The placenta is a marvel that scientists can’t match

Nothing we can engineer has come close to replicating the placenta’s ability to act as the kidney, lungs, hormone source, nutrition channel and waste disposal unit for a growing foetus.

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The unwritten rules of journalism will ensure that, for the next month, few stories will be able to string together more than 500 words without mentioning the World Cup. Luckily, Spain’s Diego Costa has used horse placenta to treat an injury; this, he claims, allowed him to recover in time for the Champions League final and be fully fit for Rio. It’s also why we can now discuss the idea for the Human Placenta Project.

At the end of last month, placenta experts (research scientists, not people who drip horse placenta extract on to desperate athletes) gathered in Maryland in the US. Their aim was to establish a project to learn how this most understudied of organs works – and what to do when it doesn’t.

Questionable medical applications aside, the placenta is a marvel. You wouldn’t be here without it. Although scientists have been trying for decades to create artificial versions, they have failed miserably. Nothing we can engineer has come close to replicating the placenta’s ability to act as the kidney, lungs, hormone source, nutrition channel and waste disposal unit for a growing foetus.

That said, not all placentas are created equal. And yet we have no scientific definition of the ideal placenta, which makes it very hard to diagnose a faulty one. Placentas that have nurtured babies who have been born weak or sick often look entirely normal. Abnormal-looking placentas are frequently associated with healthy babies. The devil, it seems, is in the detail.

The placenta grows from a layer of cells that surrounds the early foetus. These cells attach themselves to the wall of the uterus and then develop a network of tiny blood vessels that tap into the uterine blood supply, while also maintaining a barrier between the two organisms to stop the foetus from triggering the mother’s immune system. The mother-foetus connection doesn’t always work perfectly. Sometimes the placenta doesn’t attach properly or is too small to provide all the nutrition the baby needs, which can cause a range of medical problems for the mother-to-be and the foetus, often necessitating early delivery.

It can take years for some results of placental problems to manifest. Studies have shown that an abnormal placenta is linked to health issues in later life such as heart disease and diabetes. That’s because if the foetus gets too little nutrition, it builds budget versions of vital organs and tissues. Kidneys will have fewer of the nephrons that do its filtering work. The heart will have fewer muscle cells and the pancreas will skimp on insulin-producing ones.

The Human Placenta Project might do more than lead to healthier births. Understanding exactly how the placenta keeps the foetus from rejection by the pregnant mother is of great interest to the field of transplant surgery, for instance.

It could also help in the fight against cancer. Many cancers contain proteins created by a gene called PLAC1. In normal tissue, this gene is inactive; it is usually switched on only in placental tissue. PLAC1 has been found in tumours taken from breast, ovarian and prostate cancer cells and has recently been found to be active in tumours – mainly stomach cancers and lymphomas – caused by the Epstein-Barr virus. We would do well to find out why.

The answers to this and other questions about the placenta are most likely to be found through closer study of an organ that hospitals (excluding horse hospitals, it seems) routinely send to the incinerator. 

Michael Brooks holds a PhD in quantum physics. His most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article appears in the 18 June 2014 issue of the New Statesman, Islam tears itself apart

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