Oct4 controls basement membrane development during human embryogenesis

Basement membranes (BMs) are sheet-like structures of extracellular matrix (ECM) that provide structural support for many tissues and play a central role in signaling. They are key regulators of cell behavior and tissue functions, and defects in their assembly or composition are involved in numerous human diseases. Due to the differences between human and animal embryogenesis, ethical concerns, legal constraints, the scarcity of human tissue material, and the inaccessibility of the in vivo condition, BM regulation during human embryo development has remained elusive. Using the post-implantation amniotic sac embryoid (PASE), we delineate BM assembly upon post-implantation development and BM disassembly during primitive streak (PS) cell dissemination. Further, we show that the transcription factor Oct4 regulates the expression of BM structural components and receptors and controls BM development by regulating Akt signaling and the small GTPase Rac1. These results represent a relevant step toward a more comprehensive understanding of early human development.

Stage based recipient and donor outcome in twin-to-twin transfusion syndrome treated by fetoscopic laser surgery using Solomon technique

OBJECTIVE

To evaluate twin survival stratified by Quintero stage in patients with twin-to-twin transfusion syndrome (TTTS) after Solomon laser treatment.

METHODS

Single center cohort of consecutive twin pregnancies treated with Solomon laser for TTTS. Preoperative Quintero stage, perioperative characteristics and obstetric factors were related to neonatal survival of the recipient and donor at discharge. Determinants of twin survival were evaluated using univariate, logistic regression and cumulative survival probability analyses.

RESULTS

Of 402 twins with TTTS, 80 (19.9%) had stage I, 126 (31.3%) stage II, 169 (42%) stage III and 27 (6.7%) stage IV. Post laser TAPS or recurrent TTTS occurred in 19 (4.7%) patients and 11 (2.7%) required repeat laser. Preterm premature rupture of membranes occurred in 150 (37.3%) patients and median gestational age of delivery 32+1 weeks. In 303 (75.4%) both twins were alive at discharge; [66 (82.5%) in stage I, 101 (80.2%) in stage II, 114 (67.5%) in stage III and 22 (81.5%) in stage IV, p=0.062]. Compared to recipients, donor survival was only lower in stage III (155 (91.7%) recipients vs 118 (69.8%) donors, Chi square 24.685, p<0.0001). Larger intertwin size discordance and umbilical artery (UA) end-diastolic velocity (EDV) determined donor demise (Nagelkerke R2 0.38, P<0.001). Overall, spontaneous post laser donor demise accounted for the majority (39.5%) of all losses. Cumulative donor survival decreased from 92% to 65% with size discordance >30% and 48% when UA EDV was absent (p<0.001).

CONCLUSION

Solomon laser achieves TTTS resolution and double survival in a high proportion of cases. Recipient and donor survival is comparable unless there is significant size discordance and placental dysfunction. This degree of unequal placental sharing, typically found in stage III, is the primary factor preventing double survival due to a higher rate of donor demise. This article is protected by copyright. All rights reserved.

Pluripotent Stem Cell-Derived In Vitro Gametogenesis and Synthetic Embryos-It Is Never Too Early for an Ethical Debate

Recently, 2 branches of the wide area of synthetic biology-in vitro gametogenesis and synthetic embryo development-have gained considerable attention. Rodent induced pluripotent stem cells derived via reprogramming of somatic cells can in vitro be differentiated into gametes to produce fertile offspring. And even synthetic embryos with organ progenitors were generated ex utero entirely from murine pluripotent stem cells. The use of these approaches in basic research, which is rightfully accompanied by an ethical discussion, will allow hitherto unattainable insights into the processes of the beginning of life. There is a broad international consensus that currently the application of these technologies in human-assisted reproduction must be considered to be unsafe and unethical. However, newspaper headlines also addressed the putatively resulting paradigm shift in human reproduction and thereby raised expectations in patients. Due to unsolved biological and technological obstacles, most scientists do not anticipate translation of any of these approaches into human reproductive medicine, if ever, for the next 10 years. Still, whereas the usage of synthetic embryos for reproductive purposes should be banned, in the context of in vitro-derived human gametes it is not too early to initiate the evaluation of the ethical implications, which could still remain assuming all technological hurdles can ever be cleared.

Multipotent fetal stem cells in reproductive biology research

Due to the limited accessibility of the in vivo situation, the scarcity of the human tissue, legal constraints, and ethical considerations, the underlying molecular mechanisms of disorders, such as preeclampsia, the pathological consequences of fetomaternal microchimerism, or infertility, are still not fully understood. And although substantial progress has already been made, the therapeutic strategies for reproductive system diseases are still facing limitations. In the recent years, it became more and more evident that stem cells are powerful tools for basic research in human reproduction and stem cell-based approaches moved into the center of endeavors to establish new clinical concepts. Multipotent fetal stem cells derived from the amniotic fluid, amniotic membrane, chorion leave, Wharton´s jelly, or placenta came to the fore because they are easy to acquire, are not associated with ethical concerns or covered by strict legal restrictions, and can be banked for autologous utilization later in life. Compared to adult stem cells, they exhibit a significantly higher differentiation potential and are much easier to propagate in vitro. Compared to pluripotent stem cells, they harbor less mutations, are not tumorigenic, and exhibit low immunogenicity. Studies on multipotent fetal stem cells can be invaluable to gain knowledge on the development of dysfunctional fetal cell types, to characterize the fetal stem cells migrating into the body of a pregnant woman in the context of fetomaternal microchimerism, and to obtain a more comprehensive picture of germ cell development in the course of in vitro differentiation experiments. The in vivo transplantation of fetal stem cells or their paracrine factors can mediate therapeutic effects in preeclampsia and can restore reproductive organ functions. Together with the use of fetal stem cell-derived gametes, such strategies could once help individuals, who do not develop functional gametes, to conceive genetically related children. Although there is still a long way to go, these developments regarding the usage of multipotent fetal stem cells in the clinic should continuously be accompanied by a wide and detailed ethical discussion.

Amniotic Fluid Stem Cells: What They Are and What They Can Become

In the last two decades, fetal amniotic fluid stem cells progressively attracted attention in the context of both basic research and the development of innovative therapeutic concepts. They exhibit broadly multipotent plasticity with the ability to differentiate into cells of all three embryonic germ layers and low immunogenicity. They are convenient to maintain, highly proliferative, genomically stable, non-tumorigenic, perfectly amenable to genetic modifications, and do not raise ethical concerns. However, it is important to note that among the various fetal amniotic fluid cells, only c-Kit+ amniotic fluid stem cells represent a distinct entity showing the full spectrum of these features. Since amniotic fluid additionally contains numerous terminally differentiated cells and progenitor cells with more limited differentiation potentials, it is of highest relevance to always precisely describe the isolation procedure and characteristics of the used amniotic fluid-derived cell type. It is of obvious interest for scientists, clinicians, and patients alike to be able to rely on up-todate and concisely separated pictures of the utilities as well as the limitations of terminally differentiated amniotic fluid cells, amniotic fluid-derived progenitor cells, and c-Kit+ amniotic fluid stem cells, to drive these distinct cellular models towards as many individual clinical applications as possible.

OUP accepted manuscript

It is the hope of clinicians and patients alike that stem cell-based therapeutic products will increasingly become applicable remedies for many diseases and injuries. Whereas some multipotent stem cells are already routinely used in regenerative medicine, the efficacious and safe clinical translation of pluripotent stem cells is still hampered by their inherent immunogenicity and tumorigenicity. In addition, stem cells harbor the paracrine potential to affect the behavior of cells in their microenvironment. On the one hand, this property can mediate advantageous supportive effects on the overall therapeutic concept. However, in the last years, it became evident that both, multipotent and pluripotent stem cells, are capable of inducing adjacent cells to become motile. Not only in the context of tumor development but generally, deregulated mobilization and uncontrolled navigation of patient’s cells can have deleterious consequences for the therapeutic outcome. A more comprehensive understanding of this ubiquitous stem cell feature could allow its proper clinical handling and could thereby constitute an important building block for the further development of safe therapies.

Amniotic fluid stem cells and the cell source repertoire for non-invasive prenatal testing

Cell-free fetal DNA (cffDNA)-based non-invasive prenatal testing (NIPT) is considered to be a very promising screening tool for pregnant women with an increased risk of fetal aneuploidy. Already millions of women worldwide underwent NIPT. However, due to the observed false-positive and false-negative results, this screening approach does not fulfil the criteria of a diagnostic test. Accordingly, positive results still require risk-carrying invasive prenatal testing, such as amniocentesis or chorionic villus sampling (CVS), for confirmation. Such hurdles need to be overcome before NIPT could become a diagnostic approach widely used in the general population. Here we discuss new evidence that besides the placenta amniotic fluid stem cells (AFSCs) could also represent an origin of cffDNA in the mother’s blood. A comprehensive picture of the involved cell source repertoire could pave the way to more reliable interpretations of NIPT results and ameliorate counselling of advice-seeking patients.

Three-dimensional migration of human amniotic fluid stem cells involves mesenchymal and amoeboid modes and is regulated by mTORC1

Three‐dimensional (3D) cell migration is an integral part of many physiologic processes. Although being well studied in the context of adult tissue homeostasis and cancer development, remarkably little is known about the invasive behavior of human stem cells. Using two different kinds of invasion assays, this study aimed at investigating and characterizing the 3D migratory capacity of human amniotic fluid stem cells (hAFSCs), a well‐established fetal stem cell type. Eight hAFSC lines were found to harbor pronounced potential to penetrate basement membrane (BM)‐like matrices. Morphological examination and inhibitor approaches revealed that 3D migration of hAFSCs involves both the matrix metalloprotease‐dependent mesenchymal, elongated mode and the Rho‐associated protein kinase‐dependent amoeboid, round mode. Moreover, hAFSCs could be shown to harbor transendothelial migration capacity and to exhibit a motility‐associated marker expression pattern. Finally, the potential to cross extracellular matrix was found to be induced by mTORC1‐activating growth factors and reduced by blocking mTORC1 activity. Taken together, this report provides the first demonstration that human stem cells exhibit mTORC1‐dependent invasive capacity and can concurrently make use of mesenchymal and amoeboid 3D cell migration modes, which represents an important step toward the full biological characterization of fetal human stem cells with relevance to both developmental research and stem cell‐based therapy.

Fetomaternal microchimerism and genetic diagnosis: On the origins of fetal cells and cell-free fetal DNA in the pregnant woman

During pregnancy several types of fetal cells and fetal stem cells, including pregnancy-associated progenitor cells (PAPCs), traffic into the maternal circulation. Whereas they also migrate to various maternal organs and adopt the phenotype of the target tissues to contribute to regenerative processes, fetal cells also play a role in the pathogenesis of maternal diseases. In addition, cell-free fetal DNA (cffDNA) is detectable in the plasma of pregnant women. Together they constitute the well-known phenomenon of fetomaternal microchimerism, which inspired the concept of non-invasive prenatal testing (NIPT) using maternal blood. An in-depth knowledge concerning the origins of these fetal cells and cffDNA allows a more comprehensive understanding of the biological relevance of fetomaternal microchimerism and has implications for the ongoing expansion of resultant clinical applications.

Embryoid research calls for reassessment of legal regulations

It is known that in countries, in which basic research on human embryos is in fact prohibited by law, working with imported human embryonic stem cells (hESCs) can still be permitted. As long as hESCs are not capable of development into a complete human being, it might be the case that they do not fulfill all criteria of the local definition of an embryo. Recent research demonstrates that hESCs can be developed into entities, called embryoids, which increasingly could come closer to actual human embryos in future. By discussing the Austrian situation, we want to highlight that current embryoid research could affect the prevailing opinion on the legal status of work with hESCs and therefore calls for reassessment of the regulations in all countries with comparable definitions of the embryo.

The Multiple Sclerosis Inventory of Cognition for Adolescents (MUSICADO): A brief screening instrument to assess cognitive dysfunction, fatigue and loss of health-related quality of life in pediatric-onset multiple sclerosis

OBJECTIVE

Screening for cognitive impairment (CI), fatigue and also Health-related quality of life (HRQoL) in patients with pediatric-onset multiple sclerosis (POMS) is of utmost importance in clinical practice. The aim of this study was to establish a new and validated pediatric screening tool "MUSICADO" that is easy to use and time economical.

METHODS

106 patients with POMS aged 12-18 years and 210 healthy controls (HCs) stratified for age and education underwent neuropsychological testing including a screening test "Multiple Sclerosis Inventory of Cognition" for adults and 8 standardized cognitive tests and established scales to assess fatigue and HRQoL.

RESULTS

The phonemic verbal fluency task (RWT "s-words"), the Trail Making Test A (TMT-A), and the Digit Span Forward discriminated significantly between patients and HCs (p = 0.000, respectively) and showed the highest proportion of test failure in patients (24.5%, 17.9%; 15.1%, respectively). Therefore, they were put together to form the cognitive part of the "MUSICADO". After applying a scoring algorithm with balanced weighting of the subtests and age and education correction and a cut-off score for impairment, 35.8% of patients were categorized to be cognitively impaired (specificity: 88.6%). Fatigue was detected in 37.1% of the patients (specificity: 94.0%) and loss of HRQoL in 41.8% (specificity 95.7%) with the screening version, respectively.

CONCLUSION

The MUSICADO is a newly designed brief and easy to use screening test to help to early identify CI, fatigue, and loss of HRQoL in patients with POMS as cut scores are provided for all three items. Further studies will have to show its usability in independent samples of patients with POMS.

DRUGPATH - a novel bioinformatic approach identifies DNA-damage pathway as a regulator of size maintenance in human ESCs and iPSCs

Genetic and biochemical screening approaches often fail to identify functionally relevant pathway networks because many signaling proteins contribute to multiple gene ontology pathways. We developed a DRUGPATH-approach to predict pathway-interactomes from high-content drug screen data. DRUGPATH is based upon combining z-scores of effective inhibitors with their corresponding and validated targets. We test DRUGPATH by comparing homeostatic pathways in human embryonic stem cells (hESCs), human induced pluripotent stem cells (hiPSCs) and human amniotic fluid stem cells (hAFSCs). We show that hAFSCs utilize distinct interactomes compared to hESCs/hiPSCs and that pathways orchestrating cell cycle and apoptosis are strongly interconnected, while pathways regulating survival and size are not. Interestingly, hESCs/hiPSCs regulate their size by growing exact additional sizes during each cell cycle. Chemical and genetic perturbation studies show that this “adder-model” is dependent on the DNA-damage pathway. In the future, the DRUGPATH-approach may help to predict novel pathway interactomes from high-content drug screens.

Transvaginal Sonographic Diagnosis of Cataract in a Fetus

Transvaginal ultrasonography is a relatively new technique for visualizing the orbits in a fetus of 4 to 5 cm. At fifteen weeks of gestation it is possible to recognize the lenses and the hyaloid arteries in the eyes, to diagnose structural malformations such as anophthalmos, microphthalmos, buphthalmos and moderate to severe cataract. In most cases cataracts were associated with intracranial defects. We describe a case where the sonographic diagnosis of fetal cataract was confirmed by histopathological examination. A 27-year-old woman had a routine transvaginal sonography at 15 weeks’ normal gestation. Microphthalmos without a hyaloid artery and disorganization of the anterior chamber and lens consistent with cataract were demonstrated in the fetal left eye. In accordance with the parents’ decision, the pregnancy was terminated a week later. Autopsy of the fetus was done and serial sections of the left eye were studied by light microscopy. Histopathological examination verified the sonographic diagnosis of fetal cataract in a microphthalmic eye. Associated findings included malformation of the anterior segment and retinal dysplasia.

Myopia and Stature: Findings in a Population of 106,926 Males

We conducted a nation-wide study of the relationship of myopia with height, weight and body-mass index in order to confirm observations that myopic persons are taller than non-myopes. From a review of the data of 106,926, consecutive male military recruits aged 17 to 19 years, we found that myopia is associated neither with higher stature nor with greater weight. Persons with severe myopia were slightly shorter (172.8 +/- 7.1 cm) and weighed less (62.6 +/- 11.0 kg) than those with mild myopia (173.3 +/- 6.9 cm and 63.8 +/- 10.5 kg respectively), while the non-myopes were taller (173.7 +/- 6.7 cm) and heavier (63.9 +/- 10.2 kg) than the myopes (p = 0.0001). The mean body-mass index was only slightly smaller among the myopes (21.1 +/- 3.1 kg/m2) than among the non-myopes (21.2 +/- 2.9 kg/m2, p = 0.0001).

Assessing seawater intrusion in an arid coastal aquifer under high anthropogenic influence using major constituents, Sr and B isotopes in groundwater

The La Paz aquifer system (Baja California Sur, Mexico) is under severe anthropogenic pressure because of high groundwater abstraction for urban supply (city of La Paz, around 222,000 inhabitants) and irrigated agriculture (1900ha). In consequence, seawater has infiltrated the aquifer, forcing the abandonment of wells with increased salinity. The objective of this study was to assess seawater intrusion, understand the hydrogeochemical processes involved and estimate the contribution of seawater in the wells tested. The aquifer comprises mainly the alluvial filling and marine sediments of a tectonic graben oriented north-south, in contact with the Gulf of California. Groundwater samples were collected in 47 locations and analyzed for major constituents. A subset of 23 samples was analyzed for strontium and boron concentrations and isotopic signatures (⁸⁷Sr/⁸⁶Sr and δ¹¹B). Results were interpreted using standard hydrochemical plots along with ad hoc plots including isotopic data. Seawater intrusion was confirmed by several hydrogeochemical indicators, such as the high salinity in areas of intense pumping or the Na⁺-Ca²⁺ exchange occurring in sediments that were previously in chemical equilibrium with fresh water. However, seawater contribution was not sufficient to explain the observed concentrations and isotopic signatures of Sr and B. According to the isotopic data, desorption processes triggered by a modification in chemical equilibrium and an increase in ionic strength by seawater intrusion significantly increased Sr and probably B concentrations in groundwater. From a calculation of seawater contribution to the wells, it was estimated that one-third of the sampled abstraction wells were significantly affected by seawater intrusion, reaching concentrations that would limit their use for human supply or even irrigated agriculture. In addition, significant agricultural pollution (nitrates) was detected. Planned management of the aquifer and corrective measures are needed in order to invert the salinization process before it severely affects water resources in the long term.

eIF3 controls cell size independently of S6K1-activity

All multicellular organisms require a life-long regulation of the number and the size of cells, which build up their organs. mTOR acts as a signaling nodule for the regulation of protein synthesis and growth. To activate the translational cascade, mTOR phosphorylates S6 kinase (S6K1), which is liberated from the eIF3-complex and mobilized for activation of its downstream targets. How S6K1 regulates cell size remains unclear. Here, we challenged cell size control through S6K1 by specifically depleting its binding partner eIF3 in normal and transformed cell lines. We show that loss of eIF3 leads to a massive reduction of cell size and cell number accompanied with an unexpected increase in S6K1-activity. The hyperactive S6K1-signaling was rapamycin-sensitive, suggesting an upstream mTOR-regulation. A selective S6K1 inhibitor (PF-4708671) was unable to interfere with the reduced size, despite efficiently inhibiting S6K1-activity. Restoration of eIF3 expression recovered size defects, without affecting the p-S6 levels. We further show that two, yet uncharacterized, cancer-associated mutations in the eIF3-complex, have the capacity to recover from reduced size phenotype, suggesting a possible role for eIF3 in regulating cancer cell size. Collectively, our results uncover a role for eIF3-complex in maintenance of normal and neoplastic cell size - independent of S6K1-signaling.

Letter to the Editor: Human Pluripotent Stem Cells Release Oncogenic Soluble E-Cadherin

Since their discovery, human pluripotent stem cells (hPSCs) including embryonic and induced pluripotent stem cells hold great promise in disease modeling and regenerative medicine. Despite intensive research and remarkable progress, it is becoming increasingly acknowledged that their yet incomplete, biological characterisation represents one of the major drawbacks to their successful translation into the clinics. The expression of the transmembrane protein E-cadherin in hPSCs is well defined to be pivotal to the maintenance of the pluripotent state by mediating intercellular adhesion and intracellular signaling. Next to these canonical functions, were here report for the first time that hPSCs are subject to matrix metalloproteinase-dependent E-cadherin ectodomain shedding. This generates a ∼80-kD, soluble E-cadherin fragment which is released into the extracellular space, and which is well described to exert paracrine signaling activity and classified as being oncogenic. Collectively, this finding does not only improve our knowledge on the signaling crosstalk between hPSCs and their cellular environment and the type and nature of the paracrine signals produced by these cells, but also has clear implications for the development of efficient and safe stem cell-based therapies. Stem Cells 2016;34:2443-2446.

Full biological characterization of human pluripotent stem cells will open the door to translational research

Since the discovery of human embryonic stem cells (hESC) and human-induced pluripotent stem cells (hiPSC), great hopes were held for their therapeutic application including disease modeling, drug discovery screenings, toxicological screenings and regenerative therapy. hESC and hiPSC have the advantage of indefinite self-renewal, thereby generating an inexhaustible pool of cells with, e.g., specific genotype for developing putative treatments; they can differentiate into derivatives of all three germ layers enabling autologous transplantation, and via donor-selection they can express various genotypes of interest for better disease modeling. Furthermore, drug screenings and toxicological screenings in hESC and hiPSC are more pertinent to identify drugs or chemical compounds that are harmful for human, than a mouse model could predict. Despite continuing research in the wide field of therapeutic applications, further understanding of the underlying basic mechanisms of stem cell function is necessary. Here, we summarize current knowledge concerning pluripotency, self-renewal, apoptosis, motility, epithelial-to-mesenchymal transition and differentiation of pluripotent stem cells.

Rapamycin-Induced Hypoxia Inducible Factor 2A Is Essential for Chondrogenic Differentiation of Amniotic Fluid Stem Cells

Amniotic fluid stem (AFS) cells represent a major source of donor cells for cartilage repair. Recently, it became clear that mammalian target of rapamycin (mTOR) inhibition has beneficial effects on cartilage homeostasis, but the effect of mTOR on chondrogenic differentiation is still elusive. Therefore, the objectives of this study were to investigate the effects of mammalian target of rapamycin complex 1 (mTORC1) modulation on the expression of SOX9 and on its downstream targets during chondrogenic differentiation of AFS cells. We performed three-dimensional pellet culturing of AFS cells and of in vitro-expanded, human-derived chondrocytes in the presence of chondrogenic factors. Inhibition of mTORC1 by rapamycin or by small interfering RNA-mediated targeting of raptor (gene name, RPTOR) led to increased AKT activation, upregulation of hypoxia inducible factor (HIF) 2A, and an increase in SOX9, COL2A1, and ACAN abundance. Here we show that HIF2A expression is essential for chondrogenic differentiation and that AKT activity regulates HIF2A amounts. Importantly, engraftment of AFS cells in cell pellets composed of human chondrocytes revealed an advantage of raptor knockdown cells compared with control cells in their ability to express SOX9. Our results demonstrate that mTORC1 inhibition leads to AKT activation and an increase in HIF2A expression. Therefore, we suggest that mTORC1 inhibition is a powerful tool for enhancing chondrogenic differentiation of AFS cells and also of in vitro-expanded adult chondrocytes before transplantation.

SIGNIFICANCE

Repair of cartilage defects is still an unresolved issue in regenerative medicine. Results of this study showed that inhibition of the mammalian target of rapamycin complex 1 (mTORC1) pathway, by rapamycin or by small interfering RNA-mediated targeting of raptor (gene name, RPTOR), enhanced amniotic fluid stem cell differentiation toward a chondrocytic phenotype and increased their engrafting efficiency into cartilaginous structures. Moreover, freshly isolated and in vitro passaged human chondrocytes also showed redifferentiation upon mTORC1 inhibition during culturing. Therefore, this study revealed that rapamycin could enable a more efficient clinical use of cell-based therapy approaches to treat articular cartilage defects.

Clinical impact of studying epithelial-mesenchymal plasticity in pluripotent stem cells

BACKGROUND

The ability of cells to travel long distances in order to form tissues and organs is inherently connected to embryogenesis. The process in which epithelial-like embryonic cells become motile and invasive is termed 'epithelial-to-mesenchymal transition' (EMT), while the reversion of this programme--yielding differentiated cells and organs--is called 'mesenchymal-to-epithelial transition' (MET).

DESIGN

Here, we review the processes of EMT and MET in development and cancer and combine them with knowledge from pluripotent stem cell research.

RESULTS

Research has shown that these processes are activated in many cancers leading to dissemination of cancer cells throughout the body and formation of metastasis. While the regulation of EMT during cancer progression has been extensively studied for decades, many fundamental processes that govern normal development are only poorly understood. Recent discoveries, such as reprogramming to pluripotent stem cells and identification of ground and primed states of pluripotent stem cells, have redirected much attention to EMT and MET.

CONCLUSION

Findings from pluripotent stem cell research and EMT/MET should be combined in order to design future strategies aimed to improve our understanding of cancer progression and to help develop novel anticancer strategies.

Intercellular protein expression variability as a feature of stem cell pluripotency

The expression of pluripotent stem cell protein markers, self-renewal, the potential to differentiate in cell types of all three germlines and teratoma formation in nude mice form the spectrum of the stringent pluripotency criteria for human stem cells. Currently, intercellular variability is discussed as an additional putative defining property of pluripotent stem cells. In future, it will be of relevance to clarify the genesis of intercellular variability for each stem cell line/population before its application in basic science or therapy. Furthermore, for a better understanding of stemness it will be indispensable to separately investigate the issue of intercellular variability for each feature of pluripotency.

Reliable quantification of protein expression and cellular localization in histological sections

In targeted therapy, patient tumors are analyzed for aberrant activations of core cancer pathways, monitored based on biomarker expression, to ensure efficient treatment. Thus, diagnosis and therapeutic decisions are often based on the status of biomarkers determined by immunohistochemistry in combination with other clinical parameters. Standard evaluation of cancer specimen by immunohistochemistry is frequently impeded by its dependence on subjective interpretation, showing considerable intra- and inter-observer variability. To make treatment decisions more reliable, automated image analysis is an attractive possibility to reproducibly quantify biomarker expression in patient tissue samples. We tested whether image analysis could detect subtle differences in protein expression levels. Gene dosage effects generate well-graded expression patterns for most gene-products, which vary by a factor of two between wildtype and haploinsufficient cells lacking one allele. We used conditional mouse models with deletion of the transcription factors Stat5ab in the liver as well Junb deletion in a T-cell lymphoma model. We quantified the expression of total or activated STAT5AB or JUNB protein in normal (Stat5ab^+/+ or JunB^+/+), hemizygous (Stat5ab^+/Δ or JunB^+/Δ) or knockout (Stat5ab^Δ/Δ or JunB^Δ/Δ) settings. Image analysis was able to accurately detect hemizygosity at the protein level. Moreover, nuclear signals were distinguished from cytoplasmic expression and translocation of the transcription factors from the cytoplasm to the nucleus was reliably detected and quantified using image analysis. We demonstrate that image analysis supported pathologists to score nuclear STAT5AB expression levels in immunohistologically stained human hepatocellular patient samples and decreased inter-observer variability.

The decision on the "optimal" human pluripotent stem cell

Because of recent advances, the array of human pluripotent stem cells now contains embryonic stem cells, derived from "surplus" in vitro fertilization embryos or from cloned embryos; induced pluripotent stem cells; and amniotic fluid stem cells. Here, we compare these stem cell types regarding ethical and legal concerns, cultivation conditions, genomic stability, tumor developing potentials, and applicability for disease modeling and human therapy. This overview highlights that in the future appropriate methodological management must include a decision on the "optimal" stem cell to use before the specific application.

Chondrogenic differentiation of amniotic fluid stem cells and their potential for regenerative therapy

Chronic articular cartilage defects are the most common disabling conditions of humans in the western world. The incidence for cartilage defects is increasing with age and the most prominent risk factors are overweight and sports associated overloading. Damage of articular cartilage frequently leads to osteoarthritis due to the aneural and avascular nature of articular cartilage, which impairs regeneration and repair. Hence, patients affected by cartilage defects will benefit from a cell-based transplantation strategy. Autologous chondrocytes, mesenchymal stem cells and embryonic stem cells are suitable donor cells for regeneration approaches and most recently the discovery of amniotic fluid stem cells has opened a plethora of new therapeutic options. It is the aim of this review to summarize recent advances in the use of amniotic fluid stem cells as novel cell sources for the treatment of articular cartilage defects. Molecular aspects of articular cartilage formation as well as degeneration are summarized and the role of growth factor triggered signaling pathways, scaffolds, hypoxia and autophagy during the process of chondrogenic differentiation are discussed.

p38α senses environmental stress to control innate immune responses via mechanistic target of rapamycin

The MAPK p38α senses environmental stressors and orchestrates inflammatory and immunomodulatory reactions. However, the molecular mechanism how p38α controls immunomodulatory responses in myeloid cells remains elusive. We found that in monocytes and macrophages, p38α activated the mechanistic target of rapamycin (mTOR) pathway in vitro and in vivo. p38α signaling in myeloid immune cells promoted IL-10 but inhibited IL-12 expression via mTOR and blocked the differentiation of proinflammatory CD4(+) Th1 cells. Cellular stress induced p38α-mediated mTOR activation that was independent of PI3K but dependent on the MAPK-activated protein kinase 2 and on the inhibition of tuberous sclerosis 1 and 2, a negative regulatory complex of mTOR signaling. Remarkably, p38α and PI3K concurrently modulated mTOR to balance IL-12 and IL-10 expression. Our data link p38α to mTOR signaling in myeloid immune cells that is decisive for tuning the immune response in dependence on the environmental milieu.

Hsp90 stabilizes Cdc25A and counteracts heat shock-mediated Cdc25A degradation and cell-cycle attenuation in pancreatic carcinoma cells

Pancreas cancer cells escape most treatment options. Heat shock protein (Hsp)90 is frequently over-expressed in pancreas carcinomas and protects a number of cell-cycle regulators such as the proto-oncogene Cdc25A. We show that inhibition of Hsp90 with geldanamycin (GD) destabilizes Cdc25A independent of Chk1/2, whereas the standard drug for pancreas carcinoma treatment, gemcitabine (GEM), causes Cdc25A degradation through the activation of Chk2. Both agents applied together additively inhibit the expression of Cdc25A and the proliferation of pancreas carcinoma cells thereby demonstrating that both Cdc25A-destabilizing/degrading pathways are separated. The role of Hsp90 as stabilizer of Cdc25A in pancreas carcinoma cells is further supported by two novel synthetic inhibitors 4-tosylcyclonovobiocic acid and 7-tosylcyclonovobiocic acid and specific Hsp90AB1 (Hsp90β) shRNA. Our data show that targeting Hsp90 reduced the resistance of pancreas carcinoma cells to treatment with GEM.

In vitro cell migration and invasion assays

Determining the migratory and invasive capacity of tumor and stromal cells and clarifying the underlying mechanisms is most relevant for novel strategies in cancer diagnosis, prognosis, drug development and treatment. Here we shortly summarize the different modes of cell travelling and review in vitro methods, which can be used to evaluate migration and invasion. We provide a concise summary of established migration/invasion assays described in the literature, list advantages, limitations and drawbacks, give a tabular overview for convenience and depict the basic principles of the assays graphically. In many cases particular research problems and specific cell types do not leave a choice for a broad variety of usable assays. However, for most standard applications using adherent cells, based on our experience we suggest to use exclusion zone assays to evaluate migration/invasion. We substantiate our choice by demonstrating that the advantages outbalance the drawbacks e.g. the simple setup, the easy readout, the kinetic analysis, the evaluation of cell morphology and the feasibility to perform the assay with standard laboratory equipment. Finally, innovative 3D migration and invasion models including heterotypic cell interactions are discussed. These methods recapitulate the in vivo situation most closely. Results obtained with these assays have already shed new light on cancer cell spreading and potentially will uncover unknown mechanisms.

Amniotic fluid stem cells to study mTOR signaling in differentiation

The protein kinase mTOR is the central player within a pathway, which is known to be involved in the regulation of e.g., cell size, cell cycle, apoptosis, autophagy, aging and differentiation. mTOR activity responds to many signals, including cellular stress, oxygen, nutrient availability, energy status and growth factors. Deregulation of this enzyme is causatively involved in the molecular development of monogenic human diseases, cancer, obesity, type 2 diabetes or neurodegeneration. Recently, mTOR has also been demonstrated to control stem cell homeostasis. A more detailed investigation of this new mTOR function will be of highest relevance to provide more explicit insights into stem cell regulation in the near future. Different cellular tools, including adult stem cells, embryonic stem cells or induced pluripotent stem cells could be used to investigate the role of mTOR in mammalian stem cell biology. Here we discuss the potential of amniotic fluid stem cells to become a promising cellular model to study the role of signaling cascades in stem cell homeostasis.

Renal differentiation of amniotic fluid stem cells: perspectives for clinical application and for studies on specific human genetic diseases

BACKGROUND

Owing to growing rates of diabetes, hypertension and the ageing population, the prevalence of end-stage renal disease, developed from earlier stages of chronic kidney disease, and of acute renal failure is dramatically increasing. Dialysis and preferable renal transplantation are widely applied therapies for this incurable condition. However these options are limited because of morbidity, shortage of compatible organs and costs. Therefore, stem cell-based approaches are becoming increasingly accepted as an alternative therapeutic strategy.

DESIGN

This review summarizes the current findings on the nephrogenic potential of amniotic fluid stem (AFS) cells and their putative implications for clinical applications and for studies on specific human genetic diseases.

RESULTS

Since their discovery in 2003, AFS cells have been shown to be pluripotent with the potential to form embryoid bodies. Compared to adult stem cells, induced pluripotent stem cells or embryonic stem cells, AFS cells harbour a variety of advantages, such as their high differentiation and proliferative potential, no need for ectopic induction of pluripotency and no somatic mutations and epigenetic memory of source cells, and no tumourigenic potential and associated ethical controversies, respectively.

CONCLUSIONS

Recently, the results of different independent studies provided evidence that AFS cells could indeed be a powerful tool for renal regenerative medicine.

Human amniotic fluid stem cells as a model for functional studies of genes involved in human genetic diseases or oncogenesis

Besides their putative usage for therapies, stem cells are a promising tool for functional studies of genes involved in human genetic diseases or oncogenesis. For this purpose induced pluripotent stem (iPS) cells can be derived from patients harbouring specific mutations. In contrast to adult stem cells, iPS cells are pluripotent and can efficiently be grown in culture. However, iPS cells are modulated due to the ectopic induction of pluripotency, harbour other somatic mutations accumulated during the life span of the source cells, exhibit only imperfectly cleared epigenetic memory of the source cell, and are often genomically instable. In addition, iPS cells from patients only allow the investigation of mutations, which are not prenatally lethal. Embryonic stem (ES) cells have a high proliferation and differentiation potential, but raise ethical issues. Human embryos, which are not transferred in the course of in vitro fertilization, because of preimplantation genetic diagnosis of a genetic defect, are still rarely donated for the establishment of ES cell lines. In addition, their usage for studies on gene functions for oncogenesis is hampered by the fact the ES cells are already tumorigenic per se. In 2003 amniotic fluid stem (AFS) cells have been discovered, which meanwhile have been demonstrated to harbour the potential to differentiate into cells of all three germ layers. Monoclonal human AFS cell lines derived from amniocenteses have a high proliferative potential, are genomically stable and are not associated with ethical controversies. Worldwide amniocenteses are performed for routine human genetic diagnosis. We here discuss how generation and banking of monoclonal human AFS cell lines with specific chromosomal aberrations or monogenic disease mutations would allow to study the functional consequences of disease causing mutations. In addition, recently a protocol for efficient and highly reproducible siRNA-mediated long-term knockdown of endogenous gene functions in AFS cells was established. Since AFS cells are not tumorigenic, gene modulations not only allow to investigate the role of endogenous genes involved in human genetic diseases but also may help to reveal putative oncogenic gene functions in different biological models, both in vitro and in vivo. This concept is discussed and a "proof of principle", already obtained via modulating genes involved in the mammalian target of rapamycin (mTOR) pathway in AFS cells, is presented.

Blocking mTORC1 activity by rapamycin leads to impairment of spatial memory retrieval but not acquisition in C57BL/6J mice

Although the involvement of the mTOR (mammalian target of rapamycin) system in memory processes has been reported, information on the effect of rapamycin on spatial learning and memory is limited. It was therefore the aim of the study to show the effect of parenteral rapamycin administration to C57BL/6J mice on performance in the multiple T-maze (MTM) and to determine hippocampal mTOR activity. Rapamycin-treated and -untreated/trained/probed mice are the main part of the experiment considering retrieval and acquisition or consolidation of spatial memory. Six hours following euthanasia hippocampi were extirpated and used for evaluation of mTOR activity as represented by hippocampal levels of S6 protein and its phosphorylated active form (phospho S6 protein, S240,244), a read out of mTOR complex 1 activity. Mice given i.p. rapamycin learned the task of the MTM but failed at the probe trial, showing absence of the phosphorylated active form of S6 protein, indicating inhibition of mTOR activity. Herein, impairing effects of rapamycin on retrieval but not on acquisition or consolidation of spatial memory are shown. Deficient memory retrieval was paralleled by inhibition of mTOR complex 1 activity. The current study extends knowledge on rapamycin in memory mechanisms and challenges work on deeper insights into the role of mTOR in different phases of memory formation and retrieval.

Proliferation potential of human amniotic fluid stem cells differently responds to mercury and lead exposure

There are considerable gaps in our knowledge on cell biological effects induced by the heavy metals mercury (Hg) and lead (Pb). In the present study we aimed to explore the effects of these toxicants on proliferation and cell size of primary human amniotic fluid stem (AFS) cells. Monoclonal human AFS cells were incubated with three dosages of Hg and Pb (single and combined treatment; ranging from physiological to cytotoxic concentrations) and the intracellular Hg and Pb concentrations were analyzed, respectively. At different days of incubation the effects of Hg and Pb on proliferation, cell size, apoptosis, and expression of cyclins and the cyclin-dependent kinase inhibitor p27 were investigated. Whereas we found Hg to trigger pronounced effects on proliferation of human AFS cells already at low concentrations, anti-proliferative effects of Pb could only be detected at high concentrations. Exposure to high dose of Hg induced pronounced downregulation of cyclin A confirming the anti-proliferative effects observed for Hg. Co-exposure to Hg and Pb did not cause additive effects on proliferation and size of AFS cells, and on cyclin A expression. Our here presented data provide evidence that the different toxicological effects of Pb and Hg on primary human stem cells are due to different intracellular accumulation levels of these two toxicants. These findings allow new insights into the functional consequences of Pb and Hg for mammalian stem cells and into the cell biological behavior of AFS cells in response to toxicants.

Tuberin and PRAS40 are anti-apoptotic gatekeepers during early human amniotic fluid stem-cell differentiation

Embryoid bodies (EBs) are three-dimensional multicellular aggregates allowing the in vitro investigation of stem-cell differentiation processes mimicking early embryogenesis. Human amniotic fluid stem (AFS) cells harbor high proliferation potential, do not raise the ethical issues of embryonic stem cells, have a lower risk for tumor development, do not need exogenic induction of pluripotency and are chromosomal stable. Starting from a single human AFS cell, EBs can be formed accompanied by the differentiation into cells of all three embryonic germ layers. Here, we report that siRNA-mediated knockdown of the endogenous tuberous sclerosis complex-2 (TSC2) gene product tuberin or of proline-rich Akt substrate of 40 kDa (PRAS40), the two major negative regulators of mammalian target of rapamycin (mTOR), leads to massive apoptotic cell death during EB development of human AFS cells without affecting the endodermal, mesodermal and ectodermal cell differentiation spectrum. Co-knockdown of endogenous mTOR demonstrated these effects to be mTOR-dependent. Our findings prove this enzyme cascade to be an essential anti-apoptotic gatekeeper of stem-cell differentiation during EB formation. These data allow new insights into the regulation of early stem-cell maintenance and differentiation and identify a new role of the tumor suppressor tuberin and the oncogenic protein PRAS40 with the relevance for a more detailed understanding of the pathogenesis of diseases associated with altered activities of these gene products.

p70 S6K1 nuclear localization depends on its mTOR-mediated phosphorylation at T389, but not on its kinase activity towards S6

The protein kinase p70 S6K1 is regulated in response to cytokines, nutrients and growth factors, and plays an important role in the development of a variety of human diseases. Mammalian target of rapamycin (mTOR) is known to phosphorylate and thereby activate p70 S6K1. p70 S6K1 phosphorylates different cytoplasmic and nuclear substrates involved in the regulation of protein synthesis, cell cycle, cell growth and survival. Recently, we have shown that mTOR-mediated phosphorylation of p70 S6K1 at T389 also regulates its nucleocytoplasmic localization. Since this phosphorylation is associated with its kinase activity the question whether p70 S6K1 phosphorylation or kinase activity is essential for its proper localization remained elusive. Recently, the chemical compound PF-4708671 has been demonstrated to block p70 S6K1 kinase activity while inducing its phosphorylation at T389. This potential of PF-4708671 to separate p70 S6K1 activity from its T389 phosphorylation allowed us to demonstrate that the proper nucleocytoplasmic localization of this kinase depends on its mTOR-mediated phosphorylation but not on its kinase activity. These findings provide important insights into the regulation of p70 S6K1 and allow a more detailed understanding of subcellular enzyme localization processes.

Contribution of human amniotic fluid stem cells to renal tissue formation depends on mTOR

Human amniotic fluid stem cells (hAFSCs) can be grown in large quantities, have a low risk for tumour development and harbour a high differentiation potential. They are a very promising new fetal stem cell type for cell-based therapy approaches and for studying differentiation processes without raising the ethical concerns associated with embryonic stem cells. Recently, a protocol for studies on renal development has been established in which murine embryonic kidneys are dissociated into single-cell suspension and then reaggregated to form organotypic renal structures. Using this approach, we formed chimeric renal structures via mixing murine embryonic kidney cells with monoclonal hAFSCs. We demonstrate here that hAFSCs harbour the potential to contribute to renal tissue formation accompanied by induction of specific renal marker expression. As part of the two kinase complexes mTORC1 and mTORC2, mammalian target of rapamycin (mTOR) is the key component of an important signalling pathway, which is involved in the regulation of differentiation and in the development of a wide variety of human genetic diseases many with characteristic kidney symptoms. Modulating endogenous mTOR activity via specific siRNA approaches revealed that contribution of hAFSCs to renal tissue formation is regulated by mTORC1 and mTORC2. These findings (i) demonstrate renal differentiation potential of hAFSCs, (ii) prove chimeric cultures of mixtures of murine embryonic kidney cells and hAFSCs to be a powerful tool to study the effects of gene knockdowns for renal structure formation and (iii) provide new insights into the role of the mTOR pathway for renal development.

Efficient siRNA-mediated prolonged gene silencing in human amniotic fluid stem cells

Human amniotic fluid stem cells (hAFSCs) are a very promising new type of fetal stem cells with numerous applications for basic science and cell-based therapies. They harbor a high differentiation potential and a low risk for tumor development, can be grown in large quantities and do not raise the ethical concerns associated with embryonic stem cells. RNA interference (RNAi) is a powerful technology to explain specific gene functions and has important implications for the clinical usage of tissue engineering. We provide a straightforward, 72-h-long protocol for siRNA-mediated gene silencing in hAFSCs. The lipid-based forward transfection protocol described in this article is the first RNAi approach for prolonged gene knockdown in hAFSCs. This protocol allows efficient, functional and reproducible gene knockdown in human stem cells over a prolonged period of time (approximately 2 weeks). We also show the successful use of this protocol in primary nontransformed nonimmortalized fibroblasts, cervical adenocarcinoma cells, transformed embryonic kidney cells, immortalized endometrial stromal cells and acute monocytic leukemia cells, suggesting a wide spectrum of applications in various cell types.

Induction of mesenchymal/epithelial marker expression in human amniotic fluid stem cells

Although dialysis and transplantation are widely applied therapies for renal failure, drawbacks such as morbidity, shortage of compatible organs and high cost are limiting factors. Recently, interest has increased in the potential use of stem cells for the repair of kidney injury, which has been considered as an alternative therapeutic strategy. Due to their high proliferation rates, their pluripotent differentiation potential, the finding that they do not induce tumour formation and the fact that they do not raise the ethical concerns connected with human embryonic stem cells, human amniotic fluid stem cells are considered to be a very promising cell source. This study demonstrates that the expression of the mesenchymal markers CD29 and CD44, the epithelial markers CD51 and ZO-1 and the podocyte markers CD2AP and NPHS2 can be induced in these cells via incubation with epidermal growth factor/platelet-derived growth factor BB and fibroblast growth factor 4/hepatocyte growth factor, respectively. Since podocytes are visceral epithelial cells in the kidneys, which form the essential part of the glomerular filtration barrier, these findings warrant further investigation of the potential use of human amniotic fluid stem cells for cell-based kidney therapies.