Activated ovarian endothelial cells promote early follicular development and survival.

BACKGROUND: New data suggests that endothelial cells (ECs) elaborate essential "angiocrine factors". The aim of this study is to investigate the role of activated ovarian endothelial cells in early in-vitro follicular development. METHODS: Mouse ovarian ECs were isolated using magnetic cell sorting or by FACS and cultured in serum free media. After a constitutive activation of the Akt pathway was initiated, early follicles (50-150 um) were mechanically isolated from 8-day-old mice and co-cultured with these activated ovarian endothelial cells (AOEC) (n = 32), gel (n = 24) or within matrigel (n = 27) in serum free media for 14 days. Follicular growth, survival and function were assessed. RESULTS: After 6 passages, flow cytometry showed 93% of cells grown in serum-free culture were VE-cadherin positive, CD-31 positive and CD 45 negative, matching the known EC profile. Beginning on day 4 of culture, we observed significantly higher follicular and oocyte growth rates in follicles co-cultured with AOECs compared with follicles on gel or matrigel. After 14 days of culture, 73% of primary follicles and 83% of secondary follicles co-cultured with AOEC survived, whereas the majority of follicles cultured on gel or matrigel underwent atresia. CONCLUSIONS: This is the first report of successful isolation and culture of ovarian ECs. We suggest that co-culture with activated ovarian ECs promotes early follicular development and survival. This model is a novel platform for the in vitro maturation of early follicles and for the future exploration of endothelial-follicular communication. CAPSULE: In vitro development of early follicles necessitates a complex interplay of growth factors and signals required for development. Endothelial cells (ECs) may elaborate essential "angiocrine factors" involved in organ regeneration. We demonstrate that co-culture with ovarian ECs enables culture of primary and early secondary mouse ovarian follicles.

Reprogramming human endothelial cells to haematopoietic cells requires vascular induction.

Generating engraftable human haematopoietic cells from autologous tissues is a potential route to new therapies for blood diseases. However, directed differentiation of pluripotent stem cells yields haematopoietic cells that engraft poorly. Here, we have devised a method to phenocopy the vascular-niche microenvironment of haemogenic cells, thereby enabling reprogramming of human endothelial cells into engraftable haematopoietic cells without transition through a pluripotent intermediate. Highly purified non-haemogenic human umbilical vein endothelial cells or adult dermal microvascular endothelial cells were transduced with the transcription factors FOSB, GFI1, RUNX1 and SPI1 (hereafter referred to as FGRS), and then propagated on serum-free instructive vascular niche monolayers to induce outgrowth of haematopoietic colonies containing cells with functional and immunophenotypic features of multipotent progenitor cells (MPPs). These endothelial cells that have been reprogrammed into human MPPs (rEC-hMPPs) acquire colony-forming-cell potential and durably engraft into immune-deficient mice after primary and secondary transplantation, producing long-term rEC-hMPP-derived myeloid (granulocytic/monocytic, erythroid, megakaryocytic) and lymphoid (natural killer and B cell) progenies. Conditional expression of FGRS transgenes, combined with vascular induction, activates endogenous FGRS genes, endowing rEC-hMPPs with a transcriptional and functional profile similar to that of self-renewing MPPs. Our approach underscores the role of inductive cues from the vascular niche in coordinating and sustaining haematopoietic specification and may prove useful for engineering autologous haematopoietic grafts to treat inherited and acquired blood disorders.

Development of patient-specific neurons in schizophrenia using induced pluripotent stem cells.

Induced pluripotent stem cell (iPSC) technology has the potential to transform regenerative medicine. It also offers a powerful tool for establishing in vitro models of disease, in particular, for neuropsychiatric disorders where live human neurons are essentially impossible to procure. Using iPSCs derived from three schizophrenia (SZ) patients, one of whom has 22q11.2del (velocardiofacial syndrome; VCFS), the authors developed a culture system to study SZ on a molecular and cellular level. SZ iPSCs were differentiated into functional, primarily glutamatergic neurons that were able to fire action potentials after ∼8 weeks in culture. Early differentiating neurons expressed a number of transcription factors/chromatin remodeling proteins and synaptic proteins relevant to SZ pathogenesis, including ZNF804A, RELN, CNTNAP2, CTNNA2, SMARCA2, and NRXN1. Although a small number of lines were developed in this preliminary study, the SZ line containing 22q11.2del showed a significant delay in the reduction of endogenous OCT4 and NANOG expression that normally occurs during differentiation. Constitutive expression of OCT4 has been observed in Dgcr8-deficient mouse embryonic stem cells (mESCs); DGCR8 maps to the 22q11.2-deleted region. These findings demonstrate that the method of inducing neural differentiation employed is useful for disease modeling in SZ and that the transition of iPSCs with 22q11.2 deletions towards a differentiated state may be marked by subtle changes in expression of pluripotency-associated genes.

Reprogramming of embryonic human fibroblasts into fetal hematopoietic progenitors by fusion with human fetal liver CD34+ cells.

Experiments with somatic cell nuclear transfer, inter-cellular hybrid formation_ENREF_3, and ectopic expression of transcription factors have clearly demonstrated that cell fate can be dramatically altered by changing the epigenetic state of cell nuclei. Here we demonstrate, using chemical fusion, direct reprogramming of the genome of human embryonic fibroblasts (HEF) into the state of human fetal liver hFL CD34+ (hFL) hematopoietic progenitors capable of proliferating and differentiating into multiple hematopoietic lineages. We show that hybrid cells retain their ploidy and can differentiate into several hematopoietic lineages. Hybrid cells follow transcription program of differentiating hFL cells as shown by genome-wide transcription profiling. Using whole-genome single nucleotide polymorphism (SNP) profiling of both donor genomes we demonstrate reprogramming of HEF genome into the state of hFL hematopoietic progenitors. Our results prove that it is possible to convert the fetal somatic cell genome into the state of fetal hematopoietic progenitors by fusion. This suggests a possibility of direct reprogramming of human somatic cells into tissue specific progenitors/stem cells without going all the way back to the embryonic state. Direct reprogramming of terminally differentiated cells into the tissue specific progenitors will likely prove useful for the development of novel cell therapies.

Reprogramming after chromosome transfer into mouse blastomeres.

It is well known that oocytes can reprogram differentiated cells, allowing animal cloning by nuclear transfer. We have recently shown that fertilized zygotes retain reprogramming activities, suggesting that such activities might also persist in cleavage-stage embryos. Here, we used chromosome transplantation techniques to investigate whether the blastomeres of two-cell-stage mouse embryos can reprogram more differentiated cells. When chromosomes from one of the two blastomeres were replaced with the chromosomes of an embryonic or CD4(+) T lymphocyte donor cell, we observed nuclear reprogramming and efficient contribution of the manipulated cell to the developing blastocyst. Embryos produced by this method could be used to derive stem cell lines and also developed to term, generating mosaic "cloned" animals. These results demonstrate that blastomeres retain reprogramming activities and support the notion that discarded human preimplantation embryos may be useful recipients for the production of genetically tailored human embryonic stem cell lines.

Reprogramming of human somatic cells using human and animal oocytes.

There is renewed interest in using animal oocytes to reprogram human somatic cells. Here we compare the reprogramming of human somatic nuclei using oocytes obtained from animal and human sources. Comparative analysis of gene expression in morula-stage embryos was carried out using single-embryo transcriptome amplification and global gene expression analyses. Genomic DNA fingerprinting and PCR analysis confirmed that the nuclear genome of the cloned embryos originated from the donor somatic cell. Although the human-human, human-bovine, and human-rabbit clones appeared morphologically similar and continued development to the morula stage at approximately the same rate (39, 36, and 36%, respectively), the pattern of reprogramming of the donor genome was dramatically different. In contrast to the interspecies clones, gene expression profiles of the human-human embryos showed that there was extensive reprogramming of the donor nuclei through extensive upregulation, and that the expression pattern was similar in key upregulation in normal control embryos. To account for maternal gene expression, enucleated oocyte transcriptome profiles were subtracted from the corresponding morula-stage embryo profiles. t-Test comparisons (median-normalized data @ fc>4; p<0.005) between human in vitro fertilization (IVF) embryos and human-bovine or human-rabbit interspecies somatic cell transfer (iSCNT) embryos found between 2400 and 2950 genes that were differentially expressed, the majority (60-70%) of which were downregulated, whereas the same comparison between the bovine and rabbit oocyte profiles found no differences at all. In contrast to the iSCNT embryos, expression profiles of human-human clones compared to the age-matched IVF embryos showed that nearly all of the differentially expressed genes were upregulated in the clones. Importantly, the human oocytes significantly upregulated Oct-4, Sox-2, and nanog (22-fold, 6-fold, and 12-fold, respectively), whereas the bovine and rabbit oocytes either showed no difference or a downregulation of these critical pluripotency-associated genes, effectively silencing them. Without appropriate reprogramming, these data call into question the potential use of these discordant animal oocyte sources to generate patient-specific stem cells.

NMDA-receptor-mediated, cell-specific integration of new neurons in adult dentate gyrus.

New neurons are continuously integrated into existing neural circuits in adult dentate gyrus of the mammalian brain. Accumulating evidence indicates that these new neurons are involved in learning and memory. A substantial fraction of newly born neurons die before they mature and the survival of new neurons is regulated in an experience-dependent manner, raising the possibility that the selective survival or death of new neurons has a direct role in a process of learning and memory--such as information storage--through the information-specific construction of new circuits. However, a critical assumption of this hypothesis is that the survival or death decision of new neurons is information-specific. Because neurons receive their information primarily through their input synaptic activity, we investigated whether the survival of new neurons is regulated by input activity in a cell-specific manner. Here we developed a retrovirus-mediated, single-cell gene knockout technique in mice and showed that the survival of new neurons is competitively regulated by their own NMDA-type glutamate receptor during a short, critical period soon after neuronal birth. This finding indicates that the survival of new neurons and the resulting formation of new circuits are regulated in an input-dependent, cell-specific manner. Therefore, the circuits formed by new neurons may represent information associated with input activity within a short time window in the critical period. This information-specific addition of new circuits through selective survival or death of new neurons may be a unique attribute of new neurons that enables them to play a critical role in learning and memory.

Development of functional human embryonic stem cell-derived neurons in mouse brain.

Human embryonic stem cells are pluripotent entities, theoretically capable of generating a whole-body spectrum of distinct cell types. However, differentiation of these cells has been observed only in culture or during teratoma formation. Our results show that human embryonic stem cells implanted in the brain ventricles of embryonic mice can differentiate into functional neural lineages and generate mature, active human neurons that successfully integrate into the adult mouse forebrain. Moreover, this study reveals the conservation and recognition of common signals for neural differentiation throughout mammalian evolution. The chimeric model will permit the study of human neural development in a live environment, paving the way for the generation of new models of human neurodegenerative and psychiatric diseases. The model also has the potential to speed up the screening process for therapeutic drugs.

Modified herpes simplex virus delivery of enhanced GFP into the central nervous system.

Controlled expression of proteins is a key experimental approach to a deeper understanding of the molecular basis of neuronal function. Here we evaluate the HSV-1 (herpes simplex virus) amplicon vector for gene delivery into the brains of living rats. We demonstrate that HSV-1 amplicon vectors expressing enhanced green fluorescent protein (EGFP) can reliably infect neurons after it is injected into cortex, striatum and thalamus in rats, producing sufficient numbers of infected neurons for electrophysiological experiments in acute brain slices. Expression of EGFP delivered by the HSV-1 amplicon was detected for up to 5 weeks post-infection. We detected no changes in the morphology or the electrophysiological properties of thalamic, striatal or cortical neurons within a period of at least 2 weeks after HSV-1 amplicon injection. We conclude that the HSV-1 amplicon is a valuable tool for gene delivery in the rat central nervous system.