Hemopoiesis in healthy old people and centenarians: Well-maintained responsiveness of CD34+ cells to hemopoietic growth factors and remodeling of cytokine network

In vitro hemopoiesis and hemopoietic cytokines production were evaluated in 9 centenarians (median age 100.5 years, age range: 100-104 years), 10 old people (median age: 71 years, age range: 66-73 years), and 10 young people (median age: 35 years, age range: 30-45 years), all carefully selected for their healthy status. The main findings were the following: (i) a trend towards a decreased absolute number of CD34+ progenitor cells in the peripheral blood of old people and centenarians, in comparison to young subjects; (ii) a well-preserved capability of CD34+ cells from old people and centenarians to respond to hemopoietic cytokines, and to form erythroid (BFU- E), granulocyte-macrophagic (CFU-GM), and mixed colonies (CFU-GEMM) in a way (number, size, and morphology) indistinguishable from that of young subjects; (iii) an age-related decreased in vitro production of granulocyte-macrophagic colony-stimulating factor (GM-CSF) and a decreased production of interleukin- 3 (IL-3) in centenarians by phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMC); (iv) a linear increase of the serum level of stem cell factor (SCF), measured in the above-mentioned subjects and in 65 additional subjects, including 4 centenarians. These data suggest that basal hematopoietic potential is well preserved in healthy centenarians, and that the hemopoietic cytokine network undergoes a complex remodeling with age.