How Useful Are Stem Cell Transplants For Fukushima's Workers?

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Now a group of scientists has proposed a bold plan to help preserve the workers’ imperiled health.

The workers’ only protection from radiation is a synthetic suit designed only to prevent radioactive material from physically lodging on their body or clothing. Their ongoing exposure — and the chance of explosion in the plant — mean they’re at risk of reaching the upper limit of 250 millisieverts (mSv) per year of radioactive exposure that the Japanese government has deemed to be the acceptable cumulative threshold.

That’s where Dr. Shuichi Taniguchi and a team of experts in treating blood disorders come in. Last weekend, Taniguchi and his team made the short trip from Tokyo to present to a few dozen workers in Fukushima their unusual plan. Taniguchi, director of hematology at Toranomon Hospital in Tokyo, had already consulted with the doctors in charge of the plant workers’ medical care, and had received their approval to ask the workers if they would be interested in having their blood stem cells extracted.

The idea, Taniguchi says, is to harvest and store a ready supply of the workers’ own blood cells for later transplantation, should they be exposed to excessive amounts of radiation. Overexposure can destroy blood-making cells, which also populate the immune system, the body’s important defense against infection — a transplant could restore these functions.

“Many workers in Fukushima are working close to radioactive material, and if there is an explosion they might receive very high doses of exposure to radioactivity. And bone marrow and blood cells are [among]the first tissues destroyed by radiation. If they have a supply of their own blood stem cells, then just an infusion of these cells could recover their blood,” Taniguchi says.

This week, in the journal Lancet, the scientists, who hail from several academic centers in Japan, describe their proposal, which is modeled after the routine bone marrow transplants that cancer patients currently receive to replace tumor-ridden cells with healthy, cancer-free ones. Except that in the case of the Fukushima workers, they would skip the week-long process of extracting bone marrow from their bone and instead get a two-day procedure that would mobilize the stem cells out of the marrow and into their circulating bloodstream.

It makes sense, the Japanese scientists argue, because blood cells are always dividing frantically, which makes them vulnerable to attack by ingested radioactive particles. Removing such contaminated populations and replacing them with a healthy supply of the patients’ own cells could prevent serious radiation-induced illness and disease in workers who are accidentally overexposed. And if the cells are harvested from the workers themselves, they can avoid the possibility of rejection.

Taniguchi is also considering the possibility of freezing the stem cells in case the workers develop blood cancers such as leukemia or lymphoma years later, at which time the cells can be thawed and used to reconstitute diseased blood systems. “Autologous transplants for lymphoma and leukemia are recognized as a very good option for treatment,” he says.

In principle, say experts, the idea makes sense as a precautionary measure. But those familiar with blood diseases, including the authors, point out that such transplants are meant to address only the early effects of radiation exposure, when the primary cells affected are in the blood. “There is a spectrum of effects, and as you go a little higher in dose, you take out more and more of the blood system. And if you go a little bit higher still, you start to have GI problems and lung problems,” says Dr. Leonard Zon, director of the stem cell program at Children’s Hospital Boston. “Those issues cannot be fixed by a stem cell transplant. But there is a certain range of exposure that can be treated with a transplant, and that range is pretty extensive. The first problems of radiation exposure are likely to be in the blood system.”

That’s enough for the Japan Society for Hematopoetic Cell Transplantation to endorse the proposal, and the review board of the Toranomon Hospital has agreed to allow doctors to collect the blood stem cells from workers who decide to take advantage of the opportunity. Around the country, 107 transplant teams have also expressed their readiness to collect and store stem cells for workers who are interested in participating, and the cost, says Taniguchi, is being picked up by donations from Japanese companies willing to help the workers.

Still holding out, however, is the Japanese government, which decided not to support the plan because it has not been established as a standard for treating radiation exposure. At least one U.S. researcher has also cautioned that workers who have their stem cells stored may become cavalier and take unnecessary risks.

“We are proposing to be ready to support the workers in danger,” says Taniguchi. “Protecting workers from high radiation exposure remains essential. However, as a risk management procedure, collecting and storing one’s own blood stem cells is worth considering.”


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