Quantitative and qualitative characterization of hematopoietic stem cells from umbilical cord blood according to aldehyde dehydrogenase activity

ABSTRACT

Aldehyde dehydrogenase [ALDH] is a cytosolic enzyme that is responsible for the oxidation of intracellalar aldehydes. Elevated levels of ALDH have been demonstrated in murine and human progenitor cells compared with other hematopoietic cells, and this is thought to be important in chemoresistance and purification techniques and an indication of the proper function of the cell. A Flowcytometric method for the assessment of ALDH activity in viable cells recently has been developed. Forty six cord blood samples from mothers underwent normal delivery of full term infants were obtained, after informed consent. Mononuclear cells were obtained by Ficoll-Paque density centrifugation and ammonium chloride red cell lysis. Percentage of viable cells was determined by trypan blue exclusion dye. Cells were labeled with Aldefluor reagent [Stem cell technology, Vancouver., Canada] as described by the manufacturer. Cells were then stained with phycoerythrin [PE]-conjugated anti-CD34 [Miltenyi Biotec, Cologne, Germany] antibodies for 30 minutes at 4°C. Cells were washed and resuspended in phosphate-buffered saline [PBS] with 2% fetal calf serum. Cells were then analyzed on coulter epics flow cytometer. The mean percentage of ALDH enzyme expression among the, CD34[+] cells in the cord blood samples was 61.3% with a minimum of 6 and a maximum of 94.6%. Significant correlations were found between the wbcs count in the cord blood samples and both the CD34[+] cell count and the count of ALDH expressing cells, while, No correlation was found between the CD34[+] cells count or the ALDH expressing cells count in the cord blood samples and either the sex or the weight of the newborn. Identification and isolation of cells on the basis of ALDH activity provides a tool for their isolation and further analysis. In summary, a high ALDH-1 activity identifies CD34[+] cells in cord blood