Written By: Kaitlyn Sadtler
Original Article: Pettersson et al. PLOS One 2018
The Gist of It:
If you’ve ever gotten a bad cut or had surgery, you’ve gotten a scar. Scar tissue is made of fibrotic collagen, dense connective tissue that helps keep our skin together and blocks bacteria from getting inside our bodies. This fibrotic collagen can also pop up in other areas of our body and lead to disease; this is most commonly seen in the lungs and liver. These pockets of fibrotic collagen can be caused by genetic disease or environmental factors (like smoking or drinking alcohol). If our tissues turn into masses of collagen, they lose their function. In the case of the lungs, this means losing air capacity and the ability to breathe, and in the case of our liver, it means losing our ability to filter the toxins from our blood. Fibrosis is largely mediated by an imbalance and over-activation of our immune system. Recently, researchers have investigated the abilities of a drug, Paquinimod, to treat liver fibrosis and inflammation. This drug can modify our immune response, and the goal of this study was to see if this immune modification could modify fibrosis (lessen the scarring in the liver). Pettersson and colleagues showed that giving Paquinimod to mice with liver fibrosis could prevent excessive collagen formation in the liver and also reduce some of the pre-existing fibrosis. These changes led to recovery of some normal liver function even after scar tissue had formed. Furthermore, they looked at the immune cells in the liver and found that there were fewer immune cells inside the liver tissue. Also, these immune cells did not look like those that mediate fibrosis and disease. Different genes that were associated with fibrosis, including Tgfb1, Ccr2, and Mmp2, were also decreased in mice treated with Paquinimod. Understanding how our immune system creates fibrosis and damages healthy tissue, and which drugs can be used to target these immune cells, creates a window for targeting the immune system as a therapeutic for liver and lung fibrosis.
Using the drug paquinimod, it is possible to prevent more liver fibrosis, and resolve pre-existing fibrosis by modulating the immune system.
The Nitty Gritty:
Petterson et al. used a NOD-Inflammation Fibrosis mouse model (N-IF) that develops spontaneous liver fibrosis via T-cell receptor (TCR)-transgenic natural killer T (NKT) cells in a NOD.Rag2−/− model. Mice were dosed with a quinoline-3-carboxamide (Paquinimod) either via their drinking water or by subcutaneous osmotic pumps. Treatment began at 8 weeks of age and continued for 4 weeks prior to liver tissue harvest for histologic, PCR, and flow cytometric analyses. Paquinimod decreased liver fibrosis as determined by trichrome staining. The decreased fibrosis correlated with decreases in CD11b+ myeloid cells within the tissue and a decrease in CD115+ circulating monocytes. In liver tissue, 4 weeks of Paquinimod treatment greatly decreased the protein levels of IL-6, TNFα, and IL-10. On the gene expression level Ccr2 and Mmp2 were significantly decreased at 4 weeks, and Tgfb1 was decreased by 12 weeks of treatment (all mediators of fibrosis). In this specific model, which relies on transgenic NKT cells, there were fewer activated NKT cells within the spleen by 4 weeks of treatment; however, the number of NKT cells in the liver tissue remained unchanged.
Written by: Padmini S. Pillai
Original Article: Sicard et al. eLife 2019
The Gist of It:
Viruses have the power to cause disasters ranging from influenza pandemics to the widespread destruction of crops. Typically, a virus holds its entire genome (all the genetic information it needs to survive) inside a single capsule, which then enters a living cell to produce new virions. Multipartite viruses hold different segments of their genome in separate capsules. It was previously thought that these various segments had to somehow enter the same cell to multiply successfully, but this seems pretty hard to coordinate! What if genome segments enter different cells? Researchers at Université de Montpellier have made a stunning new discovery that these distinct segments can be converted into viral proteins in different cells, and that these infected cells can then share viral proteins, leading to the formation of a complete virus. Sicard and colleagues fluorescently labeled genome segments of faba bean necrotic stunt virus (FBNSV) that encode proteins that orchestrate viral replication, movement, or capsule formation. They then searched for the presence of each segment in individual cells of the faba bean plant using microscopy. The scientists found that segments accumulated in different cells and in different amounts. To determine if the full virus could still come together, they looked for the presence of the genome segment for replication (R) and its protein product M-Rep. Although segment R was only found in 40% of cells, M-Rep was found in nearly 85% of cells, indicating that viral proteins made from distinct segments can be transferred between host plant cells. In other words, infected cells were exchanging virus proteins to make complete virus particles! This study reveals a new way by which one virus can exist in multiple cells and still replicate to cause infection.
The genome segments of FBNSV enter different cells, but still end up working together to cause an infection!
The Nitty Gritty:
Colocalization of segments of FBNSV was detected using fluorescent probes and confocal microscopy. Visualization of red and green fluorophores from pairs of segments demonstrated that segments were found in different cells and accumulated to varying amounts. There was no correlation between the presence of segment R and segment S (which encodes the encapsidation function) in petioles tested. This was true for R/M and S/M pairs as well, where M is the gene segment encoding the intra-host movement function. This lack of correlation was further confirmed using qPCR. A combination of FISH and immunofluorescence was used to compare the presence of segment S and segment R and its protein product M-Rep. Although segment R was detected in ~40% cells, M-Rep was present in 85% of cells. In contrast, cells that contained segment R no longer had M-Rep detectable.
Written by: Piotr S. Kowalski
Original Articles: Williams et al. Nano Letters 2015 and Williams et al. Hypertension 2018
The Gist of it:
Delivering drugs only to cells that require treatment is a holy grail of modern medicine that holds the potential to limit toxicity and increase the efficacy of many therapies. Nanoparticles, roughly a thousand times smaller than the diameter of a human hair, are often used to carry drugs to cells in distinct parts of the body, but some destinations such as kidneys seem more challenging to reach. Kidneys are specialized organs that filter waste products from the blood and control the production of hormones that influence blood pressure and calcium levels. Due to their important functions, diseases affecting kidneys pose major health problems. Scientists have been trying to design new approaches using nanoparticles to safely deliver drugs into kidneys.
For drug delivery, researchers typically use nanoparticles with diameters of 50-200 nm or micro particles with diameters above 1000 nm. A study led by Dr. Daniel Heller focused on investigating mesoscale nanoparticles, which are made of poly(lactic-co-glycolic acid) conjugated to polyethylene glycol (PEG-PLGA) and are 300-400 nm in diameter. They found that these nanoparticles localized in the kidneys 7-times more than in other organs such the liver, lungs, or spleen; these nanoparticles preferentially targeted a specific set of kidney cells called kidney proximal tubule epithelial cells.
To explain these findings, Heller’s team studied how various characteristics of these nanoparticles, including their surface charge (like an electric charge) and surface hydrophilicity (how the particle interacts with water), affect kidney selectivity. They concluded that nanoparticle localization to the kidney is mainly dependent on the relatively large size and hydrophilicity of the particles, but not their surface charge. In a follow-up study in 2018, the researchers demonstrated that selecting the optimal dose of the nanoparticles drastically increased uptake in the kidney. Moreover, localization to the kidney was not dependent on the cargo within the particles, and this method of drug delivery did not cause negative effects on kidney and liver function. The exact mechanism of the selectivity of these nanoparticles for kidney proximal tubule epithelial cells remains unknown, but it may be related to the inability of the kidney’s filtration system to filter out such large particles.
This study shows that finding a sweet spot for nanoparticle properties, including their size, chemical composition, and surface makeup, can help design drug delivery systems that selectively target cells in the kidneys or other organs that are currently hard to reach and improve our ability to treat disease.
How do we tell nanoparticles where to go? Turns out, their size, chemical composition, and surface properties can help us direct them to specific sites — like the kidney.
The Nitty Gritty:
To test the effect of surface charge, mesoscale nanoparticles (MNPs) with a negative charge were formed using PEG-PLGA (A-MNP), while positively charged particles (C-MNPs) were prepared by modifying A-MNPs with didodecyldimethylammonium bromide. Biodistribution studies in mice intravenously injected with A-MNPs and C-MNPs encapsulating fluorescent dye showed no dependence on the charge for kidney localization. To study the effect of the surface hydrophilicity, non-PEGylated anionic PLGA particles were synthesized that predominantly localized in the liver and to a lesser extent in the intestine, suggesting their clearance though the hepatobiliary tract. Tissue localization of fluorescently labeled MNPs was investigated in mice at day 3 after nanoparticle administration using immunofluorescence. Fluorescence was brighter in proximal tubules compared to distal tubules as revealed by co-staining with E-cadherin, a marker of distal tubules. This tissue distribution pattern was confirmed by staining kidneys for the presence of PEG. This showed that both the polymer and the encapsulated dye cargo were present in the proximal tubules. In the follow-up work (Williams et al. 2018), the ability of MNPs to encapsulate both small molecules and larger biomolecules (double-stranded DNA) without affecting their kidney selectivity was shown. Toxicity of MNPs was evaluated over the course of 28 days by measuring blood metabolites (blood urea, nitrogen, and creatinine), which are cleared by healthy kidneys. No changes in the levels of these metabolites were observed in MNP-treated mice compared to control mice, demonstrating the potential of this approach for the development of renal-targeted drugs for the treatment of kidney diseases.
Original Research Articles: