NONTRANSFORMED COLONY-DERIVED STROMAL CELL-LINES FROM NORMAL HUMAN MARROWS .3. THE MAINTENANCE OF HEMATOPOIESIS FROM CD34(-POPULATIONS() CELL)

Nontransformed stromal colony-derived cell lines (CDCLs) consist of a pure stromal cell population that differentiates following a vascular smooth-muscle cell repertoire. Here we study the maintenance of hemato poiesis by this cell population. We show that CDCLs allow the generati on for several weeks of stroma-adherent colonies (comprising a cobbles tone area) from CD34(+), CD34(+)/CD38(+), and CD34(+)/CD38(-) cells. S troma-adherent colony-forming cells (CFCs) from CD34(+)/CD38(-) cells reach a maximum at week 4 and limiting dilution analysis gives a frequ ency of 1 per 10 cells seeded; in contrast to this, CFCs from CD34(+)/ CD38(+) cells are optimal by week 2 and the frequency is then only 1 p er 120 cells seeded. Stroma-adherent colonies comprise hematopoietic c ells from all lineages except the T lymphocytic, with a majority of gr anulomonocytes. CDCLs also allow the amplification of granulomonocytic colony-forming units (CFU-GMs), since cumulative outputs of CFU-GMs b y week 6 are 190 and 8 times that observed at culture inception for th e CD34(+)/CD38(-) and CD34(+)/CD38(+) cell populations, respectively. Our results suggest that stromal cells from CDCLs allow the maintenanc e of primitive hematopoietic precursors and induce their proliferation and differentiation. This study underscores the potential role of one of the microenvironmental cell populations, that of myoid cells, in t he regulation of hematopoietic precursor behavior.