There is a higher incidence of hematological clonal stem cell disorders in elderly persons. Age-related alterations of hematopoietic stem and progenitor cells (HSC) may represent one factor underlying this observation. However, the molecular changes related to stem cell aging are largely unknown. Therefore, we scrutinized gene expression patterns of HSC from umbilical cord blood (CB) as well as bone marrow from young (BM-Y, mean age 32,8, SD 12,4) and old (BM-O, mean age 88,8, SD 4,4) healthy donors. CD34+ HSC were isolated via immuno-magnetic separation and CD34+ purity was evaluated by FACS analysis. Thereafter we performed cDNA array analyses on a first set of samples (n=18). We found that the BCL2-interacting killer gene (BIK) and the gene encoding KU Antigen 70kD (KU70) show age-related mRNA expression levels. BIK is a proapoptotic gene and its expression was positively correlated with donor’s age, i.e. lowest in CB, 1.8-fold higher in BM-Y and 4.2-fold higher in BM-O. KU70 is a DNA repair gene and part of the DNA dependent protein kinase (DNA-PK). Its expression was negatively correlated with donor’s age showing highest expression levels in CB, 2.2-fold lower levels in BM-Y and 5.3-fold lower levels in BM-O. These findings were confirmed with a second set of samples (n=16) by means of quantitative RT-PCR. Elucidation of age-dependent molecular alteration in healthy HSC might facilitate a better understanding of hematological malignancies in elderly persons.

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