Myelopoietic effect of bone marrow fibroblasts cultured from patients with myelofibrosis

Osteosclerosis in idiopathic myelofibrosis is related to the overproduction of osteoprotegerin (OPG)

OBJECTIVE

The aim of this study is to investigate the mechanism of osteosclerosis in IMF in relation to OPG derangement.

METHODS

Plasma OPG level was assayed by OPG ELISA in 19 patients with IMF, 15 patients with other myeloproliferative disorders (MPDs), and 12 normal volunteers as controls and correlated with the degree of osteosclerosis. Furthermore, the level of OPG mRNA, in the cultured bone marrow stromal (BMS) cells of patients with IMF and anemia patients used as controls, in the presence or absence of TGF-beta1, was studied by real-time RT-PCR.

RESULTS

The present study showed that blood OPG level was significantly elevated in patients with IMF as compared to patients with other MPDs (p < 0.01) or normal volunteer controls (p < 0.05), and there was no significant difference in the level between patients with MPDs and controls. In addition, there was a positive correlation (r=0.67, p=0.04) between plasma OPG levels and the degree of osteosclerosis. There was no difference in the OPG mRNA in patients with IMF as compared with controls even on TGF-beta1 stimulation.

CONCLUSION

These results suggest that osteosclerosis in IMF may be related to overproduction of OPG and enhanced level of OPG is not due to the effect of TGF-beta1 on the BMS cells. It could be due to the effect of TGF-beta1 or other growth factors on cells other than BMS cells such as the osteoblasts.

Plasma soluble interleukin-2 receptor in patients with primary myelofibrosis

Using en enzyme-linked immunosorbent assay (ELISA) test, the level of soluble Tac peptide, one chain of the human interleukin-2 receptor, was measured in the plasma of 26 patients with primary myelofibrosis (MF), seven patients with polycythaemia vera and 11 normal controls. The plasma soluble interleukin-2 receptor (sIL-2R) was found to be significantly elevated in patients with primary MF compared to polycythaemia vera or controls (P < 0.001), while the plasma sIL-2R of patients with polycythaemia vera also was found to be significantly elevated compared to controls (P < 0.01). The significantly elevated value of sIL-2R seen in primary MF may be secondary to T cell activation resulting from autoimmune phenomena, and myeloblast activation with release of sIL-2R may also be a contributing factor. In primary MF, plasma sIL-2R levels were also found to be correlated to survival, circulating blast cell counts, and thrombocytopenia, but not to white blood cell counts, LDH levels, degree of marrow fibrosis, or degree of splenomegaly. Patients with primary MF with higher titre of plasma sIL-2R had a shorter survival. Further studies involving more patients and longer follow-up may substantiate that plasma sIL-2R is an important prognostic indicator in primary MF.

Recombinant alpha-interferon inhibits colony formation of bone marrow fibroblast progenitor cells (CFU-F)

Alpha-Interferon (IFN-alpha) has been shown to inhibit colony formation of hematopoietic progenitor cells, including colony-forming unit-granulocyte, erythroid, macrophage, megakaryocyte (CFU-GEMM), day 7 colony-forming unit granulocyte-macrophage (CFU-GM), day 14 CFU-GM, burst-forming unit erythroid (BFU-E), pluripotent stem cells (CFU-S), and colony-forming unit megakaryocyte (CFU-MK). The present study was designed to see whether IFN-alpha also has inhibitory effects on bone marrow fibroblast progenitors (CFU-F). We found that IFN-alpha exerted a significant inhibitory effect on both rabbit and human CFU-F formation. Inhibition of human marrow CFU-F formation by alpha interferon was unaffected by removal of 98% of monocytes/macrophages and T lymphocytes from light density marrow cells. This finding suggests that IFN-alpha probably exerts a direct inhibitory effects.