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US scientists say a kidney “grown” in the laboratory has been transplanted into animals where it started to produce urine.

Similar techniques to make simple body parts have already been used in patients, but the kidney is one of the most complicated organs made so far.

A study, in the journal Nature Medicine, showed the engineered kidneys were less effective than natural ones.

But regenerative medicine researchers said the field had huge promise.

Kidneys filter the blood to remove waste and excess water. They are also the most in-demand organ for transplant, with long waiting lists.

The researchers’ vision is to take an old kidney and strip it of all its old cells to leave a honeycomb-like scaffold. The kidney would then be rebuilt with cells taken from the patient.

This would have two major advantages over current organ transplants.

The tissue would match the patient, so they would not need a lifetime of drugs to suppress the immune system to prevent rejection.

Researchers at Massachusetts General Hospital have taken the first steps towards creating usable engineered kidneys

Researchers at Massachusetts General Hospital have taken the first steps towards creating usable engineered kidneys

It would also vastly increase the number of organs available for transplant. Most organs which are offered are rejected, but they could be used as templates for new ones.

Researchers at Massachusetts General Hospital have taken the first steps towards creating usable engineered kidneys.

They took a rat kidney and used a detergent to wash away the old cells.

The remaining web of proteins, or scaffold, looks just like a kidney, including an intricate network of blood vessels and drainage pipes.

This protein plumbing was used to pump the right cells to the right part of the kidney, where they joined with the scaffold to rebuild the organ.

It was kept in a special oven to mimic the conditions in a rat’s body for the next 12 days.

When the kidneys were tested in the laboratory, urine production reached 23% of natural ones.

The team then tried transplanting an organ into a rat. Once inside the body, the kidney’s effectiveness fell to 5%.

Lead researcher Dr. Harald Ott said that restoring a small fraction of normal function could be enough: “If you’re on haemodialysis then kidney function of 10% to 15% would already make you independent of haemodialysis. It’s not that we have to go all the way.”

Dr. Harald Ott said the potential was huge: “If you think about the United States alone, there’s 100,000 patients currently waiting for kidney transplants and there’s only around 18,000 transplants done a year.

“I think the potential clinical impact of a successful treatment would be enormous.”

There is a huge amount of further research that would be needed before this is even considered in people.

The technique needs to be more efficient so a greater level of kidney function is restored. Researchers also need to prove that the kidney will continue to function for a long time.

There will also be challenges with the sheer size of a human kidney. It is harder to get the cells in the right place in a larger organ.

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US scientists say carnitine, a chemical found in red meat, helps explain why eating too much steak, mince and bacon is bad for the heart.

Their work has been published in the journal Nature Medicine and showed that carnitine in red meat was broken down by bacteria in the gut.

This kicked off a chain of events which resulted in higher levels of cholesterol and an increased risk of heart disease.

Dieticians also warned there may be a risk to people taking carnitine supplements.

US scientists say carnitine, a chemical found in red meat, helps explain why eating too much steak, mince and bacon is bad for the heart

US scientists say carnitine, a chemical found in red meat, helps explain why eating too much steak, mince and bacon is bad for the heart

There has been a wealth of studies suggesting that regularly eating red meat may be damaging to health.

Saturated fat and the way processed meat is preserved are thought to contribute to heart problems. However, this was not thought to be the whole story.

“The cholesterol and saturated fat content of lean red meat is not that high, there’s something else contributing to increases in cardiovascular risk,” said lead researcher Dr. Stanley Hazen.

Experiments on mice and people showed that bacteria in the gut could eat carnitine.

Carnitine was broken down into a gas, which was converted in the liver to a chemical called TMAO.

In the study, TMAO was strongly linked with the build-up of fatty deposits in blood vessels, which can lead to heart disease and death.

Dr. Stanley Hazen, from the Cleveland Clinic, said TMAO was often ignored: “It may be a waste product but it is significantly influencing cholesterol metabolism and the net effect leads to an accumulation of cholesterol.

“The findings support the idea that less red meat is better.

“I used to have red meat five days out of seven, now I have cut it way back to less than once every two weeks or so.”

He said the findings raised the idea of using a probiotic yogurt to change the balance of bacteria in the gut.

Reducing the number of bacteria that feed on carnitine would in theory reduce the health risks of red meat.

Vegetarians naturally have fewer bacteria that are able to break down carnitine than meat-eaters.