[Ex vivo increase in hematopoietic progenitor cells for clinical use]

The clinical use of ex vivo expanded hematopoietic progenitor cells is currently explored.

In this study the culturing of G-CSF mobilized and purified CD34+ blood cells was investigated. The interleukins IL-1 beta, IL-3 and IL-6 (each at a dose of 300 U/ml) and stem cell factor (25 ng/ml) without or with erythropoietin (1 U/ml) were used. Cells of 10 healthy sibling donors and 10 patients with solid tumors were incubated under small-scale (n = 15, 2 ml) and large-scale (n = 7, 50 ml) culture conditions at 37 degrees C for 5 and 4 weeks, respectively. The cell density was adjusted to about 1 x 10(5) cells/ml.

The nucleated cell counts increased approximately 7-fold and 10- to 70-fold after 1 and 2 weeks of incubation. Numbers of CD34+ cells doubled to triplicated within this time interval, without any significant changes in their clonogenicity (CFU-GM and BFU-E output). Thereafter a depletion of the CD34+ cell pool was noticed. However the numbers of CD34+/CD38(-)- or CD34+/ HLA-DR(-)- cells were reduced to a lesser extent. The expanded cells generated predominantly myeloid and almost no lymphoid cells. More glycophorin-A+ cells were produced when erythropoietin was added. Replacement of non-human additives with heat-inactivated autologous plasma had no influence on cell growth. Almost no proliferation was obtained with a 10-fold higher cell density (1.7 x 10(6)/ml in 100 ml), but the cells maintained their viability for 13 to 16 days.

This study suggests, that the chosen culture conditions might be feasible for a large-scale ex vivo expansion of hematopoietic progenitor cells for clinical application. The impact of the ex vivo generated cells on hematopoietic regeneration after chemotherapy is currently under clinical investigation.