Gap junctions in hematopoietic stroma control proliferation and differentiation of blood cell precursors

Abstract

We examined gap junction communication in an in vitro model of hematopoiesis, using the murine bone marrow stroma cell line S-17, and primary cultures of murine marrow-derived blood cell precursors. S-17 cells express several connexins, the major one being connexin 43. Connexin expression and formation of functional gap junctions is modulated by stroma cell density. Transfection of S-17 cells with a vector containing connexin 43 sense or anti-sense sequences increased or decreased, respectively, connexin 43 synthesis and intercellular dye coupling. Under these conditions, modulation of gap junction-mediated communication modified the growth pattern of stroma itself, as well as the ability of the stroma to sustain hematopoiesis. Increased connexin 43 expression was associated with a delay in differentiation of blood cells, resulting in increased production of hematopoietic precursors, while decreased connexin 43 expression elicited an accelerated differentiation of myeloid blood cell precursor cells. These results suggest that connexin-mediated coupling in the stroma modulates the ratio between proliferation and differentiation of hematopoietic precursors. We therefore propose that increased gap junction communication in the stroma elicits an enhanced production of immature bone marrow cells through the delay in their terminal differentiation, inducing consequently an extended proliferation period of blood cell precursors.

AKT Signaling Prevailing in Mesenchymal Stromal Cells Modulates the Functionality of Hematopoietic Stem Cells via Intercellular Communication

“…S5J). Such intercellular GAP junction formation among stromal cells is known to positively regulate HSCs . These data suggest that the increased intercellular transfer of molecular cargo by the M2‐AKT cells may be related to deregulated formation of gap‐junctions.…”

Human and mouse microglia express connexin36, and functional gap junctions are formed between rodent microglia and neurons

“…Two other groups also reported no detectable Cx43 expression in rat microglia, including activated‐like cells, when cocultured with astrocytes (Rouach et al, 2002; Faustmann et al, 2003). Cx43 expression has been found in numerous other hematopoietically derived macrophages and other immune system cells (Rosendaal et al, 1994; Eugenin et al, 2001, 2003; Oveido‐Orta et al, 2004; Bodi et al, 2004) but apparently was absent from F4/80‐positive macrophages in bone marrow (Rosendaal et al, 1994). Additional studies will be necessary to resolve Cx expression patterns in microglia fully.…”

SDF-1α regulation in breast cancer cells contacting bone marrow stroma is critical for normal hematopoiesis

“…The diffuse red shown in stromal cells for connexin-43 served as our internal positive control because these cells express connexin. 30,31 Trypan blue exclusion indicated no evidence of BCC death. Together, these findings demonstrate gap junction formation after the BCCs have contacted BM stroma.…”

“…22 Furthermore, BM stromal cells as well as low metastatic BCCs can form gap junctions. [29][30][31] In vitro studies with cocultures of BM stroma and BCCs have shown normal hematopoietic functions. 22 We now ask whether BM stroma and BCCs form gap junctions.…”