A type of blood vessel called type H lead directional bone growth
To construct a building from scratch, you might first build a basic shell or scaffold, then replace that with the permanent structure. Building new bone is similar. An intermediate cartilage structure is established first, only to be converted to solid bone subsequently. This process is supported by a dense network of blood vessels, but exactly how they help is unclear. A new study has found that a particular type of these vessels, known as type H (yellow in the bone section pictured, with vessels stained green and red), help replace the cartilage when it’s time. Specifically, the vessels steer bone growth direction, and endothelial cells lining them lead the cartilage breakdown. Excessive cartilage damage is a hallmark of arthritis, and improving bone repair would benefit countless injured patients, so the next step is asking whether we can control and harness this important function of blood vessels.
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