The Technical Challenges of Cultured Meat November 23, 2009

In a fascinating study, Doris Taylor and her team of researchers at the University of Minnesota re-created an artificial rat heart using stem cells.  They took a heart from a dead rat, flushed out all the cells using a detergent, and then injected stem cells and progenitor cells from the hearts of newborn rats into the empty heart.  The stem cells and progenitor cells, fed with a nutritious liquid akin to artificial blood, repopulated the “empty” heart, which held the original shape of the adult rat heart, but was composed only of Extracellular Matrix (ECM), i.e., the collagen, elastin, and other materials that hold our body parts together.  Amazingly, the heart was even able to beat, albeit at only 2% strength of a normal heart.  Before this technology can be applied to creating artificial organs for humans, they will need to improve it so that it can beat at 100% normal strength.

But wait – for in-vitro meat, 2% strength is fine.  Dr. Beth Zielinski, professor of Biology at Brown University points out, “this may sound gross, but in-vitro meat could be more tender than conventional meat.  If the muscle is only contracting at 2% strength, it won’t get as tough as meat grown in an animal that’s constantly exercising its muscles.”

I then asked Jason Matheny, co-founder of New Harvest, about the feasibility of this idea.
Me: “If you could structurally analyze an animal muscle, you could use bioprinting to recreate the 3-D extracellular matrix using synthetic collagen or synthetic elastin as a scaffold, and then grow cell cultures on it that would look just like the original muscle, say, a filet mignon.”
JM: “Synthetic collagen is being used as a scaffold in tissue engineering and for cultured meat, but the problem is that without blood vessels, the culture can be only a few millimeters thick, because there needs to be a way to deliver nutrients and oxygen to the cells below the surface.  One way we’ve been trying to do this is by bioprinting in layers where you can create these vessels.  The problem is that the resolution is not high enough that you would be able to do this at the millimeter scale, because the substance is very gooey.  If you could produce these forms extremely precisely–down to the millimeter level–and then produce the proper cell types, you’re going to have to have the growth factors embedded in there, too, which can signal the cells to become vascular tissue. Growth factors have successfully been embedded into scaffolding, because that’s what’s being sought for replacement organs.  Eventually, the cultured meat industry could cannibalize the technology used for growing whole organs in vitro.  Another possibility would be vascularizing the tissue from growth factors alone, instead of using the scaffolding to do it.”

So, the problem, in short, is that scientists can “print” the 3-D structure of an animal muscle using synthetic ECM, but the substance is so gooey that it cannot form the microvasculature (capillaries) needed to deliver nutrients to the cells.

A difficult, but fascinating challenge indeed.