Tumour Suppressor Gene is the Key

Absence of a gene keeps cells
in young age; © NCI Visuals Online

These aging cells worked poorly compared to young cells and remembered their "age" even when transferred from old mice to young mice. The cells of mice bred without the gene showed less sluggishness as the animals aged and continued to function in a manner more similar to cells from younger mice.

The results show disparate cell types share a common aging mechanism and suggest that aging-related diseases such as diabetes result from a failure of cell growth, said Dr. Norman E. Sharpless, co-author on the three studies and an assistant professor of medicine and genetics at the University of North Carolina (UNC) School of Medicine. "The studies indicate that certain stem cells lose their ability to divide and replace themselves with age as the expression of p16INK4a increases," said Sharpless, a member of the UNC Lineberger Comprehensive Cancer Center.

The UNC study focused on p16INK4a effects on the function of pancreatic islet cells. Islet cells are responsible for insulin production and secretion. Because the gene stops cancer cells from dividing and demonstrates increased expression with age, the scientists suspected the gene played a similar role in aging. The researchers developed strains of mice that were either deficient in p16INK4a (the gene was 'knocked out") or genetically altered to have an excess of the protein to a degree seen in aging.

According to Sharpless, islet proliferation persisted in p16INK4a -deficient animals as they aged, "almost as if they were younger animals." In mice with an excess of p16INK4a, "islet cells aged prematurely; they stopped dividing early."

"This suggests that if we could attenuate p16INK4a expression in some way in humans, it could lead to enhanced islet re-growth in adults and a possible new treatment for diabetes," Sharpless said. Similar results were found in the other studies, which focused on brain stem cells and blood stem cells.

MEDICA.de; Source: University of North Carolina School of Medicine