Image-guided In Vivo Tracking of Transplanted Distal Lung Epithelial Progenitor Cells for Pulmonary Fibrosis Using Magnetic Particle Imaging
June 27th, 2025
Cell therapy offers a promising intervention for pulmonary fibrosis by using progenitor cells to repair damaged tissue and improve lung function. As imaging plays a pivotal role in tracking cell integration, herein, we describe magnetic particle imaging-guided in vivo tracking of cell therapy for pulmonary fibrosis in a mouse model.
This study focuses on intratracheal intubation protocol as a critical delivery method for lung cell therapy, aiming to optimize cell transplantation and non-invasive tracking using magnetic particle imaging in pulmonary fibrosis. Our protocol addresses the lack of non-invasive methods for in vivo tracking of cell therapy in pulmonary fibrosis by combining intratracheal insulation with magnetic particle imaging to monitor cell distribution. Our protocol offers precise localized cell delivery via intratracheal installation and superior tracking using magnetic particle imaging, providing high sensitivity, real-time imaging with no background noise.
To begin, weigh a 12-week-old male NOD or SCID mouse to calculate the required dose of bleomycin. Prepare the bleomycin solution in sterile saline at the desired concentration to a final volume of 50 microliters in a 1.7-milliliter microcentrifuge tube. Then load the solution into a pipette.
Preload a syringe with 200 microliters of air to ensure the entire liquid volume is expelled into the trachea while injecting. After anesthetizing the mouse, assemble the fiber light intubation kit with the optical fiber probe threaded through the laryngoscope and catheter. Pinch the animal's toe to confirm adequate anesthesia and apply ophthalmic ointment to both eyes whenever the animal is under anesthesia.
Suspend the mouse by its incisors in the supine position on an angled rodent intubation stand. Using blunt-ended forceps, grasp the tongue and gently move it upward and leftward to expose the larynx for clear visualization. Turn on the fiber optic probe and guide it into the mouth to approach the trachea.
Use the magnifier of the laryngoscope to enhance visibility and identify the vocal cords at the tracheal opening. Insert the catheter into the tracheal opening and gently remove the laryngoscope. Then place a 20 microliter droplet of saline at the upper end of the catheter.
Attach the syringe preloaded with 200 microliters of air and push the droplet into the trachea. Next, load the catheter with up to 50 microliters of bleomycin and instill it using the air-filled syringe. Keep the catheter in place for 5-7 seconds to prevent backflow of the liquid from the trachea.
Then gently remove the catheter. Maintain the mouse on the intubation stand in the same position for at least 30 seconds. Then remove the mouse from the stand and place it in a recovery cage positioned on a heating pad.
Monitor the mouse continuously until it fully recovers from anesthesia. Obtain nanoparticle labeled human airway epithelial cells from patients with idiopathic pulmonary fibrosis. 72 hours after bleomycin installation, re-anesthetize the mouse and repeat the intratracheal installation procedure to administer 50, 000 cells in 50 microliters of cell suspension.
Let the mouse recover for at least 20 minutes before magnetic particle imaging. Set up the mouse bed in the magnetic particle imaging scanner after passing the anesthesia line underneath the bed through the correct connectors. While the mouse is being anesthetized, prepare the magnetic particle imaging scanner.
After confirming adequate anesthesia with a toe pinched test, carefully position the mouse on the magnetic particle imaging bed. Push the bed with the mouse into the scanner bore and click on Start Scan in the software interface to initiate imaging. After the scan is completed, remove the mouse from the magnetic particle imaging bed and place it into a recovery cage positioned on a heating pad.
Finally, analyze the acquired images using image analysis software. The 2D magnetic particle imaging or MPI signal intensity increased proportionally with the concentration of the iron oxide tracer across all tested cell counts. A concentration of 250 micrograms per milliliter was selected as the optimal labeling concentration.
Fluorescence microscopy confirmed successful in vitro labeling of cells, showing red dextran signals in the cytoplasm and blue DAPI stained nuclei. Signal intensities in 2D MPI images increased with the number of labeled cells, confirming a positive correlation between signal and cell count. Based on this, 50, 000 cells were selected for transplantation.
The empty bed control image showed no background MPI signal, confirming specificity of the scanner to labeled cells. The four observed signals correspond to fiducial markers used as controls. Successful transplantation of labeled cells into the lungs produced a distinct butterfly-shaped MPI signal with visible distribution in both lungs, validating effective intratracheal delivery.
Incomplete cell installation led to signal appearing in both lungs and neck region, indicating leakage due to premature catheter removal. Misplacement of the catheter into the esophagus instead of the trachea caused the MPI signal to appear lower in the abdomen, indicating deposition of cells in the stomach. 14 days after transplantation, ex vivo imaging of the excised lungs confirmed the persistence of labeled cells.
Our findings will improve diagnostic accuracy and enable development of targeted therapies for pulmonary diseases, including stem cell therapy, accelerating progress and innovation in lung imaging and related biomedical fields. Our laboratory will focus on augmenting stem cell-based therapies for lung fibrosis, enhancing non-invasive imaging techniques while aiming to optimize cell delivery and monitor therapeutic efficacy for pulmonary fibrosis.
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Overview
Pulmonary fibrosis (PF) is a severe lung disease marked by progressive scarring and impaired respiratory function. This study explores the use of Magnetic Particle Imaging (MPI) to noninvasively track human distal lung epithelial progenitor cells transplanted into the lungs of immunocompromised mice, aiming to improve monitoring and efficacy of cell therapy for PF.
Key Study Components
Area of Science
- Pulmonary medicine
- Cell therapy
- Preclinical imaging
Background
- PF leads to excessive extracellular matrix deposition, tissue thickening, and respiratory dysfunction.
- Current treatments are limited and mainly slow disease progression.
- Cell therapy offers potential for lung tissue regeneration and inflammation modulation.
- Effective monitoring of transplanted cells is crucial for therapeutic success.
Purpose of Study
- To evaluate MPI as a tool for real-time, quantitative tracking of transplanted lung progenitor cells in vivo.
- To optimize SPION labeling for maximal MPI signal.
- To assess cell distribution, retention, and integration in lung tissue over time.
Methods Used
- Labeling human distal lung epithelial progenitor cells with varying concentrations of SPIONs.
- Confirmation of labeling via immunostaining and iron quantification.
- Intratracheal instillation of labeled cells into immunocompromised mice.
- Acquisition of 2D MPI scans for spatial and longitudinal tracking over 2 weeks.
- Histological validation post-mortem.
Main Results
- Optimized SPION labeling enabled strong MPI signal detection.
- Successful cell instillation showed MPI signals in both lungs.
- MPI signal decreased by approximately 65% over 2 weeks, indicating cell retention and clearance dynamics.
- Histological analysis confirmed the presence and distribution of transplanted cells.
Conclusions
- MPI is a sensitive, noninvasive modality for longitudinal tracking of cell therapy in PF models.
- SPION labeling and MPI enable real-time assessment of cell distribution and retention in vivo.
- This approach supports the development and optimization of cell-based therapies for pulmonary fibrosis.
Frequently Asked Questions
Executive Industry Relevance
Noninvasive, quantitative tracking of transplanted cell therapies is a critical challenge in pulmonary fibrosis preclinical research, directly impacting predictive confidence and translational continuity. Magnetic Particle Imaging (MPI) enables real-time, longitudinal assessment of cell distribution and retention, supporting mechanistic de-risking and target validation for regenerative strategies. This capability strengthens portfolio decision-making by providing actionable data on cell therapy integration and persistence in disease-relevant models.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables direct interrogation of cell engraftment and survival in vivo.
- Supports biological de-risking by quantifying cell retention and distribution.
- Provides functional validation of cell therapy hypotheses in pulmonary fibrosis models.
- Facilitates predictive confidence for advancing cell-based interventions.
Screening & Assay Development
- Establishes validated imaging readouts for cell localization and persistence.
- Standardizes quantitative assessment of cell delivery and integration.
- Enables reproducible, scalable evaluation of cell therapy candidates.
- Supports downstream screening of cell modifications or delivery protocols.
Translational & Preclinical Research
- Aligns preclinical imaging with disease-relevant endpoints for pulmonary fibrosis.
- Provides continuity from discovery through preclinical validation of cell therapies.
- Enables risk-adjusted advancement based on quantitative, longitudinal cell tracking.
- Supports translational biomarker development for cell therapy monitoring.
Pipeline & Workflow Integration
MPI-based cell tracking integrates into the discovery-to-preclinical continuum, bridging early hypothesis testing with translational validation in pulmonary fibrosis models.
- Discovery Biology: Quantifies cell engraftment and persistence to clarify therapeutic mechanisms.
- Screening: Provides standardized, reproducible imaging outputs for candidate evaluation.
- Analytics: Delivers quantitative, longitudinal data on cell distribution and retention.
- Translational Research: Aligns imaging endpoints with preclinical and future clinical monitoring needs.
- Enterprise Reuse: Establishes a reusable imaging platform for diverse cell therapy programs targeting lung disease.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in cell therapy development.
- Operational Value: Enables standardized, scalable, and reproducible cell tracking workflows.
- Strategic Value: Supports informed go/no-go decisions and capital-efficient portfolio advancement.
- Portfolio Impact: Facilitates risk-adjusted prioritization of cell therapy candidates for pulmonary fibrosis.
Implementation Considerations
- Requires expertise in cell labeling, preclinical imaging, and quantitative analysis.
- Demands access to MPI instrumentation and validated SPION reagents.
- Necessitates cross-team standardization of imaging protocols and data interpretation.
- May require adaptation for different cell types or lung disease models.
- Longitudinal imaging throughput and animal model constraints should be considered.
