It looks like a Day-Glo stone circle, but this picture actually shows bones of mice – ribs, tibia, femur, and scapula – that have been genetically modified to express green fluorescent protein (GFP). The lower half shows bones in which cartilage cells have been tweaked to glow green, while the upper part shows bones in which cartilage cells and bone-forming cells called osteoblasts derived from those cartilage cells are tagged green. It’s long been thought that cartilage cells die off, leaving a tissue scaffold that serves as a template on which osteoblasts lay down bone. But by using GFP to tag cartilage cells and track their offspring, researchers found that they can survive and become bone-forming cells during embryonic development or in adulthood, when bones are repaired. This discovery changes our understanding of the cast of cells that make bones, which has implications for how we view the causes of bone disorders.
Written by Daniel Cossins
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