Hematopoietic-promoting activity of the murine stromal cell line MS-5 is not related to the expression of the major hematopoietic cytokines.

As an approach for characterizing the molecules involved in the proliferation and differentiation of hematopoietic stem cells we have compared the ability of four murine stromal cell lines, MS-5, MS-K, both derived from Dexter cultures, BMS1 and BMS2 both derived from Whitlock-Witte cultures, to sustain murine long term hematopoiesis and to express the major hematopoietic cytokine genes. As opposed to the three other cell lines, MS-5 supports the maintenance of stem cells for up to 4-5 weeks. However, reconstituting stem cell output was reduced while clonogenic cell (day 12 and day 8 spleen colony-forming units, granulo-macrophagic, and erythroid progenitor cells) output was markedly increased. This hematopoietic-promoting activity is at least in part mediated by soluble molecules since medium conditioned with MS-5 cells was able to partially complement the nonsupportive cell line BMS1. The comparative study of the cytokine gene expression in MS-5 and in the nonsupportive cell lines included Northern blot and reverse transcriptase-polymerase chain reaction analysis of messenger RNA for interleukin-1, -3, -6, granulo-macrophage-colony-stimulating factor (GM-CSF), granulocyte-CSF, macrophage-CSF, stem cell factor, transforming growth factor-beta, tumor necrosis factor-alpha, macrophage inflammatory protein-1 alpha, and leukemia inhibitory factor. None of these molecules or their association were found to clearly confer to the MS-5 cell line its hematopoietic-promoting activity raising the possibility that uncharacterized molecule(s) would be involved in the proliferation and differentiation of stem cells.