A simple modification to the cells that carry oxygen around our body seems to stop severe bleeds almost immediately. When applied to serious wounds in the livers of rats, the animals formed clots in just 5 seconds and lost very little blood, raising hopes that the approach could one day help people undergoing planned or emergency surgery.

each year, with the risk rising with every minute that bleeding continues. In mild cases, blood clots normally form quickly, but more severe incidences can require costly transfusions that are hard to deliver quickly, or the use of bandages that sometimes trigger immune reactions or interfere with healing.

Although red blood cells primarily carry oxygen around the body, they also combine with platelets — cell fragments that stop bleeding — and a protein called fibrin to form a sticky mesh in response to injury, plugging the wound. Red blood cells make up the bulk of this plug, but are inherently fragile, which made at McGill University in Montreal, Canada, and his colleagues wonder whether they could be made stronger. “We saw and used the elephant in the room,” he says.

First, the researchers took blood from rats and separated out its various cellular components. They then added different chemicals that act like handles: one side randomly attaches to proteins on the surface of the red blood cells, while the other is free to join with a long-chain molecule that links cells together, which the researchers also added to the mix.

Next, the modified cells were returned to the liquid part of the blood, called the plasma, which the team injected into severe liver wounds in rats. These started clotting in less than 5 seconds, compared with 265 seconds in untreated rats. The treated rats also lost just 24 milligrams of blood, compared with nearly 2000 milligrams in the untreated group.

Unlike natural clots, which break down within days, these lasted one to two months, which Li says could give wound-healing molecules more time to act. The team also observed no safety concerns over this time.

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“It is exciting work that shows a new design method for cell-based biomaterials for surgical and regenerative applications,” says , founder of SanaHeal, a company developing bioadhesive technologies in Boston, Massachusetts.

In the future, the researchers hope that a small sample of a patient’s blood could be collected and modified in less than 30 minutes ahead of a planned surgical procedure. For emergencies, the treatment could be prepared in advance from blood-bank samples and refrigerated for at least a month. However, at the University of British Columbia, Canada, says that existing treatments can be stored for longer. “One challenge could be the shorter shelf life of such cellular materials, unlike synthetic materials,” he says.

Li says his team has applied for a patent and is planning further research.

While exercise is important for a long and healthy life, ultramarathons may accelerate the ageing of cells in our blood. Athletes who ran 170 kilometres over mountainous terrain accumulated more age-related damage to their red blood cells than those who completed a shorter distance.

Long-distance running has been linked to health issues before, such as temporary suppression of the immune system and anaemia. But we only now have an understanding of what it does to red blood cells – which transport oxygen around the body – particularly when done outside on mountainous terrain.

at the University of Colorado Anschutz and and his colleagues analysed blood samples from 11 adults aged 36, on average, within a few hours before and after they ran a trail 40-kilometre race. They did the same for a separate group of 12 people of around the same age who competed in a 170-kilometre ultramarathon over similar terrain.

The researchers found that competing in either race seemed to cause the runners’ red blood cells to accumulate more damage from molecules known as reactive oxygen species, which are produced at higher levels when these cells need to deliver more oxygen around the body.

But such damage, which naturally accumulates as red blood cells age, was substantially higher in the ultramarathon runners. “Anecdotally, the blood after an ultramarathon looks like the blood of somebody who’s just been hit by a car,” says D’Alessandro. “The red blood cells accumulate damage and become more aged.”

Running the ultramarathon, but not the shorter race, also seemed to cause their red blood cells to shift more rapidly from a disc shape to a more spherical one, which is typically seen when they age. The disc shape allows them to bend and squeeze through tiny blood vessels in the spleen, where old red blood cells are destroyed. “This spherical shape means they get stuck in the spleen and eaten up by immune cells,” says team member , also at University of Colorado Anschutz.

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This damage is probably due to exercise increasing inflammation and particularly strenuous activity pushing red blood cells more forcefully around the body, he says.

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What’s more, only the ultramarathon runners experienced a roughly 10 per cent drop in their red blood cell numbers after the race, but this isn’t necessarily a problem for their health. This change is too small to cause anaemia and the body can probably rapidly recover from it, says Nemkov.

The researchers are now studying the red blood cells of ultramarathon runners a day after they have completed a race, in order to better understand how long these effects last. They also want future work to examine whether these changes affect runners’ performance. “This could just be what the damage signals look like to make the body more resilient to endurance running, or it could have a negative impact,” says Nemkov.

A computational model that could rapidly design a blood vessel network for any 3D-printed organ may take us a step closer to transplanting artificial livers, kidneys or hearts without the need for a donor.

People with organ failure often require organ transplants, but is being met. To fill this need, scientists are developing ways to 3D-print organs in the lab. But these require blood vessel networks to stay alive, and existing experimental methods for designing these take days or even weeks.

To address this, at Stanford University in California and her colleagues built a computational model that can design these networks for any organ based on a mathematical law that describes how blood vessels branch into smaller ones in the body.

They tested their approach by having the model design a network of 25 vessels for a 1-centimetre-wide ring-shaped structure that had been 3D-printed from kidney cells, which it did in just a few minutes.

The team then printed the vessel network into the ring using cold gelatin particles, before heating it to 37°C (98.6°F), which melted the gelatin and left a network of hollow, 1-millimetre-wide channels that mimicked blood vessels. The researchers then continuously pumped a liquid containing oxygen and nutrients through the channels to simulate normal blood flow.

A week later, there were around 400 times more alive cells in the ring compared with an identical ring of kidney cells without the vessels, which the team had also bathed in the blood-like fluid.

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“We could keep the cells alive that were in close proximity to the vessels,” says Marsden. Those that were further away died because it isn’t yet possible to print the smaller, more highly branched vessels that are needed to supply nutrients to those regions, she says. The team is exploring ways to address this.

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“They’re definitely pushing the boundary of what’s possible,” says at Paris-Saclay University in France. The approach could one day allow scientists to design the vessel network for a full-sized organ in hours, rather than days or weeks, he says. “Vessel [networks] designed in this way could be used in the future to replace, or at least complement, organs that could be grown in the lab.”

First, the researchers need to develop ways to print these blood vessel networks into large organs. If all goes well, Marsden says they hope to test 3D-printed organs in pigs within about five years.

Amyotrophic lateral sclerosis (ALS) could one day be diagnosed with a blood test, after researchers have linked eight genetic markers to the condition.

People with ALS – the most common form of motor neuron disease – experience problems with walking, speaking, swallowing and breathing, which get worse over time and are eventually fatal. There is no cure, but treatments such as physiotherapy can reduce the impact of these symptoms.

Doctors generally diagnose ALS using symptom assessments, tests that measure the electrical activity of nerves and brain scans. There is a lack of awareness around ALS and doctors need to track how someone’s symptoms unfold over time before making a diagnosis, which delays treatment, says at the research organisation Brain Chemistry Labs in Wyoming.

To help diagnose the condition sooner, Banack and her colleagues have been analysing blood samples from small groups of people with and without ALS. This led them to eight genetic markers that seem to exist at different levels in the two groups.

To confirm this, the team has now looked at the blood samples of 119 people with ALS, taken from a biobank called the National ALS Biorepository, and 150 people without the condition, finding that the same eight markers still differ between these groups. The markers have been linked to neuron survival, brain inflammation, memory and learning, says Banack.

Next, the researchers trained a machine learning model to distinguish between those with and without ALS, based on the marker levels of 214 of the participants. They then put it to the test on the remaining 55 participants, finding that it correctly identified 96 per cent of ALS cases and 97 per cent of people without the condition.

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“This is fantastic stuff,” says at Kings College London. “The test performs well at distinguishing between those with and without ALS.”

The researchers estimate the test would cost less than $150 and hope it can be available within two years, says Banack. But first it needs to be validated on a separate group of people. If the team partners with the right diagnostic lab, the test could be available in a year, says Banack.