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All You Need is Time … and Some Stem Cells

A new study published in Nature shows that all that's needed to mend a "broken heart" is time — and stem cells, says Nature News' Marian Turner. The study shows that natural proteins can activate stem cells in mouse hearts to replace damaged muscle tissue after a heart attack, Turner says. Because cardiomyocytes can't be repaired after a heart attack, they need to be replaced. Heart progenitor cells do exist in humans but aren't active enough in adults to create the various tissues needed to repair damage. The researchers who conducted the study — led by the University College London Institute of Child Health's Paul Riley — injected mice with a small protein called thymosin β4, which they had previously shown could induce progenitor cells to produce new blood vessels, and then the researchers induced symptoms of heart attack in the animals. After a couple of days, they found the mice heart cells expressing the gene Wt1, which is normally switched off in adults, and these Wt1-expressing cells eventually converged to the site of the damage and began to change themselves into cardiomyocytes, Turner reports. "Riley and his team are still working out exactly how Tβ4 switches stem-cell genes in the heart cells back on, but they're betting on an epigenetic effect," she adds. "They think that the injury provides a trigger for the stem cells to go ahead and divide, making healthy new muscle cells. The researchers are also trying to work out what that injury signal actually is." Eventually, the researchers say, Tβ4, or a similar molecule, might become a preventive treatment for people with heart disease, or to treat people directly after they've had a heart attack to help rebuild the muscles. Further experiments and clinical trials are needed first to see if the molecule has the same effect on humans as it does on mice, Turner says.

The Scan

Tens of Millions Saved

The Associated Press writes that vaccines against COVID-19 saved an estimated 20 million lives in their first year.

Supersized Bacterium

NPR reports that researchers have found and characterized a bacterium that is visible to the naked eye.

Also Subvariants

Moderna says its bivalent SARS-CoV-2 vaccine leads to a strong immune response against Omicron subvariants, the Wall Street Journal reports.

Science Papers Present Gene-Edited Mouse Models of Liver Cancer, Hürthle Cell Carcinoma Analysis

In Science this week: a collection of mouse models of primary liver cancer, and more.