发布: 2020年07月05日第10卷第13期 DOI: 10.21769/BioProtoc.3663 浏览次数: 4225
评审: Xiaoyi ZhengYing ShiAnonymous reviewer(s)
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Abstract
Glomerulonephritis (GN) is a common pathological condition in chronic kidney diseases that often leads to end stage renal failure. Mac-1 (CD11b/CD18)-mediated neutrophil, macrophage, and dendritic cell glomerular infiltration leading to cellular dysfunction and destruction is an important disease mechanism. The cellular distribution and dynamics of the expression of Mac-1 ligands ICAM-1 and ICAM-2 in GN have not been well studied because of the difficulties in tissue staining and colocalizing glomerular cells with surface antigens. To improve the visualization of cell surface marker and antigen expression in kidney compartments, we have devised an even but mild fixation procedure employing p-formaldehyde-lysine-periodate (PLP) perfusion. A large panel of antibodies (Ab) against cell surface markers was used to identify kidney cell types and adhesion molecules. When confocal microscopy was used in visualizing glomerular adhesion molecule staining, the endothelial cells were found to specifically express CD31, and these cells express ICAM-2 constitutively. Though ICAM-1 was not expressed by glomerular endothelial cells in homeostasis, it was highly upregulated in mice with chronic GN and severe proteinuria. VCAM-1, a ligand for VLA-4 important in leukocyte migration, was not expressed in the glomerulus. The results highlight the importance of ICAM-1 in the infiltration of macrophages and dendritic cells in cGN. This report will provide a widely applicable procedure for yielding high quality confocal images and for the identification and quantitation of receptors and other cellular antigens expressed in different kidney compartments and cell types.
Keywords: Glomerulonephritis (肾小球肾炎)Background
The glomerulus plays a central role in the ultrafiltration function of the kidney by the formation of a semipermeable filtration barrier between the circulation and the urinary space (Dickinson, 2016). It is composed of a network of capillaries formed by fenestrated endothelial cells lined by podocytes with interdigitating foot-processes forming slit diaphragms for selective filtration and mesangial cells which provide mechanical support and contractile functions. Most chronic kidney diseases and a large percentage of end stage renal disease exhibit glomerulus involvement and glomerulonephritis (GN) is the underlying cause in 40% of patients with chronic kidney disease (Jha et al., 2013; Foster, 2016; Lindenmeyer and Kretzler, 2017). Leukocyte infiltration and immune complex deposition are largely responsible for the initiation and progression of GN with polymorphonuclear neutrophils (PMN) and macrophages constituting the predominant infiltrating cell types (Devi et al., 2013; Dickinson, 2016; Sung et al., 2017; Almarza Novoa et al., 2018). Leukocyte transmigration into the glomerulus is dependent on chemokine and adhesion molecule functions (Filippi, 2016; Sung et al., 2017). For PMN and monocyte adhesion and diapedesis into the subendothelial space and the mesangium, CD11b function is of particular significance (Ernandez and Mayadas, 2016; Filippi, 2016; Sung et al., 2017). This β2 integrin binds ICAM-1 and ICAM-2 which are expressed by glomerular intrinsic cells, especially the endothelial cells (Devi et al., 2013; Filippi, 2016; Sung et al., 2017). The expression of integrin β1 and β2 ligands including ICAM-1, ICAM-2, and VCAM-1 on endothelial cells are modulated by changes in the inflammatory environments but their expression within the glomerulus is not well-studied. To understand cellular interactions in GN pathogenesis, microscopic examination of the dynamics of cell type-specific expression of adhesion molecules is critical (Devi et al., 2013; Sung et al., 2017). Studies by confocal microscopy have provided a clearer understanding of leukocyte emigration in the glomerulus. Unequivocal definition of expression specificity in this microscopic technique requires (1) availability of glomerular cell type-specific Ab; (2) optimized methods for tissue preparation and fixation; (3) availability of Ab for detecting the antigenic epitopes; and (4) adequate signal to noise ratio. In the past, difficulties arising from one or more of these issues have resulted in suboptimal detection of integrin expression by glomerular cells. Some of the issues in kidney glomerulus staining are summarized below. The first is the high autofluorescence and nonspecific binding of renal tubules. The autofluorescence of cortical tubules is particularly notable. The problem of nonspecific staining is especially severe when secondary Ab are used. Availability of reagents poses another hurdle since fluorescence-tagged Ab for staining kidney glomerular intrinsic cell types such as podocyte and mesangial cells are not commercially available. Furthermore, with the staining of frozen sections, as is often the case, the images are diffuse and lack resolution compared to fixed tissues (Figure 1, cf. HLA-DR staining (arrows) in panel A–frozen and panel B–fixed sections). This report describes a mild kidney fixation method for preserving tissue architecture and Ab-binding antigenic epitopes. Ab conjugated with fluorescence tags for background reduction were used to identify glomerular cell expression of integrins in homeostatic and inflamed kidneys. The procedure yielded sharp images of glomerular endothelial cells expressing ICAM-1 and ICAM-2 and extraglomerular tubular cells expressing VCAM-1. The method is applicable to studies on cellular interactions and receptor and cytokine expression by other kidney cell types such as inflammatory cells, fibroblasts, and epithelial cells.
Figure 1. Comparison of immuno-fluorescence staining in frozen and fixed tissues. A. Human skin tissue was frozen in OCT, sectioned in 5 μm slices, fixed for 10 min in acetone at -20 °C, and stained with the indicated Ab as described in Procedure B. B. Human kidney tissue was fixed for 3 h in 2% phosphate-lysine-periodate (PLP), equilibrated in sucrose and OCT as described in Procedure A, sectioned, and stained with the indicated Ab as described in Procedure B. Confocal images were captured as described in Procedure C. Arrows indicate HLA-DR-stained cells. Scale bars = 25 μm.
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版权信息
© 2020 The Authors; exclusive licensee Bio-protocol LLC.
如何引用
Sung, S. J. (2020). Co-immunostaining of ICAM-1, ICAM-2, and CD31 in Mouse Kidney Glomeruli. Bio-protocol 10(13): e3663. DOI: 10.21769/BioProtoc.3663.
分类
免疫学 > 免疫细胞功能 > 巨噬细胞
细胞生物学 > 细胞成像 > 共聚焦显微镜
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