Meat, in vitro?

By Stephen Pincock

The Scientist 21(9):22

In late 1998, bioengineer Morris Benjaminson and his colleagues at Touro College in New York decided to do some cooking. They dipped fillets of goldfish muscle tissue in olive oil flavored with lemon, garlic, and pepper, and fried them. It was appetizing work. "They looked and smelled just like fish fillets," says Benjaminson. Unfortunately, all the scientists could do is look and smell - according to Food and Drug Administration rules, no one could taste the filets, because they came from a most unconventional source.

The work, funded by NASA, was driven by the premise that astronauts on long flights need easy access to meat that isn't freeze-dried. Why not grow it in vitro? So they did. Cultured in fetal bovine serum and other media, goldfish muscle grew an average of 14%.

A few years later, public health worker Jason Matheny (now at Johns Hopkins) came across a published report on the goldfish research (Acta Astronautica 51:879-89, 2002) while scanning medical literature. He had just visited a chicken farm in India, where 10,000 clucking chickens were crammed into a large metal barn, the air sharp with the scent of ammonia. He emerged dedicated to finding another way to feed the meat-hungry world, and coauthored a paper on the topic that began circulating in 2004.

Soon he was contacted by the Dutch government, which asked "whether we thought in vitro meat was possible, and in what time frame," says Matheny, a vegetarian. Some years previously, a Dutch industrialist, Willem Van Eelen, had filed a patent on a "cultured meat" method. In 2001, Van Eelen convinced University of Utrecht researcher Henk Haagsman to work on the topic. "After more than four years and several failures we succeeded in getting research money in the last quarter of 2004," Haagsman says. The government agreed to put $2 million toward a four-year project in three Dutch universities. Matheny published his paper the next year ( Tissue Eng, 11:659-62, 2005).

In broad technical terms, growing animal muscle in vitro is little different from routine tissue culture, says Haagsman. Under his leadership, teams at the three centers each agreed to tackle a different major challenge: the composition of the culture medium in which the meat would grow, the source of muscle cells, and the design of the bioreactor.

Two years into the project, there's still much to do, Haagsman says. His group is trying to isolate cells that can be used to grow pork in vitro, dividing their resources between a search for porcine embryonic stem cells and coaxing nonembryonic precursors such as muscle satellite cells to proliferate. So far neither is a standout winner. "I think that the nonembryonic stem cells will yield a cell that can be used more quickly," he says. "The embryonic stem cells of the pig might be better, but will take longer to isolate."

The biggest hurdle facing cultured meat is perhaps the challenge of developing a cheap and effective culture medium. The current standard for tissue, fetal bovine serum, costs around $500 for 500 mL, says Paul Kosnik, a tissue engineer based in Hawaii. To grow 500 mL of meat, scientists would need significantly higher volumes of serum, he adds.

Even when researchers spend that kind of cash, different batches of serum-based media have variable effects on cell growth, which is not acceptable for industrial uses, Kosnik says. To achieve the goal of excluding living farm animals in the process, vat-grown meat would require the use of a nonanimal-based medium, which might prove challenging. "I think this is one of the most difficult problems," agrees Haagsman.

In spring 2007, 13 researchers from Europe and the United States established an international consortium for in vitro meat. The consortium is the brainchild of Stig Omholt, director of the Center for Integrative Genetics in Norway. He invited the Norwegian oil and gas company, Statoil, which uses methanococci to turn natural gas into protein, to join the consortium. "Unless we have access to a cheap cell culture medium we will get nowhere ... and this bioprotein could be the carbon source for our medium," Omholt says.

All of which brings us a long way from Matheny's epiphany at the India chicken farm. "I think it is possible that in, say, five years you could have a system that could be scaled up and used to produce retail-grade meat," he says. "And this is meat that I would eat."