Expression of PAI-1 and c-Mpl mRNA during short-term culture of normal human cord blood CD34⁺ progenitor cells with TPO. The CD34⁺ cells were isolated from human cord blood using antihuman CD34 MoAb bound to magnetic microspheres and cultured in the presence of 10 ng/mL TPO. The cells were harvested at the indicated time points and subjected to morphologic examination on Wright-Giemsa staining cytospin slides (upper panel) and RT-PCR analysis for PAI-1, c-mpl P and GAPDH mRNA expression (lower panel). Amplified products were analyzed on 2% agarose gels followed by ethidium bromide staining. M, molecular size marker.