Age-related declines in stem cell function in the body and central nervous system of rodents can be reversed by exposure to a youthful systemic milieu. Conversely, the old milieu inhibits stem cell function in young rodents. In this thesis, an in vitro model is established to evaluate the impacts of the ageing human milieu upon human hippocampal progenitors. This cellular model revealed that allogenic serum derived from old cognitively healthy individuals induced a 2-fold increase in apoptotic cell death when compared to serum derived from young healthy individuals. Old serum also induced a wide range of values for markers of proliferation and differentiation. Such variability is partly attributable to epidemiological and clinical factors; for example, intake of antihypertensive medication was linked to increased proliferation. Using a single gene candidate approach revealed that the expression of many of the molecular hallmarks of ageing in hippocampal progenitors were unchanged following exposure to young or old human serum - when not taking into account the cellular phenotype induced by these samples. Some hallmarks, however, related to metabolism (NAMPT), DNA damage (PARP1), telomere integrity (TERT), proteostasis (UCHL1) and cellular senescence (CDNK2A, CDKN2B) were altered in hippocampal progenitors by a subset of old serum samples. An endophenotype approach was then employed to explore the molecular basis underlining increased cellular variation following culture with old serum. This involved selecting serum samples from young and old individuals based on the contrasting effects of these samples on the expression of the neuroblast marker DCX and apoptotic cell death marker CC3. Whole-genome expression analysis of progenitors cultured with these samples revealed differential expression of novel candidate genes and more pronounced evidence for upregulation of ageing molecular hallmarks in response to old serum linked to increased levels of DCX and CC3. In particular, validation of microarray candidates affirmed that old serum increased expression of TMEM149 and ENDOG, whereas RNF126 and MAP3K7 were downregulated in the presence of old serum. These results recapitulate findings from rodent studies by revealing for the first time that the ageing human milieu has a detrimental effect on the viability and molecular profile of human hippocampal progenitors.
|Date of Award
|Jack Price (Supervisor) & Sandrine Thuret (Supervisor)