Expression of Caspase－3 in Cord Blood CD34^＋ Cells during Culture in vitro

Objective: To investigate the expression and significance of caspase-3 protein in CD34^ cells from cord blood (CB) during culture in vitro with different growth factors. Methods: RT-PCR, Western blot and flow cytometry techniques were used to detect the expression of caspase-3 in CD34^ CB cells during culture in vitro. Results: Caspase-3 mRNA was constitutively expressed at a low level in freshly isolated CD34^ cells. The expression of caspase-3 mRNA and protein was upregulated when these cellswere first expanded in suspension culture with growth factors for 3 days. However, only the 32 kDa inactive caspase-3 proenzyme was detected in the freshly isolated CD34^ cells as well as during the first 3 days expansion with cytokines. With longer culture time in vitro, especially in the presence of the combination of IL-3, IL-6 and GM-CSF, caspase-3 was activated and a cleavage product of 20 kDa became detectable.Conclusion: Caspase-3 is involved in apoptosis of primitive CB CD34^ cells during expansion in vitro.