Biology subjects

Lindfors, L.

Publications and source records attributed to Lindfors, L..

6 recordsLinked to original sources

bioRxiv2025

Targeted delivery of mRNA to the heart via extracellular vesicles or lipid nanoparticles

Targeted mRNA transport plays a crucial role in enhancing the therapeutic efficacy of the molecule, reducing its side effects, and minimizing off-target effects. Systemic administration of mRNA through lipid nanoparticles (LNPs) or extracellular vesicles (EVs) predominantly results in mRNA accumulation in the liver. We hypothesized that cardiac-specific EVs could more effectively target the transport of mRNA to the heart, in comparison to non-cardiac-specific EVs or LNPs. In mice, after intravenous administration, EVs from cardiac progenitor cells (CPC-EVs) were the most efficient to transport the modified mRNA, encoding vascular endothelial growth factor A (VEGF-A), to mouse heart, with minimal liver accumulation compared to non-cardiac-specific EVs or LNPs. Additionally, intracardiac injections of CPC-EVs not only demonstrate that they are the most adapted vehicle for interacting with heart tissue, delivering the mRNA to cells, and inducing maximal VEGF-A protein production, but RNA-seq analyses also revealed their minimal impact on overall gene expression, compared to LNPs or non-cardiac-specific EVs. Furthermore, immunofluorescence staining of CD31 and -SMA, markers of microvascular density, showed increased vessel density in mouse aortic rings following the delivery of VEGF-A mRNA via CPC-EVs. These findings suggest that CPC-EVs are superior in mRNA targeting to heart, communication with cardiac cells, and causing minimal transcriptomic changes during VEGF-A mRNA delivery. Therefore, CPC-EVs could be promising vectors for heart-targeted mRNA delivery, potentially reducing liver accumulation.

molecular biology↗

bioRxiv2024

Cellular and biophysical barriers to lipid nanoparticle mediated delivery of RNA to the cytosol

Lipid nanoparticle (LNP) formulation was the first approved delivery strategy for liver-targeted siRNA delivery and currently represent the most advanced platform for delivery of therapeutic mRNA in clinical use, after the approval of mRNA-based vaccines against the SARS-CoV-2 coronavirus. Still, poor efficiency of LNPs to promote cytosolic delivery of both mRNA and siRNA after internalization by target cells limits their potency and thus clinical application as RNA delivery vehicles - especially in extrahepatic tissues and tumors. It is still unclear how endosomal escape of LNP-delivered RNA cargo occurs, and why only a minute proportion of all therapeutic molecules reach the cytoplasm. Here, we explored the intracellular sorting, integrity and endosomal escape of both mRNA and siRNA loaded LNPs to characterize the nature of RNA release from endosomal compartments and pinpoint current bottlenecks. Using live-cell imaging and super-resolution microscopy of LNPs with fluorescently labeled RNA payload, we identify multiple distinct steps of substantial inefficiency in the cytosolic delivery of nucleic acid cargoes. We demonstrate that membrane damages marked by recruitment of galectins are conducive to cytosolic RNA delivery, while membrane perturbations recruiting the ESCRT machinery do not permit endosomal escape. By quantitative single-vesicle analysis, we show that only a small fraction of the nucleic acid cargo contained in the endosome is released to the cytosol upon LNP-triggered membrane damage detected by galectins. Unexpectedly, we also observe that only a subset of damaged endosomes contain RNA payload. Through FRET and super-resolution microscopy, using LNPs formulated with both fluorescently labeled ionizable lipid (MC3-BODIPY) and RNA, we find that RNA cargo and ionizable lipid segregate during endosomal sorting - both within single endosomes and to different endosomal compartments. Finally, we visualize localized MC3-BODIPY enrichment in endosomal membranes and membrane damage in direct proximity to siRNA-LNPs tethered to the luminal vesicle membrane. Taken together, this work has identified multiple mechanistically distinct barriers limiting intracellular RNA delivery by LNPs.

bioengineering↗

bioRxiv2024

Time Resolved Inspection of Ionizable-Lipid Facilitated Lipid Nanoparticle Disintegration and Cargo Release at an Endosomal Membrane Mimic

This study investigates pH-triggered fusion dynamics of lipid nanoparticles (LNPs) with an endosomal membrane mimic, addressing mechanistic aspects of a crucial yet elusive process for effective mRNA delivery. Utilizing time-resolved total internal reflection fluorescence (TIRF) imaging, we observed a delayed onset of LNP fusion upon pH drop, lasting seconds to minutes depending on pH and LNP size. Once initiated, LNP fusion and cargo escape occurred rapidly within tens to hundreds of milliseconds. While LNP disintegration is observed to lead to release of a significant portion of mRNA into the acidic environment, some mRNA molecules remained mobile on the endosomal membrane mimic due to deprotonation-resistant complex salt formation. Comparison of the fusion efficiency of two LNP formulations correlated with protein translation in human primary cell transfection data, emphasizing the importance of biophysical investigations in understanding ionizable-lipid-containing LNP-assisted mRNA delivery mechanisms and providing insights for optimizing mRNA-LNP design for enhanced endosomal escape.

biophysics↗

bioRxiv2021

Time evolution of PEG-shedding and serum protein coronation determines the cell uptake kinetics and delivery of lipid nanoparticle formulated mRNA

Development of efficient lipid nanoparticle (LNP) vectors remains a major challenge towards broad clinical translation of RNA therapeutics. New lipids will be required, but also better understanding LNP interactions with the biological environment. Herein, we model protein corona formation on PEG-ylated DLin-MC3-DMA LNPs and identify time-dependent maturation steps that critically unlock their cellular uptake and mRNA delivery. Uptake requires active serum proteins and precedes after a significant ([~]2 hours) lag-time, which we show can be eliminated by pre-incubating LNPs for 3-4 hours in serum-containing media. This indicates an important role of protein corona maturation for the pharmacokinetic effects of these LNPs. We show, using single-nanoparticle imaging, NMR diffusometry, SANS, and proteomics, that the LNPs, upon serum exposure, undergo rapid PEG-shedding ([~]30 minutes), followed by a slower rearrangement of the adsorbed protein layer. The PEG-shedding coincides in time with high surface abundance of Apolipoprotein A-II, whereas the LNPs preferentially bind Apolipoprotein E when their maximum uptake-competent state is reached. Finally, we show that pre-incubation of the LNPs enables rapid uptake and allows pulse-chase video-microscopy colocalization experiments with sufficiently short pulse durations to gain improved mechanistic understanding of how intracellular trafficking events determine delivery efficacy, emphasizing early endosomes as important delivery-mediating compartments.

biophysics↗

bioRxiv2021

Quantitative intracellular retention of delivered RNAs through optimized cell fixation and immuno-staining

Detection of nucleic acids within sub-cellular compartments is key to understanding their function. Determining the intracellular distribution of nucleic acids requires quantitative retention and estimation of their association with different organelles by immunofluorescence microscopy. This is important also for the delivery of nucleic acid therapeutics which depends on endocytic uptake and endosomal escape. However, the current methods fail to preserve the majority of exogenously delivered nucleic acids in the cytoplasm. To solve this problem, by monitoring Cy5-labeled mRNA delivered to primary human adipocytes via lipid nanoparticles (LNP), we optimized cell fixation, permeabilization and immuno-staining of a number of organelle markers, achieving quantitative retention of mRNA and allowing visualization of levels which escape detection using conventional procedures. Additionally, we demonstrated the protocol to be effective on exogenously delivered siRNA, miRNA, as well as endogenous miRNA. Our protocol is compatible with RNA probes of single molecule fluorescence in-situ hybridization (smFISH) and molecular beacon, thus demonstrating that it is broadly applicable to study a variety of nucleic acids.

cell biology↗

bioRxiv2020

Endosomal escape of delivered mRNA from endosomal recycling tubules visualized at the nanoscale

Delivery of exogenous mRNA using lipid nanoparticles (LNP) is a promising strategy for therapeutics. However, a bottleneck remains the poor understanding of the parameters that correlate with endosomal escape vs. cytotoxicity. To address this problem, we compared the endosomal distribution of six LNP-mRNA formulations of diverse chemical composition and efficacy, similar to those employed in mRNA-based vaccines, in primary human adipocytes, fibroblasts and HeLa cells. Surprisingly, we found that total uptake is not a sufficient predictor of delivery and different LNP vary considerably in endosomal distributions. Prolonged uptake impaired endosomal acidification, a sign of cytotoxicity, and caused mRNA to accumulate in compartments defective in cargo transport and unproductive for delivery. In contrast, early endocytic/recycling compartments have the highest probability for mRNA escape. By super-resolution microscopy we could resolve single LNP-mRNA within sub-endosomal compartments and capture events of mRNA escape from endosomal recycling tubules. Our results change the view of the mechanisms of endosomal escape and define quantitative parameters to guide the development of mRNA formulations towards higher efficacy and lower cytotoxicity.

bioengineering↗