Significant loss of the senses of smell and taste, a condition known as anosmia, can occur with aging. Here, researchers investigate stem cell related mechanisms; this may be another case of functionality fading because the stem cell population necessary to support it is shutting down with advancing age: "Experts estimate that about 2 percent of the U.S. population suffers from [a] lack of smell known as anosmia. And research by neuroscientists [provides] hope of new therapies for those who have lost their sense of smell, whether due to aging, trauma or a viral infection. In the study published this month [the researchers found] a genetic trigger responsible for renewing smell sensors in the nose. That gene, known as p63, tells olfactory stem cells whether to replace themselves or to change into different types of cells. Under normal circumstances [there] is a balance between the two outcomes. But when p63 is absent, the cells only turn into other types of mature cells, which [could] eventually lead to the complete depletion of olfactory cells. One reason for the onset of anosmia could be that the stem cells age and are less able to regenerate, or they are just depleted. Finding a way to promote stem cell renewal could help maintain sensory functions, such as the sense of smell."