Laboratory investigation; a journal of technical methods and pathology
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Quantitative three-dimensional (3D) imaging of angiogenesis during bone repair remains an experimental challenge. We developed a novel contrast agent containing 0.07- to 0.1-μm particles of zirconium dioxide (ZrCA) and established subtraction μCT using synchrotron radiation (sSRCT) for quantitative imaging of angiogenesis and bone repair. This method was applied to a rat model of tibial bone repair 3 days (DAY3; n = 2), 5 days (DAY5; n = 8), or 10 days (DAY10; n = 8) after drill-hole injury. ⋯ All these parameters were found to be decreased after 10 days of hindlimb unloading, indicating the possible involvement of angiogenesis in bone repair impairment caused by reduced mechanical stimuli. In conclusion, the combined technique of sSRCT and ZrCA vascular casting is suitable for quantitative 3D imaging of angiogenesis and its surrounding bone regeneration. This method will be useful for better understanding the linkage between angiogenesis and bone repair.
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Tumor necrosis factor-α (TNF-α) acts as a key factor for the development of inflammatory bowel diseases (IBDs), whose function is known to be mediated by TNF receptor 1 (TNFR1) or TNFR2. However, the precise role of the two receptors in IBD remains poorly understood. Herein, chronic colitis was established by oral administration of dextran sulfate sodium (DSS) in TNFR1 or TNFR2-/- mice. ⋯ Intriguingly, despite comparable intensity of intestinal inflammation in TNFR-deficient mice after DSS, systemic inflammatory response (including splenomegaly and myeloid expansion) was augmented dramatically in TNFR1-/- mice, instead of TNFR2-/- mice. Granulocyte-macrophage colony-stimulating factor (GMCSF) was identified as a key mediator in this process, as neutralization of GMCSF dampened peripheral inflammatory reaction and reduced mortality in TNFR1-/- mice. These data suggest that signaling via TNFR1 or TNFR2 has a protective role in chronic intestinal inflammation, and that lacking TNFR1 augments systemic inflammatory response in GMCSF-dependent manner.