Impaired ability of bone marrow cells from immunodeficient mice to establish long-term cultures

Haemopoiesis is often depressed in patients suffering from acquired immune deficiency syndrome (AIDS). Although several mechanisms have been postulated to be responsible for depressed haemopoiesis in AIDS patients, the aetiology of this disorder is still unknown. We hypothesized that failure of the stromal microenvironment may account for part of the haemopoietic defect observed in patients with AIDS. We therefore studied a murine model of AIDS (MAIDS) caused by infection with LP-BM5 virus to determine the ability of bone marrow cells from immunodeficient mice to establish long-term stromal cultures. In addition, normal and MAIDS mice received AZT (2 mg/ml) in their drinking water for up to 1 month to determine the effects of AZT treatment in vivo on the ability of bone marrow cells to support haemopoiesis in long-term cultures. Decreased numbers of non-adherent cells were observed in long-term bone marrow cultures (LTBMC) of MAIDS mice when compared to cultures derived from normal mice. Decreased numbers of non-adherent cells were observed in cultures of bone marrow cells from AZT-treated normal mice, when compared to untreated normal controls. Cells from AZT-treated MAIDS mice produced the smallest number of non-adherent cells. BFU-E and CFU-G/M were decreased in cultures of MAIDS mice when compared to those of normal mice. AZT-treatment further decreased the number of colony-forming cells in both MAIDS mice and normal cultures. Stromal cell function of MAIDS mice was also assessed by inoculating non-adherent cells from normal mice onto confluent irradiated MAIDS LTBMC. Stroma from MAIDS mice was unable to support haemopoietic function of normal bone marrow cells. Polymerase chain reaction (PCR) analysis of steady state levels of cytokine mRNAs of cells from confluent cultures revealed that levels of interleukin-6 mRNA were unchanged in MAIDS mice, as compared to normal controls, but the levels of GM-CSF were decreased in MAIDS mice. These data suggest that LP-BM5 MuLV infection alters the functioning of the haemopoietic stroma and that one mechanism of this depression in haemopoiesis may be via alterations of cytokine production.