Connexin expression and gap-junction-mediated cell interactions in an in vitro model of haemopoietic stroma

12 p. : il.In addition to the steady-state production of all blood cells, bone marrow can respond to an increased requirement for one or several cell lineages. The hormonal controls involved may act directly on blood cell progenitors or indirectly through modification of the haemopoietic environment. Intercellular gap junctions formed by connexins (Cx) provide direct communication among adjacent cells and the functional integration of multicellular systems. Since haemopoietic stroma is determinant for blood cell production, we have questioned whether gap-junction-dependent controls of haemopoiesis are sensitive to hormones and vitamins. We have analysed the expression, synthesis, cell distribution and formation of functional gap junctions in the murine bone-marrow stroma cell line S-17, and between stromal cells and blood cell progenitors. Nine Cxs were identified by reverse transcription/polymerase chain reaction, and only Cx43 by Western blot and immunofluorescence. All of the studied parameters were sensitive to intrinsic controls dependent upon the pattern of cell growth and modulated by exogenous controls mediated by retinol and steroids. Positive or negative modulation was specific for different Cxs. FACS analysis showed communication among the stromal cells and between stromal cells and myeloid (Mac1+) but not lymphoid (B220+) progenitors. Calcein transfer modulation did not correspond to the modulation of Cx43 expression and formation of connexons, suggesting the participation of other Cxs. Thus, functional gap junctions among haemopoietic stroma cells and between stroma and haematopoietic cells in the bone marrow may be modulated in response to hormonal stimuli, potentially controlling overall blood cell production

The deficiency of galectin-3 in stromal cells leads to enhanced tumor growth and bone marrow metastasis

Abstract Background Galectin-3 is a multifunctional β-galactoside-binding lectin that once synthesized, is expressed in the nucleus, cytoplasm, cell surface and in the extracellular environment. Because of its unique structure, galectin-3 can oligomerize forming lattice upon binding to multivalent oligossacharides and influence several pathologic events such as tumorigenesis, invasion and metastasis. Methods In our study, balb/c Lgals3+/+ and Lgals3−/− female mice were inoculated in the fourth mammary fat pad with 4T1 breast cancer cell line. The primary tumor, inguinal lymph nodes and iliac bone marrow were evaluated 15, 21 and 28 days post-injection. The primary tumor growth was evaluated by measuring the external diameter, internal growth by ultrasound and weight of the excised tumor. The presence of cancer cells in the draining lymph nodes and iliac crest bone marrow were performed by immunohistochemistry, PCR and clonogenic metastatic assay. Results In this study we demonstrated that the deletion of galectin-3 in the host affected drastically the in vivo growth rate of 4T1 tumors. The primary tumors in Lgals3−/− mice displayed a higher proliferative rate (p < 0,05), an increased necrotic area (p < 0,01) and new blood vessels with a wider lumen in comparison with tumors from Lgals3+/+ mice (P < 0,05). Moreover, we detected a higher number of 4T1-derived metastatic colonies in the lymph nodes and the bone marrow of Lgals3−/− mice (p < 0,05). Additionally, healthy Lgals3−/− control mice presented an altered spatial distribution of CXCL12 in the bone marrow, which may explain at least in part the initial colonization of this organ in Lgals3−/− injected with 4T1 cells. Conclusions Taken together, our results demonstrate for the first time that the absence of galectin-3 in the host microenvironment favors the growth of the primary tumors, the metastatic spread to the inguinal lymph nodes and bone marrow colonization by metastatic 4T1 tumor cells

Galectin-3 regulates peritoneal B1-cell differentiation into plasma cells

11 p. : il.Extracellular galectin-3 participates in the control of B2 lymphocytemigration and adhesion and of their differentiation into plasma cells. Here, we analyzed the role of galectin- 3 in B1-cell physiology and the balance between B1a and B1b lymphocytes in the peritoneal cavity. In galectin-3−/− mice, the total number of B1a lymphocytes was lower, while B1b lymphocyte number was higher as compared to wild-type mice. The differentiation of B1a cells into plasma cells was associated with their abnormal adhesion and location on the mesentery. The B220 and CD43, constitutively expressed by B1 lymphocytes, were respectively up- and downregulated in galectin-3−/− mice. Mononuclear cells were strongly adhered to the mesenteric membranes of both CD43−/− and galectin-3−/− mice, but in contrast to CD43−/− mice, the accumulation of B1 cells in peritoneal membranes in galectin- 3−/− mice was accompanied by their functional differentiation into plasma cells.We have shown that in the absence of galectin-3, B1-cell differentiation into plasma cells is favored and the dynamic equilibrium of B1-cell populations in the peritoneum is maintained through a compensatory increase in B1b lymphocytes