Circular RNA (circRNA) are endogenous transcripts that display differential expression across species, developmental stages, and pathologies. Their lack of free ends confers increased stability when compared with linear transcripts, making them ideal candidates for future diagnostic biomarkers and therapeutic interventions. Increasing evidence has implicated circRNA in the pathogenesis of multiple cardiovascular diseases. In this paper, we summarize current understanding of circRNA biogenesis, properties, expression profiles, detection methods, functions, and their implication in cardiac pathologies including/ischemia reperfusion injury, myocardial infarction, cardiac senescence, cardiac fibrosis, cardiomyopathy, cardiac hypertrophy and heart failure, atherosclerosis, coronary artery disease, and aneurysm.

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Dendritic cells (DC), the most potent APCs, can initiate the immune response or help induce immune tolerance, depending upon their level of maturation. DC maturation is associated with activation of the NF-κB pathway, and the primary NF-κB protein involved in DC maturation is RelB, which coordinates RelA/p50-mediated DC differentiation. In this study, we show that silencing RelB using small interfering RNA results in arrest of DC maturation with reduced expression of the MHC class II, CD80, and CD86. Functionally, RelB-silenced DC inhibited MLR, and inhibitory effects on alloreactive immune responses were in an Ag-specific fashion. RelB-silenced DC also displayed strong in vivo immune regulation. An inhibited Ag-specific response was seen after immunization with keyhole limpet hemocyanin-pulsed and RelB-silenced DC, due to the expansion of T regulatory cells. Administration of donor-derived RelB-silenced DC significantly prevented allograft rejection in murine heart transplantation. This study demonstrates for the first time that transplant tolerance can be induced by means of RNA interference using in vitro-generated tolerogenic DC.

Intercellular transfer of organelles via tunneling nanotubes (TNTs) is a novel means of cell-to-cell communication. Here we demonstrate the existence of TNTs between co-cultured RT4 and T24 bladder cancer cells using light microscopy, fluorescence imaging, and scanning electron microscopy (SEM). Spontaneous unidirectional transfer of mitochondria from T24 to RT4 cells was detected using fluorescence imaging and flow cytometry. The distribution of mitochondria migrated from T24 cells was in good agreement with the original mitochondria in RT4 cells, which may imply mitochondrial fusion. We detected cytoskeleton reconstruction in RT4-Mito-T24 cells by observing F-actin redistribution. Akt, mTOR, and their downstream mediators were activated and increased. The resultant increase in the invasiveness of bladder cancer cells was detected in vitro and in vivo. These data indicate that TNTs promote intercellular mitochondrial transfer between heterogeneous cells, followed by an increase in the invasiveness of bladder cancer cells.