What happens when mice get old? They don’t use bifocals, and they don’t get retirement benefits. They do share some of our signs of aging, though, such as developing cataracts and losing muscle mass; even their ability to exercise diminishes significantly. What's going on? Both people and mice are burdened with the effects of older cells. But researchers are having success delaying the onset of old age in mice.

Can human testing be far behind? Curiosity contributing writer Susan Sherwood went looking for answers -- here's what she found:

Actually, we will have to wait a while for human testing because the procedure is still quite new. So is the field: Scientists have been attempting to influence the aging process for only a couple of decades. Researchers from the Mayo Clinic are now investigating senescent cells. These cells contain a protein (p16) that only appears as we age and seems to stop cell division. About 15 percent of a senior’s cells are senescent -- they may have little purpose other than interfering with normal cell function [source: Marcus]. Senescent cells rouse the immune system, leading to inflammation in aging tissues, such as arthritic joints and plaque-lined arteries.

Scientists have studied these cells in mice that have been genetically altered to have a 15-month life span. In two different trials, researchers administered a drug that led to the death of any cell containing p16. In the first experiment, the drug was given to the mice throughout their lives. These mice remained free of the typical age-related troubles such as arthritis and thinning skin. For the second test, the drug was not dispensed until problems surfaced. The problems abated somewhat, with the treatment, although cataracts that had already formed were unaffected. In both studies, the mice were noticeably more energetic [source: Marcus].

While that's good news for some laboratory mice, don’t expect human trials any time soon. Knowledge of the negative effects of senescent cells on the aging process is a tremendous advancement, but more animal tests are certainly needed, including ones with mice that have not been modified to age rapidly. At present, there are a couple of proposals for human treatment trials. It is believed that our immune system already works to weed out senescent cells but is just less effective with age. Perhaps the immune system could be stimulated to kill these cells in a more sustained and proficient manner. Alternatively, the success of the mice trials could be emulated with the development of a drug that could target and destroy human senescent cells [source: Wade]. The initial goal will not be to extend human life for a tremendous number of years but to improve the overall quality of life.