Browsing by Subject "Blood Vessels"

Now showing 1 - 5 of 5
  • No Thumbnail Available
    ItemOpen Access
    CLARITY and PACT-based imaging of adult zebrafish and mouse for whole-animal analysis of infections.
    (Dis Model Mech, 2015-12) Cronan, Mark R; Rosenberg, Allison F; Oehlers, Stefan H; Saelens, Joseph W; Sisk, Dana M; Jurcic Smith, Kristen L; Lee, Sunhee; Tobin, David M
    Visualization of infection and the associated host response has been challenging in adult vertebrates. Owing to their transparency, zebrafish larvae have been used to directly observe infection in vivo; however, such larvae have not yet developed a functional adaptive immune system. Cells involved in adaptive immunity mature later and have therefore been difficult to access optically in intact animals. Thus, the study of many aspects of vertebrate infection requires dissection of adult organs or ex vivo isolation of immune cells. Recently, CLARITY and PACT (passive clarity technique) methodologies have enabled clearing and direct visualization of dissected organs. Here, we show that these techniques can be applied to image host-pathogen interactions directly in whole animals. CLARITY and PACT-based clearing of whole adult zebrafish and Mycobacterium tuberculosis-infected mouse lungs enables imaging of mycobacterial granulomas deep within tissue to a depth of more than 1 mm. Using established transgenic lines, we were able to image normal and pathogenic structures and their surrounding host context at high resolution. We identified the three-dimensional organization of granuloma-associated angiogenesis, an important feature of mycobacterial infection, and characterized the induction of the cytokine tumor necrosis factor (TNF) within the granuloma using an established fluorescent reporter line. We observed heterogeneity in TNF induction within granuloma macrophages, consistent with an evolving view of the tuberculous granuloma as a non-uniform, heterogeneous structure. Broad application of this technique will enable new understanding of host-pathogen interactions in situ.
  • Thumbnail Image
    ItemOpen Access
    Critical role of TNF-α in cerebral aneurysm formation and progression to rupture.
    (J Neuroinflammation, 2014-04-16) Starke, Robert M; Chalouhi, Nohra; Jabbour, Pascal M; Tjoumakaris, Stavropoula I; Gonzalez, L Fernando; Rosenwasser, Robert H; Wada, Kosuke; Shimada, Kenji; Hasan, David M; Greig, Nigel H; Owens, Gary K; Dumont, Aaron S
    BACKGROUND: Alterations in TNF-α expression have been associated with cerebral aneurysms, but a direct role in formation, progression, and rupture has not been established. METHODS: Cerebral aneurysms were induced through hypertension and a single stereotactic injection of elastase into the basal cistern in mice. To test the role of TNF-α in aneurysm formation, aneurysms were induced in TNF-α knockout mice and mice pretreated with the synthesized TNF-α inhibitor 3,6'dithiothalidomide (DTH). To assess the role of TNF-α in aneurysm progression and rupture, DTH was started 6 days after aneurysm induction. TNF-α expression was assessed through real-time PCR and immunofluorescence staining. RESULTS: TNF-α knockout mice and those pre-treated with DTH had significantly decreased incidence of aneurysm formation and rupture as compared to sham mice. As compared with sham mice, TNF-α protein and mRNA expression was not significantly different in TNF-α knockout mice or those pre-treated with DTH, but was elevated in unruptured and furthermore in ruptured aneurysms. Subarachnoid hemorrhage (SAH) occurred between 7 and 21 days following aneurysm induction. To ensure aneurysm formation preceded rupture, additional mice underwent induction and sacrifice after 7 days. Seventy-five percent had aneurysm formation without evidence of SAH. Initiation of DTH treatment 6 days after aneurysm induction did not alter the incidence of aneurysm formation, but resulted in aneurysmal stabilization and a significant decrease in rupture. CONCLUSIONS: These data suggest a critical role of TNF-α in the formation and rupture of aneurysms in a model of cerebral aneurysm formation. Inhibitors of TNF-α could be beneficial in preventing aneurysmal progression and rupture.
  • Thumbnail Image
    ItemOpen Access
    Differentiating sensitivity of post-stimulus undershoot under diffusion weighting: implication of vascular and neuronal hierarchy.
    (PLoS One, 2008-08-13) Harshbarger, Todd B; Song, Allen W
    The widely used blood oxygenation level dependent (BOLD) signal during brain activation, as measured in typical fMRI methods, is composed of several distinct phases, the last of which, and perhaps the least understood, is the post-stimulus undershoot. Although this undershoot has been consistently observed, its hemodynamic and metabolic sources are still under debate, as evidences for sustained blood volume increases and metabolic activities have been presented. In order to help differentiate the origins of the undershoot from vascular and neuronal perspectives, we applied progressing diffusion weighting gradients to investigate the BOLD signals during visual stimulation. Three distinct regions were established and found to have fundamentally different properties in post-stimulus signal undershoot. The first region, with a small but focal spatial extent, shows a clear undershoot with decreasing magnitude under increasing diffusion weighting, which is inferred to represent intravascular signal from larger vessels with large apparent diffusion coefficients (ADC), or high mobility. The second region, with a large continuous spatial extent in which some surrounds the first region while some spreads beyond, also shows a clear undershoot but no change in undershoot amplitude with progressing diffusion weighting. This would indicate a source based on extravascular and small vessel signal with smaller ADC, or lower mobility. The third region shows no significant undershoot, and is largely confined to higher order visual areas. Given their intermediate ADC, it would likely include both large and small vessels. Thus the consistent observation of this third region would argue against a vascular origin but support a metabolic basis for the post-stimulus undershoot, and would appear to indicate a lack of sustained metabolic rate likely due to a lower oxygen metabolism in these higher visual areas. Our results are the first, to our knowledge, to suggest that the post-stimulus undershoots have a spatial dependence on the vascular and neuronal hierarchy, and that progressing flow-sensitized diffusion weighting can help delineate these dependences.
  • Thumbnail Image
    ItemOpen Access
    Pretargeting and Bioorthogonal Click Chemistry-Mediated Endogenous Stem Cell Homing for Heart Repair.
    (ACS nano, 2018-12) Li, Zhenhua; Shen, Deliang; Hu, Shiqi; Su, Teng; Huang, Ke; Liu, Feiran; Hou, Lei; Cheng, Ke
    Stem cell therapy is one of the promising strategies for the treatment of ischemic heart disease. However, the clinical application of stem cells transplantation is limited by low cell engraftment in the infarcted myocardium. Taking advantage of pretargeting and bioorthogonal chemistry, we engineered a pretargeting and bioorthogonal chemistry (PTBC) system to capture endogenous circulating stem cells and target them to the injured heart for effective repair. Two bioorthogonal antibodies were i.v. administrated with a pretargeting interval (48 h). Through bioorthogonal click reaction, the two antibodies are linked in vivo, engaging endogenous stem cells with circulating platelets. As a result, the platelets redirect the stem cells to the injured heart. In vitro and in vivo studies demonstrated that bioorthogonal click reaction was able to induce the conjugation of platelets and endothelial progenitor cells (EPCs) and enhance the binding of EPCs to collagen and injured blood vessels. More importantly, in a mouse model of acute myocardial infarction, the in vivo results of cardiac function, heart morphometry, and immunohistochemistry assessment all confirmed effective heart repair by the PTBC system.
  • Thumbnail Image
    ItemOpen Access
    Utility of telomerase-pot1 fusion protein in vascular tissue engineering.
    (Cell Transplant, 2010) Petersen, Thomas H; Hitchcock, Thomas; Muto, Akihito; Calle, Elizabeth A; Zhao, Liping; Gong, Zhaodi; Gui, Liqiong; Dardik, Alan; Bowles, Dawn E; Counter, Christopher M; Niklason, Laura E
    While advances in regenerative medicine and vascular tissue engineering have been substantial in recent years, important stumbling blocks remain. In particular, the limited life span of differentiated cells that are harvested from elderly human donors is an important limitation in many areas of regenerative medicine. Recently, a mutant of the human telomerase reverse transcriptase enzyme (TERT) was described, which is highly processive and elongates telomeres more rapidly than conventional telomerase. This mutant, called pot1-TERT, is a chimeric fusion between the DNA binding protein pot1 and TERT. Because pot1-TERT is highly processive, it is possible that transient delivery of this transgene to cells that are utilized in regenerative medicine applications may elongate telomeres and extend cellular life span while avoiding risks that are associated with retroviral or lentiviral vectors. In the present study, adenoviral delivery of pot1-TERT resulted in transient reconstitution of telomerase activity in human smooth muscle cells, as demonstrated by telomeric repeat amplification protocol (TRAP). In addition, human engineered vessels that were cultured using pot1-TERT-expressing cells had greater collagen content and somewhat better performance in vivo than control grafts. Hence, transient delivery of pot1-TERT to elderly human cells may be useful for increasing cellular life span and improving the functional characteristics of resultant tissue-engineered constructs.