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How placental stem cells can save lives following radiation exposure

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Last week we reported that the US Food and Drug Administration approved a stem cell-based therapy, derived from the human placenta, for emergency treatment following a nuclear event. Here Bryn Nelson examines how a once-dismissed waste product of birth could save lives after exposure to extreme radiation:

US President Donald Trump says he is optimistic about de-nuclearising North Korea. But, America has also just pulled out of the nuclear deal with Iran.

The threat of nuclear war has risen and waned by turns, never entirely disappearing, since the first A-bomb was dropped over the Japanese city of Hiroshima in 1945.

Since then, the world has witnessed two catastrophic events involving power plants: the Chernobyl, Ukraine disaster in 1986, which sent a plume of radiation across the world; and the Fukushima, Japan nuclear disaster in 2011.

Meanwhile, a handful of research groups have been exploring if treatments based on umbilical cord blood and placental tissue could provide a temporary lifeline in the immediate aftermath of an accidental or deliberate release of radiation.

In your bones

Following a nuclear disaster, survivors exposed to high-dose ionising radiation can fall victim to acute radiation syndrome. Around 30 people died from this illness in the first few months after the Chernobyl meltdown.

Radiation can brutalise the body’s bone marrow, which makes platelets and white and red blood cells. While radiation strong enough to wipe out someone’s marrow would likely prove fatal due to damage elsewhere, a potentially survivable dose could still wreak havoc on the spongy tissue.

Seattle start-up Nohla Therapeutics is one research group exploring the use of umbilical cord blood cells as a countermeasure. Their strategy is to isolate blood-forming stem cells from donated cord blood, multiply them in the lab until they number in the hundreds of millions or even billions, and then infuse them into a patient. Until that patient’s own bone marrow bounces back, “the idea is that these cells can come in and take over that job,” says Colleen Delaney, the company’s chief medical officer and director of the Cord Blood Program at Seattle’s Fred Hutchinson Cancer Research Center.

Unlike bone marrow from adult donors, cord blood transplants don’t require a close match of genetic identification tags between donor and recipient cells, potentially allowing Nohla to produce vials of universal donor cells that could be frozen, thawed and used on demand.

Delaney says the work is part of a larger plan to use cord-blood-derived cells to fight a wide range of diseases, disorders and injuries that can disrupt bone marrow’s function. The anti-terrorism potential has attracted considerable support − in 2009, Delaney won a multimillion-dollar grant from the Biomedical Advanced Research and Development Authority, part of the US Department of Health and Human Services. The authority’s Project BioShield backs medical measures that counter biological, chemical, radiological and nuclear agents.

Buying time

John Wagner, Director of the Blood and Marrow Transplantation Program at the University of Minnesota, says Delaney’s strategy could help a large number of victims by providing a safety net until their damaged bone marrow recovers or they receive full transplants. “It’s something that you could do immediately,” he says, “and so I think it is a very important strategy”.

Other researchers are more sceptical. Robert Peter Gale, now a visiting professor of haematology at Imperial College London, was among the experts who treated the scores of individuals exposed to radiation after Chernobyl. Those who died in hospital, he says, did so not from severe bone marrow damage, but from other bodily harm caused by the radiation.

Other reports suggest that bone marrow failure contributed to the deaths, though Gale says his experience suggests that “very, very, very few people” would benefit from a post-disaster transplant of blood-forming cells. “It’s a pyrrhic victory if we rescue them from dying from bone marrow failure, if they are going to die three weeks later or three months later from pulmonary failure,” he says.

Delaney and Wagner, however, note that cord blood research is both progressing rapidly and revealing an increasing number of benefits for individuals with damaged bone marrow, whether from radiation or other causes. In a recent study, for instance, Delaney and her colleague Filippo Milano showed that cord-blood-derived stem cells reduced the risk of infection among people with leukaemia who had received high-dose chemotherapy.

In late April Pluristem Therapeutics, an Israel-based company developing human placental adherent stromal cells for use in disease treatment, received clearance by the FDA for the emergency use of PLX-R18, a stem cell-based therapy derived from the human placenta, for treating of radiation exposure following a nuclear event. The company has said it will start preparations to stockpile an emergency store of PLX-R18.

Regardless of this promising area of stem cell therapeutics, Gale suggests that officials should prioritise efforts to educate the public about the true risks of radiation and to prevent nuclear attacks or accidents from ever occurring. “Prevention,” he says, “will always trump intervention.”

This article first appeared in Mosaic Science and is republished under a Creative Commons license.

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