cell division and senescenceIn recent weeks, medical science has delivered some pretty harsh blows to the forever-young wannabes searching for the Fountain of Youth. Seems one marker of the aging process - cellular senescence - begins in the womb. And that just might be a very good thing.

As far back as 1961, two scientists - Leonard Hayflick and Paul Moorhead - got their first hints that aging is built into our cells; it’s more than a lifestyle thing. They tested the then-current belief that youthful, healthy cells would continue to divide forever if they were given the optimum environment. Hayflick and Moorhead tested the theory on fetal human cells, assuming there are none healthier and more youthful.

It didn’t work. Even the fetal cells divided only about 50 times and then stopped dividing altogether. This end of cellular division is called senescence and it creates age-related ills such as arthritis, cataracts, and wrinkles. When lab mice had all senescent cells removed from their creaky joints, milky eyes, and wrinkled skin, they were rejuvenated to youthful vigor.

Three recently released studies of embryonic senescence describe intriguing effects and, surprisingly, the news isn’t bad at all:

William Keyes / Center for Genomic Regulation (Spain)
Building on previous studies that identified senescent cells in damaged and healthy embryonic tissue in lab mice, Dr. Keyes revisited the theory only to discover senescent cells in many parts of mice embryos, including at the tips of their perfectly developing legs.

Manuel Serrano / Spanish National Cancer Research Center
Dr. Serrano’s team was surprised to discover senescent cells in the middle ear region of the mice embryos under study.

Valery Krizhanovsky / Weizmann Institute of Science (Israel)
Dr. Krizhanovsky’s senescent cells were in the placenta.

In weighing all the evidence, Dr. Keyes hypothesizes a two-part process: the end of cellular division (senescence) causes the release of a special chemical cocktail.

This chemical cocktail is thought to signal surrounding cells to begin growing different types of cells to create different body parts and organs. If the signal is faulty, ill-timed, or missed, problems may arise. The senescent cells identified thus far are in regions of the body prone to birth defects.

To prevent dire consequences, Keyes suspects the chemical cocktail summons immune cells to destroy senescent cells so they don’t linger and continue to direct surrounding cellular development.

Each time a cell divides, DNA is altered. With enough DNA alteration, cancer develops. One theory is that cellular senescence is a self-regulating mechanism that prevents a cell from becoming cancerous by stopping division before cancer can occur. The cocktail’s invitation to the immune system may be yet another form of natural cancer prevention.

Source: Zimmer, Carl. “Signs of Aging, Even in the Embryo.” The New York Times / Science / Matter. The New York Times Company. Nov 21, 2013. Web. Dec 11, 2013.