Aubrey de Grey identified elastin and DNA copying as challenges for continuous self-repair

Aubrey de Grey identified elastin and DNA copying as challenges for continuous self-repair

On 3 August, Aubrey de Grey responded on X to a discussion about a machine that regularly replaces its own parts. He identified two problems with this analogy: how to renew durable tissue material, and what template to use when correcting altered DNA.

The body continually renews its cells through cell division, skin repair, and blood cell production. However, replacing cells does not replace all the material that makes up tissues. In his response, de Grey put it this way:

“Some proteins are not replaced at all, such as elastin. DNA is replaced only by using other DNA as a template.”

Elastin forms elastic fibers in the walls of blood vessels, the lungs, the skin, and ligaments. These fibers stretch and then restore tissues to their previous shape. Elastin is renewed extremely slowly in many adult tissues. A review estimates its half-life at about 74 years. The cells surrounding a fiber are replaced, but the fiber itself remains and retains the chemical changes and breaks that have accumulated over time.

Repair must therefore address this network as well. It must be restored or rebuilt so that the tissue can withstand mechanical loads again.

The second challenge concerns the instructions used for repair. During cell division, enzymes build a new DNA strand from an existing strand. Once a change in a single “letter” has become established as a regular base pair, the next copying cycle uses that pair as its template. This description of DNA damage and repair mechanisms explains why an enzyme recognizes such a pair as normal.

DNA copying preserves the sequence that it uses as a template. In de Grey’s model, complete self-repair requires access both to durable structures and to an independent template against which the genetic sequence can be checked.