In a UCLA laboratory, adult bone marrow stem cells face a choice: to become bone or fat. This choice is determined not by genes themselves, but by chemical marks on histones — epigenetic "stickers" that can be erased or added.
The discovery by Professor Cun-Yu Wang and his team shows that two enzymes — KDM4B and KDM6B — remove methyl groups, activating the genes that lead to bone formation while simultaneously suppressing the path to fat. The work was published on the cover of Cell Stem Cell and is based on experiments with human cells and mice of different ages.
For an aging organism, this matters: with age, repressive marks accumulate in stem cells, and the cells more often take the fat lineage. In osteoporotic mice the picture is the same — more "silent" marks, which in youth were removed by KDM4B and KDM6B. The enzymes can be chemically modulated, which makes them a potential target for therapy.
For now, the data are limited to mouse models and cell cultures. There are no human clinical trials yet, and it is unknown how safe long-term intervention in epigenetic mechanisms is. The study was funded by the US National Institute of Dental and Craniofacial Research — this reduces the risk of commercial pressure, but does not remove the need for independent verification.
Imagine a cell as an old library: the needed books (bone genes) are locked under a layer of dust (methyl marks). The enzymes KDM4B and KDM6B are librarians who wipe away the dust and open access, while at the same time closing the section with books about fat. A single chemical "eraser" changes the entire route.
The discovery underscores that the fate of an adult stem cell is not a rigid program, but a dynamic balance of epigenetic signals. The question now is whether it will be possible to precisely dose these signals in a living organism without disrupting other processes.
If epigenetic "locks" do indeed accumulate with age, then regenerative medicine may in the future work not by replacing cells, but by reprogramming them in place.
