Explore the vast range of titles available.

Hematopoietic stem cells (HSCs) are unique in their capacity to give rise to all mature cells of the immune system. For years, HSC transplantation has been used for treatment of genetic and neoplastic diseases of the hematopoietic and immune systems. The sourcing of HSCs from human umbilical cord blood has salient advantages over isolation from mobilized peripheral blood. However, poor sample yield has prompted development of methodologies to expand HSCs ex vivo. Cytokines, trophic factors, and small molecules have been variously used to promote survival and proliferation of HSCs in culture, whilst strategies to lower the concentration of inhibitors in the culture media have recently been applied to promote HSC expansion. In this paper, we outline strategies to expand HSCs in vitro, and to improve engraftment and reconstitution of human immune systems in immunocompromised mice. To the extent that these “humanized” mice are representative of the endogenous human immune system, they will be invaluable tools for both basic science and translational medicine.

Human pluripotent stem cells (hPSCs) tend to acquire genomic aberrations in culture, the most common of which is trisomy of chromosome 12. Here we dissect the cellular and molecular implications of this trisomy in hPSCs. Global gene expression analyses reveal that trisomy 12 profoundly affects the gene expression profile of hPSCs, inducing a transcriptional programme similar to that of germ cell tumours. Comparison of proliferation, differentiation and apoptosis between diploid and aneuploid hPSCs shows that trisomy 12 significantly increases the proliferation rate of hPSCs, mainly as a consequence of increased replication. Furthermore, trisomy 12 increases the tumorigenicity of hPSCs in vivo , inducing transcriptionally distinct teratomas from which pluripotent cells can be recovered. Last, a chemical screen of 89 anticancer drugs discovers that trisomy 12 raises the sensitivity of hPSCs to several replication inhibitors. Together, these findings demonstrate the extensive effect of trisomy 12 and highlight its perils for successful hPSC applications. Trisomy 12 is the most frequent chromosomal abnormality detected in cultures of human pluripotent stem cells. Here the authors show that human pluripotent stem cells carrying this abnormality exhibit gene expression profiles more similar to those of germ cell tumours, and give rise to more aggressive teratomas.

The International Stem Cell Initiative compares 125 ethnically diverse human embryonic stem cell lines at early and late passage. Data on karotype, single-nucleotide polymorphisms and methylation shed light on how the cells adapt to long-term culture. The International Stem Cell Initiative analyzed 125 human embryonic stem (ES) cell lines and 11 induced pluripotent stem (iPS) cell lines, from 38 laboratories worldwide, for genetic changes occurring during culture. Most lines were analyzed at an early and late passage. Single-nucleotide polymorphism (SNP) analysis revealed that they included representatives of most major ethnic groups. Most lines remained karyotypically normal, but there was a progressive tendency to acquire changes on prolonged culture, commonly affecting chromosomes 1, 12, 17 and 20. DNA methylation patterns changed haphazardly with no link to time in culture. Structural variants, determined from the SNP arrays, also appeared sporadically. No common variants related to culture were observed on chromosomes 1, 12 and 17, but a minimal amplicon in chromosome 20q11.21, including three genes expressed in human ES cells, ID1 , BCL2L1 and HM13 , occurred in >20% of the lines. Of these genes, BCL2L1 is a strong candidate for driving culture adaptation of ES cells.

Mammalian cells have evolved to function under Earth’s gravity, but how they respond to microgravity remains largely unknown. Neural stem cells (NSCs) are essential for the maintenance of central nervous system (CNS) functions during development and the regeneration of all CNS cell populations. Here, we examined the behavior of space (SPC)-flown NSCs as they readapted to Earth’s gravity. We found that most of these cells survived the space flight and self-renewed. Yet, some showed enhanced stress responses as well as autophagy-like behavior. To ascertain if the secretome from SPC-flown NSCs contained molecules inducing these responses, we incubated naïve, non-starved NSCs in a medium containing SPC-NSC secretome. We found a four-fold increase in stress responses. Proteomic analysis of the secretome revealed that the protein of the highest content produced by SPC-NSCs was secreted protein acidic and rich in cysteine (SPARC), which induces endoplasmic reticulum (ER) stress, resulting in the cell’s demise. These results offer novel knowledge on the response of neural cells, particularly NSCs, subjected to space microgravity. Moreover, some secreted proteins have been identified as microgravity sensing, paving a new venue for future research aiming at targeting the SPARC metabolism. Although we did not establish a direct relationship between microgravity-induced stress and SPARC as a potential marker, these results represent the first step in the identification of gravity sensing molecules as targets to be modulated and to design effective countermeasures to mitigate intracranial hypertension in astronauts using structure-based protein design.

The change in gravitational force has a significant effect on biological tissues and the entire organism. As with any alteration in the environment, microgravity (µG) produces modifications in the system inducing adaptation to the new condition. In this study, we analyzed the effect of µG on neural stem cells (NSCs) following a space flight to the International Space Station (ISS). After 3 days in space, analysis of the metabolome in culture medium revealed increased glycolysis with augmented pyruvate and glycerate levels, and activated catabolism of branched-chain amino acids (BCAA) and glutamine. NSCs flown into space (SPC-NSCs) also showed increased synthesis of NADH and formation of polyamine spermidine when compared to ground controls (GC-NSCs). Overall, the space environment appears to increase energy demands in response to the µG setting.

Staphylococcus aureus is a leading cause of skin and soft-tissue infections worldwide. Mice are the most commonly used animals for modeling human staphylococcal infections. However a supra-physiologic S. aureus inoculum is required to establish gross murine skin pathology. Moreover, many staphylococcal factors, including Panton-Valentine leukocidin (PVL) elaborated by community-associated methicillin-resistant S. aureus (CA-MRSA), exhibit selective human tropism and cannot be adequately studied in mice. To overcome these deficiencies, we investigated S. aureus infection in non-obese diabetic (NOD)/severe combined immune deficiency (SCID)/IL2rγnull (NSG) mice engrafted with human CD34+ umbilical cord blood cells. These \"humanized\" NSG mice require one to two log lower inoculum to induce consistent skin lesions compared with control mice, and exhibit larger cutaneous lesions upon infection with PVL+ versus isogenic PVL- S. aureus. Neutrophils appear important for PVL pathology as adoptive transfer of human neutrophils alone to NSG mice was sufficient to induce dermonecrosis following challenge with PVL+ S. aureus but not PVL- S. aureus. PMX53, a human C5aR inhibitor, blocked PVL-induced cellular cytotoxicity in vitro and reduced the size difference of lesions induced by the PVL+ and PVL- S. aureus, but PMX53 also reduced recruitment of neutrophils and exacerbated the infection. Overall, our findings establish humanized mice as an important translational tool for the study of S. aureus infection and provide strong evidence that PVL is a human virulence factor.

The postnatal forebrain subventricular zone (SVZ) harbors stem cells that give rise to olfactory bulb interneurons throughout life. The identity of stem cells in the adult SVZ has been extensively debated. Although, ependymal cells were once suggested to have stem cell characteristics, subsequent studies have challenged the initial report and postulated that subependymal GFAP⁺ cells were the stem cells. Here, we report that, in the adult mouse forebrain, immunoreactivity for a neural stem cell marker, prominin-1/CD133, is exclusively localized to the ependyma, although not all ependymal cells are CD133⁺. Using transplantation and genetic lineage tracing approaches, we demonstrate that CD133⁺ ependymal cells continuously produce new neurons destined to olfactory bulb. Collectively, our data indicate that, compared with GFAP expressing adult neural stem cells, CD133⁺ ependymal cells represent an additional-perhaps more quiescent-stem cell population in the mammalian forebrain.

In vivo remyelination promoted by a combination of four oligodendrocyte specific growth factors (GFs) in cuprizone-induced demyelinated mice brains was described recently by our group [ 1 ]. Here we report activation of inflammatory response in mice brain following cuprizone-induced demyelination and its further enhancement immediately after injection of growth factors in vivo, while no significant inflammatory response was evident in GFs-injected normal brains. Cuprizone-induced demyelination was accompanied by increased expression of inflammatory cytokines, TNFα and IL-1β, anti-inflammatory cytokines TGFβ, IL-10 and increased levels of chemokines, CCL2, CCL5, and CXCL10, produced by resident microglia and astrocytes. During demyelination, involvement of oxidative stress was evident by disruption of mitochondrial structure and temporal decline in reduced glutathione levels, later returning to normal. Increase in the cytokines and chemokines was further enhanced within 2 days post injection (dpi) of GFs, coinciding with signal for repair via activation of pAkt and NFκB transcription factor reported earlier. Upregulation of mRNA and protein level of antioxidant genes, metallothionein (MT) I/II and activity of a cytosolic oxidoreductase enzyme, glycerolphosphate-3 dehydrogenase (cGPDH) occurred, resulting in a metabolic shuttle with an increase in glycerol in mice brains during period of demyelination and early GF-mediated repair.

Chromosomal aneuploidies are widely recognized genetic disorders in humans that often lead to spontaneous abortion. Aneuploid fetuses that survive to term commonly exhibit impaired developmental growth and mental retardation in addition to multiple congenital malformations. Preimplantation genetic screening is used to detect chromosomal aneuploidies in early embryos. Human embryonic stem cell (ESC) cell lines generated from aneuploid embryos created a unique repository of cell lines. The spectrum of aneuploidies in these ESC lines reflects the range of common embryonic chromosomal aberrations and significantly differs from the spectrum of aneuploid human ESC lines generated by cell adaptation in culture. The aneuploid human ESC lines represent an excellent model to study human chromosomal abnormalities especially in the early stages of development.

Loss of oligodendrocytes (OLs) is often associated with demyelination. PDGF-AA, bFGF, NT3 and IGF-1 are known to regulate OL proliferation, survival and/or differentiation. Following cuprizone-induced demyelination in mice a combination of above four growth factors (GF) was intracranially injected to stimulate remyelination in vivo. Activation of cell signaling and transcription factors involved in cell proliferation, survival and differentiation was observed in response to GF. Increased cell proliferation and migration occurred in corpus callosum, lateral ventricles, rostral migratory stream and cerebri at 2-5 days post injection (dpi) of GF cocktail. The fate of these newly formed nestin or bromodeoxyuridine (BrdU) positive progenitors was traced to proteoglycan NG2 and glutathione transferase (GST) pi positive cells, early and mature OL lineage markers, respectively. Immunostaining for myelin showed the presence of more myelinated fibers in GF-injected brains at 21 dpi. Remyelination in response to GF was confirmed by electron microscopy. In conclusion, this combination of GF is a promising tool to consider for remyelination strategies.