BackgroundRecent studies show that exosomes are involved in intercellular communication and that abundant circular RNAs (circRNAs) are present within exosomes. However, whether these exosomal circRNAs contribute to tumor invasion and metastasis remains unclear, as do their associated mechanisms.MethodsQuantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to measure the expression levels of circ-IARS in 85 pancreatic ductal adenocarcinoma (PDAC) tissues, plasma exosomes, and Hs 766 T, Hs 766 T-L2 and human microvascular vein endothelial (HUVECs) cells. RhoA, ZO-1 and RhoA-GTP levels were detected by qRT-PCR and western blotting (WB); RhoA activity analysis was also performed. Transwell assays were performed to examine changes in endothelial monolayer permeability, and immunofluorescence and WB were employed to evaluate F-actin expression and focal adhesion. Finally, an animal experiment was performed to detect the contribution of circ-IARS to cancer metastasis.Resultscirc-IARS expression was up-regulated in pancreatic cancer tissues and in plasma exosomes of patients with metastatic disease. Circ-IARS was found to enter HUVECs through exosomes and promote tumor invasion and metastasis. Circ-IARS expression was positively correlated with liver metastasis, vascular invasion, and tumor-node-metastasis (TNM) stage and negatively correlated with postoperative survival time. Overexpression of circ-IARS significantly down-regulated miR-122 and ZO-1 levels, up-regulated RhoA and RhoA-GTP levels, increased F-actin expression and focal adhesion, enhanced endothelial monolayer permeability, and promoted tumor invasion and metastasis.Conclusionscirc-IRAS accesses HUVECs via exosomes derived from pancreatic cancer cells followed by increased endothelial monolayer permeability. Furthermore, this process promotes tumor invasion and metastasis. The results of this study suggest that the presence of circRNAs in exosomes may be important indicator for early diagnosis and prognostic prediction in PDAC.Electronic supplementary materialThe online version of this article (10.1186/s13046-018-0822-3) contains supplementary material, which is available to authorized users.

Rationale: Fibroblasts are believed to be the major cells responsible for the production and maintenance of extracellular matrix. Alterations in fibroblast functional capacity, therefore, could play a role in the pathogenesis of pulmonary emphysema, which is characterized by inadequate maintenance of tissue structure. Objectives: To evaluate the hypothesis that deficient fibroblast repair characterizes cells obtained from individuals with chronic obstructive pulmonary disease (COPD) compared with control subjects. Methods: Fibroblasts were cultured from lung tissue obtained from individuals undergoing thoracotomy and were characterized in vitro. Measurements and Main Results: Fibroblasts from individuals with COPD, defined by reduced FEV 1 , manifested reduced chemotaxis toward fibronectin and reduced contraction of three-dimensional collagen gels, two bioassays associated with fibroblast repair function. At least two mechanisms appear to account for these differences. Prostaglandin E (PGE), a known inhibitor of fibroblast repair functions, was produced in increased amount by fibroblasts from subjects with COPD, which also expressed increased amounts of the receptors EP2 and EP4, both of which signal through cyclic AMP. Incubation of fibroblasts with indomethacin or with the PKA inhibitor KT-5720 partially restored COPD subject fibroblast function. In addition, fibroblasts from subjects with COPD produced more transforming growth factor (TGF)-b1, but manifested reduced response to TGF-b1. The functional alterations in fibroblasts correlated with both lung function assessed by FEV 1 and, for the data available, with severity of emphysema assessed by DL CO . Conclusions: Fibroblasts from individuals with COPD have reduced capability to sustain tissue repair, which suggests that this may be one mechanism that contributes to the development of emphysema.

miR-146a seems to play a pathogenetic role in the abnormal inflammatory response in COPD. Increased half-life of inflammatory mRNAs is a mechanism of abnormal inflammation in this disease.

is a matrix-degrading enzyme implicated in many biological processes, including inflammation. It is produced by many cells, including fibroblasts. When cultured in three-dimensional (3D) collagen gels, fibroblasts contract the surrounding matrix, a function that is thought to model the contraction that characterizes both normal wound repair and fibrosis. The current study was designed to evaluate the role of endogenously produced MMP-9 in fibroblast contraction of 3D collagen gels. Fibroblasts from mice lacking expression of MMP-9 and human lung fibroblasts (HFL-1) transfected with MMP-9 smallinterfering RNA (siRNA) were used. Fibroblasts were cast into type I collagen gels and floated in culture medium with or without transforming growth factor (TGF)-␤1 for 5 days. Gel size was determined daily using an image analysis system. Gels made from MMP-9 siRNA-treated human fibroblasts contracted less than control fibroblasts, as did fibroblasts incubated with a nonspecific MMP inhibitor. Similarly, fibroblasts cultured from MMP-9-deficient mice contracted gels less than did fibroblasts from control mice. Transfection of the MMP-9-deficient murine fibroblasts with a vector expressing murine MMP-9 restored contractile activity to MMP-9-deficient fibroblasts. Inhibition of MMP-9 reduced active TGF-␤1 and reduced several TGF-␤1-driven responses, including activity of a Smad3 reporter gene and production of fibronectin. Because TGF-␤1 also drives fibroblast gel contraction, this suggests the mechanism for MMP-9 regulation of contraction is through the generation of active TGF-␤1. This study provides direct evidence that endogenously produced MMP-9 has a role in regulation of tissue contraction of 3D collagen gels mediated by fibroblasts. lung; repair; transforming growth factor-␤

Bone marrow (stem/progenitor) cells have been shown to "differentiate" into cells in multiple tissues, including lung. A low number of hematopoietic stem/progenitor cells also circulate in peripheral blood. The physiologic roles of these cells are still uncertain. This study was designed to test, using parabiotic mice that were joined surgically, whether stem/progenitor cells in blood contributed to the regeneration of lung after injury. Parabiotic mice were generated surgically by joining green fluorescent protein transgenic mice and wild-type littermates. These mice developed a common circulation (approximately 50% green cells in blood) by 2 weeks after surgery. The wild-type mouse was either uninjured or lethally irradiated or received intratracheal elastase or the combination of radiation with intratracheal elastase injection. Radiation or the combination of radiation with elastase significantly increased the proportion of bright green cells in the lungs of the wild-type mice. Morphologically, interstitial monocytes/macrophages, subepithelial fibroblast-like interstitial cells, and additionally type I alveolar epithelial cells immunostained for green fluorescent protein in wild-type mice. Approximately 5 to 20% of lung fibroblasts primary cultured from injured wild-type mice were green fluorescent protein expressing cells, indicating their blood derivation. This study demonstrates that stem/progenitor cells in blood contribute to the repair of lung injury in irradiated mice.

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Exposure to cigarette smoke is associated with airway epithelial mucus cell hyperplasia and a decrease in cilia and ciliated cells. Few models have addressed the long-term effects of chronic cigarette smoke exposure on ciliated epithelial cells. Our previous in vitro studies showed that cigarette smoke decreases ciliary beat frequency (CBF) via the activation of protein kinase C (PKC). We hypothesized that chronic cigarette smoke exposure in an in vivo model would decrease airway epithelial cell ciliary beating in a PKCdependent manner. We exposed C57BL/6 mice to whole-body cigarette smoke 2 hours/day, 5 days/week for up to 1 year. Tracheal epithelial cell CBF and the number of motile cells were measured after necropsy in cut tracheal rings, using high-speed digital video microscopy. Tracheal epithelial PKC was assayed according to direct kinase activity. At 6 weeks and 3 months of smoke exposure, the baseline CBF was slightly elevated (z 1 Hz) versus control mice, with no change in b-agonist-stimulated CBF between control mice and cigarette smoke-exposed mice. By 6 months of smoke exposure, the baseline CBF was significantly decreased (2-3 Hz) versus control mice, and a b-agonist failed to stimulate increased CBF. The loss of b-agonist-increased CBF continued at 9 months and 12 months of smoke exposure, and the baseline CBF was significantly decreased to less than one third of the control rate. In addition to CBF, ciliated cell numbers significantly decreased in response to smoke over time, with a significant loss of tracheal ciliated cells occurring between 6 and 12 months. In parallel with the slowing of CBF, significant PKC activation from cytosol to the membrane of tracheal epithelial cells was detected in mice exposed to smoke for 6-12 months.

Whether DNA damage caused by cigarette smoke leads to repair or apoptosis has not been fully elucidated. The current study demonstrates that cigarette smoke induces single-strand DNA damage in human bronchial epithelial cells. Cigarette smoke also stimulated caspase 3 precursors as well as intact poly (ADP-ribose) polymerase (PARP) production, but did not activate caspase 3 or cleave PARP, while the alkaloid camptothecin did so. Neither apoptosis nor necrosis was induced by cigarette smoke when the insult was removed within a designated time period. In contrast, DNA damage following cigarette smoke exposure was repaired as evidenced by decreasing terminal dUTP-biotin nick-end labeling positivity. The PARP inhibitor, 3-aminobenzamide blocked this repair. Furthermore, cells subjected to DNA damage were able to survive and proliferate clonogenically when changed to smoke-free conditions. These results suggest that cigarette smoke-induced DNA damage in bronchial epithelial cells is not necessarily lethal, and that PARP functions in the repair process. Our data also suggest that the potency of cigarettes as a carcinogen may result from their ability to induce DNA damage while failing to trigger the apoptotic progression permitting survival of cells harboring potentially oncogenic mutations.