Expression of caspase-3 in CD34+ cord blood cells and its significance

To evaluate expression of caspase-3 protein in CD34(+) cells from cord blood (CB) and its significance during culture in vitro with various growth factors, RT-PCR, Western blot and flow cytometry were used to determine cell proliferation, apoptosis and expression of caspase-3 in CD34(+) cells during culture in vitro. The results demonstrated that caspase-3 mRNA was constitutively expressed at a low level in freshly isolated CD34(+) cells. Expression of caspase-3 mRNA and protein was upregulated when these cells were expanded in suspension culture with growth factors for 3 days. However, only the 32 kD inactive caspase-3 proenzyme was detected in the freshly isolated CD34(+) cells and those cells after 3 days expansion with cytokines. Along with the culture time extension (7 days) in vitro, especially without early-effective cytokines SCF or FL existence, caspase-3 was activated and a cleavage 20 kD was detected. It is concluded that the caspase-3 is involved in apoptosis of primitive CD34(+) cells during expansion in vitro, and early-effective cytokines, SCF and FL, could conserve hematopoietic stem cells and suppress apoptosis.