Microglia-derived ASC specks cross-seed amyloid-ß in Alzheimer's disease.

The spreading of pathology within and between brain areas is a hallmark of neurodegenerative disorders. In patients with Alzheimer's disease, deposition of amyloid-ß is accompanied by activation of the innate immune system and involves inflammasome-dependent formation of ASC specks in microglia. ASC specks released by microglia bind rapidly to amyloid-ß and increase the formation of amyloid-ß oligomers and aggregates, acting as an inflammation-driven cross-seed for amyloid-ß pathology. Here we show that intrahippocampal injection of ASC specks resulted in spreading of amyloid-ß pathology in transgenic double-mutant APPSwePSEN1dE9 mice. By contrast, homogenates from brains of APPSwePSEN1dE9 mice failed to induce seeding and spreading of amyloid-ß pathology in ASC-deficient APPSwePSEN1dE9 mice. Moreover, co-application of an anti-ASC antibody blocked the increase in amyloid-ß pathology in APPSwePSEN1dE9 mice. These findings support the concept that inflammasome activation is connected to seeding and spreading of amyloid-ß pathology in patients with Alzheimer's disease.

Measuring NLR Oligomerization II: Detection of ASC Speck Formation by Confocal Microscopy and Immunofluorescence.

Inflammasome assembly results in the formation of a large intracellular protein scaffold driven by the oligomerization of the adaptor protein apoptosis-associated speck-like protein containing a CARD (ASC). Following inflammasome activation, ASC polymerizes to form a large singular structure termed the ASC "speck," which is crucial for recruitment of caspase-1 and its inflammatory activity. Hence, due to the considerably large size of these structures, ASC specks can be easily visualized by microscopy as a simple upstream readout for inflammasome activation. Here, we provide two detailed protocols for imaging ASC specks: by (1) live-cell imaging of monocyte/macrophage cell lines expressing a fluorescently tagged version of ASC and (2) immunofluorescence of endogenous ASC in cell lines and human immune cells. In addition, we outline a protocol for increasing the specificity of ASC antibodies for use in immunofluorescence.

Generation of functional endothelial cells with progenitor-like features from murine induced pluripotent stem cells.

Induced pluripotent stem cells (iPSCs) have shown great potential in regenerative medicine and research applications like disease modeling or drug discovery. Endothelium is indispensable for vascular homeostasis, whereas endothelial dysfunction could lead to different diseases. Therefore, generating autologous cells, able to restore the endothelial lining, can be crucial for slowing or reversing certain pathological processes. In the current study we show efficient differentiation of murine iPSCs into endothelial cells (ECs) with stable CD34+/Tie-2+/Sca-1+/CD45- phenotype and proven functionality. iPS-derived ECs (iPS-ECs) were positive for phospho-eNOS and von Willebrand factor, and responded to shear stress with up-regulation of KLF-2, KDR, HO-1, and increased nitric oxide and VEGF production. These cells reacted to cytokine stimulation through increase in VCAM-1 and inflammatory cytokine secretion. iPS-ECs showed also certain progenitor features, like expression of progenitor markers (CD34, Sca-1, c-kit) and high clonogenic potential. The angiogenic capacity of iPS-ECs in spheroid sprouting assay was similar to primary ECs, whereas on Matrigel, tube structures could be formed only in the presence of other support cells. Angiogenic potential of iPS-ECs in vivo, was similar to murine endothelial cell line MS-1. Summarizing, our approach enabled generation of functional progenitor-like ECs, which can be used as a research model.