MicroRNAs and reprogramming

Exosomal miR-302b rejuvenates aging mice by reversing the proliferative arrest of senescent cells

Cellular senescence, a hallmark of aging, involves a stable exit from the cell cycle. Senescent cells (SnCs) are closely associated with aging and aging-related disorders, making them potential targets for anti-aging interventions. In this study, we demonstrated that human embryonic stem cell-derived exosomes (hESC-Exos) reversed senescence by restoring the proliferative capacity of SnCs in vitro. In aging mice, hESC-Exos treatment remodeled the proliferative landscape of SnCs, leading to rejuvenation, as evidenced by extended lifespan, improved physical performance, and reduced aging markers. Ago2 Clip-seq analysis identified miR-302b enriched in hESC-Exos that specifically targeted the cell cycle inhibitors Cdkn1a and Ccng2. Furthermore, miR-302b treatment reversed the proliferative arrest of SnCs in vivo, resulting in rejuvenation without safety concerns over a 24-month observation period. These findings demonstrate that exosomal miR-302b has the potential to reverse cellular senescence, offering a promising approach to mitigate senescence-related pathologies and aging.

MiR-302 enhances the viability and stemness of male germline stem cells

MicroRNAs were reported to be able to regulate mGSCs' self-renewal through post-transcriptional inhibition of gene expression. miR-302 worked as one important microRNA family existed mainly in human ESCs, and its role in mGSCs has not been reported yet. To elucidate the role of miR-302 in dairy goat mGSCs, the expression profile of miR-302 was explored through qPCR and FISH. Furthermore, to detect the function of miR-302, the expression vector containing miR-302 was transfected into mGSCs, and then, the cell cycle, the cell apoptosis and the genes associated with mGSCs' self-renewal and differentiation were examined. The results showed that miR-302 expressed in testis moderately and located on the basement of seminiferous tubes which shared the same location as mGSCs. Transfection of the vector containing miR-302 fragment into the immortalized mGSCs obviously enhanced the cell proliferation ability and the attachment ability, also, promoted the expression level of CD49f and OCT4. Also, miR-302 reduced the cell apoptosis and downregulated the expression of P21. miR-302 sustained mGSCs' proliferation in vitro.

Obstacles in Renal Regenerative Medicine: Metabolic and Epigenetic Parallels Between Cellular Reprogramming and Kidney Cancer Oncogenesis

CONTEXT

Regenerative medicine has recently presented a revolutionary solution to end-stage kidney disease. Reprogramming patients' own cells generates induced pluripotent stem cells that are subsequently differentiated to "kidney organoid," a structure that is anatomically and functionally similar to the kidney. This approach holds the promise of a transplantable, immunocompetent, and functional kidney that could be produced in vitro. However, caution must be taken due to the molecular-level similarities between induced pluripotent stem cells and renal cell carcinomas. As such, if cell reprogramming is not tightly controlled, it can lead to carcinogenic changes.

OBJECTIVE

Based on recent next-generation sequencing results and other supporting data, we identified three major molecular attributes of renal cell carcinoma: metabolic alterations, epigenetic changes, and miRNA-based alterations. Strikingly, these variations are mirrored in induced pluripotent stem cells, which are the main cell source of renal regenerative medicine. Our objective was to discuss the shared metabolic, epigenetic and miRNA-regulated characteristics and to abridge their significance in renal regenerative medicine.

EVIDENCE ACQUISITION

English-language literature was retrieved through PubMed.

EVIDENCE SYNTHESIS

Authors collected the published evidence and evaluated the content based on independent literature findings. Articles were filtered to include only highly relevant, recent publications that presented reproducible results by authorities of the field.

CONCLUSIONS

The kidney represents a unique metabolic environment that could be hijacked by induced pluripotent stem cells or by partially differentiated cells for oncogenic transformation. Future differentiation protocols must produce kidney organoids that are fully engaged in filtration function.

PATIENT SUMMARY

A new technology can produce mini-kidneys or kidney organoids. This review discusses some of the challenges this technology has to face, including its high oncogenic potential. Understanding these similarities will lead to the safe creation of new functional kidney units in patients with kidney failure.

Epigenetic reprogramming in mammalian species after SCNT-based cloning

The birth of "Dolly," the first mammal cloned from an adult mammary epithelial cell, abolished the decades-old scientific dogma implying that a terminally differentiated cell cannot be reprogrammed into a pluripotent embryonic state. The most dramatic epigenetic reprogramming occurs in SCNT when the expression profile of a differentiated cell is abolished and a new embryo-specific expression profile, involving 10,000 to 12,000 genes, and thus, most genes of the entire genome is established, which drives embryonic and fetal development. The initial release from somatic cell epigenetic constraints is followed by establishment of post-zygotic expression patterns, X-chromosome inactivation, and adjustment of telomere length. Somatic cell nuclear transfer may be associated with a variety of pathologic changes of the fetal and placental phenotype in a proportion of cloned offspring, specifically in ruminants, that are thought to be caused by aberrant epigenetic reprogramming. Improvements in our understanding of this dramatic epigenetic reprogramming event will be instrumental in realizing the great potential of SCNT for basic research and for important agricultural and biomedical applications. Here, current knowledge on epigenetic reprogramming after use of SCNT in livestock is reviewed, with emphasis on gene-specific and global DNA methylation, imprinting, X-chromosome inactivation, and telomere length restoration in early development.

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

Embryonic stem cells (ESCs) and induced pluripotent stem cells can be induced to differentiate into retinal pigment epithelium (RPE). MiRNAs have been characterized and found playing important roles in the differentiation process of ESCs, but their length and sequence heterogeneity (isomiRs), and their non-canonical forms of miRNAs are underestimated or ignored. In this report, we found some non-canonical miRNAs (dominant isomiRs) in all differentiation stages, and 27 statistically significant editing sites were identified in 24 different miRNAs. Moreover, we found marked major-to-minor arm-switching events in 14 pre-miRNAs during the hESC to RPE cell differentiation phases. Our study for the first time reports exploring the variability of miRNA expression during the differentiation of hESCs into RPE cells and the results show that miRNA variability is a ubiquitous phenomenon in the ESC differentiation.

All roads lead to induced pluripotent stem cells: the technologies of iPSC generation

Generation of induced pluripotent stem cells (iPSCs) via the ectopic expression of reprogramming factors is a simple, advanced, yet often perplexing technology due to low efficiency, slow kinetics, and the use of numerous distinct systems for factor delivery. Scientists have used almost all available approaches for the delivery of reprogramming factors. Even the well-established retroviral vectors confuse some scientists due to different tropisms in use. The canonical virus-based reprogramming poses many problems, including insertional mutagenesis, residual expression and re-activation of reprogramming factors, uncontrolled silencing of transgenes, apoptosis, cell senescence, and strong immunogenicity. To eliminate or alleviate these problems, scientists have tried various other approaches for factor delivery and transgene removal. These include transient transfection, nonintegrating viral vectors, Cre-loxP excision of transgenes, excisable transposon, protein transduction, RNA transfection, microRNA transfection, RNA virion, RNA replicon, nonintegrating replicating episomal plasmids, minicircles, polycistron, and preintegration of inducible reprogramming factors. These alternative approaches have their own limitations. Even iPSCs generated with RNA approaches should be screened for possible transgene insertions mediated by active endogenous retroviruses in the human genome. Even experienced researchers may encounter difficulty in selecting and using these different technologies. This survey presents overviews of iPSC technologies with the intention to provide a quick yet comprehensive reference for both new and experienced reprogrammers.

Trim71 cooperates with microRNAs to repress Cdkn1a expression and promote embryonic stem cell proliferation

Pluripotent embryonic stem cells have a shortened cell cycle that enables their rapid proliferation. The embryonic stem cell-specific miR-290 and miR-302 microRNA families promote proliferation whereas let-7 microRNAs inhibit self-renewal, and promote cell differentiation. Lin28 suppresses let-7 expression in embryonic stem cells. Here to gain further insight into mechanisms controlling embryonic stem cell self-renewal, we explore the molecular and cellular role of the let-7 target Trim71 (mLin41). We show that Trim71 associates with Argonaute2 and microRNAs, and represses expression of Cdkn1a, a cyclin-dependent kinase inhibitor that negatively regulates the G1-S transition. We identify protein domains required for Trim71 association with Argonaute2, localization to P-bodies, and for repression of reporter messenger RNAs. Trim71 knockdown prolongs the G1 phase of the cell cycle and slows embryonic stem cell proliferation, a phenotype that was rescued by depletion of Cdkn1a. Thus, we demonstrate that Trim71 is a factor that facilitates the G1-S transition to promote rapid embryonic stem cell self-renewal.

Advances and applications of induced pluripotent stem cells

Direct reprogramming of somatic cells into pluripotent cells is an emerging technology for creating patient-specific cells, and potentially opens new scenarios in medical and pharmacological fields. From the discovery of Shinya Yamanaka, who first obtained pluripotent cells from fibroblasts by retrovirus-derived ectopic expression of defined embryonic transcription factors, new methods have been developed to generate safe induced pluripotent stem (iPS) cells without genomic manipulations. This review will focus on the recent advances in iPS technology and their application in pharmacology and medicine.

In vivo delivery of cytoplasmic RNA virus-derived miRNAs

The discovery of microRNAs (miRNAs) revealed an unappreciated level of post-transcriptional control used by the cell to maintain optimal protein levels. This process has represented an attractive strategy for therapeutics that is currently limited by in vivo delivery constraints. Here, we describe the generation of a single-stranded, cytoplasmic virus of negative polarity capable of producing functional miRNAs. Cytoplasmic RNA virus-derived miRNAs accumulated to high levels in vitro, generated significant amounts of miRNA star strand, associated with the RNA-induced silencing complex (RISC), and conferred post transcriptional gene silencing in a sequence-specific manner. Furthermore, we demonstrate that these vectors could deliver miRNAs to a wide range of tissues, and sustain prolonged expression capable of achieving measurable knockdown of physiological targets in vivo. Taken together, these results validate noncanonical processing of cytoplasmic-derived miRNAs and provide a novel platform for small RNA delivery.