3a1	Collagen synthesis key genes
TGF-β1、CTGF	Profibrotic factors
MMP-9, TIMP-1	Extracellular matrix remodeling regulator

ELISA : Detect inflammatory factors such as IL-6, TNF-α, PDGF in serum or bronchoalveolar lavage fluid (BALF).

3. Pulmonary function test

Non-invasive pulmonary function tester (FlexiVent system)

Lung compliance (Cdyn) ：The compliance of fibrotic lung tissue decreases.

Airway resistance (Rn) ：It increases significantly in advanced fibrosis.

4. Determination of Hydroxyproline Content

principle : Hydroxyproline is a characteristic amino acid of collagen, and its content reflects the degree of fibrosis.

Normal reference value ： Mouse lung tissue ≈10 μg/g, model group can reach 30-50 μg/g.

III. Comparison of Model Advantages and Disadvantages

Model Type	advantage	limitation
Bleomycin-induced	Simple operation, low cost, short molding cycle (3-4 weeks)	There are large individual differences, and some animals tend to heal on their own
Genetic Engineering Model	Targeting specific pathways with clear mechanisms	High cost and long phenotypic latency (3-6 months)
Radiation Induced	Simulate clinical fibrosis after radiotherapy	Requires special equipment, high mortality rate (acute phase)

IV. Application Scenarios

Drug Development : Testing anti-fibrotic drugs (e.g., nintedanib, pirfenidone) or natural compounds (curcumin, resveratrol).

Mechanism studies :

The role of epithelial-mesenchymal transition (EMT) in fibrosis.

Regulation of macrophage polarization (M1/M2) on fibrosis.

Stem Cell Therapy : To evaluate the effect of mesenchymal stem cells (MSC) or exosomes in repairing lung injury.

Biomaterials Evaluation : Targeted delivery efficiency of nanoparticle or hydrogel drug delivery systems.

V. Notes

Bleomycin dosage control : Overdose causes acute pulmonary edema (mortality rate in mice >50%).

Anesthesia risks : Tracheal intubation requires skilled operation to avoid airway perforation.

Code of Ethics :

Pain management: Administer ibuprofen or carprofen postoperatively.

End point criteria: euthanasia is required when body weight loss > 20% or respiratory distress occurs.

VI. Sample Data

Group	Ashcroft Rating	Hydroxyproline (μg/g)	Lung compliance (mL/cmH2O)
Control group	1.2 ± 0.3	12 ± 3	0.055 ± 0.005
Bleomycin model group	5.8 ± 1.1	42 ± 8	0.028 ± 0.003
Nintedanib treatment group	3.2 ± 0.7	25 ± 5	0.045 ± 0.004

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