It is a widely held view that accumulating stochastic nuclear DNA damage is one contributer to aging. This is debated for degenerations other than cancer, however. Here is a different way of looking at DNA damage in stem cells, connected to the immortal DNA strand (IDS) hypothesis: "Cairns noted a mathematical discrepancy between predicted human tissue cell mutation rates and human cancer incidence [and predicted] the existence of IDSs as the essential elements of a mutation-defense mechanism in [stem cells]. ... several laboratories have identified IDSs in diverse mammalian [stem cells]. Past studies focused on the potential roles of IDSs as originally envisioned in [stem cell] genetic fidelity or in the maintenance of the [stem cell] phenotype. Another possible consequence of IDSs, aging, has received little attention. Herein, the potential for cumulative chemical modifications and decompositions (i.e., 'age spots') of IDSs in [stem cells] to act as a major determinant of human aging is considered. If accrued chemical alterations of IDSs prove to be essential determinants of aging, then a means to restore IDSs may yield new strategies for tissue rejuvenation."

Link: http://www.ncbi.nlm.nih.gov/pubmed/19029623