Polycythemia vera: studies of hemopoiesis in continuous long-term culture of human marrow

Abstract

Long-term cultures of marrow cells from ten normal subjects and three patients with polycythemia vera were established to compare normal and neoplastic hemopoiesis in vitro. Suspended cells were removed periodically from the cultures and assayed from their content of various colony-forming cells, including erythroid colony- and burst-forming cells (CFU-E and BFU-E), granulocyte/macrophage colony-forming (CFU-C), and "mixed cell" colony progenitors (CFU-GEMM). To determine if mixed cell colonies arise from a single progenitor, we used the cellular mosaicism conferred by X-chromosome inactivation. The isoenzymes of glucose-6-phosphate dehydrogenase (G-6-PD) were used as markers of the mosaicism. Preliminary results suggest that these colonies are clonal only at low plating densities. The G-6-PD system was also used to determine whether selection or "drift" occurs in continuous long-term cultures. The ratios of G-6-PD isoenzyme types in pooled colonies from cultures of two normal heterozygotes remained similar, indicating stable cultures. Long-term cultures of normal marrow and marrow from the patients with polycythemia vera maintained BFU-E for a mean of 8.7 (+/- 0.6) and 12.5 (+/- 0.5) weeks (P = 0.03), respectively. The fractions of total BFU-E detected as endogenous erythroid colonies remained similar over the culture period. These results demonstrate that 1) hemopoiesis in polycythemia vera can be analyzed in long-term culture; 2) polycythemia vera marrow grows as well or better than normal in long-term culture; and 3) the proportion of the neoplastic clone in polycythemia vera represented by endogenous erythroid colony growth is unchanged over time, suggesting no reemergence of normal stem cell progeny in this system.