Naïve or ground state pluripotency is a cellular state in vitro which resembles cells of the preimplantation epiblast in vivo. This state was first observed in mouse embryonic stem cells and is characterized by high rates of proliferation, the ability to differentiate widely, and global hypomethylation. Human pluripotent stem cells (hPSCs) correspond to a later or “primed” stage of embryonic development. The conversion of hPSCs to a naïve state is desirable as their features should facilitate techniques such as gene editing and more efficient differentiation. Here we review protocols which now allow derivation of naïve human pluripotent stem cells by transgene expression or the use of media formulations containing inhibitors and growth factors and correlate this with pathways involved. Maintenance of these ground state cells is possible using a combination of basic fibroblast growth factor and human leukemia inhibitory factor together with dual inhibition of glycogen synthase kinase 3 beta, and mitogen‐activated protein kinase kinase (MEK). Close similarity between the ground state hPSC and the in vivo preimplantation epiblast have been shown both by demonstrating similar upregulation of endogenous retroviruses and correlation of global RNA‐seq data. This suggests that the human naïve state is not an in vitro artifact. Stem Cells 2015;33:3181–3186

Naïve human pluripotent stem cells (hPSC) resemble the embryonic epiblast at an earlier time-point in development than conventional, 'primed' hPSC. We present a comprehensive miRNA profiling of naïve-to-primed transition in hPSC, a process recapitulating aspects of early in vivo embryogenesis. We identify miR-143-3p and miR-22-3p as markers of the naïve state and miR-363-5p, several members of the miR-17 family, miR-302 family as primed markers. We uncover that miR-371-373 are highly expressed in naïve hPSC. MiR-371-373 are the human homologs of the mouse miR-290 family, which are the most highly expressed miRNAs in naïve mouse PSC. This aligns with the consensus that naïve hPSC resemble mouse naive PSC, showing that the absence of miR-371-373 in conventional hPSC is due to cell state rather than a species difference.Naïve human pluripotent stem cells (hPSC) are cells in vitro resembling the inner cell mass of human embryonic day (E) 6-7 preimplantation blastocysts 1,2 . Conventional hPSC are not considered naïve but instead are referred to as primed, since they resemble a later stage found in the post-implantation epiblast [2][3][4][5][6][7][8] . A plethora of methods currently exist to generate naïve hPSC 9 , which can be evaluated using various molecular markers, particularly gene and transposon expression profiles, cell surface protein expression and genome-wide DNA demethylation (reviewed in 10 ).MicroRNAs (miRNAs) are a class of small non-coding RNAs (∼ 22 nucleotides) which inhibit complementary mRNAs by binding to the 3′ untranslated region (UTR) and either flagging it for degradation or blocking translation. Early miRNAseq experiments in mouse embryonic stem cells (mESC) have shown that pluripotent stem cells have a miRNA expression patterns dominated by a few miRNAs which have been defined as the ESCspecific cell cycle-regulating (ESCC) miRNAs. ESCCs have the seed sequence AAG UGC and make up 20-50% of all miRNAs in mESC [11][12][13][14][15] . ESCC miRNAs are specifically expressed in naïve and primed pluripotent states and are downregulated upon differentiation. Upregulation of these miRNAs in somatic cells has also been associated with proliferation and cancer in mouse and human (reviewed in 16 ).In murine cells both in vivo and in vitro, there is a switch in dominant ESCC miRNA expression in pluripotent cells from the preimplantation/naïve miR-290 family to the postimplantation/primed miR-302 family both containing the seed sequence AAG UGC [17][18][19][20][21] . However, the miR-290 family does not exist in the same genomic context in the human. The human homolog, the miR-371-373 cluster, is reported to be variably, if at all, expressed in conventional human PSC and this discrepancy has previously been viewed as a key difference between the two species 13,14,22 . Conversely, high expression of the miR-302 family has been reported as a key marker of primed human ES and iPS cells 13,14,23 and mouse EpiSC 11 .Here we present a comprehensive miRNAseq dataset of naïve, intermediate and primed hPSC. This ...

The integrity of the epithelium is maintained by a complex but regulated interplay of processes that allow conversion of a proliferative state into a stably differentiated state. In this study, using human embryonic stem cell (hESC) derived Retinal Pigment Epithelium (RPE) cells as a model; we have investigated the molecular mechanisms that affect attainment of the epithelial phenotype. We demonstrate that RPE undergo a Mesenchymal–Epithelial Transition in culture before acquiring an epithelial phenotype in a FOXM1 dependent manner. We show that FOXM1 directly regulates proliferation of RPE through transcriptional control of cell cycle associated genes. Additionally, FOXM1 modulates expression of the signaling ligands BMP7 and Wnt5B which act reciprocally to enable epithelialization. This data uncovers a novel effect of FOXM1 dependent activities in contributing towards epithelial fate acquisition and furthers our understanding of the molecular regulators of a cell type that is currently being evaluated as a cell therapy.

Background Early identification of patients at risk for postoperative delirium is essential because adequate well-timed interventions could reduce the occurrence of delirium and the related detrimental outcomes. Methods We will conduct a systematic review and individual patient data (IPD) meta-analysis of prognostic studies evaluating the predictive value of risk factors associated with an increased risk of postoperative delirium in elderly patients undergoing elective surgery. We will identify eligible studies through systematic search of MEDLINE, EMBASE, and CINAHL from their inception to May 2020. Eligible studies will enroll older adults (≥ 50 years) undergoing elective surgery and assess pre-operative prognostic risk factors for delirium and incidence of delirium measured by a trained individual using a validated delirium assessment tool. Pairs of reviewers will, independently and in duplicate, screen titles and abstracts of identified citations, review the full texts of potentially eligible studies. We will contact chief investigators of eligible studies requesting to share the IPD to a secured repository. We will use one-stage approach for IPD meta-analysis and will assess certainty of evidence using the GRADE approach. Discussion Since we are using existing anonymized data, ethical approval is not required for this study. Our results can be used to guide clinical decisions about the most efficient way to prevent postoperative delirium in elderly patients. Systematic review registration CRD42020171366.