The placenta is vital for a growing fetus, providing it with the nourishment needed to develop as it prepares to enter the world. But a poorly functioning placenta is problematic as doctors are unable to treat it with drugs and are instead forced to induce labor early, inviting a range of health risks for the prematurely born baby. But scientists have now found a way in by using existing cancer drugs that mistake the placenta for a tumor, selectively targeting the organ and boosting its health.

"Placentas behave like well-controlled tumors," explains lead author Lynda Harris of the University of Manchester in England. "They grow quickly, produce growth hormones and evade the immune system. A lot of cancer research focuses on finding ways of delivering drugs to kill the tumor without affecting the rest of the body. We had the idea that if we could selectively target the placenta in the same way, we could deliver other drugs to help improve placental function and therefore treat pregnancy complications."

Harris and scientists from the University of California, Santa Barbara were able to show that a pair of tumor-targeting peptides can have the same effect on the placenta as on tumors, zeroing in on the organ and precisely delivering drugs to improve its function. Working with a mouse model the researchers used the technique to deliver a growth hormone to the placenta inside peptide-coated nanoparticles.

Their work showed that the technique had no effect on healthy-sized fetuses, while it did cause undersized ones to grow. They also detected no signs of the drug in the fetuses themselves or the mother's organs, suggesting the peptides' selective targeting worked as the researchers had hoped.

The researchers say that more than 10 percent of pregnant women are affected by complications, with a poorly functioning placenta often the cause. Complications can include preeclampsia, a condition that leads to high blood pressure in the mother and growth problems for the baby, and placental abruption, where the placenta separates from the wall of the uterus.

Avoiding these by inducing an early delivery can heighten the risk of infection, cerebral palsy, heart disease and diabetes for the baby. By allowing for drugs to be delivered to the placenta to address health issues, the scientists hope to limit the problems associated with such pregnancies.

"Only one drug for use during pregnancy has been licensed in the last 20 years," says Harris. "By developing this platform, we have opened up the possibility that any number of new drugs can be adapted and then used safely to treat common and serious pregnancy complications."

The team notes that one of the potential dangers of such an approach is that the drugs could be drawn towards undiagnosed cancers rather than the placenta, but say that this risk could be avoided through screening programs.

The research was published in the journal Science Advances.

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