By Avery Parkinson
Cellular agriculture is the science of creating animal products without the animal. There are two main kinds of cellular agriculture: “cellular agriculture” which is concerned with making products containing once living cells (like meat and leather)
and “acellular agriculture” which is about creating animal derived products (like cheese and milk).
For now, we’re going to focus on cellular agriculture (that is, not acellular agriculture). When we produce meat using cellular agriculture, we are said to be “culturing it in vitro”. This is done in three main steps.
- Stem cells are extracted from the animal. Stem cells have the potential to become many or all of the different types of cells found in an animal which makes them ideal for creating the different parts of meat. In the case of a primary culture, adult stem cells are taken from the reserves of an animal’s specialized tissues — tissues that already have a specific purpose (like skin or muscle) — and are called progenitors. In the case of secondary cultures, cells might be cryopreserved (frozen) from previous experiments.
- Stem cells are immersed in a culture medium and proliferate. A culture medium is a substance containing everything cells need to grow like carbohydrates, fats, amino acids, salts and vitamins. As these molecules diffuse into the cells, they grow and eventually split into two smaller genetically identical cells. In this way, our population of stem cells increases exponentially, or “proliferates”.
- Stem cells are put into a bioreactor and differentiate. Bioreactors are machines which expose the cells to a variety of different environmental cues — for instance, electrical stimulation and mechanical contractions. This encourages the cells to differentiate into the types of specialized cells we get in meat (like muscle, fat… etc). These myoblasts then fuse to form multi nucleated myofibers— i.e. tissue.
And bam, we have perfect steak…well, not quite.
This process would be just about where everything ends for unstructured meat, but not for structured meat. Unstructured meat is, as it sounds, meat that doesn’t have a real structure (like ground beef). Structured meat, on the other hand, is meat that has a specific composition of cells — it’s not just the type of cells that characterize it, but the arrangement, too (like steak).
Getting a particular arrangement is not reliable by just allowing the cells to float around in the bioreactor and crossing our fingers. So, we need something called a scaffold. A scaffold is a mold which the cells grow in and around to form the specific shape and structure of the meat. The proliferated cells are usually seeded onto the scaffold (i.e. attached to it) and then put inside the bioreactor.
Some popular scaffolding materials include decellularized plant tissue, chitosan from fungi or recombinant collagen. Researchers at the University of Ottawa and University of Western Australia have been looking into the benefits and downsides of each type, and found the following:
Decellularized plant tissue is abundant and has a great structure and texture. However, it lacks many of the growth cues deemed vital for growing mammalian cells.
Chitosan is abundant, and has antibacterial properties. It can also be blended easily with other polymers which suggests that it could easily be tailored to what a scientist is trying to grow. However, in the presence of lysozymes (a naturally occurring enzyme), chitosan will start to break down in unpredictable ways.
Recombinant collagen is highly biocompatible but is hard to produce and source.
All of these scaffold variations are favoured by researchers because of their commonality: they can be produced by plants or fungus, and are hence unreliant on animals.
So there, now we have our perfect steak. Well again…there’s more.
We may have a nicely structured cut of meat, but now we have a scaffold in it. Scientists have proposed using edible scaffolds, but since the whole idea behind the cultured meat is to perfectly replicate meat, scientists are leaning towards figuring out a way to make biodegradable scaffolds. But this in itself introduces some new issues, most notably the rate of decay. If our scaffold literally disappears while the meat is growing on it, it kind of defeats the purpose.
Now, of course, this entire process is easier said than done. Key challenges include the cost of the culture media, media composition, finding biomaterials that are compatible for scaffolding, commercial regulations and of course, public perception. But, there are a number of startups working to overcome these obstacles so that hopefully, the technology will become more mainstream.