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Exercise in tissue engineering, Halloween decoration, or mad scientist show piece? Take your pick...

Some people like to make their Halloween decorations from papier mache. We used raw, bleeding pig's hearts!

Last year, we tried to decellularize some chicken hearts and gizzards at BioCurious for Halloween. This year, we tackled a full-size pig heart, with members of Counter Culture Labs, our new DIYbio group in the SF East Bay, with some help from friends at BioCurious.

Decellularization is a tissue engineering technique designed to strip out all the cells from a donor organ, leaving nothing but the connective tissue that used to hold the cells in place. This scaffold of connective tissue - called a "ghost organ" for its pale and almost translucent appearance - can then be reseeded with a patient's own cells, with the goal of regenerating an organ that can be transplanted into the patient without fear of tissue rejection. A decellularized mouse heart regenerated with human heart precursor cells will actually start beating autonomously! Here's some amazing videos on this work by Doris Taylor at U. Minnesota:

Creating a beating heart in the lab
Surprising Beauty, Holding A Pig's Heart

Getting all the cells to coordinate correctly in a large heart is still a big challenge. That part is still years away from clinical use. We're just doing the first part though: decellularization of a pig heart. Why? Well, what self-respecting mad scientist wouldn't want to have a Ghost Heart in a Jar!

If any of this seems way too challenging to you - note that none of us had ever done anything like this before! We just read up on what it took to do this, figured out where to get a pig heart, got a few pieces of equipment, ordered some chemicals, and got to it! The results look absolutely spectacular, and we learned tons along the way. Yes, this project is a bit complex, and there's lots of long words in the steps below - but don't let that scare you away! The whole thing can be accomplished in a single day, and we'll tell you about DIY alternatives for all the equipment and chemicals used here.

The decellularization is achieved using enzymes and detergents to break open the cells and flush out the cellular content. The solutions need to be perfused throughout the heart muscle using a pump. Not just through the chambers of the heart, mind you, but actually through the coronary arteries that provide blood supply to the muscle of the heart itself. The published protocol takes approximately 10 hours, but since we are planning this as a show piece and not to reseed them with cells, we have taken some shortcuts.

Please use appropriate safety equipment and measures. One of the nice aspects of this experiment is that all the chemicals you're working with are fairly non-toxic. But you're also working with lots of fluids under pressure, and you really, really don't want assorted pig heart juices squirting into your eyes - trust me on that! So make sure to wear some goggles at least. A lab coat to protect your clothes from giant blood stains wouldn't hurt either (unless you're into that kinda thing).

If you use something like an aquarium pump please note the problems the solutions used could cause the pump, as well as contamination issues. A fountain pump from the hardware store might be another interesting alternative for high volume and relative high pressure. But most fountain pumps are immersion pumps, and are *not* designed to handle salty, conductive water - try at your own risk!

Check out the timelapse video we made we made of the whole procedure:

Step 1: Obtain a Pig "bio-heart"

If you hunt around, you can probably find some pig hearts for sale in a Chinese supermarket, or from an adventurous butcher. However, hearts that have been butchered for food typically have the arteries at the top of the heart cut off, and a slash through the chambers of the heart to let the blood drain out. Unfortunately, that makes them entirely unsuited for what we need.

What you need is a pig heart that has been butchered specifically for biological experiments - what's called a "bio-heart" in the trade. The good folks at the California Academy of Sciences recommended C&M Meat Company, a meat wholesaler in Berkeley that should be able to get us a bio-heart fairly cheap.

Unfortunately, when you're trying to get a single heart from a wholesaler... you're not exactly a high priority for them. They agreed to get us some bio-hearts, but only if we ordered at least five at a time. So after getting the runaround and wasting a couple more weeks of our time, we finally received a surprisingly neat cardboard box, containing five very raw, and very bloody pig hearts!

Our bio-hearts came with about a foot or more of extra arteries attached. You'll need no more than about an inch of the aorta to attach a hose for the perfusion, so you may want to chop off some of the obviously extraneous bits at this point. While you're at it, rinse the heart under tap water to get rid of blood that might be left in the chambers, check that the aorta is intact, and that there aren't any nicks on the surface of the heart muscle.

The first step in almost all decellularization protocols is to freeze the organ. That's partly for convenience, but the formation of ice crystals will also start breaking open the cells, starting the decellularization. So wrap your bio-hearts in separate plastic bags, chuck them in the freezer, and above all - don't tell your vegetarian wife!
Hey I was wondering what volumes of the reagents you were using? Like the water has 3L but for example there's no volume for oxyclean <br>Are they left as percentages because it doesn't matter?
Excellent 'ible, I wish more high-caliber experiments like this were on this website. Good call on the sodium azide though; I'm fond of dangerous chemicals, but metal azides are too much even for me.
That is too intensely wonderful. Great fun and a positive way of illustrating what can soon be done. I have a congenital heart problem, perhaps the wife will soon fix it in the kitchen... better still the cellar. <br>Thank you so very much for cutting through the jargon (and a porker's chest) <br>Incidentally I worked in pharmaceutical research and love to tell people that inside a pig looks nearly identical to inside us.
truly mad scientist stuff, well done, seeing the steps written in proper scientific lingo was scary and so were the ingredient names but glad i read further and saw the explanations and the household substitutes for it....well done to bring that level of understanding for the masses.
Super interesting writeup!