Proliferation Kinetics Of Subpopulations Of Human Marrow Cells Determined By Quantifying In Vivo Incorporation Of [H-2(2)]-Glucose Into Dna Of S-Phase Cells

This report investigated in vivo turnover kinetics of marrow hematopoietic progenitors and precursors using a recently developed stable isotope-mass spectrometric technique (SIMST). Human subjects were administered a 2-day infusion of 6,6-[H-2(2)]-glucose, a nontoxic stable isotope-labeled form of glucose, which becomes incorporated into DNA of all S-phase cells. The percent [H-2(2)]-glucose incorporated into DNA in the form of [H-2(2)]-deoxyadenosine (%[H-2(2)]-dA enrichment) was determined by gas chromatography-mass spectrometry. The rate constant of replacement of unlabeled by labeled DNA strands (labeling kinetics) was used to calculate population turnover kinetics of CD34(+) cells, CD133(+) cells, and CD133(-)CD34(+) cells. The observed mean replacement half-life (t(1/2)) was 2.6 days for CD34(+) cells, 2.5 days for CD133(-)CD34(+) cells, and 6.2 days for CD133(+) cells. Results from the estimated rate constant of replacement of labeled by unlabeled DNA (delabeling kinetics) also demonstrated slower turnover rates for CD133(+) cells than for CD133(-)CD34(+) cells. Although there was a relatively rapid initial decrease in the %[H-2(2)]-dA enrichment, low levels of labeled DNA persisted in CD34(+) cells for at least 4 weeks. The results indicate the presence of subpopulations of CD34(+) cells with relatively rapid turnover rates and subpopulations With a slower t(1/2) of 28 days. Results also demonstrate that in vivo [H-2(2)]-glucose-SIMST is sensitive enough to detect differences in turnover kinetics between erythroid and megakaryocyte lineage cells. These studies are the first to demonstrate the use of in Vivo [H-2(2)]-glucose-SIMST to measure in vivo turnover kinetics of subpopulations of CD34(+) cells and precursors in healthy human subjects.