Endogenous growth factor patterns modulate hemopoietic lineage development.

Abstract

Hemopoietic growth factors play an important role during stem cell differentiation, and multipotent hemopoietic cells expressing abl oncogenes can cause stem cell diseases in mice. To further elucidate the mechanism of disease development, we examined the initial changes of normal and abl-transduced progenitor cells early in culture, including the endogenous production of growth factors. From 2-3 days methylcellulose cultures, we isolated colonies of early cells and subjected them to RT-PCR analysis. They were found to produce endogenous IL-1 alpha and IL-4. Treatment of these early cells with the antisense oligonucleotides directed against the mRNA of the growth factors did not prevent colony formation. However, the percentage of pure macrophage colonies in cultures containing the antisense IL-1 alpha was increased from 26-60%. This effect was not observed when the antisense oligomers were added 2 days after initiation of culture. We also transduced the progenitor cells with retrovirus vectors carrying either a neor gene (N2) or a v-abl oncogene (A-MuLV or NSabl). After their culture in methylcellulose, we examined the types of colonies developed, growth factor expression by the early cells and their proliferation rate. While the ratio of erythroid to non-erythroid hemopoietic colonies in uninfected culture and N2-infected culture was 0.8, the ratio in A-MuLV-infected culture was 6.0, and in NSabl-infected culture, 3.1. RT-PCR analysis on colonies of abl-transduced cells from 2-3 day cultures indicated a reduction of IL-4 and IL-1 alpha in these cells, and they entered cell division sooner. Our data suggest that hematopoietic lineage development may be a function of the pattern of endogenous as well as exogenous growth factors, and alteration of this pattern either through antisense treatment or v-abl transduction affects the hemopoietic differentiation program.