Generation and trapping of a mesoderm biased state of human pluripotency

Transcriptome and open chromatin analysis reveals the process of myocardial cell development and key pathogenic target proteins in Long QT syndrome type 7

OBJECTIVE

Long QT syndrome type 7 (Andersen-Tawil syndrome, ATS), which is caused by KCNJ2 gene mutation, often leads to ventricular arrhythmia, periodic paralysis and skeletal malformations. The development, differentiation and electrophysiological maturation of cardiomyocytes (CMs) changes promote the pathophysiology of Long QT syndrome type 7(LQT7). We aimed to specifically reproduce the ATS disease phenotype and study the pathogenic mechanism.

METHODS AND RESULTS

We established a cardiac cell model derived from human induced pluripotent stem cells (hiPSCs) to the phenotypes and electrophysiological function, and the establishment of a human myocardial cell model that specifically reproduces the symptoms of ATS provides a reliable platform for exploring the mechanism of this disease or potential drugs. The spontaneous pulsation rate of myocardial cells in the mutation group was significantly lower than that in the repair CRISPR group, the action potential duration was prolonged, and the Kir2.1 current of the inward rectifier potassium ion channel was decreased, which is consistent with the clinical symptoms of ATS patients. Only ZNF528, a chromatin-accessible TF related to pathogenicity, was continuously regulated beginning from the cardiac mesodermal precursor cell stage (day 4), and continued to be expressed at low levels, which was identified by WGCNA method and verified with ATAC-seq data in the mutation group. Subsequently, it indicated that seven pathways were downregulated (all p < 0.05) by used single sample Gene Set Enrichment Analysis to evaluate the overall regulation of potassium-related pathways enriched in the transcriptome and proteome of late mature CMs. Among them, the three pathways (GO: 0008076, GO: 1990573 and GO: 0030007) containing the mutated gene KCNJ2 is involved that are related to the whole process by which a potassium ion enters the cell via the inward rectifier potassium channel to exert its effect were inhibited. The other four pathways are related to regulation of the potassium transmembrane pathway and sodium:potassium exchange ATPase (p < 0.05). ZNF528 small interfering (si)-RNA was applied to hiPSC-derived cardiomyocytes for CRISPR group to explore changes in potassium ion currents and growth and development related target protein levels that affect disease phenotype. Three consistently downregulated proteins (KCNJ2, CTTN and ATP1B1) associated with pathogenicity were verificated through correlation and intersection analysis.

CONCLUSION

This study uncovers TFs and target proteins related to electrophysiology and developmental pathogenicity in ATS myocardial cells, obtaining novel targets for potential therapeutic candidate development that does not rely on gene editing.

A short history of pluripotent stem cells markers

The expression of one or more of a small number of molecules, typically cell surface-associated antigens, or transcription factors, is widely used for identifying pluripotent stem cells (PSCs) or for monitoring their differentiation. However, none of these marker molecules are uniquely expressed by PSCs and all are expressed by stem cells that have lost the ability to differentiate. Consequently, none are indicators of pluripotency, per se. Here we summarize the nature and characteristics of several markers that are in wide use, including the cell surface antigens, stage-specific embryonic antigen (SSEA)-1, SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, GCTM2, and the transcription factors POUF5/OCT4, NANOG, and SOX2, highlighting issues that must be considered when interpreting data about their expression on putative PSCs.

Identification of SALL4 Expressing Islet-1+ Cardiovascular Progenitor Cell Clones

The utilization of cardiac progenitor cells (CPCs) has been shown to induce favorable regenerative effects. While there are various populations of endogenous CPCs in the heart, there is no consensus regarding which population is ideal for cell-based regenerative therapy. Early-stage progenitor cells can be differentiated into all cardiovascular lineages, including cardiomyocytes and endothelial cells. Identifying an Islet-1+ (Isl-1+) early-stage progenitor population with enhanced stemness, multipotency and differentiation potential would be beneficial for the development of novel regenerative therapies. Here, we investigated the transcriptome of human neonatal Isl-1+ CPCs. Isl-1+ human neonatal CPCs exhibit enhanced stemness properties and were found to express Spalt-like transcription factor 4 (SALL4). SALL4 plays a role in embryonic development as well as proliferation and expansion of hematopoietic progenitor cells. SALL4, SOX2, EpCAM and TBX5 are co-expressed in the majority of Isl-1+ clones isolated from neonatal patients. The pre-mesendodermal transcript TFAP2C was identified in select Isl-1, SALL4, SOX2, EpCAM and TBX5 expressing clones. The ability to isolate and expand pre-mesendodermal stage cells from human patients is a novel finding that holds potential value for applications in regenerative medicine.

Compact automated culture machine for human induced pluripotent stem cell maintenance and differentiation

The technologies used to generate human induced pluripotent stem cell (iPSC) from somatic cells potentially enable the wide application of iPSC-derived differentiated cells in industrial research fields as a replacement for animals. However, as highly trained individuals are required to obtain reproducible results, this approach has limited social implementation. In the research field of iPSC, it is believed that documentable information is not enough for reproducing the quality of the differentiated cells. Therefore, automated culture machines for cell processing should make the starting of iPSC-using researches easier. We developed a programmable all-in-one automated culture machine, with dense and compact constitution that fits within a normal biosafety cabinet (200 mm wide, 233 mm height, and 110 mm depth). This instrument was fabricated using novel x-y-z-axes-rail-system, such as an overhead traveling crane, in a factory, which served as the main handling machinery. This machine enabled stable and efficient expansion of human iPSC under the feeder-free condition, without karyotype alterations, and simultaneously differentiated the cells into various cell types, including cardiomyocytes, hepatocytes, neural progenitors, and keratinocytes. Overall, this machine would facilitate the social implementation of human pluripotent stem cells and contribute to the accumulation of sharable knowledge for the standardization of the entire handling processes of iPSC in pharmaceutical, food, and cosmetic research.

Designing Dual Inhibitors of Autotaxin-LPAR GPCR Axis

The ATX-LPA-LPAR1 signaling pathway plays a universal role in stimulating diverse cellular responses, including cell proliferation, migration, survival, and invasion in almost every cell type. The ATX-LPAR1 axis is linked to several metabolic and inflammatory diseases including cancer, fibrosis, and rheumatoid arthritis. Numerous selective ATX or LPAR1 inhibitors have been developed and so far, their clinical efficacy has only been evaluated in idiopathic pulmonary fibrosis. None of the ATX and LPAR1 inhibitors have advanced to clinical trials for cancer and rheumatoid arthritis. Nonetheless, several research groups, including ours, have shown considerable benefit of simultaneous ATX and LPAR1 inhibition through combination therapy. Recent research suggests that dual-targeting therapies are superior to combination therapies that use two selective inhibitors. However, limited reports are available on ATX-LPAR1 dual inhibitors, potentially due to co-expression of multiple different LPARs with close structural similarities at the same target. In this review, we discuss rational design and future directions of dual ATX-LPAR1 inhibitors.

Cell type determination for cardiac differentiation occurs soon after seeding of human-induced pluripotent stem cells

BACKGROUND

Cardiac differentiation of human-induced pluripotent stem (hiPS) cells consistently produces a mixed population of cardiomyocytes and non-cardiac cell types, even when using well-characterized protocols. We sought to determine whether different cell types might result from intrinsic differences in hiPS cells prior to the onset of differentiation.

RESULTS

By associating individual differentiated cells that share a common hiPS cell precursor, we tested whether expression variability is predetermined from the hiPS cell state. In a single experiment, cells that shared a progenitor were more transcriptionally similar to each other than to other cells in the differentiated population. However, when the same hiPS cells were differentiated in parallel, we did not observe high transcriptional similarity across differentiations. Additionally, we found that substantial cell death occurs during differentiation in a manner that suggested all cells were equally likely to survive or die, suggesting that there is no intrinsic selection bias for cells descended from particular hiPS cell progenitors. We thus wondered how cells grow spatially during differentiation, so we labeled cells by expression of marker genes and found that cells expressing the same marker tended to occur in patches. Our results suggest that cell type determination across multiple cell types, once initiated, is maintained in a cell-autonomous manner for multiple divisions.

CONCLUSIONS

Altogether, our results show that while substantial heterogeneity exists in the initial hiPS cell population, it is not responsible for the variability observed in differentiated outcomes; instead, factors specifying the various cell types likely act during a window that begins shortly after the seeding of hiPS cells for differentiation.

Human pluripotent stem cells: tools for regenerative medicine

Human embryonic stem cells and induced pluripotent stem cells, together denoted as pluripotent stem cells have opened up unprecedented opportunities for developments in human healthcare over the past 20 years. Although much about the properties and behaviour of these cells required to underpin their applications has been discovered over this time, a number of issues remain. This brief review considers the history of these developments and some of the underlying biology, pointing out some of the problems still to be resolved, particularly in relation to their genetic stability and possible malignancy.

Improving Human Induced Pluripotent Stem Cell-Derived Megakaryocyte Differentiation and Platelet Production

Several protocols exist for generating megakaryocytes (MKs) and platelets from human induced pluripotent stem cells (hiPSCs) with limited efficiency. We observed previously that mesoderm induction improved endothelial and stromal differentiation. We, therefore, hypothesized that a protocol modification prior to hemogenic endothelial cell (HEC) differentiation will improve MK progenitor (MKP) production and increase platelet output. We further asked if basic media composition affects MK maturation. In an iterative process, we first compared two HEC induction protocols. We found significantly more HECs using the modified protocol including activin A and CHIR99021, resulting in significantly increased MKs. MKs released comparable platelet amounts irrespective of media conditions. In a final validation phase, we obtained five-fold more platelets per hiPSC with the modified protocol (235 ± 84) compared to standard conditions (51 ± 15; p < 0.0001). The regenerative potency of hiPSC-derived platelets was compared to adult donor-derived platelets by profiling angiogenesis-related protein expression. Nineteen of 24 angiogenesis-related proteins were expressed equally, lower or higher in hiPSC-derived compared to adult platelets. The hiPSC-platelet's coagulation hyporeactivity compared to adult platelets was confirmed by thromboelastometry. Further stepwise improvement of hiPSC-platelet production will, thus, permit better identification of platelet-mediated regenerative mechanisms and facilitate manufacture of sufficient amounts of functional platelets for clinical application.

Unraveling the Spatiotemporal Human Pluripotency in Embryonic Development

There have been significant advances in understanding human embryogenesis using human pluripotent stem cells (hPSCs) in conventional monolayer and 3D self-organized cultures. Thus, in vitro models have contributed to elucidate the molecular mechanisms for specification and differentiation during development. However, the molecular and functional spectrum of human pluripotency (i.e., intermediate states, pluripotency subtypes and regionalization) is still not fully understood. This review describes the mechanisms that establish and maintain pluripotency in human embryos and their differences with mouse embryos. Further, it describes a new pluripotent state representing a transition between naïve and primed pluripotency. This review also presents the data that divide pluripotency into substates expressing epiblast regionalization and amnion specification as well as primordial germ cells in primates. Finally, this work analyzes the amnion's relevance as an "signaling center" for regionalization before the onset of gastrulation.

Long noncoding RNA LYPLAL1-AS1 regulates adipogenic differentiation of human mesenchymal stem cells by targeting desmoplakin and inhibiting the Wnt/β-catenin pathway

Long noncoding RNAs are crucial factors for modulating adipogenic differentiation, but only a few have been identified in humans. In the current study, we identified a previously unknown human long noncoding RNA, LYPLAL1-antisense RNA1 (LYPLAL1-AS1), which was dramatically upregulated during the adipogenic differentiation of human adipose-derived mesenchymal stem cells (hAMSCs). Based on 5' and 3' rapid amplification of cDNA ends assays, full-length LYPLAL1-AS1 was 523 nt. Knockdown of LYPLAL1-AS1 decreased the adipogenic differentiation of hAMSCs, whereas overexpression of LYPLAL1-AS1 enhanced this process. Desmoplakin (DSP) was identified as a direct target of LYPLAL1-AS1. Knockdown of DSP enhanced adipogenic differentiation and rescued the LYPLAL1-AS1 depletion-induced defect in adipogenic differentiation of hAMSCs. Further experiments showed that LYPLAL1-AS1 modulated DSP protein stability possibly via proteasome degradation, and the Wnt/β-catenin pathway was inhibited during adipogenic differentiation regulated by the LYPLAL1-AS1/DSP complex. Together, our work provides a new mechanism by which long noncoding RNA regulates adipogenic differentiation of human MSCs and suggests that LYPLAL1-AS1 may serve as a novel therapeutic target for preventing and combating diseases related to abnormal adipogenesis, such as obesity.