Saul A. Villeda 1 , 2 , Jian Luo 1 , Kira I. Mosher 1 , 2 , Bende Zou 3 , Markus Britschgi 1 , Gregor Bieri 1 , 4 , Trisha M. Stan 1 , 5 , Nina Fainberg 1 , Zhaoqing Ding 1 , 5 , Alexander Eggel 1 , Kurt M. Lucin 1 , Eva Czirr 1 , Jeong-Soo Park 1 , Sebastien Couillard-Després 6 , Ludwig Aigner 6 , Ge Li 7 , Elaine R. Peskind 7 , 8 , Jeffrey A. Kaye 9 , Joseph F. Quinn 9 , Douglas R. Galasko 10 , Xinmin S. Xie 3 , Thomas A. Rando 1 , 11 , 12 , Tony Wyss-Coray 1 , 2 , 5 , 11
31 August 2011
In the central nervous system (CNS), aging results in a precipitous decline in adult neural stem/progenitor cells (NPCs) and neurogenesis, with concomitant impairments in cognitive functions 1 . Interestingly, such impairments can be ameliorated through systemic perturbations such as exercise 1 . Here, using heterochronic parabiosis we show that blood-borne factors present in the systemic milieu can inhibit or promote adult neurogenesis in an age dependent fashion in mice. Accordingly, exposing a young animal to an old systemic environment, or to plasma from old mice, decreased synaptic plasticity and impaired contextual fear conditioning and spatial learning and memory. We identify chemokines - including CCL11/Eotaxin – whose plasma levels correlate with reduced neurogenesis in heterochronic parabionts and aged mice, and whose levels are increased in plasma and cerebral spinal fluid of healthy aging humans. Finally, increasing peripheral CCL11 chemokine levels in vivo in young mice decreased adult neurogenesis and impaired learning and memory. Together our data indicate that the decline in neurogenesis, and cognitive impairments, observed during aging can be in part attributed to changes in blood-borne factors.