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Telocytes (TCs), a novel interstitial cell entity promoting tissue regeneration, have been described in various tissues. Their role in inter‐cellular signalling and tissue remodelling has been reported in almost all human tissues. This study hypothesizes that TC also contributes to tissue remodelling and regeneration of the human thoracic aorta (HTA). The understanding of tissue homeostasis and regenerative potential of the HTA is of high clinical interest as it plays a crucial role in pathogenesis from aortic dilatation to lethal dissection. Therefore, we obtained twenty‐five aortic specimens of heart donors during transplantation. The presence of TCs was detected in different layers of aortic tissue and characterized by immunofluorescence and transmission electron microscopy. Further, we cultivated and isolated TCs in highly differentiated form identified by positive staining for CD34 and c‐kit. Aortic‐derived TC was characterized by the expression of PDGFR‐α, PDGFR‐β, CD29/integrin β‐1 and αSMA and the stem cell markers Nanog and KLF‐4. Moreover, TC exosomes were isolated and characterized for soluble angiogenic factors by Western blot. CD34+/c‐kit+ TCs shed exosomes containing the soluble factors VEGF‐A, KLF‐4 and PDGF‐A. In summary, TC occurs in the aortic wall. Correspondingly, exosomes, derived from aortic TCs, contain vasculogenesis‐relevant proteins. Understanding the regulation of TC‐mediated aortic remodelling may be a crucial step towards designing strategies to promote aortic repair and prevent adverse remodelling.

Background/Aims: Clinical studies have reported a better outcome of smokers after myocardial infarction compared to non-smokers. The data are controversial, as some clinical studies did not observe this effect. The cell biological processes involved, which might account for a ‘Smoker’s Paradox’, have not been investigated yet. Therefore, the aim was to elucidate the effect of cigarette smoke on the viability of cardiomyocytes in the context of hypoxia and reperfusion. Methods: HL-1 cells were incubated with different concentrations of cigarette smoke extract (CSE) and subjected to hypoxia/reperfusion to further evaluate influence of CSE on viability of HL-1 cells using flow cytometry analyses, Western Blot and immunofluorescence staining. Results: Incubation with CSE led to a concentration-dependent reduction in HL-1 viability. Adding hypoxia as a stressor enhanced cell death. Caspase-independent apoptosis was the observed type of cell death partly induced by P53 and apoptosis-inducing-factor. Yet a significant increase in LDH release in cardiomyocytes incubated with 4%, 8% and 16% CSE suggests necrosis with rapid DNA depletion. Interestingly, after hypoxia a decreased LDH release under lower CSE concentrations was observed. Moreover, a concentration-dependent increase in proliferation and a trend for increased ATP availability under hypoxic conditions was shown. Conclusions: The trend for less LDH release in hypoxia after low-level CSE incubation might represent a switch from necrosis to apoptosis, which in combination with the increase in metabolic activity and ATP availability might account for the ‘Smoker’s Paradox’. These findings could partly explain inconsistent results of previous clinical studies as the data showed strong evidence for the crucial relevance of the amount of cigarettes smoked. We are in need of future studies distinguishing between different types of smokers to finally verify or falsify the ‘Smoker’s Paradox’.

Pathological impairment of elastic fiber and other extracellular matrix (ECM) components are described for the aortic media of ascending thoracic aortic aneurysms (aTAA) but the exact pathological impairment of the structure and its degree still needs further investigations. To evaluate the quantity and quality of elastic fiber sheets and other ECM structures (e.g. collagen), cells were removed from different types of aneurysmal tissues (tricuspid aortic valve [TAV] associated-, bicuspid aortic valve [BAV] associated-aneurysmal tissue and acute aortic dissections [AAD]) using 2.5% sodium hydroxide (NaOH) and compared to decellularized control aortic tissue. Likewise, native tissue has been analysed. To evaluate the 2D- (histological evaluation, fluorescence- and auto-fluorescence based staining methods) and the 3D structure (scanning electron microscopic [SEM] examination) of the medial layer we first analysed for a successful decellularization. After proving for successful decellularization, we quantified the amount of elastic fiber sheets, elastin and other ECM components including collagen. Aside from clearly visible focal elastic fiber loss in TAV-aTAA tissue, decellularization resulted in reduction of elastic fiber auto-fluorescence properties, which is perhaps an indication from a disease-related qualitative impairment of elastic fibers, visible only after contact with the alkaline solution. Likewise, the loss of collagen amount in BAV-aTAA and TAV-aTAA tissue (compared to non-decellularized tissue) after contact with NaOH indicates a prior disease-associated impairment of collagen. Although the amount of ECM was not changed in type A dissection tissue, detailed electron microscopic evaluation revealed changes in ECM quality, which worsened after contact with alkaline solution but were not visible after histological analyses. Apart from the improved observation of the samples using electron microscopy, contact of aneurysmal and dissected tissue with the alkaline decellularization solution revealed potential disease related changes in ECM quality which can partly be connected to already published data, but have to be proven by further studies.

The influence of an acellular porcine matrix on proinflammatory activation of endothelial cells (EC) during normoxia and hypoxia was investigated by a newly established semi-quantitative electron microscopic procedure. As a model, three adhesion molecules (E-selectin, ICAM-1, and VCAM-1) were localized by silver-enhanced immunogold staining and energy dispersive X-ray microanalysis after normoxic or hypoxic pretreatment of the cells and subsequent stimulation with IL-1beta. Morphology of EC grown on porcine matrix or coverslips was recorded simultaneously using secondary electron imaging. EC appeared tightly attached to the underlying surfaces with their typical cobblestone-like morphology. Statistically significant upregulations upon stimulation with IL-1beta were observed in both groups for all three adhesion molecules. Hypoxic pretreatment of the specimens with subsequent reoxygenation neither induced morphological changes nor caused an upregulation of adhesion molecule expression in cells grown on acellular porcine tissue. Unexpectedly, in cells seeded onto the acellular matrix, IL-1beta failed to upregulate ICAM-1 expression after a short period of hypoxia. The surface expression of VCAM-1 was also significantly lower even under normoxic conditions, which might indicate the development of functional impairment of cells in contact with acellular porcine tissue. The method presented in this study has proven valuable for the determination of antigen expression on scaffold materials in parallel with the characterization of surface morphology.

The execution phase of apoptosis involves many processes which modify cellular molecules for an efficient and quiet elimination of the dead cell. These include exposure and secretion of "eat-me" signals, to attract phagocytes, as well as degradation of immune-stimulating cell debris. During this phase apoptotic microparticles (MPs) are released from the dying cell. The remaining cell remnant forms large late apoptotic cell-derived membranous vesicles (ACMV(L)) on its surface which remain attached. Phagocytosis is enhanced by cell non-autonomous factors such as complement component C1q and serum DNase I. We studied the formation and retraction of ACMV(L) and the influence of serum on their dynamics. We furthermore investigated the immunogenicity of cell remnants compared to released MPs. ACMV(L) were examined using time-lapse, electron microscopy and confocal microscopy. These blebs were observed on cell remnants with intact and with permeable membrane. This suggests that ACMV(L) remain on the surface by the time the cell remnant enters secondary necrosis. Bleb retraction could also be observed, but was radically enhanced in the presence of serum. Additionally, MPs stimulate peripheral blood mononuclear cells to produce similar IL-1beta, IL-6, IL-8, IL-10, and TNF-alpha levels as LPS. In contrast, cell remnants only induce high levels of IL-8. These data show that cell non-autonomous factors contribute to morphological rearrangements during late apoptosis. In addition, they implicate that apoptotic MPs are released to attract phagocytes, while apoptotic cell remnants further process their potentially immunogenic content to prevent an inflammatory response upon secondary necrosis.

We examined the potential of a trans-coronary sinus catheter intervention activating endothelium to induce angiogenesis and the potential of temporal coronary venous pressure elevation (PICSO) to initiate cardiac repair in an ischemia/reperfusion model. 32 open chest pigs were divided: sham

Background— Tissue-engineered or decellularized heart valves have already been implanted in humans or are currently approaching the clinical setting. The aim of this study was to examine the migratory response of human monocytic cells toward decellularized porcine and human heart valves, a pivotal step in the early immunologic reaction. Methods and Results— Porcine and human pulmonary valve conduits were decellularized, and migration of U-937 monocytic cells toward extracted heart valve proteins was examined in a transmigration chamber in vitro. Homogenized tissue specimens were size fractionated by SDS-PAGE. The decellularization procedure effectively reduced the migration of human monocytes toward all heart valve tissue. However, only the antigen reduction of human pulmonary valves abolished the monocytic response (wall, 0.88±0.19% versus 30.20±3.93% migrated cells [mean±SEM]; cusps, 0.10±0.06% versus 10.24±1.83%) and was significantly lower ( P Conclusions— We describe for the first time that the remaining potential of decellularized pulmonary heart valves to attract monocytic cells depends strongly on whether porcine or human scaffolds were used. These findings will have an important impact on further investigations in the field of heart valve tissue engineering.

Cigarette smoking is one of the most important and preventable risk factors for atherosclerosis. However, because of the complex composition of cigarette smoke, the detailed pathophysiological mechanisms are not fully understood. Based on controversial reports on the pro-atherogenic activity of cigarette smoke condensate, also called tar fraction (CSC), we decided to analyse the effects of CSC on the viability of endothelial cells in vitro. The results of this study show that low concentrations of the hydrophobic tar fraction induces DNA damage resulting in a P53-dependent and BCL-XL-inhibitable death cascade. Western blot analyses showed that this cascade is caspase-independent and immunofluorescence analysis have shown that the apoptotic death signalling is mediated by the release of apoptosis-inducing factor. Higher CSC concentrations also induce apoptotic-like signalling but the signalling cascade is then redirected to necrosis. Despite the fact that CSC induces a profound increase in cellular reactive oxygen species production, antioxidants exhibit only a minimal cell death protective effect. Our data indicates that not only hydrophilic constituents of cigarette smoke extract, but also CSC is harmful to endothelial cells. The mode and the outcome of CSC-induced cell death signalling are highly concentration dependent: lower concentrations induce caspase-independent apoptosis-like cell death, whereas incubation with higher concentrations interrupts apoptotic signalling and induces necrosis.