| 1. |
- Lindskog, Henrik, 1977, et al.
(författare)
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New insights to vascular smooth muscle cell and pericyte differentiation of mouse embryonic stem cells in vitro.
- 2006
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Ingår i: Arteriosclerosis, thrombosis, and vascular biology. - 1524-4636. ; 26:7, s. 1457-64
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The molecular mechanisms that regulate pericyte differentiation are not well understood, partly because of the lack of well-characterized in vitro systems that model this process. In this article, we develop a mouse embryonic stem (ES) cell-based angiogenesis/vasculogenesis assay and characterize the system for vascular smooth muscle cell (VSMC) and pericyte differentiation. METHODS AND RESULTS: ES cells that were cultured for 5 days on OP9 stroma cells upregulated their transcription of VSMC and pericyte selective genes. Other SMC marker genes were induced at a later time point, which suggests that vascular SMC/pericyte genes are regulated by a separate mechanism. Moreover, sequence analysis failed to identify any conserved CArG elements in the vascular SMC and pericyte gene promoters, which indicates that serum response factor is not involved in their regulation. Gleevec, a tyrosine kinase inhibitor that blocks platelet-derived growth factor (PDGF) spell-receptor signaling, and a neutralizing antibody against transforming growth factor (TGF) beta1, beta2, and beta3 failed to inhibit the induction of vascular SMC/pericyte genes. Finally, ES-derived vascular sprouts recruited cocultured MEF cells to pericyte-typical locations. The recruited cells activated expression of a VSMC- and pericyte-specific reporter gene. CONCLUSIONS: We conclude that OP9 stroma cells induce pericyte differentiation of cocultured mouse ES cells. The induction of pericyte marker genes is temporally separated from the induction of SMC genes and does not require platelet-derived growth factor B or TGFbeta1 signaling.
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| 2. |
- Petit, Marleen MR, et al.
(författare)
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Smooth muscle expression of lipoma preferred partner is mediated by an alternative intronic promoter that is regulated by serum response factor/myocardin.
- 2008
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Ingår i: Circulation research. - 1524-4571. ; 103:1, s. 61-9
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Tidskriftsartikel (refereegranskat)abstract
- Lipoma preferred partner (LPP) was recently recognized as a smooth muscle marker that plays a role in smooth muscle cell migration. In this report, we focus on the transcriptional regulation of the LPP gene. In particular, we investigate whether LPP is directly regulated by serum response factor (SRF). We show that the LPP gene contains 3 evolutionarily conserved CArG boxes and that 1 of these is part of an alternative promoter in intron 2. Quantitative RT-PCR shows that this alternative promoter directs transcription specifically to smooth muscle containing tissues in vivo. By using chromatin immunoprecipitation, we demonstrate that 2 of the CArG boxes, including the promoter-associated CArG box, bind to endogenous SRF in cultured aortic smooth muscle cells. Electrophoretic mobility-shift assays show that the conserved CArG boxes bind SRF in vitro. In reporter experiments, we show that the alternative promoter has transcriptional capacity that is dependent on SRF/myocardin and that the promoter associated CArG box is required for that activity. Finally, we show by quantitative RT-PCR that the alternative promoter is strongly downregulated in SRF-deficient embryonic stem cells and in smooth muscle tissues derived from conditional SRF knockout mice. Collectively, our data demonstrate that expression of LPP in smooth muscle is mediated by an alternative promoter that is regulated by SRF/myocardin.
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| 3. |
- Breuer, Silke, et al.
(författare)
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Introduction of embryonic stem cells into vein grafts reduces intimal hyperplasia in mice.
- 2014
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Ingår i: The Journal of cardiovascular surgery. - 0021-9509. ; 55:2, s. 235-46
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Atherosclerosis with its cardiovascular events including cardiac and peripheral ischemia represents the main cause of death in the developed countries. Although interventional treatments like percutaneous transluminal angioplasty (PTA) or stents are increasingly applied for the treatment of peripheral arterial disease, they are not always technically applicable or durable and bypass surgery is needed. Compared to synthetic grafts, vein grafts show a better patency especially when used for the lower leg as well as a lower risk for infection compared to synthetic grafts. Still the long-term patency rates are unsatisfactory due to accelerated intimal hyperplasia, a thickening of the vessel wall. The aim of this study was to elucidate, if the implantation of embryonic stem cells into vein grafts can reduce the development of intimal hyperplasia in a mouse in vivo model. Methods: In this study we implanted LacZ-tagged (ROSA26) murine embryonic stem cells into decellularized vein grafts. Control groups were: 1) untreated veins; 2) decellularized veins; 3) decellularized veins with gel and plastic film; and 4) decellularized veins with smooth muscle cells in gel surrounded by plastic film. Six weeks after insertion into the carotid artery of mice, the grafts were excised and analyzed immunohistochemically, morphologically, and by x-gal staining and compared to the control groups. The Mann-Whitney-U test was used to compare groups. Statistical significance was indicated by a value of P<0.05. Results: Decellularized veins with implanted stem cells showed significantly less intimal thickening compared to all control groups (intimal hyperplasia vs. luminal circumference mean±SD 7.3±3.5 µm, median 8 µm). The control groups: 1) untreated veins (60.3±25.5 µm, median 58.5 µm); 2) decellularized veins (53.9±22.4 µm, median 48.4 µm); 3) decellularized veins with gel and plastic film (70.6±22.4 µm, median 72.6 µm); and 4) decellularized veins with smooth muscle cells in gel surrounded by plastic film (73.5±18.1 µm, median 73.6 µm) all showed the same high degree of intimal hyperplasia. Conclusion: This study demonstrates that embryonic stem cells have a therapeutic competence to favourably modulate intimal hyperplasia in vivo.
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| 4. |
- Lindskog, Henrik, 1977
(författare)
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Regulation of the vascular smooth muscle cell phenotype
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Smooth muscle cells (SMC) are present in many internal organs such as the blood vessels and the gastrointestinal channel. Their main functions are to provide stability to the tissue and to provide contractile capability. SMC are not terminally differentiated but can switch between several phenotypes, which is also known as phenotypic modulation. Unfavourable SMC phenotypes have been proposed to contribute to pathological processes such as atherosclerosis and asthma. The focus of this thesis has been to further elucidate the mechanisms that regulate gene expression in vascular SMC (VSMC).We developed a vascular differentiation system based on mouse embryonic stem cells and confirmed differentiation of VSMC as shown by expression of several marker genes. Moreover, VSMC markers and SMC markers were independently regulated in this system, which correlated with absence of CArG boxes in VSMC gene promoters. We could finally show that PDGF-B and TGFâ1, two molecules that have been implicated in VSMC development, were dispensable for VSMC differentiation.We have previously identified lipoma preferred partner (LPP) as a SMC-selective gene, and investigated its transcriptional regulation. We identified three evolutionary conserved CArG boxes and showed that two of these bind SRF in vivo. We further identified an alternative promoter that is regulated by one of the CArG boxes as indicated in reporter assays. We finally show that the alternative promoter directs expression specifically to SMC in vivo.Finally, the role of zinc finger protein 148 (ZFP148) as a regulator of extra-cellular matrix (ECM) gene expression was examined. Potential binding sites for ZFP148 were overrepresented in the promoter regions of 51 genes involved in production and regulation of ECM. We confirmed binding of ZFP148 to 10 ECM genes in vitro. siRNA-knockdown of zfp148 did however not affect the regulation of ECM genes in primary VSMC as indicated by quantitative PCR. Two genes, cspg4 and col5a1, were upregulated in the siRNA treated cells, which indicates that they might be regulated by ZFP148.
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| 5. |
- Olsson, Henrik, et al.
(författare)
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Estimating diagnostic uncertainty in artificial intelligence assisted pathology using conformal prediction
- 2022
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Unreliable predictions can occur when an artificial intelligence (AI) system is presented with data it has not been exposed to during training. We demonstrate the use of conformal prediction to detect unreliable predictions, using histopathological diagnosis and grading of prostate biopsies as example. We digitized 7788 prostate biopsies from 1192 men in the STHLM3 diagnostic study, used for training, and 3059 biopsies from 676 men used for testing. With conformal prediction, 1 in 794 (0.1%) predictions is incorrect for cancer diagnosis (compared to 14 errors [2%] without conformal prediction) while 175 (22%) of the predictions are flagged as unreliable when the AI-system is presented with new data from the same lab and scanner that it was trained on. Conformal prediction could with small samples (N = 49 for external scanner, N = 10 for external lab and scanner, and N = 12 for external lab, scanner and pathology assessment) detect systematic differences in external data leading to worse predictive performance. The AI-system with conformal prediction commits 3 (2%) errors for cancer detection in cases of atypical prostate tissue compared to 44 (25%) without conformal prediction, while the system flags 143 (80%) unreliable predictions. We conclude that conformal prediction can increase patient safety of AI-systems.
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| 6. |
- Perman, Jeanna, 1981, et al.
(författare)
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The VLDL receptor promotes lipotoxicity and increases mortality in mice following an acute myocardial infarction.
- 2011
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Ingår i: The Journal of clinical investigation. - : American Society for Clinical Investigation. - 1558-8238 .- 0021-9738. ; 121:7, s. 2625-40
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Tidskriftsartikel (refereegranskat)abstract
- Impaired cardiac function is associated with myocardial triglyceride accumulation, but it is not clear how the lipids accumulate or whether this accumulation is detrimental. Here we show that hypoxia/ischemia-induced accumulation of lipids in HL-1 cardiomyocytes and mouse hearts is dependent on expression of the VLDL receptor (VLDLR). Hypoxia-induced VLDLR expression in HL-1 cells was dependent on HIF-1α through its interaction with a hypoxia-responsive element in the Vldlr promoter, and VLDLR promoted the endocytosis of lipoproteins. Furthermore, VLDLR expression was higher in ischemic compared with nonischemic left ventricles from human hearts and was correlated with the total lipid droplet area in the cardiomyocytes. Importantly, Vldlr-/- mice showed improved survival and decreased infarct area following an induced myocardial infarction. ER stress, which leads to apoptosis, is known to be involved in ischemic heart disease. We found that ischemia-induced ER stress and apoptosis in mouse hearts were reduced in Vldlr-/- mice and in mice treated with antibodies specific for VLDLR. These findings suggest that VLDLR-induced lipid accumulation in the ischemic heart worsens survival by increasing ER stress and apoptosis.
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