A Minimally Invasive Transthoracic Injection Technique for Reproducible Intrapleural Delivery in Mice

Our plain-English summary of A Minimally Invasive Transthoracic Injection Technique for Reproducible Intrapleural Delivery in Mice, by S. Rovers, P. Farahmand, D. Liu, et al (Methods and Protocols, 2025).

The study

• Authors: S. Rovers, P. Farahmand, D. Liu, L. Brants, C. Hermans, D. Peeters, D. McKinven, J. Doig, F. Lardon, J. van Meerbeeck, E. Marcq, D.J. Murphy, E. Smits
• Journal: Methods and Protocols
• Published: 2025;8(3)
• Read it: PubMed · Publisher · Free full text

Abstract

The development of standardised, reproducible preclinical models is essential for advancing pleural mesothelioma (PM) research. Here, we present a simple and reliable minimally invasive transthoracic intrapleural injection technique that could improve the efficiency of orthotopic PM model generation. By incorporating a simple needle sleeve to control the injection depth, this method eliminates the need for surgery or general anaesthesia, reducing technical complexity and animal stress while ensuring precise delivery into the pleural cavity. We demonstrate the effectiveness of this approach by achieving a 100% tumour engraftment rate following the injection of AE17 tumour cells. Additionally, this technique has been successfully used for asbestos fibre injection in mesothelioma models, highlighting its versatility. By providing a more accessible, standardised alternative to existing methods, this protocol improves the reliability of PM models and facilitates broader adoption by researchers, including those with limited experience in invasive procedures.

In plain English

This was a published laboratory protocol describing a minimally invasive transthoracic intrapleural injection technique in mice, with accompanying validation experiments. The authors fitted a 27 G needle with a cut pipette tip sleeve so that no more than 2.5 mm of needle tip was exposed, allowing injection below the axilla in a scruffed, conscious mouse without surgery or general anaesthesia. Female C57BL6/J mice (6 weeks old) were used at the University of Antwerp under approval ECD 2019-32. Correct placement was first demonstrated by injecting Trypan Blue and examining the thoracic cavity immediately after euthanasia. In a demonstration experiment, mice received 0.1 x 10(6) AE17 murine mesothelioma cells in 100 microlitres; weight was tracked daily and two mice were euthanised per day from day 15. Some mice had no macroscopically visible tumours at days 15 to 18, but tumour was confirmed microscopically, giving what the authors described as a 100% tumour engraftment rate, with no procedure-related mortality and about 2 minutes per mouse. Asbestos fibre injection was cited as a previous application of the technique, not performed here.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Methods/protocol paper describing a mouse intrapleural injection technique, with validation animal experiments (dye injection and tumour cell inoculation)
• Who was studied: Female C57BL6/J mice, 6 weeks old, from Charles River Laboratories, housed at the animal facility of the University of Antwerp, Belgium; exact total number not stated
• Exposure: Intrapleural injection of 100 microlitres of liquid: Trypan Blue dye for training/validation, and 0.1 x 10(6) AE17 murine mesothelioma cells for the demonstration experiment; asbestos fibre injection is cited as a prior use of the technique, not done in this study
• Main results:
  • Trypan Blue injection followed by immediate post-mortem examination confirmed dye at the thoracic entry site and within the pleural cavity
  • In mice injected with AE17 cells, some had no macroscopically visible tumours at days 15 to 18 but tumour was confirmed microscopically; the authors reported a 100% tumour engraftment rate
  • Weight tracking after injection of AE17 cells showed three patterns among the mice: weight gain with ascites, stable weight with tumour confirmed post-mortem, and sudden weight loss
  • The authors reported no procedure-related mortality and a procedure duration of about 2 minutes per mouse with their technique
  • Histology of lung, heart, thymus, diaphragm and tumour tissue showed increasing tumour burden over time with variation between individual mice
• The authors' conclusion: The authors concluded that the technique offers a tool for preclinical pleural mesothelioma research that improves accessibility and reduces technical barriers
• Limitations the authors state:
  • The authors noted that needle length and individual mouse anatomy could affect depth control, and that proper restraint is needed
  • The authors stated the method is only for liquid injections, not solid tumour fragments
  • The authors stated the method gives no real-time confirmation of tumour establishment
  • The authors stated that no standardised quantitative measures of tumour burden were included
  • The authors stated that use for repeated intrapleural drug delivery or immune cell injection needs further study

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Pleural Cavity, Mesothelioma.

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