While there are many ways to improve the unit economics of cultivated meat, from reducing the cost of producing expensive growth factors used in cell culture media, to exploring ways to recycle media, to developing more efficient cell lines; ProFuse Technology is addressing the process of skeletal muscle tissue formation (myogenesis) such that firms can produce more meat, more quickly.
Speeding up the skeletal muscle formation process
Phase one of the myogenesis process begins with rapid cell division and multiplication (the proliferation phase) of myoblasts (muscle stem cells) in a nutrient-rich media.
In the second phase (the differentiation phase), the myoblasts stop dividing and start to differentiate by fusing to form nascent myotubes (developing muscle fibers with a tubular appearance). Next, in a secondary fusion stage, these small myotubes start fusing with myoblasts to form bigger myotubes, which finally mature into muscle fibers (the maturation phase).
‘We’ve found a way to enhance the signaling process so that it happens bigger and better’
Typically, to move from the proliferation phase to the differentiation phase, companies will reduce the growth factors in the media and the cells will stop dividing in this ‘depleted’ or ‘reduced’ media and gradually start to differentiate and mature.
Depending on the species, this differentiation and maturation phase can take days or even weeks, and is not always super-efficient, in that only a certain percentage of myoblasts will fuse to form muscle fibers in any given production cycle, says ProFuse Technology, which was formed last summer to apply science developed at the Weizmann Institute of Science.
By administering a cocktail of small molecules (a media supplement) that target a molecular signaling pathway regulated by an enzyme called ERK, ProFuse effectively flicks a biological switch that triggers all the myoblasts to immediately start to differentiate, and activates another protein (CaMKII or ‘Cam kinase’) that is involved in the secondary fusion phase, where small myotubes fuse with myoblasts to create bigger muscle fibers, co-founder Tamar Eigler-Hirsh, PhD, told FoodNavigator-USA.
“It’s the natural process of myogenesis to activate cam kinase, so that takes place naturally, but we’ve found a way to enhance the signaling process so that it happens bigger and better.”
VIDEO: The video above, courtesy of Dr. Tamar Eigler-Hirsh, shows muscle stem cells under a microscope: “When exposed to a molecule blocking the ERK enzyme (right panel), the cells differentiate and undergo massive fusion…”
‘Not only are we accelerating the process, we are also increasing the amount of differentiation and increasing the amount of fusion’
For poultry cells, in a laboratory setting at least, ProFuse’s media supplement can slash the length of the differentiation and maturation stage from seven days to three days, and cause muscle fibers to ‘bulk up’ more, improving protein and texture at the same time, which could have exciting implications for the cultivated meat industry if these effects can be replicated in an industrial setting, said Dr Eigler-Hirsh.
“All we do is add our media supplement, and we are able to get this process started at a much earlier time point, so already by 24 hours after treatment, you can see the initiation of muscle fiber formation. And if you look at the endpoint at 72 hours post treatment, we’ve reached a maximum threshold.”
‘Significant increase in protein content’
If you just run out the growth factors and don’t add ProFuse’s media supplement, she said, differentiation will “still take place, it will just be much less efficient. There’s a maximum capacity that you can get just by serum reduction. Where the common practice is getting about 10%, we’re getting about 60% efficiency in the process.”
Without ProFuse, she claimed, “You would never get to this threshold of 60% fusion, it just doesn’t happen.”
She said: “So not only are we accelerating the process, we are also increasing the amount of differentiation and increasing the amount of fusion, and we’ve tested it on mouse, chicken, bovine and sheep cells with similar effects across all four species, and are now just diving into fish.”
Undifferentiated myoblasts that have not fused in the first production cycle still have the ability to turn into muscle in future production cycles, but there are obvious benefits to increasing the fusion index first time around, she said, noting that ProFuse Technology’s small molecules reduce the number of required production cycles, and enhance the meat production in each cycle, improving the quality of the muscle fibers, and increasing protein content.
“In data we acquired from chicken cultures, using ProFuse, the muscle fibers are larger; we’re getting about a four and a half fold increase in protein content using ProFuse compared to the common practice… and we are seeing similar data in bovine [muscle tissue].”
A word of caution: Lab-scale vs commercial-scale
Before we start cracking open the champagne, however, it’s important to stress that all of these numbers could change dramatically in an industrial setting, cautioned scientific co-founder Professor Eldad Tzahor.
“It’s important to remember that what we are talking here is based on basic research in a laboratory, not in an industrial setting. Every company and every cell type is different, and we haven’t tested this in a 10,000 liter bioreactor or in a 3D printing setting and so on.”
Collaboration with cultivated meat startups
So what happens next?
“Probably within a few months,” said CEO Guy Nevo Michrowski, “we will announce our generation two cocktail.”
In the meantime, he said: “We are engaged in collaboration with some of the cultivated meat companies, testing the efficiency and the effect of our cocktails in their production environment.”
Asked about the regulatory status of the small molecules in the ProFuse cocktail, he said: “The big challenge is regulation, but we’re very optimistic we’re going to be considered as a GRAS material in the US or as some kind of processing aid in other countries, at the beginning of next year.
“When you test the residual level in the [final] meat product, it’s extremely low to almost undetectable.”
GFI: ‘Having full control over the skeletal muscle differentiation pathway is an important scientific advance’
Asked for his take on the significance of ProFuse Technology’s work, Elliot Swartz, PhD, lead scientist, cultivated meat, at the Good Food Institute, told FoodNavigator-USA that its data and results were “impressive.”
He added: “Having full control over the skeletal muscle differentiation pathway is an important scientific advance. Skeletal muscle differentiation is typically a fairly slow process (days to even weeks long), and the ProFuse additive cuts down this time significantly, which could translate to cost savings, as shorter timeframes mean that fewer bioreactors and less media will be needed to create a given quantity of cultivated meat.”
Meanwhile, as the muscle fibers ‘bulk up’ more quickly, “which means that amino acids are efficiently being converted into biomass,” he said, “this in turn could translate into better protein and nutritional content as well as texture for structured products.”
Another important factor, he added, “is that the additive is still effective in an otherwise proliferation media formulation. This means that cultivated meat manufacturers can easily attain differentiation without dramatically altering the formulation of the media. In general, a less complex media is likely to be desirable for supply chain and other practical considerations.”