Regulation of early hematopoiesis in serum-deprived cultures of mafosfamide-treated and untreated CD34-enriched bone marrow cells.

Our experiments have addressed the regulation of early hematopoietic progenitor cell expansion by interleukin 3 (IL-3) and interleukin 1 beta (IL-1 beta) and its modulation by bone marrow fibroblasts in vitro. In a two-stage assay utilizing serum-deprived (SD) presuspension cultures of CD34-enriched bone marrow (BM) cells followed by clonal cultures, absolute numbers of granulocyte-macrophage progenitor cells (day-14 granulocyte-macrophage colony-forming units [CFU-GM]) increased progressively to 164% and 204% of input levels after 12 days of culture in the presence of IL-3 alone or in combination with IL-1 beta, respectively. Multilineage (granulocyte erythrocyte macrophage megakaryocyte colony-forming units, CFU-GEMM) and erythroid (erythroid burst-forming units, BFU-E) progenitor cell numbers increased above or were maintained at input levels after 4 and 7 days of liquid culture in the presence of IL-3 and IL-3 plus IL-1 beta, respectively, but in contrast to granulocyte-macrophage colony-forming units (CFU-GM) they were essentially undetectable after 12 days of culture. Progenitors more primitive than colony-forming cells (pre-CFU) were assessed in SD-presuspension cultures of CD34-enriched BM cells purged with mafosfamide to eliminate base-line CFU-GM, CFU-GEMM, and BFU-E. Under these conditions and in the absence of stromal elements, CFU-GM but neither CFU-GEMM nor BFU-E developed in response to cytokines alone. In the additional presence of passaged bone marrow fibroblasts, however, IL-3 plus IL-1 beta and to a lesser degree IL-3 alone induced a pronounced amplification of BFU-E and CFU-GEMM, indicating that their development from a more primitive progenitor compartment requires growth activities in addition to IL-3 and IL-1 beta that are provided by marrow-derived stromal cells such as fibroblasts.

Influence of human recombinant interferon-alpha and interferon-gamma on bone marrow progenitor cells of HIV-positive individuals.

As a result of a pathophysiologically unexplainable bone marrow failure, most patients with progressive stages of human immunodeficiency virus (HIV) infection develop anemia, leukopenia, and thrombocytopenia. Besides the possibility of immune-mediated cytolysis or of direct viral infection of hemopoietic progenitor cells, the inhibitory influence of cytokines, for example interferon-alpha (IFN-alpha) and IFN-gamma, on hemopoiesis of HIV-infected patients might be considered as one parameter that contributes to myelosuppression. Therefore, progenitor cells from the bone marrow of HIV+ and HIV- persons were exposed to increasing concentrations of recombinant human IFN-alpha and IFN-gamma in methylcellulose assays. The colony formation of pluripotent (CFU-GEMM), erythroid (BFU-E), and granulocyte-macrophage (CFU-GM) progenitor cells was inhibited by both interferons. The 50% inhibitory doses (ID50) of IFN-alpha were 125.6 U/mL and 131.5 U/mL for BFU-E from HIV-infected persons and normal controls, respectively; the corresponding ID50 of IFN-alpha for CFU-GM growth was 1095.8 U/ml and above 3000 U/ml. When IFN-gamma was studied the ID50 was 341.7 and 2794.6 U/ml for BFU-E from HIV-infected and healthy individuals, respectively, while the ID50 for CFU-GM was above the highest dose levels in both groups (greater than 3000 U/ml). The ID50 for CFU-GEMM was below the lowest dose levels of IFN alpha and IFN gamma tested in both groups (less than 10 U/ml). The inhibitory effects could be specifically neutralized by monoclonal antibodies against IFN-alpha and IFN-gamma, thus confirming that the suppressive effects were due to the cytokines used.

TIBO R82913, a new HIV-1 inhibiting agent, does not inhibit hematopoietic progenitor cells.

In progressive stages of infection with human immunodeficiency virus type 1 (HIV-1), the majority of patients develop a pathophysiologically not yet completely explainable bone marrow failure with anemia, leukopenia, and thrombocytopenia. The clinically most widely used HIV-inhibiting antiviral drugs azidothymidine (AZT) and dideoxyinosine (ddI) frequently are hematotoxic to the host, resulting in dose reduction or discontinuation of antiviral therapy. In recent studies, a novel series of benzodiazepine derivatives highly active against HIV-1 was synthesized. These antiviral compounds have a much more favorable therapeutical index than the well-known 2'3'-dideoxyribosides, like AZT. In the experiments presented here, the authors investigated the most promising derivative R82913 [(+)-S-4,5,6,7-tetrahydro-9-chloro-5-methyl- 6-(3-methyl-2-butenyl)-imidazo[4,5,1-jk] [1,4]-benzodiazepin-2(1H)-thione] (TIBO) with regard to its toxicity on bone marrow-derived hematopoietic progenitor cells from six HIV-1+ and HIV- persons, respectively. In methylcellulose assays for hematopoietic colony growth any hematotoxic effects of R82913 in vitro were excluded, as both groups showed no difference of progenitor cell growth with or without the TIBO derivative, even at concentrations 6.7 x 10(4) times higher than the 50% inhibitory concentration for cytopathicity by HIV-1.