Decreases of hematopoietic stem cells in early Alzheimer's disease

Hematopoietic stem cells (HSC) contribute to mammalian brain tissue regeneration by transdifferentiation processes suggesting that a regenerative interface exists between the nervous and hematopoietic organ systems. Transdifferentiation of HSC might also be relevant for the diagnosis and therapy of neurodegenerative diseases. We evaluated the frequency of circulating CD34+ HSC in the blood of patients with early Alzheimer's disease (AD). The early AD group (n=23) fulfilled the NINCDS-ADRDA criteria for probable AD and the diagnosis was supported by cerebrospinal fluid-based neurochemical dementia diagnostics. Spouses or caregivers served as non-demented age, sex and environmentally matched controls (n=25). CD34+/CD45R0low HSC were assessed by flow cytometry. We found decreased counts of circulating HSC in early AD (p=.01), which significantly correlated with age (r=-.661; p=.001), cerebrospinal fluid Aβ 1–42 (r=-.467; p=.025) and most pronounced the Aβ 42/40 ratio (r=.688; p=.005). The correlations between HSC counts and total tau or phospho-tau protein were not significant. Decreased HSC counts may reflect an accelerated aging process and a premature exhaustion of the stem cell pool suggesting a deficient regenerative hematopoietic support for the central nervous system in early AD.