Rapid Detection of Senescent Mesenchymal Stromal Cells by a Fluorescent Probe.

Despite intense interest in human mesenchymal stromal cells (MSCs), monitoring of the progressive occurrence of senescence has been hindered by the lack of efficient detection tools. Here, the discovery of a novel MSC senescence-specific fluorescent probe (CyBC9) identified by a high-throughput screen is reported. Compared with the prototypical senescence-associated ß-galactosidase (SA-ß-gal) staining, the CyBC9 assay is rapid (2 h) and nontoxic and can thus be applied to live cells. It is shown that CyBC9 is able to stain early and late senescent populations both in monolayer- and in microcarrier-based cultures. Finally, to investigate the mechanism of CyBC9, colocalization assays are performed and it is found that CyBC9 is accumulated in the mitochondria of senescent MSCs presumably due to the loss of membrane potential. Taken together, it is expected that CyBC9 will be a useful tool to ameliorate cell therapy through rapid and early screening of senescent phenotypes in clinically relevant MSCs.

Unraveling the Inconsistencies of Cardiac Differentiation Efficiency Induced by the GSK3ß Inhibitor CHIR99021 in Human Pluripotent Stem Cells.

Cardiac differentiation efficiency is hampered by inconsistencies and low reproducibility. We analyzed the differentiation process of multiple human pluripotent stem cell (hPSC) lines in response to dynamic GSK3ß inhibition under varying cell culture conditions. hPSCs showed strong differences in cell-cycle profiles with varying culture confluency. hPSCs with a higher percentage of cells in the G1 phase of the cell cycle exhibited cell death and required lower doses of GSK3ß inhibitors to induce cardiac differentiation. GSK3ß inhibition initiated cell-cycle progression via cyclin D1 and modulated both Wnt signaling and the transcription factor (TCF) levels, resulting in accelerated or delayed mesoderm differentiation. The TCF levels were key regulators during hPSC differentiation with CHIR99021. Our results explain how differences in hPSC lines and culture conditions impact cell death and cardiac differentiation. By analyzing the cell cycle, we were able to select for highly cardiogenic hPSC lines and increase the experimental reproducibility by predicting differentiation outcomes.

New aspects of the regulation of glycosphingolipid receptor function.

We propose that the fatty acid heterogeneity of glycosphingolipids may compensate for the relative few and simple glycosphingolipid structures found in mammalian cells. Variation in GSL fatty acid composition may mediate aglycone regulation of GSL membrane receptor function by a differential interaction with cholesterol and other membrane components which may be differentially organized within plasma membrane lipid domains. These concepts are specifically illustrated in model membrane studies and in relation to the role of the glycolipid, globotriaosyl ceramide (Gb(3)) in verotoxin-induced renal pathology and gp120 binding in HIV infection.

Detergent-resistant globotriaosyl ceramide may define verotoxin/glomeruli-restricted hemolytic uremic syndrome pathology.

Verotoxin binding to its receptor, globotriaosyl ceramide(Gb(3)) mediates the glomerular pathology of hemolytic uremic syndrome, but Gb(3) is expressed in both tubular and glomerular cells. Gb(3) within detergent-resistant membranes, an index of glycolipid-cholesterol enriched lipid rafts, is required for in vitro cytotoxicity. We found that verotoxin 1 and 2 binding to human adult renal glomeruli is detergent resistant, whereas the strong verotoxin binding to renal tubules is detergent sensitive. Verotoxin binding to pediatric glomeruli was detergent resistant but binding to adult glomeruli was enhanced, remarkably for some samples, by detergent extraction. Detergent-sensitive glomerular components may provide age-related protection against verotoxin glomerular binding. Mouse glomeruli remained verotoxin unreactive after detergent extraction, whereas tubular binding was lost. Cholesterol extraction induced strong verotoxin binding in poorly reactive adult glomeruli, suggesting cholesterol can mask Gb(3) in glomerular lipid rafts. Binding of the human immunodeficiency virus (HIV) adhesin, gp120 (another Gb(3) ligand) was detergent sensitive, tubule-restricted, and inhibited by verotoxin B subunit pretreatment, and may relate to HIV nephropathy. Our study shows that differential membrane Gb(3) organization in glomeruli and tubules provides a basis for the age- and glomerular-restricted pathology of hemolytic uremic syndrome.

Alterations of cell adhesion molecules in human glomerular endothelial cells in response to nephritis-associated plasminogen receptor.

BACKGROUND: Acute post-streptococcal glomerulonephritis (APSGN) is induced by glomerular deposition of nephritogenic streptococcal antigen-antibody complexes. Recently, a streptococcal antigen, nephritis-associated plasminogen receptor (NAPlr) was purified from ruptured streptococcal cell supernatants (RCS). However, the cellular and molecular mechanisms of NAPlr action on the glomerular vas culature are still unknown. METHODS: Expression of cell adhesion molecules were measured by cellular ELISA (enzyme-linked immunosorbent assay), immunofluorescence microscopy and Western blot analysis. RESULTS: RCS and NAPlr significantly decreased the PECAM-1 expression in human glomerular endothelial cells (HGECs) as compared to that in the control cells. Plasminogen treatment reversed the RCS or NAPlr-induced decrease of PECAM-1 expression and increase of MCP-1 expression. Immunofluorescent microscopy and Western blot analysis also showed that PECAM-1 expression in HGECs was downregulated upon treatment with RCS or NAPlr and this effect was reversed by plasminogen treatment. Furthermore, we found that tumor necrosis factor-alpha production in culture medium of HGECs was increased at the lower level when the culture system was treated with RCS. CONCLUSION: RCS and NAPlr modulated PECAM-1 expression and MCP-1 production in HGECs, indicating the involvement of NAPlr in inflammatory cell accumulation in glomerular tufts and functional abnormality of glomerular microvasculature such as hyperpermeability.

Bone marrow cells contribute to regeneration of damaged glomerular endothelial cells.

BACKGROUND: There is accumulating evidence that adult bone marrow (BM) cells show unexpected plasticity, and can differentiate into a wide range of specialized cells. In the case of intrinsic renal glomerular cells, BM-derived cells have been reported to differentiate into both mesangial cells and podocytes. However, there is controversy on recruitment of glomerular endothelial cells, although endothelial cells in other tissues are known to be recruited from the BM. METHODS: Sprague-Dawley (SD) rats and SD rats made chimeric by transplantation of bone marrow cells from enhanced green fluorescent protein (EGFP) transgenic littermate rats, were injected with anti-Thy-1.1 antibody, followed by unilateral nephrectomy (1-kidney model). Chimeric rats used in 1-kidney model were sacrificed for histologic examination at weeks 2, 4, 8, and 11. We examined isolated glomeruli and frozen sections of kidneys from rats of each group at weeks 2 and 11 by confocal laser scan microsopy (CLSM), both immunohistologically and three dimensionally. RESULTS: In the 1-kidney group, using chimeric rats transplanted with EGFP(+) bone marrow cells, most rats died, presumably of uremia, after 8 to 11 weeks. A CLSM study using isolated glomeruli and frozen sections of kidneys revealed that bone marrow-derived PECAM-1(+), RECA-1(+) cells, and OX-7(+) cells contributed to the structural support for the glomerular capillaries during the chronic course. Global glomerular sclerotic lesions and diffuse tubular atrophic changes, with interstitial cell infiltration, were remarkable at weeks 8 and 11. CONCLUSION: Bone marrow-derived endothelial progenitor cells participated in glomerular endothelial cell turnover after severe damage. Treatment that could target bone marrow-derived endothelial progenitor cells and promote angiogenesis in regions of progressive glomerular lesions may be a promising therapeutic approach for preventing end-stage renal disease.