Modification of human long-term bone marrow cultures: establishment of a functional stromal microenvironment devoid of myeloid progenitors

Functional disturbance of marrow stromal microenvironment in the myelodysplastic syndromes

The potential contribution of abnormal marrow stromal function to ineffective haemopoiesis in the myelodysplastic syndromes is unclear. We have compared the ability of stromal layers from normal (n = 7) and myelodysplastic (n = 9) marrow to alter proliferation and survival of the granulocyte-macrophage colony-stimulating factor/interleukin-3-dependent cell line F-36P. Co-cultures for 72 h in the absence of exogenous cytokines were either in direct contact with stroma or separated by transwell inserts. On normal stromal layers, the ratio of adherent F-36P cells relative to stromal cells increased from a mean of 0.2 +/- 0.01 (s.d.) at 4 h of co-culture to 0.34 +/- 0.08 after 72 h (n = 7). Corresponding values on myelodysplastic stroma (0.2 +/- 0.02 at 4 h and 0.35 +/- 0.05 at 72 h; n = 9) indicated that the ability of myelodysplastic stromal layers to regulate short-term proliferation of F-36P cells may be similar to normal. Apoptosis of F-36P cells was quantified after co-culture with normal or myelodysplastic stroma: results from myelodysplastic co-cultures were standardized as a fraction of values from co-cultures with paired normal stroma (apoptotic ratio). Augmented apoptosis of F-36P cells was detected in 8/9 co-cultures with myelodysplastic stroma (mean = 15.7 +/- 9.7%, n = 9), compared with corresponding normal stroma (mean = 12.4 +/- 4.6%, n = 7, P < 0.05) with a mean apoptotic ratio of 1.4 +/- 0.5 (P < 0.05). There was no correlation between stroma-related apoptosis and FAB type, tumour necrosis factor-alpha concentrations in the culture supernatant or numbers of stromal macrophages, and no evidence of involvement of the Fas pathway. Increased apoptosis was detected in cells grown in transwell inserts over stroma (23.8 +/- 3%, n = 5) compared to adherent cells in cultures with normal stromal layers, but this survival difference was not observed in co-cultures with myelodysplastic stroma. These results suggest that abnormal stromal function in patients with myelodysplastic syndromes may contribute to increased apoptosis of haemopoietic cells within the marrow microenvironment. The effect appears to be dependent on close cellular contact, rather than the release of soluble factors, but the exact mechanism remains unclear.

Bone marrow fibroblasts in patients with advanced lung cancer

In a previous study we demonstrated that the incidence of fibroblast colony-forming units (CFU-F) was very low in bone marrow primary cultures from the majority of untreated advanced non-small lung cancer patients (LCP) compared to normal controls (NC). For this reason, we studied the ability of bone marrow stromal cells to achieve confluence in primary cultures and their proliferative capacity following four continuous subcultures in consecutive untreated LCP and NC. We also evaluated the production of interleukin-1beta (IL-1beta) and prostaglandin E2 (PGE2) by pure fibroblasts. Bone marrow was obtained from 20 LCP and 20 NC. A CFU-F assay was used to investigate the proliferative and confluence capacity. Levels of IL-1beta and PGE2 in conditioned medium (CM) of pure fibroblast cultures were measured with an ELISA kit and RIA kit, respectively. Only fibroblasts from 6/13 (46%) LCP confluent primary cultures had the capacity to proliferate following four subcultures (NC = 100%). Levels of spontaneously released IL-1beta were below 10 pg/ml in the CM of LCP, while NC had a mean value of 1,217 +/- 74 pg/ml. In contrast, levels of PGE2 in these CM of LCP were higher (77.5 +/- 23.6 pg/ml) compared to NC (18.5 +/- 0.9 pg/ml). In conclusion, bone marrow fibroblasts from LCP presented a defective proliferative and confluence capacity, and this deficiency may be associated with the alteration of IL-1beta and PGE2 production.

Bone marrow fibroblastic progenitors in patients with advanced breast cancer

Bone marrow fibroblast colony-forming cells (CFU-F) were studied in fifteen consecutive untreated breast cancer patients (BCP) with clinical stages III and IV, and in sixteen normal controls (NC). A decreased number of CFU-F was observed in BCP compared to NC (p < 0.004). Confluence of the adherent cell layer was observed in all normal bone marrow mononuclear cells (MC) cultures, while a lower proportion of cultures from BCP (11/15) showed confluent adherent cell layers. When MC cultures of BCP were treated with indomethacin (Indo, 10(-6)M) 50% of them increased the number of CFU-F compared to the value obtained without treatment. In addition, a significant increase in the release of PGE2 in BCP cultures was observed before Indo treatment. Moreover, after MC were fractionated into adherent and non-adherent progenitors, the CFU-F decreased in both types of fractions of BCP compared to NC value (p < 0.02 and < 0.05, respectively). The number of light density MC per 10 ml of bone marrow aspirate and the number of trypsin-sensitive adherent progenitors were lower than NC in BCP (p < 0.02 and 0.013, respectively). Total MC and fibroblasts (fourth passage) were cultivated to evaluate the production of interleukin-1 beta (IL-1 beta) by ELISA methodology. Results indicated no difference of IL 1 beta spontaneous release when total MC cultures of both groups were compared. However, the levels of this cytokine were lower (< 10 pg/ml) in fibroblast culture supernatants of BCP compared to NC (1,217 +/- 74 pg/ml). Fibroblast cultures from BCP showed low or no release of IL-1 beta after muramyl-dipeptide (MDP. 1 microgram/ml) stimulation. In conclusion, the defective proliferative and confluence capacity of BCP fibroblastic progenitors may be related to the decrease in the production of IL-1 beta by these precursors.

Adhesive interactions between tumour cells and bone marrow stromal elements in human multiple myeloma

Long-term bone marrow cultures (LTBMC) were established from marrow samples obtained from 6 myeloma patients and 5 healthy donors and were examined by in situ immunogold-silver staining. During the culture period, the established stroma in myeloma LTBMC revealed a lower level of confluency compared to the normal LTBMC. In addition, an increasing proportion of macrophages and osteoclasts was observed in the myeloma stroma throughout the culture period. Moreover, plasma cells were detectable by wk 8, mostly organized in small clusters. They strongly expressed VLA-4 (6/6), H-CAM (6/6), ICAM-1 (6/6) and N-CAM (3/6). In most cases, a weak expression of the other members of beta 1-integrins was observed. The expression of beta 2-integrins was always absent. Stromal fibroblasts were found to be weakly positive for VLA-2, VLA-3 and VLA-5 and showed strong expression of VCAM-1, H-CAM and ICAM-1. N-CAM expression could not be detected. By comparing the adhesion molecule profile of the stromal cells in myeloma cultures with normal bone marrow (BM) cultures, no particular defects could be observed. The stroma displayed most of the potential ligands which could interact with adhesion molecules detected on the myeloma cells. Among these ligands we could find fibronectin and VCAM-1 for VLA-4, collagen I for VLA-2 and VLA-3 and laminin for VLA-2, 3 and 6. Four myeloma cell lines, i.e. OPM-1, U266, RPMI 8226 and JJN3, with a representative phenotype, were used to study the adhesive interactions of myeloma cells with the BM microenvironment. All the myeloma cell lines bound strongly to the marrow cell layers and also showed a high binding to purified fibronectin (FN). However, the adhesion of the cell lines to intact stroma could not be significantly inhibited by anti-FN receptors antibodies. Nor could it be prevented when the latter were combined with anti-H-CAM, V-CAM and ICAM-1 antibodies, as tested in the JJN3 cell line. This implies that other unknown mechanisms contribute to the myeloma cell binding.