A genetically modified pig’s kidney kept a man with organ failure off dialysis for nine months while he waited for a suitable human donor’s kidney to become available. This suggests pig kidneys could act as a temporary measure amid lengthy organ waiting lists, but they may also work as a permanent replacement one day.

“I think it’s incredible in terms of the science behind it and what they’ve achieved,” says at Imperial College London, who wasn’t involved in the work.

For people with severe kidney disease, where these organs are failing and dialysis is needed, a kidney transplant provides the best chance of survival and better quality of life. However, demand for donor organs exceeds supply.

One possible solution is xenotransplantation, the transfer of organs from other animals into humans. In January 2022, a pig heart was transplanted into a person for the first time, but the recipient died several months later, possibly due to the presence of a pig virus. A pig liver transplant also occurred last year.

A pig’s kidney was transplanted into a living person for the first time in 2024. The recipient, Richard Slayman, aged 62, died 52 days later from cardiac-related causes. In the latest development, Tim Andrews, a 66-year-old man with end-stage kidney failure, opted to receive a kidney from a pig to avoid dialysis while he waited for a suitable human organ.

at Mass General Brigham hospital in Boston and his colleagues transplanted the kidney, which came from a Yucatan miniature pig, into Andrews in January 2025. The organ had been genetically modified to improve compatibility with the human immune system, such as by removing some sugars that we produce antibodies against and adding seven human genes.

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The transplant was initially a success, and Andrews – who also received immunosuppression drugs to stop his body rejecting the organ – came off dialysis and resumed normal life. However, after about six months, he was admitted to hospital with a methicillin-resistant Staphylococcus aureus (MRSA) infection, which most antibiotics can’t kill.  

Riella and his colleagues reduced the immunosuppression drugs Andrews was on, but then damage started to develop in the kidney’s blood vessels. This progressed to organ failure, and the kidney was removed a record 271 days after transplantation. “He had a kidney that lasted nine months, which is mind-blowing,” says Riella.

Andrews went back onto dialysis for about three months, before finally receiving a suitable human kidney in January 2026. This marks the first time a pig kidney has been used as a temporary bridge to a human transplant.

“Such transplants may allow patients to avoid going through dialysis, which is so important because it causes so much wear and tear to the body,” says Riella. “Hopefully, maybe 15 years from now, pig kidneys will compete with a human kidney transplant, but you’re not there yet.”

2024 saw the first living people to receive pig kidney transplants

Three people in the US received a genetically modified pig kidney in 2024, marking another step towards animal-to-human organ transplants becoming routine

The procedure is experimental, and Riella couldn’t give an estimate of how much it might cost. But in the US, there are about 600,000 people on dialysis, which can cost about $100,000 a year per individual, he says.

Riella says the team has now done five such transplants and two more case reports will be published this year, including one of a person who has already beaten Andrews’s record of nine months with a functioning pig kidney.

“I think these will be carried out more widely in the future, but it’ll be a little while,” says Willicombe, largely due to their probable high cost. Scientists should also continue researching artificial kidneys, as well as ways to regenerate damaged organs and optimise donated ones, she says.

Some of the benefits of a rigorous workout might one day be achievable without any physical exertion. A study in mice shows that injecting muscle cells beneath the skin creates a patch of these cells that continuously contracts, delivering some of the benefits of exercise around the clock. While this should never replace physical activity, it may be helpful for people who are unable to exercise, such as those in hospital.

Initially, at the Beijing Institute for Stem Cell and Regenerative Medicine in China and his colleagues injected muscle cells into mice with the aim of increasing their muscle mass, but this had an unexpected result. “This thing was contracting under the skin continuously, and we thought, ‘This thing is like non-stop exercise’,” says Shyh-Chang.

They started by taking samples of muscle stem cells from live mice, which they cultured until the cells differentiated into mature, contractile muscle cells known as myocytes. They then injected these just beneath the skin on the backs of the same mice. “The original intention was to increase muscle mass by injecting muscle cells,” says Shyh-Chang.

With an injection of about 6 million myocytes, a patch of cells formed, creating its own network of mini blood vessels. This then began to pulse continuously, even when the mice were asleep.

Various experiments showed the patches had widespread effects around the mice’s bodies. For instance, the mice given the muscle patches had a higher whole-body muscle mass and better immune function compared with those that got a sham injection. All the mice were free to move around their cages as normal during the study.

What’s more, in mice that were 18 months old (roughly equivalent to a person in their late 50s or 60s) and those fed to induce obesity, the patches improved muscle mass, bone density, physical strength and endurance.

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These mice also showed reversal in signs of liver damage, as well as reduced inflammation and the ability to navigate a maze faster. “So, it also has effects on its brain,” says Shyh-Chang. “This is known from exercise, but here, we’re seeing it from a small muscle graft.”

The patch’s wide-ranging effects may be due to it mimicking how . “What I find particularly interesting is that the effects appear to go beyond the graft itself,” says at Duke-NUS Medical School in Singapore. “The study suggests that the contracting muscle can act as an endocrine organ, with changes in circulating factors that may contribute to effects in other tissues.”

Imaging showed that the muscle patches survived for at least 81 days, when the researchers stopped taking measurements, but Shyh-Chang says that follow-up work indicates they are still stable after six months. “So far, there’s no limit to its lifespan as far as I can tell,” he says. There also seems to be very little reduction in volume over time and no evidence of tumour growth, which can be a risk after implanting stem cells.

Just 1 minute of vigorous exercise a day could add years to your life

People who do several very short bouts of strenuous activity each day are much less likely to die in the next few years than those who do no exercise at all

Shyh-Chang hopes the patch could help people with medical conditions that stop them from exercising. The researchers are talking to several hospitals about starting clinical trials in people with limited mobility, which could begin within a year, he says. “We always say we should exercise to keep muscle mass, but the folks that need exercise the most are actually the ones least likely to be able to exercise,” he says.

“The idea of mimicking exercise for people who can’t exercise is amazing,” says at King’s College London, but he questions how comfortable a continuously contracting graft like this would be.

Tang stresses that the patch should be thought of as mimicking some aspects of exercise, rather than replacing it. “Exercise has many other effects – including cardiovascular, neuromuscular, mechanical and bone-loading effects – that a small subcutaneous muscle graft cannot fully reproduce,” he says.

Researchers have identified specific groups of neurons in the brains of mice that are activated after the rodents have been awake for a long time, driving them to get some sleep.ĚýIf a similar system exists in humans, it could be targeted to help improve treatments for some sleep disorders.

Inside the brain, several neural circuits , including neurons in the hypothalamus that .Ěý

One or more of these circuits might be involved in why it is that, the longer we are awake, the more irresistible the urge to close our eyes becomes. But what actually drives this impulse has long been a mystery.

To find out,  at the University of Basel in Switzerland and his colleagues have compared brain activation patterns in mice during normal sleep-wake cycles, sleep deprivation and recovery sleep. They did this by tracing how much protein is produced in cells by a gene calledĚýšó´Ç˛ő, which is turned on when neurons are in the process of activating.

“We saw that very specific parts of the brain were correlated with wakefulness,” says Joo. This allowed the researchers to identify areas in which activity correlated with time spent awake.Ěý

Within one of these regions, the median raphe nucleus, they found two distinct neuronal populations that were increasingly activated the longer the animals stayed awake and that got quieter again after sleep started. These populations are the GABAergic and serotonergic neurons, so named because the chemical messenger molecules they respond to are gamma-aminobutyric acid (GABA) and serotonin, respectively.

“This is an outstanding study. The whole-brain Fos mapping is a real tour de force,” says  at the University of Wisconsin–Madison.

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To see whether these neuronal populations became more active simply because the mice had been awake for a long time or whether they do something more, Joo and his colleagues then used viruses to deliver a genetic package to the neurons to either activate or inhibit their action.

When both sets of neurons were artificially activated, the mice slept for twice or three times as long as control mice and spent more time in non-REM slow-wave sleep – in a way that resembles the deeper recovery sleep humans have after we have been up for a long time.Ěý

“Not only does it increase the amount of time the animal spends sleeping, but it also increases the quality of the sleep,” says Joo.

When the neurons were inhibited, the mice slept about 70 per cent less than control mice – spending around 6.5 extra hours awake a day – without showing more of the anxiety-like behaviours that usually come with sleep deprivation for mice. However, the lack of sleep was lethal in about 17 per cent of the mice.Ěý

The strong effect of activating and inhibiting the neurons means they don’t just signal that an animal has been awake, says team member , also at the University of Basel. “They are crucial to promote sleep, and may be key components of the neural circuitry that generates sleep drive.” 

The study “adds to a growing body of work showing that there are distinct sleep circuits that are activated by wakefulness, yet promote sleep”, says  at Johns Hopkins University in Maryland, whose research has shown that neurons in a brain region called the thalamic nucleus reuniens track the gap between how much sleep we need and how much we actually get.

It isn’t known if the same sleep-driving neuron populations exist in humans, but if they do, the findings could open doors to new therapies for some sleep-related conditions – once we know how the cells are communicating with other brain regions, say the researchers.Ěý

Projections from these neurons in the median raphe nucleus , and these areas are known to work together to control the sleep-wake cycle.

“The effect of this major neuronal path on sleep is very strong, but, as we have learned since we started manipulating neuronal circuits, each path provides nuances. The brain has many ways to wake up and fall asleep,” says  at Stanford University in California.

For example, there are hints from experiments in fruit flies that mitochondria, which power cells, in the brain may play a crucial role in the onset of sleep.Ěý

Ancient Egyptian princesses were probably trained in using bows and daggers and put themselves at risk of serious injury. Rediscovering mummies from about 3800 years ago has revealed that some of these women had enlarged bones in their arms and bowing of the bones in their palms, which suggests they were active users of the weapons they were often buried with.

“They carried their bows and daggers into the afterlife not just as ornaments, but as testaments to the active, resilient and powerful lives they led,” says at Beni-Suef University in Egypt.

Weapons have been found throughout history. But there has been much debate about whether this was symbolic or meant the women used them.

Now, Hashesh and her colleagues have studied six royal mummies – five female – found at the Dahshur complex of pyramids and tombs from Egypt’s Middle Kingdom between about 1850 and 1700 BC. The mummies, some of which were found with bows and arrows alongside them, were excavated in the 1890s, and were rediscovered in the Egyptian Museum in Cairo during a curation project in 2020.  

The team has analysed the bones to learn about the lives of these royal individuals, four of whom are thought to be daughters of the pharaoh Amenemhat II.

A key finding was that Princess Ita – who had an elaborate gold and lapis lazuli dagger in her burial assemblage and was aged between 28 and 34 when she died – would have had very strong connections between the bones in her forearm and strong hand muscles. This implies the habitual gripping of weapons like daggers or maces, says Hashesh.

Princesses Noub-Hotep (aged between 40 and 44) and Itaweret (aged 20 to 34) both showed enlargement of the radius bone in the forearm, which could be an adaptation to . The former princess, who was buried alongside arrows, also had bowing of the second right metacarpal bone in the palm and strengthened attachments of finger muscles. These hint at the sustained mechanical load required to hold a bow and are indicative of “archer’s grip”.

“I imagine the lives of princesses like Noub-Hotep and Ita were far from the sedentary, purely decorative existence we often associate with ancient royalty,” says Hashesh. “To develop the archer’s grip and the structural bowing of the hand bones observed in Noub-Hotep, they must have begun training in archery and martial arts from a young age.”

at Griffith University in Australia says this study gives us real insight into these princesses’ lives. “Royal women were not simply sitting around a palace or following their menfolk around, but living active and skilled lives. They were trained in very practical martial and hunting arts, just as we imagine their fathers and brothers were,” she says.

The bones also revealed that injuries were common. For example, Princess Itaweret survived broken ribs and foot fractures, which Hashesh says were probably caused by accidents or hard blows.

“This tells us that they were out in the world, perhaps engaged in high-impact activities where falls and blows were a real danger,” she says. When injured, their status gave them access to surgeons capable of setting bones so well that they healed without infection or misalignment, she says.

But at the University of Southampton, UK, says that other activities could result in similar alterations to arm and hand bones, such as frequent juggling or using a scythe. “If we were to find a tennis player buried with a club, we cannot simply argue that this [similar] bony change was a result of clubbing people,” she says.