But the flask in Roelen's hands today is just filled with a thin layer of fluid, the color of red Kool-Aid but slightly more viscous. Floating within this growth medium, but not quite visible to the naked eye, is the protomeat. "I get all these phone calls and e-mails from people saying, 'Can I taste something?'" Roelen recounts. "You can scrape the cells on the surface, and then you may have this snotty substance, but that would not be so good." I decline his offer of a taste, and he places the gooey mass under a microscope and adjusts the focus knob. Suddenly, I see that the entire wall is speckled with the elusive embryonic stem cells that have the potential to transform into any part of the pig's body—bones, blood, brains or, for Roelen's work, muscle.
The process begins, ironically, with a nearby slaughterhouse, from which Roelen has retrieved pig ovaries. The eggs mature in vitro and are then fertilized with pig semen, transforming them into embryos. Placed in a nutrient bath, the embryonic cells divide and grow, changing along the way. Some are just motionless blobs, but others pulse to an eerie rhythm, having spontaneously transformed into heart muscle despite Roelen's desire to keep them in their undifferentiated state.
"You can see the cells have started to align, but they have not fused yet," Roelen says. "You want that process to be as efficient as possible." In the future, meat-growers may forgo the dish and culture stem cells on an edible, three-dimensional scaffold, and, with the right chemical signal, they would transform into sumptuous fibers of skeletal muscle protein. Roelen's colleagues at the Eindhoven University of Technology are even working on ways to "exercise" tissue through electrical stimulation to give them a more natural texture.
Unfortunately, Roelen's cultures only survive a few months before they sputter, failing to reproduce because of genetic problems—their chromosomes become deformed or cells end up with too many copies. His group also works with adult stem cells extracted from skeletal muscle—a direct approach for in vitro meat.
Tor Erling Lea, a biologist at the Norwegian University of Life Sciences in Aas who is also pursuing test-tube meat, acknowledges that Roelen is the leader in the field, but he's not impressed with either the embryonic or adult approach so far. "I think what they have achieved is what we could expect to achieve," he says. At last year's In Vitro Meat Symposium, Lea presented his preliminary work on stem cells derived from the umbilical cords of pigs. They are easier to work with, and he calculates that it's possible to culture up to 10,000 pounds (4,500 kilograms) at a time, but so far he has only produced fat and cartilage.
Even if Roelen's team succeeds in culturing enough muscle cells for a bacon substitute, the team still faces with the problem of what to feed their disembodied animal. The red Kool-Aid–colored medium has just about everything a growing muscle needs; the only problem is that it's derived from cow blood. Vegetarians certainly aren't going to stomach bovine serum albumin. Alternatives exist, but they are far too costly for food production. Molecular microbiologist Klaas Hellingwerf of the University of Amsterdam believes that a suitable substitute lies in a medium based on yeast or algae. He has done preliminary experiments to get genetically modified algae to produce a growth factor that will encourage Roelen's stem cells to multiply.
Before I leave, I can't help but ask Roelen if he would consider eating his lab-grown meat. "Why not?" he responds, noting that people have no problem scarfing down imitation cheese and other processed foods. He has a point, assuming he can get his meat past the snot phase.