Functions and mechanisms of circular RNAs in regulating stem cell differentiation.

Stem cells are a class of undifferentiated cells with great self-renewal and differentiation capabilities that can differentiate into mature cells in specific tissue types. Stem cell differentiation plays critical roles in body homoeostasis, injury repair and tissue generation. The important functions of stem cell differentiation have resulted in numerous studies focusing on the complex molecular mechanisms and various signalling pathways controlling stem cell differentiation. Circular RNAs (circRNAs) are a novel class of noncoding RNAs with a covalently closed structure present in eukaryotes. Numerous studies have highlighted important biological functions of circRNAs, and they play multiple regulatory roles in various physiological and pathological processes. Importantly, multiple lines of evidence have shown the abnormal expression of numerous circRNAs during stem cell differentiation, and some play a role in regulating stem cell differentiation, highlighting the role of circRNAs as novel biomarkers of stem cell differentiation and novel targets for stem cell-based therapy. In this review, we systematically summarize and discuss recent advances in our understanding of the roles and underlying mechanisms of circRNAs in modulating stem cell differentiation, thus providing guidance for future studies to investigate stem cell differentiation and stem cell-based therapy.Abbreviations: CircRNAs: circular RNAs; ESCs: embryonic stem cells; ADSCs: adipose-derived mesenchymal stem cells; ecircRNAs: exonic circRNAs; EIciRNAs: exon-intron circRNAs; eiRNAs: circular intronic RNAs; tricRNAs: tRNA intronic circRNAs; pol II: polymerase II; snRNP: small nuclear ribonucleoprotein; m6A: N6-methyladenosine; AGO2: Argonaute 2; RBPs: RNA-binding proteins; MBNL: muscleblind-like protein 1; MSCs: mesenchymal stem cells; hiPSCs: human induced pluripotent stem cells; hiPSC-CMs: hiPSC-derived cardiomyocytes; hBMSCs: human bone marrow mesenchymal stem cells; hADSCs: human adipose-derived mesenchymal stem cells; hDPSCs: human dental pulp stem cells; RNA-seq: high-throughput RNA sequencing; HSCs: haematopoietic stem cells; NSCs: neural stem cells; EpSCs: epidermal stem cells; hESCs: human embryonic stem cells; mESCs: murine embryonic stem cells; MNs: motor neurons; SSUP: small subunit processome; BMSCs: bone marrow-derived mesenchymal stem cells; OGN: osteoglycin; GIOP: glucocorticoid­induced osteoporosis; CDR1as: cerebellar degeneration-related protein 1 transcript; SONFH: steroid-induced osteogenesis of the femoral head; rBMSCs: rat bone marrow-derived mesenchymal stem cells; QUE: quercetin; AcvR1b: activin A receptor type 1B; BSP: bone sialoprotein; mADSCs: mouse ADSCs; PTBP1: polypyrimidine tract-binding protein; ER: endoplasmic reticulum; hUCMSCs: MSCs derived from human umbilical cord; MSMSCs: maxillary sinus membrane stem cells; SCAPs: stem cells from the apical papilla; MyoD: myogenic differentiation protein 1; MSTN: myostatin; MEF2C: myocyte enhancer factor 2C; BCLAF1: BCL2-associated transcription factor 1; EpSCs: epidermal stem cells; ISCs: intestinal stem cells; NSCs: neural stem cells; Lgr5+ ISCs: crypt base columnar cells; ILCs: innate lymphoid cells.

Intestinal miRNAs regulated in response to dietary lipids.

The role of miRNAs in intestinal lipid metabolism is poorly described. The small intestine is constantly exposed to high amounts of dietary lipids, and it is under conditions of stress that the functions of miRNAs become especially pronounced. Approaches consisting in either a chronic exposure to cholesterol and triglyceride rich diets (for several days or weeks) or an acute lipid challenge were employed in the search for intestinal miRNAs with a potential role in lipid metabolism regulation. According to our results, changes in miRNA expression in response to fat ingestion are dependent on factors such as time upon exposure, gender and small intestine section. Classic and recent intestinal in vitro models (i.e. differentiated Caco-2 cells and murine organoids) partially mirror miRNA modulation in response to lipid challenges in vivo. Moreover, intestinal miRNAs might play a role in triglyceride absorption and produce changes in lipid accumulation in intestinal tissues as seen in a generated intestinal Dicer1-deletion murine model. Overall, despite some variability between the different experimental cohorts and in vitro models, results show that some miRNAs analysed here are modulated in response to dietary lipids, hence likely to participate in the regulation of lipid metabolism, and call for further research.

Alginate encapsulated multipotent adult progenitor cells promote corneal stromal cell activation via release of soluble factors.

To reduce the increasing need for corneal transplantation, attempts are currently aiming to restore corneal clarity, one potent source of cells are multipotent adult progenitor cells (MAPC®). These cells release a powerful cocktail of paracrine factors that can guide wound healing and tissue regeneration. However, their role in corneal regeneration has been overlooked. Thus, we sought to explore the potential of combining the cytoprotective storage feature of alginate, with MAPC to generate a storable cell-laden gel for corneal wound healing. 72 hours following hypothermic storage, alginate encapsulation was shown to maintain MAPC viability at either 4 or 15°C. Encapsulated MAPC (2 x106 cells/mL) stored at 15°C presented the optimum temperature that allowed for cell recovery. These cells had the ability to reattach to tissue culture plastic whilst exhibiting normal phenotype and this was maintained in serum-free and xenobiotic-free medium. Furthermore, corneal stromal cells presented a significant decrease in scratch-wounds in the presence of alginate encapsulated MAPC compared to a no-cell control (p = 0.018). This study shows that immobilization of MAPC within an alginate hydrogel does not hinder their ability to affect a secondary cell population via soluble factors and that these effects are successfully retained following hypothermic storage.

Bone tissue engineering: Adult stem cells in combination with electrospun nanofibrous scaffolds.

Since bone tissue lesions caused by several reasons and has global outbreak without any attentions to the modernity level of the countries. In the other hands treatment of patients with this problem faced to the several limitations, in this because the future of the bone lesions treatments is related to the future of the bone tissue engineering. This review tries to cover the most suitable stem cells and materials from either natural or synthetic sources for bone tissue engineering. These understanding points would help researchers to further uncover the application of different adult stem cell sources in electrospinning scaffolds, promotion of nanofibrous composite construct design and adult stem cell type selection to enhance cell function and bone tissue engineering, and link laboratory investigations to clinical applications.

Methylcellulose Based Thermally Reversible Hydrogels.

The creation of single and multilayered adult stem cells (ASCs) sheets is presented. The stem cell sheets preserve the cell-cell and cell-extracellular matrices and are developed by utilizing a thermally reversible methylcellulose (MC) coated tissue culture polystyrene (TCPS) dish. This technique is an improvement and a simplification of earlier noninvasive cell retrieval methods based on the use of a temperature-responsive poly(N-isopropylacrylamide) (PIPAAm) coated TCPS dishes. The optimal combination of MC-water-salt was determined to be 12-14% of MC (mol. wt. of 15,000) in water with 0.5× PBS (~150 mOsm). This solution exhibited a gel formation temperature of ~32 °C. The addition (evenly spread) of 1 ml of 3 mg/ml rat tail type-I (pH adjusted to 7.5) over the MC coated surface at 37 °C improves ASC adhesion and proliferation on the methylcellulose system. Upon confluence, a continuous monolayer ASC sheet was formed on the surface of the MC hydrogel system. When the grown cell sheet was removed from the incubator and exposed to room temperature (~30 °C), it spontaneously and gradually detached from the surface of the thermoresponsive hydrogel, creating an ASC sheet.

A Protocol to Prepare Decellularized Stem Cell Matrix for Rejuvenation of Cell Expansion and Cartilage Regeneration.

Traditional ex vivo expansion of adult stem cells yields an insufficient quantity of less potent cells. Here we describe the fabrication of decellularized matrix deposited by synovium-derived stem cells (SDSCs). This matrix could serve as a three-dimensional expansion system to rejuvenate cells for proliferation and tissue-specific differentiation potential, which could benefit cartilage regeneration. The decellularized stem cell matrix (DSCM) might be a powerful system for tissue engineering and regeneration.

Long-Term Outcome of Administration of c-kit(POS) Cardiac Progenitor Cells After Acute Myocardial Infarction: Transplanted Cells Do not Become Cardiomyocytes, but Structural and Functional Improvement and Proliferation of Endogenous Cells Persist for at Least One Year.

RATIONALE: Cardiac progenitor cells (CPCs) improve left ventricular remodeling and function after acute or chronic myocardial infarction. However, the long-term (>5 weeks) effects, potential tumorigenicity, and fate of transplanted CPCs are unknown. OBJECTIVE: To assess the outcome of CPC therapy at 1 year. METHODS AND RESULTS: Female rats underwent a 90-minute coronary occlusion; 4 hours after reperfusion, they received intracoronarily vehicle or 1 million male, syngeneic CPCs. One year later, CPC-treated rats exhibited smaller scars and more viable myocardium in the risk region, along with improved left ventricular remodeling and regional and global left ventricular function. No tumors were observed. Some transplanted (Y-chromosome(POS)) CPCs (or their progeny) persisted and continued to proliferate, but they failed to acquire a mature cardiomyocyte phenotype and were too few (4-8% of nuclei) to account for the benefits of CPC therapy. Surprisingly, CPC transplantation triggered a prolonged proliferative response of endogenous cells, resulting in increased formation of endothelial cells and Y-chromosome(NEG) CPCs for 12 months and increased formation, for at least 7 months, of small cells that expressed cardiomyocytic proteins (α-sarcomeric actin) but did not have a mature cardiomyocyte phenotype. CONCLUSIONS: The beneficial effects of CPCs on left ventricular remodeling and dysfunction are sustained for at least 1 year and thus are likely to be permanent. Because transplanted CPCs do not differentiate into mature myocytes, their major mechanism of action must involve paracrine actions. These paracrine mechanisms could be very prolonged because some CPCs engraft, proliferate, and persist at 1 year. This is the first report that transplantation of any cell type in the heart induces a proliferative response that lasts at least 1 year. The results strongly support the safety and clinical utility of CPC therapy.

Exploring analytical proteomics platforms toward the definition of human cardiac stem cells receptome.

Human cardiac stem cells (hCSC) express a portfolio of plasma membrane receptors that are involved in the regulatory auto/paracrine feedback loop mechanism of activation of these cells, and consequently contribute to myocardial regeneration. In order to attain a comprehensive description of hCSC receptome and overcoming the inability demonstrated by other technologies applied in receptor identification, mainly due to the transmembrane nature, high hydrophobic character and relative low concentration of these proteins, we have exploited and improved a proteomics workflow. This approach was based on the enrichment of hCSC plasma membrane fraction and addition of prefractionation steps prior to MS analysis. More than 100 plasma membrane receptors were identified. The data reported herein constitute a valuable source of information to further understand cardiac stem cells activation mechanisms and the subsequent cardiac repair process. All MS data have been deposited in the ProteomeXchange with identifier PXD001117 (http://proteomecentral.proteomexchange.org/dataset/PXD001117).

Markers of epidermal stem cell subpopulations in adult mammalian skin.

The epidermis is the outermost layer of mammalian skin and comprises a multilayered epithelium, the interfollicular epidermis, with associated hair follicles, sebaceous glands, and eccrine sweat glands. As in other epithelia, adult stem cells within the epidermis maintain tissue homeostasis and contribute to repair of tissue damage. The bulge of hair follicles, where DNA-label-retaining cells reside, was traditionally regarded as the sole epidermal stem cell compartment. However, in recent years multiple stem cell populations have been identified. In this review, we discuss the different stem cell compartments of adult murine and human epidermis, the markers that they express, and the assays that are used to characterize epidermal stem cell properties.

Effect of sugar molecules on the cryopreservation of mouse spermatogonial stem cells.

OBJECTIVE: To study the influence of sugars and establish a serum-free freezing method for the cryopreservation of spermatogonial stem cells (SSCs). DESIGN: Animal study. SETTING: University laboratory. ANIMAL(S): C57BL/6-TgEGFP, C57BL/6 mice. INTERVENTION(S): Germ cells enriched from testis cells were frozen using standard freezing medium containing sugars, including monosaccharides, disaccharides, and trisaccharides at 50, 100, and 200 mM, respectively. To study the feasibility of establishing a serum-free freezing method, fetal bovine serum was substituted with knockout serum replacement. MAIN OUTCOME MEASURE(S): Freeze-thawed germ cells were evaluated for recovery rate, proliferation capacity, and stem cell activity after transplantation to recipient testes. RESULT(S): Supplementation of freezing medium with 200 mM disaccharide is an effective method for cryopreservation of SSCs. Trehalose is the most effective cryoprotectant among all the sugars tested and only lactose was comparable to trehalose. Our proliferation and transplantation data show that serum-free freezing can be achieved in freezing medium supplemented with 200 mM trehalose, 10% knockout serum replacement, and 10% dimethyl sulfoxide (DMSO) for cryopreservation of SSCs. CONCLUSION(S): These findings raise the possibility of effectively banking frozen SSCs from various species, including humans, in a traditional serum-free medium for germ cell research and male infertility treatments.