MicroRNAs (miRNAs) are members of a non-coding RNA family. They act as negative regulators of protein translation by affecting messenger RNA (mRNA) stability; they modulate numerous signaling pathways and cellular processes, and are involved in cell-to-cell communication. Thus, studies on miRNAs offer an opportunity to improve our understanding of complex biological mechanisms. In the cardiovascular system, miRNAs control functions of various cells, such as cardiomyocytes, endothelial cells, smooth muscle cells and fibroblasts. The pivotal role of miRNAs in the cardiovascular system provides a new perspective on the pathophysiology of disorders like myocardial infarction, hypertrophy, fibrosis, heart failure, arrhythmia, inflammation and atherosclerosis. MiRNAs are differentially expressed in diseased tissue and can be released into circulation. Manipulation of miRNA activity may influence the course of a disease. Therefore, miRNAs have become an active field of research for developing new diagnostic and therapeutic tools. This review discusses emerging functions of miRNAs in cardiogenesis, heart regeneration and the pathophysiology of cardiovascular diseases.

Established cell lines are widely used in research, however an appealing question is the comparability of the cells between various laboratories, their characteristics and stability in time. Problematic is also the cell line misidentification, genetic and phenotypic shift or Mycoplasma contamination which are often forgotten in research papers. The monocyte/macrophage-like cell line RAW 264.7 has been one of the most commonly used myeloid cell line for more than 40 years. Despite its phenotypic and functional stability is often discussed in literature or at various scientific discussion panels, their stability during the consecutive passages has not been confirmed in any solid study. So far, only a few functional features of these cells have been studied, for example their ability to differentiate into osteoclasts. Therefore, in the present paper we have investigated the phenotype and functional stability of the RAW 264.7 cell line from passage no. 5 till passage no. 50. We found out that the phenotype (expression of particular macrophage-characteristic genes and surface markers) and functional characteristics (phagocytosis and NO production) of RAW 264.7 cell line remains stable through passages: from passage no. 10 up to passage no. 30. Overall, our results indicated that the RAW 264.7 cell line should not be used after the passage no. 30 otherwise it may influence the data reliability.

It was previously reported that the activation of antitumor immune response by photodynamic therapy (PDT) is crucial for its therapeutic outcome. Excessive PDT-mediated inflammation is accompanied by immunosuppressive mechanisms that protect tissues from destruction. Thus, the final effect of PDT strongly depends on the balance between the activation of an adoptive arm of immune response and a range of activated immunosuppressive mechanisms. Here, with flow cytometry and functional tests, we evaluate the immunosuppressive activity of tumor-associated myeloid cells after PDT. We investigate the antitumor potential of PDT combined with indoleamine 2,3-dioxygenase 1 (IDO) inhibitor in the murine 4T1 and E0771 orthotopic breast cancer models. We found that the expression of IDO, elevated after PDT, affects the polarization of T regulatory cells and influences the innate immune response. Our results indicate that, depending on a therapeutic scheme, overcoming IDO-induced immunosuppressive mechanisms after PDT can be beneficial or can lead to a systemic toxic reaction. The inhibition of IDO, shortly after PDT, activates IL-6-dependent toxic reactions that can be diminished by the use of anti-IL-6 antibodies. Our results emphasize that deeper investigation of the physiological role of IDO, an attractive target for immunotherapies of cancer, is of great importance.

Stimulation of Toll-like receptor 7 (TLR7) activates myeloid cells and boosts the immune response. Previously, we have shown that stimulation of the inhibitory CD200 receptor (CD200R) suppresses TLR7 signaling and that the absence of CD200R signaling leads to a decreased number of papillomas in mice. Here, we investigated the effects of agonistic anti-CD200R on the antitumor activity of a TLR7 agonist (R848) in a syngeneic mouse tumor model. Intratumoral administration of R848 inhibited the growth of the CT26 colon carcinoma and simultaneously decreased CD200R expression in tumor-infiltrating immune cells. The antitumor effects of R848 were potentiated by anti-CD200R. Successfully treated mice were resistant to rechallenge with the same tumor cells. However, the immediate antitumor effects were independent of lymphocytes, because treatment efficacy was similar in wild-type and mice. Administration of R848, particularly in combination with anti-CD200R, changed the phenotype of intratumoral myeloid cells. The infiltration with immature MHC-II macrophages decreased and in parallel monocytes and immature MHC-II macrophages increased. Combined treatment decreased the expression of the macrophage markers F4/80, CD206, CD86, CD115, and the ability to produce IL1β, suggesting a shift in the composition of intratumor myeloid cells. Adoptively transferred CD11b myeloid cells, isolated from the tumors of mice treated with R848 and anti-CD200R, inhibited tumor outgrowth in recipient mice. We conclude that administration of agonistic anti-CD200R improves the antitumor effects of TLR7 signaling and changes the local tumor microenvironment, which becomes less supportive of tumor progression. .