Functional neuronal cells generated by human parthenogenetic stem cells

Crosstalk between RNA m6A and DNA methylation regulates transposable element chromatin activation and cell fate in human pluripotent stem cells

Transposable elements (TEs) are parasitic DNA sequences accounting for over half of the human genome. Tight control of the repression and activation states of TEs is critical for genome integrity, development, immunity and diseases, including cancer. However, precisely how this regulation is achieved remains unclear. Here we develop a targeted proteomic proximity labeling approach to capture TE-associated proteins in human embryonic stem cells (hESCs). We find that the RNA N6-methyladenosine (m6A) reader, YTHDC2, occupies genomic loci of the primate-specific TE, LTR7/HERV-H, specifically through its interaction with m6A-modified HERV-H RNAs. Unexpectedly, YTHDC2 recruits the DNA 5-methylcytosine (5mC)-demethylase, TET1, to remove 5mC from LTR7/HERV-H and prevent epigenetic silencing. Functionally, the YTHDC2/LTR7 axis inhibits neural differentiation of hESCs. Our results reveal both an underappreciated crosstalk between RNA m6A and DNA 5mC, the most abundant regulatory modifications of RNA and DNA in eukaryotes, and the fact that in hESCs this interplay controls TE activity and cell fate.

IL-1β promotes disc degeneration and inflammation through direct injection of intervertebral disc in a rat lumbar disc herniation model

BACKGROUND CONTEXT

Lumbar intervertebral disc herniation (LDH) is a common disease that causes low back pain, radiating leg pain, and sensory impairment. Preclinical studies rely heavily upon standardized animal models of human diseases to predict clinical treatment efficacy and to identify and investigate potential adverse events in human subjects. The current method for making the LDH model involves harvesting the nucleus pulposus (NP) from autologous coccygeal discs and applying to the lumbar nerve roots just proximal to the corresponding dorsal root ganglion. However, this surgical method generates a model that exhibits very different characteristics of disc herniation than that observed in human.

PURPOSE

To produce a rat LDH model that better resembles disc herniation in humans and a standardized and uniform LDH model using Interleukin-1 beta (IL-1β).

STUDY DESIGN

Experimental rat LDH model.

METHODS

We exposed the L5-6 disc dorsolaterally on the right side through hemi-laminectomy without nerve compression. Herniation was initiated by puncturing the exposed disc with a 30-gauge needle at a depth of 4 mm. Interleukin-1 beta (IL-1β) was injected simultaneously to heighten the pathological processes of disc degeneration, including inflammatory responses, matrix destruction, and herniation of the NP. We performed histological staining to assess morphological changes, immunohistochemistry to analyze inflammation- and pain-related expression within and around the puncture site of the L5-6 disc, and real-time polymerase chain reaction to examine expression of markers for degenerative processes. In addition, we performed locomotor tests on the rats.

RESULTS

We found that the IL-1β groups showed that the border between the annulus fibrosis and nucleus pulposus was severely interrupted compared to that of the control (puncture only) group. And, the injection of IL-1β leads to accelerated disc degeneration and inflammation in a more consistent manner in LDH model. Functional deficit was consistently induced by puncturing and injection of IL-1β in the exposed disc.

CONCLUSIONS

The method proposed here can be used as an index to control the severity of disc degeneration and inflammation through the injected IL-1β concentration concurrent with surgically induced herniation.

CLINICAL SIGNIFICANCE

Our proposed model may facilitate research in drug development to evaluate the efficacy of potential therapeutic agents for disc herniation and neuropathic pain and may also be used for nonclinical studies to more accurately assess the effectiveness of various treatment strategies according to the severity of disc degeneration.

Generation of human androgenetic induced pluripotent stem cells

In humans, parthenogenesis and androgenesis occur naturally in mature cystic ovarian teratomas and androgenetic complete hydatidiform moles (CHM), respectively. Our previous study has reported human parthenogenetic induced pluripotent stem cells from ovarian teratoma-derived fibroblasts and screening of imprinted genes using genome-wide DNA methylation analysis. However, due to the lack of the counterparts of uniparental cells, identification of new imprinted differentially methylated regions has been limited. CHM are inherited from only the paternal genome. In this study, we generated human androgenetic induced pluripotent stem cells (AgHiPSCs) from primary androgenetic fibroblasts derived from CHM. To investigate the pluripotency state of AgHiPSCs, we analyzed their cellular and molecular characteristics. We tested the DNA methylation status of imprinted genes using bisulfite sequencing and demonstrated the androgenetic identity of AgHiPSCs. AgHiPSCs might be an attractive alternative source of human androgenetic embryonic stem cells. Furthermore, AgHiPSCs can be used in regenerative medicine, for analysis of genomic imprinting, to study imprinting-related development, and for disease modeling in humans.

Mouse Parthenogenetic Embryonic Stem Cells with Biparental-Like Expression of Imprinted Genes Generate Cortical-Like Neurons That Integrate into the Injured Adult Cerebral Cortex

One strategy for stem cell-based therapy of the cerebral cortex involves the generation and transplantation of functional, histocompatible cortical-like neurons from embryonic stem cells (ESCs). Diploid parthenogenetic Pg-ESCs have recently emerged as a promising source of histocompatible ESC derivatives for organ regeneration but their utility for cerebral cortex therapy is unknown. A major concern with Pg-ESCs is genomic imprinting. In contrast with biparental Bp-ESCs derived from fertilized oocytes, Pg-ESCs harbor two maternal genomes but no sperm-derived genome. Pg-ESCs are therefore expected to have aberrant expression levels of maternally expressed (MEGs) and paternally expressed (PEGs) imprinted genes. Given the roles of imprinted genes in brain development, tissue homeostasis and cancer, their deregulation in Pg-ESCs might be incompatible with therapy. Here, we report that, unexpectedly, only one gene out of 7 MEGs and 12 PEGs was differentially expressed between Pg-ESCs and Bp-ESCs while 13 were differentially expressed between androgenetic Ag-ESCs and Bp-ESCs, indicating that Pg-ESCs but not Ag-ESCs, have a Bp-like imprinting compatible with therapy. In vitro, Pg-ESCs generated cortical-like progenitors and electrophysiologically active glutamatergic neurons that maintained the Bp-like expression levels for most imprinted genes. In vivo, Pg-ESCs participated to the cortical lineage in fetal chimeras. Finally, transplanted Pg-ESC derivatives integrated into the injured adult cortex and sent axonal projections in the host brain. In conclusion, mouse Pg-ESCs generate functional cortical-like neurons with Bp-like imprinting and their derivatives properly integrate into both the embryonic cortex and the injured adult cortex. Collectively, our data support the utility of Pg-ESCs for cortical therapy. Stem Cells 2018;36:192-205.

Morphogenesis of human embryonic stem cells into mature neurons under in vitro culture conditions

AIM

To describe the morphogenesis of different neuronal cells from the human embryonic stem cell (hESC) line, SCT-N, under in vitro culture conditions.

METHODS

The directed neuronal cell line was produced from a single, spare, pre-implantation stage fertilized ovum that was obtained during a natural in vitro fertilization process. The hESCs were cultured and maintained as per our proprietary in-house technology in a Good Manufacturing Practice, Good Laboratory Practice and Good Tissue Practice compliant laboratory. The cell line was derived and incubated in aerobic conditions. The cells were examined daily under a phase contrast microscope for their growth and differentiation.

RESULTS

Different neural progenitor cells (NPCs) and differentiating neurons were observed under the culture conditions. Multipotent NPCs differentiated into all three types of nervous system cells, i.e., neurons, oligodendrocytes and astrocytes. Small projections resembling neurites or dendrites, and protrusion coming out of the cells, were observed. Differentiating cells were observed at day 18 to 20. The differentiating neurons, neuronal bodies, axons, and neuronal tissue were observed on day 21 and day 30 of the culture. On day 25 and day 30, prominent neurons, axons and neuronal tissue were observed under phase contrast microscopy. 4’, 6-diamidino-2-phenylindole staining also indicated the pattern of differentiating neurons, axonal structure and neuronal tissue.

CONCLUSION

This study describes the generation of different neuronal cells from an hESC line derived from biopsy of blastomeres at the two-cell cleavage stage from a discarded embryo.

Directing the Differentiation of Parthenogenetic Stem Cells into Tenocytes for Tissue-Engineered Tendon Regeneration

Uniparental parthenogenesis yields pluripotent stem cells without the political and ethical concerns surrounding the use of embryonic stem cells (ESCs) for biomedical applications. In the current study, we hypothesized that parthenogenetic stem cells (pSCs) could be directed to differentiate into tenocytes and applied for tissue‐engineered tendon. We showed that pSCs displayed fundamental properties similar to those of ESCs, including pluripotency, clonogenicity, and self‐renewal capacity. pSCs spontaneously differentiated into parthenogenetic mesenchymal stem cells (pMSCs), which were positive for mesenchymal stem cell surface markers and possessed osteogenic, chondrogenic, and adipogenic potential. Then, mechanical stretch was applied to improve the tenogenic differentiation of pMSCs, as indicated by the expression of tenogenic‐specific markers and an increasing COL1A1:3A1 ratio. The pSC‐derived tenocytes could proliferate and secrete extracellular matrix on the surface of poly(lactic‐co‐glycolic) acid scaffolds. Finally, engineered tendon‐like tissue was successfully generated after in vivo heterotopic implantation of a tenocyte‐scaffold composite. In conclusion, our experiment introduced an effective and practical strategy for applying pSCs for tendon regeneration. Stem Cells Translational Medicine2017;6:196–208

Establishment of Homozygote Mutant Human Embryonic Stem Cells by Parthenogenesis

We report on the derivation of a diploid 46(XX) human embryonic stem cell (HESC) line that is homozygous for the common deletion associated with Spinal muscular atrophy type 1 (SMA) from a pathenogenetic embryo. By characterizing the methylation status of three different imprinted loci (MEST, SNRPN and H19), monitoring the expression of two parentally imprinted genes (SNRPN and H19) and carrying out genome-wide SNP analysis, we provide evidence that this cell line was established from the activation of a mutant oocyte by diploidization of the entire genome. Therefore, our SMA parthenogenetic HESC (pHESC) line provides a proof-of-principle for the establishment of diseased HESC lines without the need for gene manipulation. As mutant oocytes are easily obtained and readily available during preimplantation genetic diagnosis (PGD) cycles, this approach should provide a powerful tool for disease modelling and is especially advantageous since it can be used to induce large or complex mutations in HESCs, including gross DNA alterations and chromosomal rearrangements, which are otherwise hard to achieve.

Gene expression in breastmilk cells is associated with maternal and infant characteristics

Breastmilk is a rich source of cells with a heterogeneous composition comprising early-stage stem cells, progenitors and more differentiated cells. The gene expression profiles of these cells and their associations with characteristics of the breastfeeding mother and infant are poorly understood. This study investigated factors associated with the cellular dynamics of breastmilk and explored variations amongst women. Genes representing different breastmilk cell populations including mammary epithelial and myoepithelial cells, progenitors, and multi-lineage stem cells showed great variation in expression. Stem cell markers ESRRB and CK5, myoepithelial marker CK14, and lactocyte marker α-lactalbumin were amongst the genes most highly expressed across all samples tested. Genes exerting similar functions, such as either stem cell regulation or milk production, were found to be closely associated. Infant gestational age at delivery and changes in maternal bra cup size between pre-pregnancy and postpartum lactation were associated with expression of genes controlling stemness as well as milk synthesis. Additional correlations were found between genes and dyad characteristics, which may explain abnormalities related to low breastmilk supply or preterm birth. Our findings highlight the heterogeneity of breastmilk cell content and its changes associated with characteristics of the breastfeeding dyad that may reflect changing infant needs.

Human Parthenogenetic Embryonic Stem Cell-Derived Neural Stem Cells Express HLA-G and Show Unique Resistance to NK Cell-Mediated Killing

Parent-of-origin imprints have been implicated in the regulation of neural differentiation and brain development. Previously we have shown that, despite the lack of a paternal genome, human parthenogenetic (PG) embryonic stem cells (hESCs) can form proliferating neural stem cells (NSCs) that are capable of differentiation into physiologically functional neurons while maintaining allele-specific expression of imprinted genes. Since biparental ("normal") hESC-derived NSCs (N NSCs) are targeted by immune cells, we characterized the immunogenicity of PG NSCs. Flow cytometry and immunocytochemistry revealed that both N NSCs and PG NSCs exhibited surface expression of human leukocyte antigen (HLA) class I but not HLA-DR molecules. Functional analyses using an in vitro mixed lymphocyte reaction assay resulted in less proliferation of peripheral blood mononuclear cells (PBMC) with PG compared with N NSCs. In addition, natural killer (NK) cells cytolyzed PG less than N NSCs. At a molecular level, expression analyses of immune regulatory factors revealed higher HLA-G levels in PG compared with N NSCs. In line with this finding, MIR152, which represses HLA-G expression, is less transcribed in PG compared with N cells. Blockage of HLA-G receptors ILT2 and KIR2DL4 on natural killer cell leukemia (NKL) cells increased cytolysis of PG NSCs. Together this indicates that PG NSCs have unique immunological properties due to elevated HLA-G expression.