HYDROCORTISONE DIFFERENTIALLY AFFECTS THE ABILITY OF MURINE STROMAL CELLS AND HUMAN MARROW-DERIVED ADHERENT CELLS TO PROMOTE THE DIFFERENTIATION OF CD34(-) LONG-TERM CULTURE-INITIATING CELLS(+) CD38()

Very primitive human hematopoietic progenitor cells are identified ind irectly by their ability to give rise to clonogenic progenitors in the presence of either human or murine stromal cells. These long-term cul ture-initiating cell (LTC-IC) assays are usually performed in the pres ence of hydrocortisone based on the initial observation that hydrocort isone was required for prolonged hematopoiesis in standard longterm bo ne marrow cultures. In this report, we investigated the role of hydroc ortisone in LTC-IC assays initiated with CD34(++)/CD38(-) cells seeded onto either human bone marrow LTC-derived adherent cells or a murine marrow-derived stromal cell line, MS-5, It was found that weekly addit ion of hydrocortisone to the cultures reduced the frequency of LTC-IC (from 1/5 to 1/20) calculated from limiting dilution experiments and a lso reduced fivefold to 10-fold the number of their progeny clonogenic cells detected after 4 to 5 weeks, In contrast, the frequency and dif ferentiative potential of CD34(++)/CD38(-) grown in the presence of hu man marrow feeders was unaltered by the addition of glucocorticoids. D ata are consistent with the hypothesis that hydrocortisone inhibited L TC-IC differentiation by downregulating the expression of a synergisti c factor produced by MS-5 cells. (1) In the absence of hydrocortisone, the number of clonogenic progenitors generated by LTC-IC was much hig her in cultures seeded on MS-5 than in cultures seeded on human marrow adherent cells, which was also true when cytokines were added to the cocultures. However, based on the phenotype of the colonies, progenito rs produced in MS-5 cocultures were more mature than those generated o n human marrow adherent cells, (2) Hydrocortisone counteracted the sti mulatory effect of recombinant human cytokines (interleukin-3, interle ukin-6, and steel factor) in assays performed on MS-5 but not on human marrow feeders, (3) Hydrocortisone led to a 50% decrease in the numbe rs of colony-forming units-granulocyte-macrophage found in methycellul ose colony assays of CD34(++)/CD38(-) cells performed in the presence of MS-5 cells, Taken together, our results indicate that hydrocortison e acts differently on a murine stromal cell line and on marrow-derived human stromal cells and may suppress the expression by MS-5 cells of an activity selectively promoting amplification of clonogenic cells de rived from primitive LTC-IC. (C) 1994 by The American Society of Hemat ology.