Microscopic observation of cell function in live tissue, awesome! But don’t ignore the methods, and the animals they required

It has been far too long since I wrote a blog post. Look out internet, I have a blogging itch that needs scratching, and it’ll probably cause a rash!

…I apologize for that mental image.

The NIH sent me an email this week (via the various government listservs I’m enrolled in) that was proudly declaring that the mysteries of the cell were being solved right now, so I took the clickbait. In it was a cool study where we were able to actively watch mitochondria oscillate inside a living animal.

Fig from the article
http://dx.doi.org/10.1016/j.celrep.2014.09.022

There are two rabbit holes to enter with this article. The first is the observation of interest, which was mitochondrial oscillation. While these slinky moves have been observed in cell cultures, the authors wanted to see if there were any differences in cells that were part of a living, breathing animal.

Movement isn’t a surprising thing. If you’ve ever drawn the ATP synthase lollipop (totally relatable experience for everyone, right?), you already know that some of the main membrane proteins in mitochondria are constantly rolling around attaching phosphates to create ATP. The cool thing though, is that since they’re synching up with each other, that means there could be cellular communication mechanisms that are helping coordinate mitochondrial efforts to produce energy as needed. Which makes sense if you’re generating ATP in response to a stress event on a cellular level.

But what if you’re an animal? A slice of muscle tissue is made up of many muscle fibers, all of which contain mitochondria. It seems like there would be a need to coordinate increased energy production if you were planning to use all those fibers in sync to move. When looking at the cellular tissue inside a living rat’s salivary gland epithelium (the covering layer of the gland), the authors observed that mitochondria oscillated in sync not only within individual cells, but in sync with other cells in the tissue. The authors describe it in their press release wonderfully:

“You look through the microscope, and it almost looks like a synchronized dance”

It’s always more fun looking at living cells and tissue, it reminds you that all of that stuff we can’t see is always buzzing around without our notice and crawling all over our skin and gut.

Hypochondriacs I apologize for that second image.

So since we like looking at living things, let’s get to the second cool part that the press release seems to gloss over, how the hell were we observing cell structures in a living animal!

The principal author, Roberto Weigert, was the first one to publish this technique, so I went to that article to better understand what’s going on. I don’t want to dig into the microscopy so much, as the technical information is a little overwhelming. I’ll just say that there are really cool microscopes that can use near-infrared light to penetrate deep into different tissues (segregated visually by the injection of fluorescent dyes). The article has some amazing images of mouse vasculature that are both easy to observe and understand. But that technology isn’t what this blog is about. What I want to know is, what did this study entail for the animals used?

For this procedure, the research rats were anesthetized and had their salivary glands “externalized”, meaning that they gained access to them presumably by opening/removing the skin, fat, and muscle layers and segregating the gland as far as they could for the procedure (you’d be surprised how far you can pull things out while they’re still attached). Then, they bathed/saturated the glands with various dyes and chemical/hormone baths depending on what they were observing in that particular instance.

Once the images were taken, presumably these brave rats were euthanized, I couldn’t find a reference in the procedure but ultimately it had no bearing on the ability to replicate the experiment and was not included.

Now imagining these experiments in vivo (in living animals) brings up nasty words like vivisection. However it’s always important that the authors of the study aren’t left to singly decide if the research is necessary or not, it’s up to the Animal Care and Use Committee to allow the use of animal subjects for research at the NIH.

In order to use and ultimately euthanize these animals, the authors had to prove that: the information learned from the study will benefit humans and/or animals, there is a rationale for using animals including why a surrogate (e.g. cell culture) would not work (the authors make a great statement in their press release by describing the observations as if you’re looking at a tree vs. the forest), and a description of how the authors have actively attempted to minimize pain and discomfort for the animals used.

Ultimately I chose to write about this article because the methods were cool, but also to acknowledge the animal use inherent, but understated, in this type of research. It’s important to remember that often new information comes at the cost of continuing to support animal research when justified, and to not hide the facts from ourselves.

In order to responsibly care for all of our domestic species, we need to remember that before they were beef, eggs, milk, nuggets, or a data point, they needed to be cared for and euthanized humanely.

ResearchBlogging.org

Natalie Porat-Shliom, Yun Chen, Muhibullah Tora, Akiko Shitara, Andrius Masedunskas, & Roberto Weigertemail (2014). In Vivo Tissue-wide Synchronization of Mitochondrial Metabolic Oscillations Cell Reports : http://dx.doi.org/10.1016/j.celrep.2014.09.022

Weigert R, Porat-Shliom N, & Amornphimoltham P (2013). Imaging cell biology in live animals: ready for prime time. The Journal of cell biology, 201 (7), 969-79 PMID: 23798727

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