New [Mouse] Surgeon on the Block
by Lorien E. Menhennett
Until a couple of weeks ago, I had mainly been doing genotyping at my lab job. I’ve got it down to a “science” (pun intended). I’ve been getting great results, which is wonderful. But I was itching to learn some new techniques. Well, I’ve gotten my wish.
My supervisor is teaching me animal surgeries. She has dozens of these to perform in the coming weeks and months, and wants someone to help reduce her load. And of course, I’m thrilled to learn something so practical for my future career as a physician-scientist, especially given that the mouse is the most frequently used animal model for diabetes research, which is what I want to do.
The first technique I learned (and am now pretty good at) is called an ELW (Excess Lung Water) procedure. It involves nebulizing mice with LPS, which basically gives the mice a septic lung infection, and then measuring various aspects of their lungs and blood. The most difficult part is taking a blood sample from the inferior vena cava, which you can imagine is pretty tiny in a mouse. And given that I’ve never really handled a syringe before, getting that needle in and then pulling the plunger back (with the same hand) was at first a challenge. But Thursday I performed my first ELWs on experimental, as opposed to practice, mice, and all went relatively well. (Except for one thing, which I will talk about in another post.)
The other procedure I’m learning is much tricker, and I’ve only mastered the first half. The purpose of it is to clear the mouse’s lungs of blood so they can be used for other experiments, such as histology, sectioning, etc. Cutting out the lungs is the easy part. The more difficult parts are putting the mouse on a ventilator (yep) and catheterizing the heart. Getting the mouse ventilated involves cutting part way through the trachea (again, quite small in a mouse), inserting a trach tube, and then hooking that up to a ventilator machine. The hard part is all the manipulations you have to do with your forceps prior to getting the trach tube in – for example, getting the 90-degree forceps under the trachea without causing the mouse to go into tracheal spasms (so you can pull through silk thread to eventually secure the trach tube). At first, I really struggled with getting that trach tube in. But I am quite good at it now, which is very exciting progress for me.
After getting the mouse on the ventilator, I heparinize the mouse to prevent blood clots, again through the IVC. Not that bad, considering I now am pretty decent with the ELWs. Another challenge after heparinization is catheterizing the heart. A mouse’s heart is literally the size of my pinky fingernail (and I have small hands). You have to get silk thread under the pulmonary artery, cut off half of the atrium, cut the aorta/IVC, and then slice slightly into the left ventricle to insert a small catheter. You then feed the catheter up the heart, into the pulmonary artery, so the fluid (PBS) going through the catheter will clear the lungs. This part of the procedure I am not so good with yet, but I am making progress. “Paso a paso,” one step at a time.
It’s slightly amusing to me that I am doing these procedures, and really enjoying learning them, given my past history with animal dissections. When I was a kid in homeschool, my mom would go to the butcher and get meat remnants (eyeballs, a pig head, various organs) for us to dissect. My sister would totally go to town with them, using a surgical kit that my dad, a physician, lent us. I wasn’t afraid of the dissections, but neither was I interested in them, so I hung back, watching. Now I’m totally into it, and thrilled to be expanding my skill set, as well as becoming more useful in the lab.
So at the end of it all, is the mouse sacrificed? As in DEAD?
Yes, in the two procedures I referenced, the mouse dies. Both of them involve removing the mouse’s lungs for further experiments.