Exosomes derived from grapes communicate with intestinal stem cells

Posted by Kasra

I worked on exosomes for some time, so I have written about them and other secreted vesicles every now and then. I still try to follow up the research in the field and get excited with the new findings, methods and applications. Here is exciting work by by Ju et al.  where they study the interaction between grape (yes the fruit) exosomes with mouse intestinal cells.

They purified exosome-like vesicles from grapes that they bought from grocery stores. Given to mice, the exosomes appeared to be absorbed by intestinal stem cells present in the intestinal crypts. Interestingly, the authors show that picking up these vesicles induce the Wnt/β-Catenin pathway. Generally, activation of this pathway promotes proliferation of stem cells. Ju et al. show grape exosomes induce proliferation of stem cells by putting stem cells together with the vesicles ex vivo and looking at crypt formation in organoids. Finally, to provide a health-related application for their vesicles, the authors show that grape exosomes protect mice and delay death in a murine colitis model. This can be because the vesicles induce proliferation of the stem cells and thus enhance tissue regeneration to revert the damage caused by colitis.

Formation of crypts from a single intestinal stem cell ex vivo is quickened when exposed to grape exosomes. From Ju et al. Molecular Therpay 2013

Formation of crypts from a single intestinal stem cell ex vivo is quickened when exposed to grape exosomes. From Ju et al. 11 June 2013;doi: 0.1038/mt.2013.64

This study contains so many buzz-words, I could think of terrible ways by which it can be mis-interpretted by media: grapes heal gut disease, nano-particles in fruit protect against gut disease, … As the authors say in the first paragraphs of the paper, this study is a proof of concept and there is still a lot more to learn. Thankfully, they show enough evidence to tickle other scientists to look at application of plant-derived exosomes and exosome-like vesicles as means for drug delivery and therapy. For one thing, plants-derived products are available in higher abundance compared to their animal-derived counterparts and can be cheaper to purify in commercial quantities.  Also, humans have been exposed to them (maybe not in such high concentrations) for millions of years, so they are no strangers to the gut cells.

Ju S, Mu J, Dokland T, Zhuang X, Wang Q, Jiang H, Xiang X, Deng ZB, Wang B, Zhang L, Roth M, Welti R, Mobley J, Jun Y, Miller D, & Zhang HG (2013). Grape Exosome-like Nanoparticles Induce Intestinal Stem Cells and Protect Mice From DSS-Induced Colitis. Molecular therapy : the journal of the American Society of Gene Therapy PMID: 23752315



Detecting picograms of protein in the secretome

Posted by Kasra

When designing experiments in the lab, we usually say we cannot check for everything. Well, what if we could?! Meissner et al. used only 150,000 macrophages per sample to analyze their secretome. They have been able to detect and quantify protein abundances at the picogram level in a label-free system. Picogram detection limit means that cytokines are readily quantifiable, and Meisner et al. claim it matches with the detection limit of ELISA. I could imagine that in not so long this technology can become more readily accessible, allowing researchers to acquire more pertinent data per sample. We can know the statuses of a multitude of proteins (from cytokines to nonconventionally secreted proteins) simultaneously, not through multiple ELISAs and western blots, and therefore draw much more sensible conclusions from experiments. It will actually be more affordable than separate quantification of each protein, not mentioning dramatically time-saving.

Also, this data can be integrated with other high throughput quantitative analyses of the cell. For instance, Meissner et al. have compared the changes in protein abundance in the secretome to changes in their transcript levels, and roles of different adaptor molecules (in this case MyD88 versus TRIF) and tried to explain how they all relate.

Meissner F, Scheltema RA, Mollenkopf HJ, & Mann M (2013). Direct proteomic quantification of the secretome of activated immune cells. Science (New York, N.Y.), 340 (6131), 475-8 PMID: 23620052


Tracking exosomes in vivo

Posted by: Kasra

Application of exosomes for therapeutic, especially as drug delivery agents has been always an interest. However, there is limited knowledge on how these vesicles interact with the variety of the cells inside the body and how does the body react to their presence.

Takahashi et al. have used exosomes released by a melanoma cell line that also produces Gaussia luciferase (gLuc) to shed some light on this question. They intravenously injected the chemiluminescent exosomes into mice and watched how they go around in the body. Benefiting from the strong chemiluminescence of gLuc, they used in vivo imaging systems to visualize the localization of exosomes in the mouse during time. Surprisingly, they observed that exosomes were cleared from the serum very rapidly, with less than 5% remaining 5 minutes after administration. Also, the organs taking most shares of the exosomes were the liver and later the lungs. In the discussion, the authors mention that the reason for rapid clearance of exosomes from the serum could be unspecific interactions of the vesicles with blood cells. Exosomes express a multitude of adhesion proteins on their surface, allowing them to potentially bind various kinds of cells. We are far from fully understanding the dynamics of cell adhesion. But maybe careful engineering of proteins expressed on exosome surface could help in that direction, besides making progress in development of better targeted exosome therapeutics.

Tracking of localization of exosomes after intravenous injection. From Takahashi et al. J Biotechnol. 2013 Apr 2. pii: S0168-1656(13)00164-8. doi: 10.1016/j.jbiotec.2013.03.013

Tracking of localization of exosomes after intravenous injection. From Takahashi et al. J Biotechnol. 2013 Apr 2. pii: S0168-1656(13)00164-8. doi: 10.1016/j.jbiotec.2013.03.013

Takahashi Y, Nishikawa M, Shinotsuka H, Matsui Y, Ohara S, Imai T, & Takakura Y (2013). Visualization and in vivo tracking of the exosomes of murine melanoma B16-BL6 cells in mice after intravenous injection. Journal of biotechnology PMID: 23562828