The build-up of fat cells in the bone marrow could explain why bones grow weaker and heal more slowly with age.

Tim Schulz at the German Institute of Human Nutrition in Potsdam-Rehbrücke and his colleagues identified a population of stem-cell-like cells in the bones of mice that gives rise to both bone and fat cells. These progenitors produced more fat cells than bone cells in older animals and in those that ate a high-fat diet, compared with younger mice and those eating a normal diet, respectively. In mice with a fractured tibia, fat-cell precursors injected near the injury site slowed the healing process.

The researchers found that cells in the fat-cell lineage produced a protein called dipeptidyl peptidase-4 that impaired bone regeneration. These cells also inhibited the generation of stem cells in the bone marrow that give rise to blood and immune cells.

Cell Stem Cell http://doi.org/b4dv (2017)