Our organs are like a city: they have dense neighborhoods of cells, streets of blood vessels, and plazas where cells work together. As we age, that city gets redeveloped. Scientists examined 14,788 tissue slices from 980 donors and counted 3.5 billion cells across 16 organs.
It turned out that in half of the organs, cell numbers decline. The ovaries, lungs, and liver take the hardest hit. Cells that line organ surfaces and form glands are especially likely to be lost. For instance, in the ovary, the cells that support egg cells nearly vanish, and in the lung, so do the cells through which oxygen enters the blood.
Doctors now have a map of age-related changes for each organ. It will help spot problems earlier and test whether anti-aging drugs actually work.
Cell density in the spleen is more than 8 times higher than in the skin: over 8,000 cells per square millimeter versus less than 1,000.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.