HEMATOPOIETIC-PROMOTING ACTIVITY OF THE MURINE STROMAL CELL-LINE MS-5IS NOT RELATED TO THE EXPRESSION OF THE MAJOR HEMATOPOIETIC CYTOKINES

As an approach for characterizing the molecules involved in the prolif eration and differentiation of hematopoietic stem cells we have compar ed the ability of four murine stromal cell lines, MS-5, MS-K, both der ived from Dexter cultures, BMS1 and BMS2 both derived from Whitlock-Wi tte cultures, to sustain murine long term hematopoiesis and to express the major hematopoietic cytokine genes. As opposed to the th ree othe r cell lines, MS-5 supports the maintenance of stem eel Is for up to 4 -5 weeks. However, reconstituting stem cell output was reduced while c lonogenic cell (day 12 and day 8 spleen colony-forming units, granule- macrophagic, and erythroid progenitor cells) output was markedly incre ased. This hematopoietic-promoting activity is at least in part mediat ed by soluble molecules since medium conditioned with MS-5 cells was a ble to partially complement the nonsupportive cell line BMS1. The comp arative study of the cytokine gene expression in MS-5 and in the nonsu pportive cell lines included Northern blot and reverse transcriptase-p olymerase chain reaction analysis of messenger RNA for interleukin-l, -3, -6, granulo-macrophagic-colony-stimulating factor (GM-CSF), granul ocyte-CSF, macrophage-CSF, stem cell factor, transforming growth facto r-beta, tumor necrosis factor-alpha, macrophage inflammatory protein-1 alpha, and leukemia inhibitory factor. None of these molecules or the ir association were found to clearly confer to the MS-5 cell line its hematopoietic-promoting activity raising the possibility that uncharac terized molecule(s) would be involved in the proliferation and differe ntiation of stem cells. (C) 1995 Wiley-Liss, Inc.