Hematopoietic stem cell antigen-1 (Sca-1) expression in different lymphoid tissues of female mice treated with GnRH agonist.

PROBLEM

Our earlier studies have demonstrated a general suppression of leukocyte maturation upon GnRH agonist treatment in mice and suggested a potential effect at an early stem cell stage of leukocyte development.

METHOD

Three-week old Balb/c and C57BL/6 female mice received 50 micrograms injections of Lupron depot or placebo. Sequential changes in Sca-1+ cells in the bone marrow, thymus, blood and spleen were studied by flow cytometry.

RESULTS

In bone marrow, the absolute numbers of Sca-1+ cells were significantly decreased at 2 weeks in C57BL/6 mice whereas a decreasing trend was noted in Balb/c mice following agonist administration. Concomitantly, thymocytes expressing Sca-1+ cells were significantly increased at 2 weeks in C57BL/6 mice, but were significantly decreased in Balb/c mice. Significant decreases in Sca-1+ cells were also observed in spleen and blood in Balb/c mice whereas no significant differences were observed in C57BL/6 mice.

CONCLUSIONS

These data suggest GnRH agonists affect hematopoietic stem cell development in mice. The effects observed vary with different genetic backgrounds. In Balb/c mice these effects are more pronounced, and appear to result in the inhibition of stem cell maturation. In contrast, GnRH agonist enhances stem cell maturation in C57BL/6 mice.