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Cardiomyocytes display low mitochondrial priming and are highly resistant toward cytotoxic T-cell killing.

ABSTRACT: Following heart transplantation, alloimmune responses can cause graft rejection by damaging donor vascular and parenchymal cells. However, it remains unclear whether cardiomyocytes are also directly killed by immune cells. Here, we used two-photon microscopy to investigate how graft-specific effector CD8(+) T cells interact with cardiomyocytes in a mouse heart transplantation model. Surprisingly, we observed that CD8(+) T cells are completely impaired in killing cardiomyocytes. Even after virus-mediated preactivation, antigen-specific CD8(+) T cells largely fail to lyse these cells although both cell types engage in dynamic interactions. Furthermore, we established a two-photon microscopy-based assay using intact myocardium to determine the susceptibility of cardiomyocytes to undergo apoptosis. This feature, also known as mitochondrial priming reveals an unexpected weak predisposition of cardiomyocytes to undergo apoptosis in situ. These observations together with the early exhaustion phenotype of graft-infiltrating specific T cells provide an explanation why cardiomyocytes are largely protected from direct CD8(+) T-cell-mediated killing.

SUBMITTER: Zheng X

PROVIDER: S-EPMC5071700 | biostudies-other | 2016 Jun

REPOSITORIES: biostudies-other

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Cardiomyocytes display low mitochondrial priming and are highly resistant toward cytotoxic T-cell killing.

Zheng Xiang X Halle Stephan S Yu Kai K Mishra Pooja P Scherr Michaela M Pietzsch Stefan S Willenzon Stefanie S Janssen Anika A Boelter Jasmin J Hilfiker-Kleiner Denise D Eder Matthias M Förster Reinhold R

European journal of immunology 20160331 6

Following heart transplantation, alloimmune responses can cause graft rejection by damaging donor vascular and parenchymal cells. However, it remains unclear whether cardiomyocytes are also directly killed by immune cells. Here, we used two-photon microscopy to investigate how graft-specific effector CD8(+) T cells interact with cardiomyocytes in a mouse heart transplantation model. Surprisingly, we observed that CD8(+) T cells are completely impaired in killing cardiomyocytes. Even after virus- ...[more]

PMID: 26970349

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Project description:Human embryonic and induced pluripotent stem cells (hESCs/iPSCs) are promising cell sources for cardiac regenerative medicine. To realize hESC/iPSC-based cardiac cell therapy, efficient induction, purification, and transplantation methods for cardiomyocytes should be required. Though marker gene transduction or fluorescent-based purification methods were reported, fast, efficient and scalable purification methods with no genetic modification are essential for clinical purposes but have not been established yet. In this study, we used microarrays to detail the global gene program during cardiac differentiation and to identify cardiac-specific cell surface markers. hiPSCs (201B6) were differentiated toward cardiomyocytes using a modified-directed differentiation protocol (high density culture in RPMI+B27-insulin, sequential administration of Activin A 100ng/mL 1 day, BMP4 10ng/mL+bFGF 10ng/mL 4 days, and Dkk1 100ng/mL 2 days). Beating clusters were first observed at day 8-9 and spread by day 11 after Activin A administration. Cardiac troponin-T (cTnT)-positive cells appeared at day 7-8 after induction and were observed in 30-70% of cells at day 11. qPCR and genome-wide analysis reflected differentiation processes from the undifferentiated state to cardiomyocytes. Rapid downregulation of pluripotent stem cell markers such as NANOG and POU5F1 was observed within 2 days of differentiation. Early and cardiac mesodermal genes (T, MESP1, KDR, ISL1) were expressed during day 2-5, and cardiac genes (NKX2-5, MYH6, MYH7, MYL2, and MYL7) were expressed after day 7. We identified VCAM1 as a cardiac-specific cell surface marker by microarray and flow cytometry. Human induced pluripotent stem cells (iPSCs; 201B6) were differentiated toward cardiomyocytes (RPMI+B27 medium supplemented d0-1 Activin A, d1-5 BMP4+bFGF, d5-7 Dkk1). RNA was extracted from cells at day 0, day 2, day 5, day 7, day 9, and day 11. Cardiomyocytes appeared after day 7 and reached about 50% of total cells at day 11.

Project description:OBJECTIVE:In vitro production of a definitive endoderm (DE) is an important issue in stem cell-related differentiation studies and it can assist with the production of more efficient endoderm derivatives for therapeutic applications. Despite tremendous progress in DE differentiation of human embryonic stem cells (hESCs), researchers have yet to discover universal, efficient and cost-effective protocols. MATERIALS AND METHODS:In this experimental study, we have treated hESCs with 200 nM of Stauprimide (Spd) for one day followed by activin A (50 ng/ml; A50) for the next three days (Spd-A50). In the positive control group, hESCs were treated with Wnt3a (25 ng/ml) and activin A (100 ng/ml) for the first day followed by activin A for the next three days (100 ng/ml; W/A100-A100). RESULTS:Gene expression analysis showed up regulation of DE-specific marker genes (SOX17, FOXA2 and CXCR4) comparable to that observed in the positive control group. Expression of the other lineage specific markers did not significantly change (p<0.05). We also obtained the same gene expression results using another hESC line. The use of higher concentrations of Spd (400 and 800 nM) in the Spd-A50 protocol caused an increase in the expression SOX17 as well as a dramatic increase in mortality rate of the hESCs. A lower concentration of activin A (25 ng/ml) was not able to up regulate the DE-specific marker genes. Then, A50 was replaced by inducers of definitive endoderm; IDE1/2 (IDE1 and IDE2), two previously reported small molecule (SM) inducers of DE, in our protocol (Spd-IDE1/2). This replacement resulted in the up regulation of visceral endoderm (VE) marker (SOX7) but not DE-specific markers. Therefore, while the Spd-A50 protocol led to DE production, we have shown that IDE1/2 could not fully replace activin A in DE induction of hESCs. CONCLUSION:These findings can assist with the design of more efficient chemically-defined protocols for DE induction of hESCs and lead to a better understanding of the different signaling networks that are involved in DE differentiation of hESCs.

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Cardiomyocytes display low mitochondrial priming and are highly resistant toward cytotoxic T-cell killing.

Publications

Cardiomyocytes display low mitochondrial priming and are highly resistant toward cytotoxic T-cell killing.

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