Expression of Neurodevelopmental Markers by Cultured Porcine Neural Precursor Cells

Single-cell transcriptional regulation and genetic evolution of neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC) is a lethal subtype of prostate cancer, with a 10% five-year survival rate. However, little is known about its origin and the mechanisms governing its emergence. Our study characterized ADPC and NEPC in prostate tumors from 7 patients using scRNA-seq. First, we identified two NEPC gene expression signatures representing different phases of trans-differentiation. New marker genes we identified may be used for clinical diagnosis. Second, integrative analyses combining expression and subclonal architecture revealed different paths by which NEPC diverges from the original ADPC, either directly from treatment-naïve tumor cells or from specific intermediate states of treatment-resistance. Third, we inferred a hierarchical transcription factor (TF) network underlying the progression, which involves constitutive regulation by ASCL1, FOXA2, and selective regulation by NKX2-2, POU3F2, and SOX2. Together, these results defined the complex expression profiles and advanced our understanding of the genetic and transcriptomic mechanisms leading to NEPC differentiation.

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Single-cell RNA sequencing revealed two distinct transcriptional programs of NEPC

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Cell-level clonal evolution analysis extended the divergent model of ADPC to NEPC

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Screening of NEPC-specific transcription factors through network-based approaches

Isolation and characterization of neural stem cells from fetal canine spinal cord

Neurogenesis in adult mammals occurs mainly in the subventricular and subgranular areas of the brain, but there are also reports of its occurrence in the spinal cord. In a study on rats, neural stem cells and neuroprogenitor cells could be obtained through primary spinal cord culture, but there are no studies on these cells in canine species, to date. Dogs represent an appropriate animal model for studies on neurogenesis and neurological disorders. In addition, they are animals of great affective value, and the therapeutic use of neural stem cells can represent a breakthrough in regenerative veterinary medicine. Therefore, this study aimed to determine a protocol for the isolation, culture, and characterization of neural and neuroprogenitor stem cells derived from the spinal cord of canine fetuses. The cells were isolated from spinal cord fragments and cultured in serum-free culture medium supplemented with EGF and FGF-2 growth factors. These cells were observed daily by optical microscopy to analyze their morphological characteristics. From the third day in vitro, it was possible to observe translucent cell groupings, similar to the neurospheres, which approximately ranged from 50 µm to 200 µm at seven days in vitro. Throughout the culture period, the neurospheres developed ribbons in their periphery that migrated and communicated with other neurospheres. RT-PCR revealed that the cells expressed the characteristic genes SOX2, NESTIN, and GFAP. In addition to gene expression, the cells were phenotypically marked in the immunofluorescence assay for the proteins Nestin, GFAP, and β-tubulin III, characterizing them as neurospheres. Our results suggest that the spinal cord may be a source of neural stem cells and neural progenitor cells in canine fetuses. These cells may be an interesting option for neurogenesis and neuroregenerative therapy studies.

Generation of neural progenitor cells from porcine-induced pluripotent stem cells

In this study, porcine embryonic fibroblasts (pEFs) were reprogrammed into porcine-induced pluripotent stem cells (piPSCs) using either human or mouse specific sequences for the OCT4, SOX2, c-Myc, and KLF4 transcription factors. In total, three pEFs lines were reprogrammed, cultured for at least 15 passages, and characterized regarding their pluripotency status (alkaline phosphatase expression, embryoid body formation, expression of exogenous and endogenous genes, and immunofluorescence). Two piPSC lines were further differentiated, using chemical inhibitors, into putative neural progenitor-like (NPC-like) cells with subsequent analyses of their morphology and expression of neural markers such as NESTIN and GFAP as well as immunofluorescent labeling of NESTIN, β-TUBULIN III, and VIMENTIN. NPC-like cells were positive for all the neural markers tested. These results evidence of the generation of porcine NPC-like cells after in vitro induction with chemical inhibitors, representing an adequate model for future regenerative and translational medicine research.

Grafted Miniature-Swine Neural Stem Cells of Early Embryonic Mesencephalic Neuroepithelial Origin can Repair the Damaged Neural Circuitry of Parkinson's Disease Model Rats

Although recent progress in the use of human iPS cell-derived midbrain dopaminergic progenitors is remarkable, alternatives are essential in the strategies of treatment of basal-ganglia-related diseases. Attention has been focused on neural stem cells (NSCs) as one of the possible candidates of donor material for neural transplantation, because of their multipotency and self-renewal characteristics. In the present study, miniature-swine (mini-swine) mesencephalic neuroepithelial stem cells (M-NESCs) of embryonic 17 and 18 days grafted in the parkinsonian rat striatum were assessed immunohistochemically, behaviorally and electrophysiologically to confirm their feasibility for the neural xenografting as a donor material. Grafted mini-swine M-NESCs survived in parkinsonian rat striatum at 8 weeks after transplantation and many of them differentiated into tyrosine hydroxylase (TH)-positive cells. The parkinsonian model rats grafted with mini-swine M-NESCs exhibited a functional recovery from their parkinsonian behavioral defects. The majority of donor-derived TH-positive cells exhibited a matured morphology at 8 weeks. Whole-cell recordings from donor-derived neurons in the host rat brain slices incorporating the graft revealed the presence of multiple types of neurons including dopaminergic. Glutamatergic and GABAergic post-synaptic currents were evoked in the donor-derived cells by stimulation of the host site, suggesting they receive both excitatory and inhibitory synaptic inputs from host area. The present study shows that non-rodent mammalian M-NESCs can differentiate into functionally active neurons in the diseased xenogeneic environment and could improve the parkinsonian behavioral defects over the species. Neuroepithelial stem cells could be an attractive candidate as a source of donor material for neural transplantation.

Generation of a Stable Transgenic Swine Model Expressing a Porcine Histone 2B-eGFP Fusion Protein for Cell Tracking and Chromosome Dynamics Studies

Transgenic pigs have become an attractive research model in the field of translational research, regenerative medicine, and stem cell therapy due to their anatomic, genetic and physiological similarities with humans. The development of fluorescent proteins as molecular tags has allowed investigators to track cell migration and engraftment levels after transplantation. Here we describe the development of two transgenic pig models via SCNT expressing a fusion protein composed of eGFP and porcine Histone 2B (pH2B). This fusion protein is targeted to the nucleosomes resulting a nuclear/chromatin eGFP signal. The first model (I) was generated via random insertion of pH2B-eGFP driven by the CAG promoter (chicken beta actin promoter and rabbit Globin poly A; pCAG-pH2B-eGFP) and protected by human interferon-β matrix attachment regions (MARs). Despite the consistent, high, and ubiquitous expression of the fusion protein pH2B-eGFP in all tissues analyzed, two independently generated Model I transgenic lines developed neurodegenerative symptoms including Wallerian degeneration between 3–5 months of age, requiring euthanasia. A second transgenic model (II) was developed via CRISPR-Cas9 mediated homology-directed repair (HDR) of IRES-pH2B-eGFP into the endogenous β-actin (ACTB) locus. Model II transgenic animals showed ubiquitous expression of pH2B-eGFP on all tissues analyzed. Unlike the pCAG-pH2B-eGFP/MAR line, all Model II animals were healthy and multiple pregnancies have been established with progeny showing the expected Mendelian ratio for the transmission of the pH2B-eGFP. Expression of pH2B-eGFP was used to examine the timing of the maternal to zygotic transition after IVF, and to examine chromosome segregation of SCNT embryos. To our knowledge this is the first viable transgenic pig model with chromatin-associated eGFP allowing both cell tracking and the study of chromatin dynamics in a large animal model.

Comparison of the characteristics and multipotential and in vivo cartilage formation capabilities between porcine adipose-derived stem cells and porcine skin-derived stem cell-like cells

OBJECTIVE

To compare the characteristics and multipotential and in vivo cartilage formation capabilities of porcine adipose-derived stem cells (pASCs) with those of porcine skin-derived stem cell-like cells (pSSCs).

ANIMALS

Three 6-month-old female pigs and four 6-week-old female athymic mice.

PROCEDURES

Adipose and skin tissue specimens were obtained from each pig following slaughter and digested to obtain pASCs and pSSCs. For each cell type, flow cytometry and reverse transcription PCR assays were performed to characterize the expression of cell surface and mesenchymal stem cell markers, and in vitro cell cultures were performed to determine the adipogenic, osteogenic, and chondrogenic capabilities. Each cell type was then implanted into athymic mice to determine the extent of in vivo cartilage formation after 6 weeks.

RESULTS

The cell surface and mesenchymal stem cell marker expression patterns, multipotential capability, and extent of in vivo cartilage formation did not differ significantly between pASCs and pSSCs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that pSSCs may be a viable alternative to pASCs as a source of progenitor cells for tissue engineering in regenerative medicine.

Transcriptomic analysis of Rongchang pig brains and livers

Recent developments in high-throughput RNA sequencing (RNA-seq) technology have led to a dramatic impact on our understanding of the structure and expression profiles of the mammalian transcriptome. To gain insights into the usefulness of swine production and biomedical model, the transcriptome profiling of Rongchang pig brains and livers was characterized using RNA-seq technology to uncover functional candidate molecules. In the study, total RNAs from brains and livers of Rongchang pig were sequenced and 8.6Gb sequencing data was obtained. This analysis revealed tissue specificity through the identification of 5575 and 4600 differentially expressed genes (DEGs) in brains and livers, respectively and the functional analysis of DEGs. Furthermore, 83 neuropeptide gene transcripts, 69 neuropeptide receptor gene transcripts, 10 pro-neuropeptide convertase gene transcripts and many other neuropeptide related protein gene transcripts were identified. Totally, the major characteristics of the transcriptional profiles of Rongchang pig brains and livers were present.

Time course of spinal doublecortin expression in developing rat and porcine spinal cord: implication in in vivo neural precursor grafting studies

Expression of doublecortin (DCX), a 43-53 kDa microtubule binding protein, is frequently used as (i) an early neuronal marker to identify the stage of neuronal maturation of in vivo grafted neuronal precursors (NSCs), and (ii) a neuronal fate marker transiently expressed by immature neurons during development. Reliable identification of the origin of DCX-immunoreactive cells (i.e., host vs. graft) requires detailed spatial and temporal mapping of endogenous DCX expression at graft-targeted brain or spinal cord regions. Accordingly, in the present study, we analyzed (i) the time course of DCX expression in pre- and postnatal rat and porcine spinal cord, and (ii) the DCX expression in spinally grafted porcine-induced pluripotent stem cells (iPS)-derived NSCs and human embryonic stem cell (ES)-derived NSCs. In addition, complementary temporospatial GFAP expression study in porcine spinal cord was also performed. In 21-day-old rat fetuses, an intense DCX immunoreactivity distributed between the dorsal horn (DH) and ventral horn was seen and was still present in the DH neurons on postnatal day 20. In animals older than 8 weeks, no DCX immunoreactivity was seen at any spinal cord laminae. In contrast to rat, in porcine spinal cord (gestational period 113-114 days), DCX was only expressed during the pre-natal period (up to 100 days) but was no longer present in newborn piglets or in adult animals. Immunohistochemical analysis was confirmed with a comparable expression profile by western blot analysis. Contrary, the expression of porcine GFAP started within 70-80 days of the pre-natal period. Spinally grafted porcine iPS-NSCs and human ES-NSCs showed clear DCX expression at 3-4 weeks postgrafting. These data indicate that in spinal grafting studies which employ postnatal or adult porcine models, the expression of DCX can be used as a reliable marker of grafted neurons. In contrast, if grafted neurons are to be analyzed during the first 4 postnatal weeks in the rat spinal cord, additional markers or grafted cell-specific labeling techniques need to be employed to reliably identify grafted early postmitotic neurons and to differentiate the DCX expression from the neurons of the host.

Intestinal gene expression profiles of piglets benefit from maternal supplementation with a yeast mannan-rich fraction during gestation and lactation

The objective was to study the effect of maternal supplementation with a yeast cell wall-based product containing a mannan-rich fraction (MRF) during gestation and lactation on piglet intestinal gene expression. First parity sows were fed experimental gestation and lactation diets with or without MRF (900 mg/kg). After farrowing, piglets were fostered within treatment, as necessary. Sow and litter production performance data were collected until weaning. On day 10 post farrowing, jejunum samples from piglets were collected for gene expression analysis using the Affymetrix Porcine GeneChip array. Most performance parameters did not differ between the treatments. However, protein (P<0.01), total solids less fat (P<0.03) and the concentration of immunoglobulin G (IgG) in milk were greater (P<0.05) in the MRF-supplemented group. Gene expression results using hierarchical clustering revealed an overall dietary effect. Further analysis elucidated activation of pathways involved in tissue development, functioning and immunity, as well as greater cell proliferation and less migration of cells in the jejunum tissue. In conclusion, feeding the sow MRF during pregnancy and lactation was an effective nutritional strategy to bolster colostrum and milk IgG that are essential for development of piglet immune system and gut. In addition, the gene expression patterns affected by the passive immunity transfer showed indicators that could benefit animal performance long term.

Classification of subpopulations of cells within human primary brain tumors by single cell gene expression profiling

Brain tumors are heterogeneous with respect to genetic and histological properties of cells within the tumor tissue. To study subpopulations of cells, we developed a protocol for obtaining viable single cells from freshly isolated human brain tissue for single cell gene expression profiling. We evaluated this technique for characterization of cell populations within brain tumor and tumor penumbra. Fresh tumor tissue was obtained from one astrocytoma grade IV and one oligodendroglioma grade III tumor as well as the tumor penumbra of the latter tumor. The tissue was dissociated into individual cells and the expression of 36 genes was assessed by reverse transcription quantitative PCR followed by data analysis. We show that tumor cells from both the astrocytoma grade IV and oligodendroglioma grade III tumor constituted cell subpopulations defined by their gene expression profiles. Some cells from the oligodendroglioma grade III tumor proper shared molecular characteristics with the cells from the penumbra of the same tumor suggesting that a subpopulation of cells within the oligodendroglioma grade III tumor consisted of normal brain cells. We conclude that subpopulations of tumor cells can be identified by using single cell gene expression profiling.

Production of healthy cloned pigs with neural stem cells as nuclear donors

The objectives of the present study were to establish a porcine neural stem cell (NSC) line and to determine if these NSCs could be used to produce cloned pigs. NSCs were isolated from the brains of three embryonic day 30 fetal pigs and were induced to differentiate in vitro . NSCs and the differentiated cells were harvested for analysis of markers by immunostaining and reverse-transcription polymerase chain reaction (RT-PCR). The NSCs at passage 10 were used for nuclear transfer, and the cloned embryos at the two-cell stage were transferred into the oviducts of surrogate mothers. The results showed that three NSC lines (2 male and 1 female) were successfully established. All NSCs at passage 17 continued to express nestin and Sox2. NSCs could differentiate into neurons (TUBB3+), astrocytes (GFAP+), and oligodendrocytes (O4+). After NSC nuclear transfer, 2020 two-cell stage embryos formed. After embryo transfer, 6 of 10 surrogates were pregnant, and 40 piglets (18 males and 22 females) were born. Twenty-two of these piglets reached sexual maturity and were found to be fertile. The other piglets died within 45 days post-partum. In conclusion, 3 porcine NSC lines capable of self-renewal and differentiation were established, and the cloned embryos derived from these cells could develop to term. Thus, NSCs could be efficient alternative nuclear donors for pig cloning.

The olfactory bulb in newborn piglet is a reservoir of neural stem and progenitor cells

The olfactory bulb (OB) periventricular zone is an extension of the forebrain subventricular zone (SVZ) and thus is a source of neuroprogenitor cells and neural stem cells. While considerable information is available on the SVZ-OB neural stem cell (NSC)/neuroprogenitor cell (NPC) niche in rodents, less work has been done on this system in large animals. The newborn piglet is used as a preclinical translational model of neonatal hypoxic-ischemic brain damage, but information about the endogenous sources of NSCs/NPCs in piglet is needed to implement endogenous or autologous cell-based therapies in this model. We characterized NSC/NPC niches in piglet forebrain and OB-SVZ using western blotting, histological, and cell culture methods. Immunoblotting revealed nestin, a NSC/NPC marker, in forebrain-SVZ and OB-SVZ in newborn piglet. Several progenitor or newborn neuron markers, including Dlx2, musashi, doublecortin, and polysialated neural cell adhesion molecule were also detected in OB-SVZ by immunoblotting. Immunohistochemistry confirmed the presence of nestin, musashi, and doublecortin in forebrain-SVZ and OB-SVZ. Bromodeoxyuridine (BrdU) labeling showed that the forebrain-SVZ and OB-SVZ accumulate newly replicated cells. BrdU-positive cells were immunolabeled for astroglial, oligodendroglial, and neuronal markers. A lateral migratory pathway for newly born neuron migration to primary olfactory cortex was revealed by BrdU labeling and co-labeling for doublecortin and class III β tubulin. Isolated and cultured forebrain-SVZ and OB-SVZ cells from newborn piglet had the capacity to generate numerous neurospheres. Single cell clonal analysis of neurospheres revealed the capacity for self-renewal and multipotency. Neurosphere-derived cells differentiated into neurons, astrocytes, and oligodendrocytes and were amenable to permanent genetic tagging with lentivirus encoding green fluorescent protein. We conclude that the piglet OB-SVZ is a reservoir of NSCs and NPCs suitable to use in autologous cell therapy in preclinical models of neonatal/pediatric brain injury.

First survey and functional annotation of prohormone and convertase genes in the pig

Background

The pig is a biomedical model to study human and livestock traits. Many of these traits are controlled by neuropeptides that result from the cleavage of prohormones by prohormone convertases. Only 45 prohormones have been confirmed in the pig. Sequence homology can be ineffective to annotate prohormone genes in sequenced species like the pig due to the multifactorial nature of the prohormone processing. The goal of this study is to undertake the first complete survey of prohormone and prohormone convertases genes in the pig genome. These genes were functionally annotated based on 35 gene expression microarray experiments. The cleavage sites of prohormone sequences into potentially active neuropeptides were predicted.

Results

We identified 95 unique prohormone genes, 2 alternative calcitonin-related sequences, 8 prohormone convertases and 1 cleavage facilitator in the pig genome 10.2 assembly and trace archives. Of these, 11 pig prohormone genes have not been reported in the UniProt, UniGene or Gene databases. These genes are intermedin, cortistatin, insulin-like 5, orexigenic neuropeptide QRFP, prokineticin 2, prolactin-releasing peptide, parathyroid hormone 2, urocortin, urocortin 2, urocortin 3, and urotensin 2-related peptide. In addition, a novel neuropeptide S was identified in the pig genome correcting the previously reported pig sequence that is identical to the rabbit sequence. Most differentially expressed prohormone genes were under-expressed in pigs experiencing immune challenge relative to the un-challenged controls, in non-pregnant relative to pregnant sows, in old relative to young embryos, and in non-neural relative to neural tissues. The cleavage prediction based on human sequences had the best performance with a correct classification rate of cleaved and non-cleaved sites of 92% suggesting that the processing of prohormones in pigs is similar to humans. The cleavage prediction models did not find conclusive evidence supporting the production of the bioactive neuropeptides urocortin 2, urocortin 3, torsin family 2 member A, tachykinin 4, islet amyloid polypeptide, and calcitonin receptor-stimulating peptide 2 in the pig.

Conclusions

The present genomic and functional characterization supports the use of the pig as an effective animal model to gain a deeper understanding of prohormones, prohormone convertases and neuropeptides in biomedical and agricultural research.

Differential expression of CD133 based on microsatellite instability status in human colorectal cancer

The association between the types of genomic instability and cancer stem cell (CSC) has not been elucidated. We aimed to investigate the expressions of CSC markers with respect to microsatellite instability (MSI) status in human colorectal cancer (CRC). Immunostainings for CD133, CD44, and CD166, and K-ras mutation analysis were performed on 50 MSI-high (MSI-H), and 50 microsatellite stable (MSS) CRC tissues. In 11 MSS and MSI-H CRC cell lines, CD133 expression and DNA methylation statuses of the CD133 promoter were determined. The proportion of CD133 positive cells and the ability of colosphere formation were compared between HCT116 cells and HCT116 + Chr3 cells (hMLH1-restored HCT116 cells). Immunohistochemistry for CSC markers revealed that high CD133 expression was more frequent in MSS cancers than in MSI-H (P < 0.001, 74.0% vs. 28.0%, respectively), and related with short disease-free survival. Neither CD44 nor CD166 expression differed significantly with respect to MSI status. K-ras mutation showed no association with expressions of CD133, CD44, or CD166. CD133 expression was relatively high in the MSS cell lines compared to those in MSI-H, and showed a reverse correlation with DNA methylation of the CD133 promoter. hMLH1-restored HCT116 cells increased proportions of CD133 positive cells and colosphere forming ability, compared to those in HCT116 cells. In conclusion, high levels of CD133 expression were observed more frequently in MSS CRC than in MSI-H, suggesting that differential expression of colon CSC markers may be linked to tumor characteristics dependent on MSI status.

Comparison of chemical-induced changes in proliferation and apoptosis in human and mouse neuroprogenitor cells

There is a need to develop rapid and efficient models to screen chemicals for their potential to cause developmental neurotoxicity. Use of in vitro neuronal models, including human cells, is one approach that allows for timely, cost-effective toxicity screening. The present study compares the sensitivity of human (ReN CX) and mouse (mCNS) neuroprogenitor cell lines to chemicals using a multiplex assay for proliferation and apoptosis, endpoints that are critical for neural development. Cells were exposed to 0.001-100 μM concentrations of 11 chemicals (cadmium, chlorpyrifos oxon, dexamethasone, dieldrin, ketamine, lead, maneb, methylmercury, nicotine, trans-retinoic acid, and trimethyltin) reported in the literature to affect proliferation and/or apoptosis, and 5 chemicals (dimethyl pthalate, glyphosate, omeprazole, saccharin, and d-sorbitol) with no reports of effects on either endpoint. High-content screening of markers for proliferation (BrdU incorporation) and apoptosis (activated caspase 3 and p53) was used to assess the effect of chemicals in both cell lines. Of the chemicals tested, methylmercury, cadmium, dieldrin, chlorpyrifos oxon, trans-retinoic acid, and trimethyltin decreased proliferation by at least 50% of control in either the ReN CX or mCNS cells. None of the chemicals tested activated caspase 3 or p53 in the ReN CX cells, while methylmercury, cadmium, dieldrin, chlorpyrifos oxon, trimethyltin, and glyphosate all induced at least a doubling in these apoptotic markers in the mCNS cells. Compared to control, cadmium, trans-retinoic acid, and trimethyltin decreased cell viability (ATP levels) by at least 50% in the ReN CX cells, while cadmium, dieldrin, and methylmercury decreased viability by at least 50% in the mCNS cells. Based on these results, BrdU is an appropriate marker for assessing chemical effects on proliferation, and human cells are more sensitive than mouse cells for this endpoint. By contrast, caspase 3 and p53 were altered by environmental chemicals in mouse, but not in human cells. Therefore, these markers are not appropriate to assess the ability of environmental chemicals to induce apoptosis in the ReN CX cells.

Feline Neural Progenitor Cells I: Long-Term Expansion under Defined Culture Conditions

Neural progenitor cells (NPCs) of feline origin (cNPCs) have demonstrated utility in transplantation experiments, yet are difficult to grow in culture beyond the 1 month time frame. Here we use an enriched, serum-free base medium (Ultraculture) and report the successful long-term propagation of these cells. Primary cultures were derived from fetal brain tissue and passaged in DMEM/F12-based or Ultraculture-based proliferation media, both in the presence of EGF + bFGF. Cells in standard DMEM/F12-based medium ceased to proliferate by 1-month, whereas the cells in the Ultraculture-based medium continued to grow for at least 5 months (end of study) with no evidence of senescence. The Ultraculture-based cultures expressed lower levels of progenitor and lineage-associated markers under proliferation conditions but retained multipotency as evidenced by the ability to differentiate into neurons and glia following growth factor removal in the presence of FBS. Importantly, later passage cNPCs did not develop chromosomal aberrations.

Photoreceptor Differentiation following Transplantation of Allogeneic Retinal Progenitor Cells to the Dystrophic Rhodopsin Pro347Leu Transgenic Pig

Purpose. Transplantation of stem, progenitor, or precursor cells has resulted in photoreceptor replacement and evidence of functional efficacy in rodent models of retinal degeneration. Ongoing work has been directed toward the replication of these results in a large animal model, namely, the pig. Methods. Retinal progenitor cells were derived from the neural retina of GFP-transgenic pigs and transplanted to the subretinal space of rhodopsin Pro347Leu-transgenic allorecipients, in the early stage of the degeneration and the absence of immune suppression. Results. Results confirm the survival of allogeneic porcine RPCs without immune suppression in the setting of photoreceptor dystrophy. The expression of multiple photoreceptor markers by grafted cells included the rod outer segment-specific marker ROM-1. Further evidence of photoreceptor differentiation included the presence of numerous photoreceptor rosettes within GFP-positive grafts, indicative of the development of cellular polarity and self-assembly into rudiments of outer retinal tissue. Conclusion. Together, these data support the tolerance of RPCs as allografts and demonstrate the high level of rod photoreceptor development that can be obtained from cultured RPCs following transplantation. Strategies for further progress in this area, together with possible functional implications, are discussed.

In vitro development of nuclear transfer embryos derived from porcine embryonic germ cells and their descendent neural precursor cells

Undifferentiated stem cells may support a greater development of cloned embryos compared with differentiated cell types due to their ease of reprogramming during the nuclear transfer (NT) process. Hence, stem cells may be more suitable as nuclear donor cells for NT procedures than are somatic cells. Embryonic germ (EG) cells are undifferentiated stem cells that are isolated from cultured primordial germ cells (PGC) and can differentiate into several cell types. In this study, the in vitro development of NT embryos using porcine EG cells and their derivative neural precursor (NP) cells was investigated, thus eliminating any variation in genetic differences. The rates of fusion did not differ between NT embryos from EG and NP cells; however, the rate of cleavage in NT embryos derived from EG cells was significantly higher (p < 0.05) than that from NP cells (141/247 [57.1%] vs. 105/228 [46.1%]). Similarly, the rate of blastocyst development was significantly higher (P < 0.05) in NT using EG cells than the rate using NP cells (43/247 [17.4%] vs. 18/228 [7.9%]). The results obtained from the present study in pigs demonstrate a reduced capability for nuclear donor cells to be reprogrammed following the differentiation of porcine EG cells. Undifferentiated EG cells may be more amenable to reprogramming after reconstruction compared with differentiated somatic cells.

Spontaneous differentiation of porcine neural progenitors in vitro

The pig is the non-primate species that is immunologically closest to humans, and has been considered as an alternative source to human allografts for transplantation. In fact, there has been recent interest in identifying and culturing porcine neural progenitor cells (PNPCs) in vitro, but the long-term culturing has not yet been characterized. Here, we reported the spontaneous differentiation of PNPCs into neuronal and glial cells. For in vitro cultures, the primary cells of the subventricular zone of the forebrain striatum were cultured in the presence of epidermal growth factor and basic fibroblast growth factor to allow the growth of spherical masses that exhibit sustained growth and self-renewal capacity. After growth factor removal, the neurospheres with 10 and 130 days of culture spontaneously differentiated into Tuj1-positive neurons and GFAP-positive astrocytes as seen by double immunocytofluorescence. Molecular characterization using reverse transcription-polymerase chain reaction showed that neurospheres expressed nestin, neuron-specific enolase, and glial fibrillary acidic protein (GFAP). In addition, after cultured in the differentiation medium for 3 months, the growth of neurosphere became slow and displayed cystic structures with the same morphology as that of embryonic bodies derived from embryonic stem cells. It is concluded that PNPCs have the ability to provide an expandable source of neural cells that can develop into neuronal and glial subtypes.

Defining cell populations with single-cell gene expression profiling: correlations and identification of astrocyte subpopulations

Single-cell gene expression levels show substantial variations among cells in seemingly homogenous populations. Astrocytes perform many control and regulatory functions in the central nervous system. In contrast to neurons, we have limited knowledge about functional diversity of astrocytes and its molecular basis. To study astrocyte heterogeneity and stem/progenitor cell properties of astrocytes, we used single-cell gene expression profiling in primary mouse astrocytes and dissociated mouse neurosphere cells. The transcript number variability for astrocytes showed lognormal features and revealed that cells in primary cultures to a large extent co-express markers of astrocytes and neural stem/progenitor cells. We show how subpopulations of cells can be identified at single-cell level using unsupervised algorithms and that gene correlations can be used to identify differences in activity of important transcriptional pathways. We identified two subpopulations of astrocytes with distinct gene expression profiles. One had an expression profile very similar to that of neurosphere cells, whereas the other showed characteristics of activated astrocytes in vivo.

Osteogenic and neurogenic differentiation of EGFP gene transfected neural stem cells derived from the brain of porcine fetuses at intermediate and late gestational age

The aims of this study were (i) to determine whether NSCs (neural stem cells) could be isolated from the brain of porcine fetuses at intermediate and late gestational age and (ii) to determine if these stem cells could be differentiated in vitro into osteogenic and neurogenic lineages following transfection with a reporter gene, EGFP (enhanced green fluorescence protein). The NSCs were isolated from the brains of porcine fetuses at intermediate and late gestational age and transfected with EGFP gene using lipofection. The transfected NSCs cells were induced to differentiate into cells of osteogenic and neurogenic lineages. Markers associated with NSCs and their osteogenic and neurogenic derivatives were tested by PCR. The results demonstrated that NSCs could be isolated from the brain of porcine fetus at intermediate and late gestational age and that transfected NSCs expressed EGFP and could be induced to differentiate in vitro. NSCs expressed CD-90, Hes1, Oct4, Sox2 and Nestin, while following differentiation cells expressed markers for osteogenic (osteocalcin and osteonectin) and neurogenic cells such as astrocyte [GFAP (glial fibrillary acidic protein)], oligodendrocyte [GALC (galactosylceramide)] and neuron [NF (neurofilament), ENO2 (enolase 2) and MAP (microtubule-associated protein)].

Neuro-muscular differentiation of adult porcine skin derived stem cell-like cells

Background

Due to the genetic relationship to humans, porcine stem cells are a very important model system to investigate cell differentiation, associated cell signaling pathways, and cell fate. Porcine skin derived stem cells have been isolated from mid-gestation porcine fetus recently. To our knowledge, stem cells from the skin of the adult porcine organism have not been isolated until now. Hence, to our knowledge, we here describe the isolation, expansion, characterization and differentiation of multipotent porcine skin derived stem cell-like cells (pSSCs) from the adult porcine organism for the first time.

Methodology/Principal Findings

pSSCs had a spindle shaped morphology similar to mesenchymal stem cells (MSCs). They could be maintained proliferatively active in vitro for more than 120 days and were able to form colonies from single cells. pSSCs expressed Sox2 and Oct3/4, both transcription factors essential to the pluripotent and self-renewing phenotypes of embryonic stem cells, which recently gained attention due to their function in inducing pluripotent stem cells. Furthermore, the expression of the progenitor marker nestin, the somatic stem cell markers Bcrp1/ABCG2, Bmi1, and Stat3 was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) in undifferentiated pSSCs. Flow cytometry revealed the expression of the MSC related proteins CD9, CD29, CD44 and CD105, but not CD90. After neuronal differentiation cells with a characteristic morphology of neuronal and smooth muscle-like cells were present in the cultures. Subsequent immunochemistry and flow cytometry revealed the down-regulation of nestin and the up-regulation of the neuron specific protein beta-III-tubulin and the astrocyte marker GFAP. Also, alpha-SMA expressing cells increased during differentiation suggesting the neuro-muscular differentiation of these skin derived cells. pSSCs could also be induced to differentiate into adipocyte-like cells when cultured under specific conditions.

Conclusions/Significance

Adult porcine skin harbors a population of stem cell-like cells (pSSCs) that can be isolated via enzymatic digestion. These pSSCs show characteristic features of MSCs originated in other tissues and express the embryonic stem cell marker Oct3/4, Sox2, and Stat3. Furthermore, pSSCs have the potential to differentiate into cells from two different germ lines, the ectoderm (neurons, astrocytes) and the mesoderm (smooth muscle cells, adipocytes).

Development of cloned embryos from porcine neural stem cells and amniotic fluid-derived stem cells transfected with enhanced green fluorescence protein gene

We assessed the developmental ability of embryos cloned from porcine neural stem (NS) cells, amniotic fluid-derived stem (AFS) cells, fetal fibroblast cells, adult fibroblast, and mammary gland epithelial cells. The five cell lines were transfected with enhanced green fluorescence protein gene respectively using lipofection. NS and AFS cells were induced to differentiate in vitro. Stem cells and their differentiated cells were harvested for analysis of the markers using RT-PCR. The five cell lines were used for nuclear transfer. The two-cell stage-cloned embryos derived from each cell line were transferred into the oviducts of surrogate mothers. The results showed that both NS and AFS cells expressed POU5F1, THY1 and SOX2, and they were both induced to differentiate into astrocyte (GFAP+), oligodendrocyte (GalC+), neuron (NF+, ENO2+, and MAP2+), adipocyte (LPL+ and PPARG-D+), osteoblast (osteonectin+ and osteocalcin+), myocyte (MYF6+ and MYOD+), and endothelium (PECAM1+, CD34+, CDH5+, and NOS3+) respectively. Seven cloned fetuses (28 days and 32 days) derived from stem cells were obtained. The in vitro developmental ability (morula-blastocyst rate was 28.26-30.07%) and in vivo developmental ability (pregnancy rate were 1.67-2.17%) of the embryos cloned from stem cells were higher (P<0.05) than that of the embryos cloned from somatic cells (morula-blastocyst rate was 16.27-19.28% and pregnancy rate was 0.00%), which suggests that the undifferentiated state of the donor cells increases cloning efficiency.

AQP4 knockout impairs proliferation, migration and neuronal differentiation of adult neural stem cells

Aquaporin-4 (AQP4), a key molecule for maintaining water and ion homeostasis in the central nervous system, is expressed in adult neural stem cells (ANSCs) as well as astrocytes. However, little is known about the functions of AQP4 in the ANSCs in vitro. Here we show that AQP4 knockout inhibits the proliferation, survival, migration and neuronal differentiation of ANSCs derived from the subventricular zone of adult mice. Flow cytometric cell cycle analysis revealed that AQP4 knockout increased the basal apoptosis and induced a G2-M arrest in ANSCs. Using Fluo-3 Ca2+ imaging, we show that AQP4 knockout alters the spontaneous Ca2+ oscillations by frequency enhancement and amplitude suppression, and suppresses KCl-induced Ca2+ influx. AQP4 knockout downregulated the expression of connexin43 and the L-type voltage-gated Ca2+ channel CaV1.2 subtype in ANSCs. Together, these findings suggest that AQP4 plays a crucial role in regulating the proliferation, migration and differentiation of ANSCs, and this function of AQP4 is probably mediated by its action on intracellular Ca2+ dynamics.

Gene expression profiling of rat cerebral cortex development using cDNA microarrays

A large amount of genetic information is devoted to brain development. In this study, the cortical development in rats at eight developmental time points (four embryonic [E15, E16, E18, E20] and four postnatal [P0, P7, P14, P21]) was studied using a rat brain 10K cDNA microarray. Significant differential expression was observed in 467 of the 9,805 genes represented on the microarray. Two major Gene Ontology classes-cell differentiation and cell-cell signaling-were found to be important for cortical development. Genes for ribosomal proteins, heterogeneous nuclear ribonucleoproteins, and tubulin proteins were up-regulated in the embryonic stage, coincidently with extensive proliferation of neural precursor cells as the major component of the cerebral cortex. Genes related to neurogenesis, including neurite regeneration, neuron development, and synaptic transmission, were more active in adulthood, when the cerebral cortex reached maturity. The many developmentally modulated genes identified by this approach will facilitate further studies of cortical functions.

Isolation of progenitor cells from GFP-transgenic pigs and transplantation to the retina of allorecipients

Work in rodents has demonstrated that progenitor transplantation can achieve limited photoreceptor replacement in the mammalian retina; however, replication of these findings on a clinically relevant scale requires a large animal model. To evaluate the ability of porcine retinal progenitor cells to survival as allografts and integrate into the host retinal architecture, we isolated donor cells from fetal green fluorescent protein (GFP)-transgenic pigs. Cultures were propagated from the brain, retina, and corneo-scleral limbus. GFP expression rapidly increased with time in culture, although lower in conjunction with photoreceptor markers and glial fibrillary acid protein (GFAP), thus suggesting downregulation of GFP during differentiation. Following transplantation, GFP expression allowed histological visualization of integrated cells and extension of fine processes to adjacent plexiform layers. GFP expression in subretinal grafts was high in cells expressing vimentin and lower in cells expressing photoreceptor markers, again consistent with possible downregulation during differentiation. Cells survived transplantation to the injured retina of allorecipients at all time points examined (up to 10 weeks) in the absence of exogenous immune suppression without indications of rejection. These findings demonstrate the feasibility of allogeneic progenitor transplantation in a large mammal and the utility of the pig in ocular regeneration studies.

Comparative Analysis of Progenitor Cells Isolated from the Iris, Pars Plana, and Ciliary Body of the Adult Porcine Eye

Photoreceptor loss causes irreversible blindness in many retinal diseases. The identification of suitable donor cell populations is of considerable interest because of their potential use to replace the photoreceptors lost in disease. Stem or progenitor cells that give rise to neurons and glia have been identified in several regions of the brain, including the embryonic retina and the ciliary epithelium of the adult eye, raising the possibility of autologous transplantation. However, there has been little systematic investigation into precisely which regions of the large mammalian adult eye give rise to such cells. Here, we show for the first time using the porcine eye the presence of progenitor cells in additional regions of the adult eye, including the pars plana and iris, regions that, in the human, are readily accessible during routine eye surgery. When cultured in the presence of growth factors, these cells proliferate to form neurospheres comprised of cells expressing retinal progenitor markers. Using an adherent monolayer culture system, these cells could be readily expanded to increase their number more than 1 million-fold and maintain a progenitor phenotype. When grown on the substrate laminin in the presence of serum, cells derived from both spheres and monolayer cultures differentiated into neurons and glia. These results suggest that a population of cells derived from the adult iris, pars plana, and ciliary body of a large mammalian species, the pig, has progenitor properties and neurogenic potential, thereby providing novel sources of donor cells for transplantation studies. Disclosure of potential conflicts of interest is found at the end of this article.

Cell-by-cell reconstruction in reaggregates from neonatal gerbil retina begins from the inner retina and is promoted by retinal pigmented epithelium

For future retinal tissue engineering, it is essential to understand formation of retinal tissue in a 'cell-by-cell' manner, as can be best studied in retinal reaggregates. In avians, complete laminar spheres can be produced, with ganglion cells internally and photoreceptors at the surface; a similar degree of retinal reconstruction has not been achieved for mammals. Here, we have studied self-organizing potencies of retinal cells from neonatal gerbil retinae to form histotypic spheroids up to 15 days in culture (R-spheres). Shortly after reaggregation, a first sign of tissue organization was detected by use of an amacrine cell (AC)-specific calretinin (CR) antibody. These cells sorted out into small clusters and sent unipolar processes towards the centre of each cluster. Thereby, inner cell-free spaces developed into inner plexiform layer (IPL)-like areas with extended parallel CR(+) fibres. Occasionally, IPL areas merged to combine an 'inner half retina', whereby ganglion cells (GCs) occupied the outer sphere surface. This tendency was much improved in the presence of supernatants from retinal pigmented cells (RPE-spheres), e.g. cell organization and proliferation was much increased, and cell death shortened. As shown by several markers, a perfect outer ring was formed by GCs and displaced ACs, followed by a distinct IPL and 1-2 rows of ACs internally. The inner core of RPE spheres consisted of horizontal and possibly bipolar cells, while immunostaining and RT-PCR analysis proved that photoreceptors were absent. This shows that (1) mammalian retinal histogenesis in reaggregates can be brought to a hitherto unknown high level, (2) retinal tissue self-organizes from the level of the IPL, and (3) RPE factors promote formation of almost complete retinal spheres, however, their polarity was opposite to that found in respective avian spheroids.

Neural precursors isolated from the developing cat brain show retinal integration following transplantation to the retina of the dystrophic cat

The cat has served as an important nonrodent research model for neurophysiology and retinal degenerative disease processes, yet very little is known about feline neural precursor cells. To culture these cells and evaluate marker expression, brains were dissected from 45-day-old fetuses, enzymatically dissociated, and grown in the presence of EGF, bFGF and PDGF. Expanded cells widely expressed nestin, Sox2, Ki-67, fusin (CXCR4) and vimentin, while subpopulations expressed A2B5, GFAP, or beta-III tubulin. Precursors prelabeled with BrdU and/or transduced with a recombinant lentivirus that expresses GFP were transplanted subretinally in five dystrophic Abyssinian cats. Two to 4 weeks following surgery, histology showed survival of grafted cells in three of the animals. Labeled cells were found in the neuroretina and RPE layer, as well as in the vitreous and the vicinity of Bruch's membrane. There was no evidence of an immunologic response in any of the eyes. Neural precursor cells can therefore be cultured from the developing cat brain and survive as allografts for up to 4 weeks without immune suppression. The feasibility of deriving and transplanting feline neural precursor cells, combined with the availability of the dystrophic Abyssinian cat, provide a new feline model system for the study of retinal repair.

Developmental ability of cloned embryos from neural stem cells

The success rate is generally higher when cloning mice from embryonic stem (ES) cell nuclei than from somatic cell nuclei, suggesting that the embryonic nature or the undifferentiated state of the donor cell increases cloning efficiency. We assessed the developmental ability of cloned embryos derived from cultured neural stem cell (NSC) nuclei and compared the success rate with that of embryos cloned from other donor cells such as differentiated NSCs, cumulus cells, Sertoli cells and ES cells in the mouse. The transfer of two-cell cloned embryos derived from cultured NSC nuclei into surrogate mothers produced five live cloned mice. However, the success rate (0.5%) was higher in embryos cloned from cultured NSC nuclei than from differentiated NSCs (0%), but lower than that obtained by cloning mice from other cell nuclei (2.2-3.5%). Although the in vitro developmental potential to the two-cell stage of the cloned embryos derived from NSC nuclei (73%) was similar to that of the cloned embryos derived from other somatic cell nuclei (e.g., 85% in Sertoli cells and 75% in cumulus cells), the developmental rate to the morula-blastocyst stage was only 7%. This rate is remarkably lower than that produced from other somatic cells (e.g., 50% in Sertoli cells and 54% in cumulus cells). These results indicate that the undifferentiated state of neural cells does not enhance the cloning efficiency in mice and that the arrest point for in vitro development of cloned embryos depends on the donor cell type.

NOGO-A induction and localization during chick brain development indicate a role disparate from neurite outgrowth inhibition

Background

Nogo-A, a myelin-associated protein, inhibits neurite outgrowth and abates regeneration in the adult vertebrate central nervous system (CNS) and may play a role in maintaining neural pathways once established. However, the presence of Nogo-A during early CNS development is counterintuitive and hints at an additional role for Nogo-A beyond neurite inhibition.

Results

We isolated chicken NOGO-A and determined its sequence. A multiple alignment of the amino acid sequence across divergent species, identified five previously undescribed, Nogo-A specific conserved regions that may be relevant for development. NOGO gene transcripts (NOGO-A, NOGO-B and NOGO-C) were differentially expressed in the CNS during development and a second NOGO-A splice variant was identified. We further localized NOGO-A expression during key phases of CNS development by in situ hybridization. CNS-associated NOGO-A was induced coincident with neural plate formation and up-regulated by FGF in the transformation of non-neural ectoderm into neural precursors. NOGO-A expression was diffuse in the neuroectoderm during the early proliferative phase of development, and migration, but localized to large projection neurons of the optic tectum and tectal-associated nuclei during architectural differentiation, lamination and network establishment.

Conclusion

These data suggest Nogo-A plays a functional role in the determination of neural identity and/or differentiation and also appears to play a later role in the networking of large projection neurons during neurite formation and synaptogenesis. These data indicate that Nogo-A is a multifunctional protein with additional roles during CNS development that are disparate from its later role of neurite outgrowth inhibition in the adult CNS.

Progenitor cells from the porcine neural retina express photoreceptor markers after transplantation to the subretinal space of allorecipients

Work in rodents has shown that cultured retinal progenitor cells (RPCs) integrate into the degenerating retina, thus suggesting a potential strategy for treatment of similar degenerative conditions in humans. To demonstrate the relevance of the rodent work to large animals, we derived progenitor cells from the neural retina of the domestic pig and transplanted them to the laser-injured retina of allorecipients. Prior to grafting, immunocytochemical analysis showed that cultured porcine RPCs widely expressed neural cell adhesion molecule, as well as markers consistent with immature neural cells, including nestin, Sox2, and vimentin. Subpopulations expressed the neurodevelopmental markers CD-15, doublecortin, beta-III tubulin, and glial fibrillary acidic protein. Retina-specific markers expressed included the bipolar marker protein kinase Calpha and the photoreceptor-associated markers recoverin and rhodopsin. In addition, reverse transcription-polymerase chain reaction showed expression of the transcription factors Dach1, Hes1, Lhx2, Pax6, Six3, and Six6. Progenitor cells prelabeled with vital dyes survived as allografts in the subretinal space for up to 5 weeks (11 of 12 recipients) without exogenous immune suppression. Grafted cells expressed transducin, recoverin, and rhodopsin in the pig subretinal space, suggestive of differentiation into photoreceptors or, in a few cases, migrated into the neural retina and extended processes, the latter typically showing radial orientation. These results demonstrate that many of the findings seen with rodent RPCs can be duplicated in a large mammal. The pig offers a number of advantages over mice and rats, particularly in terms of functional testing and evaluation of the potential for clinical translation to human subjects. Disclosure of potential conflicts of interest is found at the end of this article.

Transplantation of cultured progenitor cells to the mammalian retina

Multipotent progenitor cells have now been isolated from the brain and retina, expanded in culture, and transplanted to the central nervous system (CNS). Work in rodent models has shown that progenitor cells derived from the CNS readily engraft in the diseased retina of mature recipients, where they develop morphologies appropriate to the local microenvironment and express mature markers, including the photoreceptor protein rhodopsin. There is also evidence for graft-associated rescue of host photoreceptors and preservation of light sensitivity in the degenerating retina. Graft survival does not necessarily require immune suppression, as CNS progenitors can behave as an immunoprivileged cell type. The use of biodegradable polymers results in an organised implant and further improves graft survival. Efforts are underway at present to extend this work to the pig, with initial results showing engraftment in both the neural retina and retinal pigment epithelium (RPE).