Aging in the central nervous system can be traced to impairments of cognitive functioning as well as a sudden decline in adult tissue-specific neural stem/progenitor cells and proliferative activity/neurogenesis. Adult neurogenesis occurs in ‘neurogenic niches,’ or local microenvironments of the subventicular zone of the lateral ventricle and the subgranular zone of the hippocampus. Believed to play an essential role in the formation of cognitive processes such a learning and memory, neurogenesis drives the production of new neurons and their subsequent neuronal circuitry integration. Most importantly, however, the neurogenic niche is localized around blood vessels thus implying a potential communication with the systemic environment. If so, …show more content…
Since these other studies showed that this kind of exposure lead to increased muscle regeneration, Wyss-Coray et al. researched the individual systemic factors not yet classified, and their associations with aging and tissue degeneration. A proteomic approach was used, otherwise known as a large-scale study of proteins, specifically in regards to their structures and functions. They found seventeen proteins whose level increased in congruence with decreased neurogenesis during aging. From there, they narrowed down the systemic factors to just those associated with heterochronic parabiosis and more specifically, those that were shown to be elevated in old unpaired mice and young heterochronic groups. Only six factors were identified, with the most significant being CCL11, a chemokine associated with allergic responses not previously linked to aging, neurogenesis, and cognition. The plasma of mice during normal aging, and the plasma of mice in heterochronic cohorts showed an increased prevalence of CCL11. It was then determined that CCL11 levels increase in both the plasma and the cerebrospinal fluid of healthy humans as they age from 20yrs to