Variability of miRNA expression during the differentiation of human embryonic stem cells into retinal pigment epithelial cells

Therapeutic effects of mesenchymal stem cells-derived extracellular vesicles' miRNAs on retinal regeneration: a review

Extracellular vesicles (EVs), which consist of microvesicles and exosomes, are secreted from all cells to transform vital information in the form of lipids, proteins, mRNAs and small RNAs such as microRNAs (miRNAs). Many studies demonstrated that EVs' miRNAs have effects on target cells. Numerous people suffer from the blindness caused by retinal degenerations. The death of retinal neurons is irreversible and creates permanent damage to the retina. In the absence of acceptable cures for retinal degenerative diseases, stem cells and their paracrine agents including EVs have become a promising therapeutic approach. Several studies showed that the therapeutic effects of stem cells are due to the miRNAs of their EVs. Considering the effects of microRNAs in retinal cells development and function and studies which provide the possible roles of mesenchymal stem cells-derived EVs miRNA content on retinal diseases, we focused on the similarities between these two groups of miRNAs that could be helpful for promoting new therapeutic techniques for retinal degenerative diseases.

MicroRNAs and Stem-like Properties: The Complex Regulation Underlying Stemness Maintenance and Cancer Development

Embryonic stem cells (ESCs) have the extraordinary properties to indefinitely proliferate and self-renew in culture to produce different cell progeny through differentiation. This latter process recapitulates embryonic development and requires rounds of the epithelial-mesenchymal transition (EMT). EMT is characterized by the loss of the epithelial features and the acquisition of the typical phenotype of the mesenchymal cells. In pathological conditions, EMT can confer stemness or stem-like phenotypes, playing a role in the tumorigenic process. Cancer stem cells (CSCs) represent a subpopulation, found in the tumor tissues, with stem-like properties such as uncontrolled proliferation, self-renewal, and ability to differentiate into different cell types. ESCs and CSCs share numerous features (pluripotency, self-renewal, expression of stemness genes, and acquisition of epithelial-mesenchymal features), and most of them are under the control of microRNAs (miRNAs). These small molecules have relevant roles during both embryogenesis and cancer development. The aim of this review was to recapitulate molecular mechanisms shared by ESCs and CSCs, with a special focus on the recently identified classes of microRNAs (noncanonical miRNAs, mirtrons, isomiRs, and competitive endogenous miRNAs) and their complex functions during embryogenesis and cancer development.

miR-21-5p: A viable therapeutic strategy for regulating intraocular pressure

Lowering intraocular pressure (IOP) is the most effective treatment of glaucoma, however most of the current available glaucoma drugs target a single molecule. MicroRNAs (miRNAs) are noncoding RNAs that target a network of molecules. This study aims to investigate the role of miR-21-5p in regulating IOP and the mechanism of function. miR-21-5p mimics was topically applied to C57/BL6 mouse eyes, which significantly increased miR-21-5p expression in the conventional outflow tissue and reduced IOP by a maximum of 17.77% at 24 h after treatment. The conventional outflow facility measured by ex vivo moue eye perfusion of miR-21-5p was significantly increased by 60.14%. Moreover, miR-21-5p overexpression significantly reduced the transendothelial electrical resistance in porcine angular aqueous plexus cells. Transcriptome analysis and further quantification by Western blot and PCR revealed that SMAD7 and FGF18 might be the downstream target of miR-21-5p in regulating aqueous humor outflow. The predicted functional pathways PTEN/eNOS, RhoB/pMLC and TIMP3/MMP9 were significantly altered after miR-21-5p transfection. Dual luciferase assay verified the direct targets of miR-21-5p. In conclusion, miR-21-5p seems to regulate IOP by modulating multiple genes that are associated with aqueous humor outflow, including genes those regulating cell adhesion, cytoskeletal dynamics and extracellular matrix turnover. Thus, miR-21-5p represents a new therapeutic strategy for glaucoma and a viable alternative to existing multidrug regimens.

Overexpression of MiR-183/96/182 Triggers Retina-Like Fate in Human Bone Marrow-Derived Mesenchymal Stem Cells (hBMSCs) in Culture

Retinal degeneration is considered as a condition ensued by different blinding disorders such as retinitis pigmentosa, age-related macular degeneration, and diabetic retinopathy, which can cause loss of photoreceptor cells and also lead to significant vision deficiencies. Although there is no efficient treatment in this domain, transplantation of stem cells has been regarded as a therapeutic approach for retinal degeneration. Thus, the purpose of this study was to analyze the potential of human bone marrow-derived mesenchymal stem cells (hBMSCs) to differentiate into photoreceptor cells via transfection of microRNA (miRNA) in vitro for regenerative medicine purposes. To this end, miR-183/96/182 cluster was transfected into hBMSCs; then, qRT-PCR was performed to measure the expression levels of miR-183/96/182 cluster and some retina-specific neuronal genes such as OTX2, NRL, PKCα, and recoverin. CRX and rhodopsin (RHO) levels were also measured through qRT-PCR and immunocytochemistry, and subsequently, cellular change morphology was detected. The findings showed no changes in the morphology of the given cells, and the expression of the neuroretinal genes such as OTX2, NRL, and PKCα. Moreover, recoverin was upregulated upon miR-183/-96/-182 overexpression in cultured hBMSCs. Ectopic overexpression of the miR-183 cluster could further increase the expression of CRX and RHO at the messenger RNA (mRNA) and protein levels. Furthermore, the data indicated that the miR-183 cluster could serve as a crucial function in photoreceptor cell differentiation. In fact, miRNAs could be assumed as potential targets to exploit silent neuronal differentiation. Ultimately, it was suggested that in vitro overexpression of miR-183 cluster could trigger reprogramming of the hBMSCs to retinal neuron fate, especially photoreceptor cells.

Dicer partner protein tunes the length of miRNAs using base-mismatch in the pre-miRNA stem

Dicer partner proteins Drosophila Loquacious-PB (Loqs-PB) and human TRBP tune the length of miRNAs produced by Dicer from a subset of pre-miRNAs and thereby alter their target repertoire, by an unknown mechanism. Here, we developed a novel high-throughput method that we named Dram-seq (Dice randomized pre-miRNA pool and seq) to study length distributions of miRNAs produced from thousands of different pre-miRNA variants. Using Dram-seq, we found that a base-mismatch in the pre-miRNA stem can alter the length of miRNAs compared with a base-pair at the same position in both Drosophila and human, and is important for the miRNA length tuning by Loqs-PB. Loqs-PB directly bound base-mismatched nucleotides in the pre-miRNA stem. We speculate that Loqs-PB tunes miRNA length by changing the conformation of base-mismatched nucleotides in the pre-miRNA stem to that of base-paired ones and thereby altering the distance of the pre-miRNA stem.

Low expression of microRNA-320b correlates with tumorigenesis and unfavorable prognosis in glioma

Accumulating evidence demonstrates that dysregulated microRNAs (miRNAs) play a critical role in tumorigenesis and progression of various cancers. miR-320b, a member of miR‑320 family, was revealed downregulated in numerous human cancers, including nasopharyngeal carcinoma and colorectal cancer. However, the function of miR‑320b in human glioma remained poorly defined. In this study, we report that miR‑320b was lowly expressed in glioma tissues and cell lines in contrast with controls, being closely correlated with histological malignancy of glioma. Furthermore, patients with low expression of miR‑320b were associated with poor prognostic outcomes. In vitro functional assays indicated that overexpression of miR‑320b could markedly enhance cell apoptosis rate and suppress cell proliferation, migration and invasion. miR-320b mimic impaired cell cycle and metastasis through inhibiting the expression of G1/S transition key regulator Cyclin D1 as well as decreasing the expression level of MMP2 and MMP9. Additionally, upregulation of miR‑320b could markedly promote apoptosis by increasing the level of Bax and reducing Bcl-2 expression in glioma. Taken together, our data suggested that miR‑320b might serve as a novel prognostic marker and potential therapeutic target for glioma.

The miR-204-3p-targeted IGFBP2 pathway is involved in xanthohumol-induced glioma cell apoptotic death

Xanthohumol (XN), a prenylated chalcone extracted from hop plant Humulus lupulus L. (Cannabaceae), has potential for cancer therapy, including gliomas. Micro (mi)RNAs are small noncoding RNAs that control gene expression. Several miRNAs have been identified to participate in regulating glioma development. However, no studies have demonstrated whether miRNA is involved in XN cytotoxicity resulting in glioma cell death. This study investigated the effects of XN-mediated miRNA expression in activating apoptotic pathways in glioblastoma U87 MG cells. First, we found that XN significantly reduced cell viability and induced apoptosis via pro-caspase-3/8 cleavage and poly(ADP ribose) polymerase (PARP) degradation. We also identified that pro-caspase-9 cleavage, Bcl2 family expression changes, mitochondrial dysfunction, and intracellular ROS generation also participated in XN-induced glioma cell death. With a microarray analysis, miR-204-3p was identified as the most upregulated miRNA induced by XN cytotoxicity. The extracellular signal-regulated kinase (ERK)/c-Fos pathway was validated to participate in XN-upregulated miR-204-3p expression. With a promoter assay and ChIP analysis, we found that c-Fos dose-dependently bound to the miR-204-3p gene promoter region. Furthermore, miR-204-3p levels decreased in several glioma cell lines compared to astrocytes. Overexpression of miR-204-3p enhanced glioma cell apoptosis. IGFBP2, an upregulated regulator of glioma proliferation, was validated by a TCGA analysis as a direct target gene of miR-204-3p. XN's inhibition of the IGFBP2/AKT/Bcl2 pathway via miR-204-3p targeting played a critical role in mediating glioma cell death. These results emphasized that the XN-mediated miR-204-3p network may provide novel therapeutic strategies for future glioblastoma therapy and drug development.

Methods for culturing retinal pigment epithelial cells: a review of current protocols and future recommendations

The retinal pigment epithelium is an important part of the vertebrate eye, particularly in studying the causes and possible treatment of age-related macular degeneration. The retinal pigment epithelium is difficult to access in vivo due to its location at the back of the eye, making experimentation with age-related macular degeneration treatments problematic. An alternative to in vivo experimentation is cultivating the retinal pigment epithelium in vitro, a practice that has been going on since the 1970s, providing a wide range of retinal pigment epithelial culture protocols, each producing cells and tissue of varying degrees of similarity to natural retinal pigment epithelium. The purpose of this review is to provide researchers with a ready list of retinal pigment epithelial protocols, their effects on cultured tissue, and their specific possible applications. Protocols using human and animal retinal pigment epithelium cells, derived from tissue or cell lines, are discussed, and recommendations for future researchers included.