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24 August 2013 | NewScientist | 17 Chimera heart springs back to life A HYBRID heart, part-mouse, part- human, has begun to beat. It is the first time a mouse heart rebuilt with human cells has been made to pulse again. To create the hybrid organ, Lei Yang at the University of Pittsburgh, Pennsylvania, and colleagues took the heart from a mouse and removed all its cells, leaving a protein scaffold. They then repopulated it with human heart precursor cells – stem cells that had differentiated into the three types of cell needed to build a heart. After a few weeks, the organ spontaneously started beating again (Nature Communications, doi.org/nhp). Although the designer heart beats rhythmically (see video at bit.ly/mouseheart), it is not strong enough to pump blood effectively. Yang’s long-term goal is to create human hearts that can be used either for transplants or for drug testing. “Using our method, we could generate both muscle and vascular-like structures in the engineered heart constructs,” says Yang. “We hope to make a piece of human heart tissue soon, but our dream is to regenerate a whole human heart.” Suicide risk could show up in a blood test COULD a blood test predict whether a person is at risk of committing suicide? For the first time, a set of proteins in the blood have been linked to suicidal behaviour. People who commit suicide appear to share a number of biological traits, regardless of any underlying conditions. This hints that suicidal behaviour may be a distinct disorder. To investigate, Alexander Niculescu of Indiana University in Indianapolis and colleagues collected blood from the cadavers of nine men who had bipolar disorder and suicidal tendencies, and nine with bipolar but no suicidal thoughts. They compared levels of all the genes expressed in their blood. Four genes were expressed at significantly higher levels in the blood of people who had been suicidal. Some proteins that these genes code for are known to be involved in stress and cell death. The team then measured levels of these proteins in 42 people with bipolar disorder who had been hospitalised for attempting suicide. People who had been WANT to lose weight fast? No need to adjust your diet – just move to higher ground. This weight change is the result of fluctuations in Earth’s gravity, which a new high-resolution map shows are greater than thought. Gravity is often assumed to be the same everywhere on Earth, but it varies because the planet is not a perfect sphere. For instance, gravity is weaker at higher altitudes, further from Earth’s centre, as seen in the section of its gravity map showing Mount Everest (large red area, above). Christian Hirt of Curtin University in Perth, Australia, and colleagues combined gravity data from satellites and topographic data to map gravity changes between latitude 60° north and latitude 60° south, covering 80 per cent of Earth’s land mass. The model pinpoints more extreme differences in gravitational acceleration than previously seen (Geophysical Research Letters, doi. org/nht). Mount Nevado Huascarán in Peru is the lowest point and the highest is in the Arctic Ocean. You would lose 1 per cent of your body weight by moving from one spot to the other, although your mass wouldn’t change. Gravity map gets more extreme GGMPLUS/CURTIN UNIVERSITY hospitalised more often tended to have higher levels of the proteins. Finally, the team collected blood from the cadavers of a further nine men who had committed suicide but did not have bipolar, and found elevated levels of some of the proteins (Molecular Psychiatry, DOI: 10.1038/mp.2013.95). The team is now looking for the proteins in more people with a range of underlying conditions, with the hope of developing a blood test to identify people at risk of suicide. Mole rats immune to carcinogens AS ANTI-CANCER regimes go, this one is not going to get many takers. The Middle East blind mole rat (Spalax ehrenbergi) spends almost all of its 20 years of life hurrying down dark, fusty tunnels full of oxygen-deprived air. But for reasons unknown, it works: in 50 years of research on the rodents, none has ever spontaneously developed cancer. Now it turns out that even exposure to potent carcinogens does not trigger tumours in these hardy animals. Aaron Avivi of the University of Haifa in Israel exposed 20 mole rats to one of two cancer-causing chemicals – DMBA/TPA or 3-MCA. Even after three years, only one of the animals developed any tumours. By contrast, rats and mice exposed to the same chemicals developed tumours in a matter of months (BMC Biology, doi.org/nhn). “We’ve shown that whether the mole rats are young or old, it is almost impossible to induce cancer in them,” says Avivi. He is now trying to identify what substances within their cells offer such strong protection. Avivi’s team has found out that fibroblast skin cells from the armpits of the rats can kill human cancer cells in a dish. So did fluids secreted by the fibroblasts, suggesting that they contain something of great value for combatting cancer. EYAL BARTOVE For new stories every day, visit newscientist.com/news
