Pigs: They're not just for eating anymore
This article first appeared in the St. Louis Beacon, Nov. 24, 2011 - Dr. Marc Hammerman, a Washington University scientist, may be closing in on the day when the lowly pig is valued for its medicinal use in addition to being a holiday treat for pork lovers. Scientists are convinced that insulin-producing cells from embryonic pigs will eventually be transplanted into humans as one approach to controlling what has become a worldwide spike in diabetes.
Diabetes is a health problem for as many as 10 percent of the world's population, including more than 23 million people in the United States. Worse, the Centers for Disease Control and Prevention project that as many as 1 in every 3 Americans could have diabetes by 2050 if the current trend continues. That trend is driven mainly by growing rates of obesity, too much unhealthy food and too little exercise.
Pig-to-human cell transplants for diabetes are still years away and have to survive many medical and safety hurdles. But Hammerman, a professor of renal diseases Washington University School of Medicine, thinks such transplants could become a more effective treatment for diabetes than current therapies.
Diabetes is now treated mainly through insulin, as well as pills that increase insulin secretion to control glucose. These treatments work relatively well if taken correctly, Hammerman says. But a bigger issue is that certain complications stemming from diabetes cause lots of pain and add plenty of cost to the health care system. Potential complications include kidney failure, heart failure and blindness.
"The current therapies don't reduce the chances for these complications," Hammerman says. "Only transplantation therapy that delivers the right amount of insulin at precisely the right amount of time can do that."
Human islets can deliver appropriate levels of insulin, but there is a shortage of donors. Hammerman believes that shortage is another reason pig cells offer the best alternative. He says these cells are ideal because "pig insulin is almost exactly the same as human insulin." Moreover, he says, research suggests that unlike in the case of human islets, pig cells "could prevent transplant patients from having to take anti-rejection drugs for life."
He envisions the time when diabetics might receive injections of pig cells through a portal vein, for example, with the procedure being less complicated than an operation.
"To be realistic, I think five to 10 years would be an optimistic estimate" before pig cells are transplanted to humans, he says. "It would have to be proved that this is both safe and effective. We don't want to do anything that's not safe, and we certainly don't want to take any risk if the therapy is not effective."
Could Humans Catch Diseases from Pigs?
Which raises what is a worrisome issue to some. What about the possibility of unknown infections in pigs reaching humans through cell transplants? That question is being raised by Robin Weiss, a professor of virology at University College in London. In a recent interview with the London Independent, Weiss said the transplanted cells and tissues raised concerns about a retrovirus moving from pigs to humans and causing a pandemic in the same way that HIV has. Still, he predicts that human trials could begin within three years. He says these should move forward under "very close monitoring to ensure they (humans) were not picking something up from pigs."
Agreeing with Weiss, Hammerman acknowledges concerns about humans being infected by a virus that resides in the pig's DNA.
However, he adds that "the chances of that happening are extraordinarily low. I think over the last 10 years most people who have expressed concerns about that happening are less worried now. It's something that theoretically could happen, but the chances of it happening are extraordinarily small."
Hammerman's research has focused on the impact of transplanting clusters of embryonic pig cells for producing islet cells into three diabetic monkeys (rhesus macaques). He said the monkeys "adopted" the pig cells as their own without needing powerful immune-suppression drugs to prevent rejection. His research was published in the journal Organogenesis.
Hammerman concedes the team still has a lot of work to do. He says one major goal is to figure out the amount of islet cells needed to cause glucose control to continue to improve in animals. He is not taking his eyes off the long-term prize of making the therapy available for humans.
"That's the hope," he says. While the new therapy wouldn't cure diabetes, "we would be able to treat millions of people around the world."
Funding for the Beacon's health reporting is provided in part by the Missouri Foundation for Health, a philanthropic organization that aims to improve the health of the people in the communities it serves.