Related Experiment Video
Updated: Apr 12, 2026
Non-invasive Skeletal Muscle Quantification in Small Animals Using Micro-computed Tomography
Published on: November 8, 2024
Long-term distribution of biodegradable microparticles in rat muscle quantified noninvasively by MRI
Jacques Kameni Tcheudji1, Catherine Cannet2, Christelle Gérard2
1Novartis Institutes for BioMedical Research, Drug Metabolism and Pharmacokinetics, Basel, Switzerland.
Purpose:
To demonstrate the feasibility of MRI to monitor longitudinally the fate of PLGA microparticles in muscle tissue after intramuscular injection in rats using standard equipment.
Methods:
MRI was performed at different time points and until day 28 after intramuscular administration of microparticles. Image segmentation was used to quantify the MRI signals. Histology was performed at selected time points to validate the in vivo observations. The SOM230-long acting release formulation was used as test compound.
Results:
Microparticles were detected in vivo until 28 days following their administration. Imaging and histology data indicated that the MRI signals followed three phases: in an early phase (≤ 48 h after injection), vehicle, edema and hydration of microparticles contributed to the signals. In the second (days 3-17) and third phases (day 17 onward), microparticle hydration was the main contributor. SOM230 in blood displayed peaks at days 2 and 17.
Conclusion:
MRI was suitable to follow longitudinally the presence of PLGA microparticles in the rat muscle without labeling them. This is advantageous, because labeling could potentially alter the properties and pharmacokinetics of the microparticles. Data were consistent with an initial compound release followed by diffusion and microparticle erosion as main mechanisms of SOM230 release.
Insights
Magnetic resonance imaging (MRI) can track unlabeled poly(lactic-co-glycolic) acid (PLGA) microparticles in rat muscle for 28 days. This non-invasive method monitors drug delivery systems without altering their properties.
Area of Science:
- Biomedical Engineering
- Pharmacokinetics
- Medical Imaging
Background:
- Poly(lactic-co-glycolic) acid (PLGA) microparticles are widely used for controlled drug delivery.
- Monitoring the in vivo fate of microparticles is crucial for understanding drug release kinetics and optimizing formulations.
- Non-invasive imaging techniques are needed to track microparticles longitudinally without affecting their properties.
Purpose of the Study:
- To assess the feasibility of using standard Magnetic Resonance Imaging (MRI) equipment to longitudinally monitor the fate of intramuscularly injected PLGA microparticles in rat muscle.
- To validate MRI findings with histological data.
Main Methods:
- Intramuscular injection of PLGA microparticles (SOM230 formulation) in rats.
- Longitudinal MRI scans at various time points up to 28 days post-injection.
- Image segmentation for quantitative analysis of MRI signals.
- Histological analysis at selected time points for validation.
Main Results:
- PLGA microparticles were successfully detected in vivo for up to 28 days using MRI.
- MRI signals exhibited three distinct phases, influenced by vehicle, edema, hydration, and microparticle erosion.
- Blood concentration peaks of SOM230 were observed at days 2 and 17, correlating with release phases.
Conclusions:
- Standard MRI is a feasible and effective tool for longitudinal monitoring of unlabeled PLGA microparticles in muscle tissue.
- This non-invasive approach avoids potential alterations to microparticle properties and pharmacokinetics caused by labeling.
- The observed release patterns suggest a combination of initial compound release, diffusion, and microparticle erosion.
