(T1330-01-05) Exploring the Spatial Distribution of mRNA-Lipid Nanoparticles in Mouse Whole-Body and Isolated Organs Using MALDI MSI

Purpose: Exploring lipid nanoparticles (LNPs) is crucial because they serve as effective carriers for various therapeutic agents, notably mRNA-based treatments. It is essential to study their biodistribution and assess potential toxicity to enhance their composition and confirm their safety and efficacy in drug delivery within medical contexts. This study aimed to monitor the lipid components of mRNA-lipid nanoparticles after administering them to both male and female mice, analyzing their distribution in whole-body carcasses and specific organs using MALDI-MSI.

Methods: Our experimental setup involved using both female and male mice, examining their whole bodies and isolated organs at various intervals after administering mRNA lipid nanoparticles (LNPs). Sections of isolated organs were prepared on Indium-Tin-Oxide (ITO) glass slides for mass spectrometry imaging (MSI) and on SuperFrost (SF) slides for H&E staining. Whole-body sections were exclusively mounted on ITO slides. We chose sagittal section planes near both the left and right areas adjacent to the left eye, targeting organs such as the liver, kidney, pancreas, spleen, lung, heart, and testis. MSI data collection and analysis were conducted using FlexImaging and Data Analysis software from Bruker Daltonics, alongside Multimaging^TM v1.2.6.1. For histological analysis, NDP.view2 by Hamamatsu was utilized. The MSI signal of the administered substance was standardized using the signal from an internal standard, which is a stable isotopic labeled compound applied onto the tissue sections within the MALDI matrices. We then correlated the calibration curve with the tissue signals to measure the concentration of the test substances in µg/g of each histological structure.

Results: LNP1 exhibited a pronounced and enduring presence in both male and female mice, with detectability extending up to 168 hours post-intravenous administration in females and up to 72 hours in males, as illustrated in Figure 1. This compound was quickly and broadly distributed among crucial organs such as the spleen, liver, kidney, heart, and intestinal areas with adjacent white fat. Both genders showed particularly high exposure levels in the liver and spleen. For females, the tissue half-lives were measured between 57 to 88 hours, while in males, these ranged from 30 to 168 hours, with the most minimal clearance rates found in the liver and spleen. In contrast, LNP2 was not detected in female whole-body sections or isolated organs by the 6-hour mark, indicating either limited distribution, rapid metabolism and elimination, or potentially insufficient sensitivity to assess LNP2 exposure.

Conclusion: The study indicates that LNP1 maintains a prolonged presence and wide organ distribution in mice, with significant retention in the liver and spleen. This suggests LNP1's potential as an effective drug delivery system. However, the distinct pharmacokinetic differences between genders underline the necessity for more detailed studies to explore these variances. Meanwhile, the absence of detectable LNP2 in early assessments in females points to potential issues in its distribution or stability, calling for further investigation to assess its delivery efficacy. These results emphasize the importance of thorough preclinical evaluations for lipid nanoparticle-based therapies.