Telocytes in the human ascending aorta: Characterization and exosome-related KLF-4/VEGF-A expression.

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-ß, CD29/integrin ß-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.

To Be Or Not to Be: the "Smoker's Paradox" - An in-Vitro Study.

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'.

Serum-dependent processing of late apoptotic cells and their immunogenicity.

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.