Flowcytometric analysis of aldehyde dehydrogenase activity in mononuclear cells from umbilical cord blood

Aldehyde dehydrogenase (ALDH) is a cytosolic enzyme that is responsible for the oxidation of intracellular 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 which 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 (Vancouver Canada) as described by the manufacturer. Cells were then stained with phycoerythrin (PE)–conjugated anti-CD34 (Miltenyi Biotec, Cologne, Germany) antibodies for 30 min at 4°C. Cells were washed and re-suspended 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 28% and a maximum of 94.6%. Significant correlations were found between the white blood cell (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. Key words: Umbilical cord blood, stem cells, aldehyde dehydrogenase (ALDH), CD34.