Small extracellular vesicles secreted from human amniotic fluid mesenchymal stromal cells possess cardioprotective and promigratory potential

Mesenchymal stromal cells (MSCs) exhibit antiapoptotic and proangiogenic functions in models of myocardial infarction which may be mediated by secreted small extracellular vesicles (sEVs). However, MSCs have frequently been harvested from aged or diseased patients, while the isolated sEVs often contain high levels of impurities. Here, we studied the cardioprotective and proangiogenic activities of size-exclusion chromatography-purified sEVs secreted from human foetal amniotic fluid stem cells (SS-hAFSCs), possessing superior functional potential to that of adult MSCs. We demonstrated for the first time that highly pure (up to 1.7 × 1010 particles/µg protein) and thoroughly characterised SS-hAFSC sEVs protect rat hearts from ischaemia-reperfusion injury in vivo when administered intravenously prior to reperfusion (38 ± 9% infarct size reduction, p < 0.05). SS-hAFSC sEVs did not protect isolated primary cardiomyocytes in models of simulated ischaemia-reperfusion injury in vitro, indicative of indirect cardioprotective effects. SS-hAFSC sEVs were not proangiogenic in vitro, although they markedly stimulated endothelial cell migration. Additionally, sEVs were entirely responsible for the promigratory effects of the medium conditioned by SS-hAFSC. Mechanistically, sEV-induced chemotaxis involved phosphatidylinositol 3-kinase (PI3K) signalling, as its pharmacological inhibition in treated endothelial cells reduced migration by 54 ± 7% (p < 0.001). Together, these data indicate that SS-hAFSC sEVs have multifactorial beneficial effects in a myocardial infarction setting.

Human mid-trimester amniotic fluid (stem) cells lack expression of the pluripotency marker OCT4A

Expression of OCT4A is one of the hallmarks of pluripotency, defined as a stem cell's ability to differentiate into all the lineages of the three germ layers. Despite being defined as non-tumorigenic cells with high translational potential, human mid-trimester amniotic fluid stem cells (hAFSCs) are often described as sharing features with embryonic stem cells, including the expression of OCT4A, which could hinder their clinical potential. To clarify the OCT4A status of hAFSCs, we first undertook a systematic review of the literature. We then performed extensive gene and protein expression analyses to discover that neither frozen, nor fresh hAFSCs cultivated in multipotent stem cell culture conditions expressed OCT4A, and that the OCT4A positive results from the literature are likely to be attributed to the expression of pseudogenes or other OCT4 variants. To address this issue, we provide a robust protocol for the assessment of OCT4A in other stem cells.

Micro-computed tomography reconstructions of tibiae of stem cell transplanted osteogenesis imperfecta mice

Micro-computed tomography (micro-CT) is commonly used to assess bone quality and to evaluate the outcome of experimental therapies in animal models of bone diseases. Generating large datasets is however challenging and data are rarely made publicly available through shared repositories. Here we describe a dataset of micro-CT reconstructed scans of the proximal part of 21 tibiae from wild-type mice, osteogenesis imperfecta mice (homozygous oim/oim) and oim/oim mice transplanted with human amniotic fluid stem cells. The dataset contains, for each sample, 991 8-bit Bitmap reconstructed images and a 3D reconstruction of the bone in the PLY format, available at the online repository Figshare. In line with the increasing effort to make scientific datasets open-access, our data can be downloaded and used by other researchers to compare their observations with ours and to directly test scientific questions on osteogenesis imperfecta bones without the need to generate complete datasets.

The presence of human mesenchymal stem cells of renal origin in amniotic fluid increases with gestational time

Background

Established therapies for managing kidney dysfunction such as kidney dialysis and transplantation are limited due to the shortage of compatible donated organs and high costs. Stem cell-based therapies are currently under investigation as an alternative treatment option. As amniotic fluid is composed of fetal urine harboring mesenchymal stem cells (AF-MSCs), we hypothesized that third-trimester amniotic fluid could be a novel source of renal progenitor and differentiated cells.

Methods

Human third-trimester amniotic fluid cells (AFCs) were isolated and cultured in distinct media. These cells were characterized as renal progenitor cells with respect to cell morphology, cell surface marker expression, transcriptome and differentiation into chondrocytes, osteoblasts and adipocytes. To test for renal function, a comparative albumin endocytosis assay was performed using AF-MSCs and commercially available renal cells derived from kidney biopsies. Comparative transcriptome analyses of first, second and third trimester-derived AF-MSCs were conducted to monitor expression of renal-related genes.

Results

Regardless of the media used, AFCs showed expression of pluripotency-associated markers such as SSEA4, TRA-1-60, TRA-1-81 and C-Kit. They also express the mesenchymal marker Vimentin. Immunophenotyping confirmed that third-trimester AFCs are bona fide MSCs. AF-MSCs expressed the master renal progenitor markers SIX2 and CITED1, in addition to typical renal proteins such as PODXL, LHX1, BRN1 and PAX8. Albumin endocytosis assays demonstrated the functionality of AF-MSCs as renal cells. Additionally, upregulated expression of BMP7 and downregulation of WT1, CD133, SIX2 and C-Kit were observed upon activation of WNT signaling by treatment with the GSK-3 inhibitor CHIR99201. Transcriptome analysis and semiquantitative PCR revealed increasing expression levels of renal-specific genes (e.g., SALL1, HNF4B, SIX2) with gestational time. Moreover, AF-MSCs shared more genes with human kidney cells than with native MSCs and gene ontology terms revealed involvement of biological processes associated with kidney morphogenesis.

Conclusions

Third-trimester amniotic fluid contains AF-MSCs of renal origin and this novel source of kidney progenitors may have enormous future potentials for disease modeling, renal repair and drug screening.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0864-7) contains supplementary material, which is available to authorized users.

Embryonic Stem Cell-Derived Mesenchymal Stem Cells (MSCs) Have a Superior Neuroprotective Capacity Over Fetal MSCs in the Hypoxic-Ischemic Mouse Brain

Human mesenchymal stem cells (MSCs) have huge potential for regenerative medicine. In particular, the use of pluripotent stem cell‐derived mesenchymal stem cells (PSC‐MSCs) overcomes the hurdle of replicative senescence associated with the in vitro expansion of primary cells and has increased therapeutic benefits in comparison to the use of various adult sources of MSCs in a wide range of animal disease models. On the other hand, fetal MSCs exhibit faster growth kinetics and possess longer telomeres and a wider differentiation potential than adult MSCs. Here, for the first time, we compare the therapeutic potential of PSC‐MSCs (ES‐MSCs from embryonic stem cells) to fetal MSCs (AF‐MSCs from the amniotic fluid), demonstrating that ES‐MSCs have a superior neuroprotective potential over AF‐MSCs in the mouse brain following hypoxia‐ischemia. Further, we demonstrate that nuclear factor (NF)‐κB‐stimulated interleukin (IL)‐13 production contributes to an increased in vitro anti‐inflammatory potential of ES‐MSC‐conditioned medium (CM) over AF‐MSC‐CM, thus suggesting a potential mechanism for this observation. Moreover, we show that induced pluripotent stem cell‐derived MSCs (iMSCs) exhibit many similarities to ES‐MSCs, including enhanced NF‐κB signaling and IL‐13 production in comparison to AF‐MSCs. Future studies should assess whether iMSCs also exhibit similar neuroprotective potential to ES‐MSCs, thus presenting a potential strategy to overcome the ethical issues associated with the use of embryonic stem cells and providing a potential source of cells for autologous use against neonatal hypoxic‐ischemic encephalopathy in humans. Stem Cells Translational Medicine2018;7:439–449

TGFβ-induced osteogenic potential of human amniotic fluid stem cells via CD73-generated adenosine production

The human amniotic fluid stem cell (hAFSC) population consists of two morphologically distinct subtypes, spindle-shaped and round-shaped cells (SS-hAFSCs and RS-hAFSCs). Whilst SS-hAFSCs are routinely expanded in mesenchymal-type (MT) conditions, we previously showed that they acquire broader differentiation potential when cultured under embryonic-type (ET) conditions. However, the effects of culture conditions on RS-hAFSCs have not been determined. Here, we show that culturing RS-hAFSCs under ET conditions confers faster proliferation and enhances the efficiency of osteogenic differentiation of the cells. We show that this occurs via TGFβ-induced activation of CD73 and the associated increase in the generation of extracellular adenosine. Our data demonstrate that culture conditions are decisive for the expansion of hAFSCs and that TGFβ present in ET conditions causes the phenotype of RS-hAFSCs to revert to an earlier state of stemness. Cultivating RS-hAFSCs in ET conditions with TGFβ may therefore increase their therapeutic potential for clinical applications.

Human Amniocytes Are Receptive to Chemically Induced Reprogramming to Pluripotency

Restoring pluripotency using chemical compounds alone would be a major step forward in developing clinical-grade pluripotent stem cells, but this has not yet been reported in human cells. We previously demonstrated that VPA_AFS cells, human amniocytes cultivated with valproic acid (VPA) acquired functional pluripotency while remaining distinct from human embryonic stem cells (hESCs), questioning the relationship between the modulation of cell fate and molecular regulation of the pluripotency network. Here, we used single-cell analysis and functional assays to reveal that VPA treatment resulted in a homogeneous population of self-renewing non-transformed cells that fulfill the hallmarks of pluripotency, i.e., a short G1 phase, a dependence on glycolytic metabolism, expression of epigenetic modifications on histones 3 and 4, and reactivation of endogenous OCT4 and downstream targets at a lower level than that observed in hESCs. Mechanistic insights into the process of VPA-induced reprogramming revealed that it was dependent on OCT4 promoter activation, which was achieved independently of the PI3K (phosphatidylinositol 3-kinase)/AKT/mTOR (mammalian target of rapamycin) pathway or GSK3β inhibition but was concomitant with the presence of acetylated histones H3K9 and H3K56, which promote pluripotency. Our data identify, for the first time, the pluripotent transcriptional and molecular signature and metabolic status of human chemically induced pluripotent stem cells.

Immune regulatory properties of CD117(pos) amniotic fluid stem cells vary according to gestational age

Amniotic Fluid Stem (AFS) cells are broadly multipotent fetal stem cells derived from the positive selection and ex vivo expansion of amniotic fluid CD117/c-kit(pos) cells. Considering the differentiation potential in vitro toward cell lineages belonging to the three germ layers, AFS cells have raised great interest as a new therapeutic tool, but their immune properties still need to be assessed. We analyzed the in vitro immunological properties of AFS cells from different gestational age in coculture with T, B, and natural killer (NK) cells. Nonactivated (resting) first trimester-AFS cells showed lower expression of HLA class-I molecules and NK-activating ligands than second and third trimester-AFS cells, whose features were associated with lower sensitivity to NK cell-mediated lysis. Nevertheless, inflammatory priming with interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) enhanced resistance of all AFS cell types to NK cytotoxicity. AFS cells modulated lymphocyte proliferation in a different manner according to gestational age: first trimester-AFS cells significantly inhibited T and NK cell proliferation, while second and third trimester-AFS cells were less efficient. In addition, only inflammatory-primed second trimester-AFS cells could suppress B cell proliferation, which was not affected by the first and third trimester-AFS cells. Indolamine 2,3 dioxygenase pathway was significantly involved only in T cell suppression mediated by second and third trimester-AFS cells. Overall, this study shows a number of significant quantitative differences among AFS cells of different gestational age that have to be considered in view of their clinical application.

Induced pluripotent stem (iPS) cells from human fetal stem cells

Pluripotency defines the ability of stem cells to differentiate into all the lineages of the three germ layers and self-renew indefinitely. Somatic cells can regain the developmental potential of embryonic stem cells following ectopic expression of a set of transcription factors or, in certain circumstances, via modulation of culture conditions and supplementation with small molecule, that is, induced pluripotent stem (iPS) cells. Here, we discuss the use of fetal tissues for reprogramming, focusing in particular on stem cells derived from human amniotic fluid, and the development of chemical reprogramming. We next address the advantages and disadvantages of deriving pluripotent cells from fetal tissues and the potential clinical applications.

In utero therapy for congenital disorders using amniotic fluid stem cells

Congenital diseases are responsible for over a third of all pediatric hospital admissions. Advances in prenatal screening and molecular diagnosis have allowed the detection of many life-threatening genetic diseases early in gestation. In utero transplantation (IUT) with stem cells could cure affected fetuses but so far in humans, successful IUT using allogeneic hematopoietic stem cells (HSCs), has been limited to fetuses with severe immunologic defects and more recently IUT with allogeneic mesenchymal stem cell transplantation, has improved phenotype in osteogenesis imperfecta. The options of preemptive treatment of congenital diseases in utero by stem cell or gene therapy changes the perspective of congenital diseases since it may avoid the need for postnatal treatment and reduce future costs. Amniotic fluid stem (AFS) cells have been isolated and characterized in human, mice, rodents, rabbit, and sheep and are a potential source of cells for therapeutic applications in disorders for treatment prenatally or postnatally. Gene transfer to the cells with long-term transgenic protein expression is feasible. Recently, pre-clinical autologous transplantation of transduced cells has been achieved in fetal sheep using minimally invasive ultrasound guided injection techniques. Clinically relevant levels of transgenic protein were expressed in the blood of transplanted lambs for at least 6 months. The cells have also demonstrated the potential of repair in a range of pre-clinical disease models such as neurological disorders, tracheal repair, bladder injury, and diaphragmatic hernia repair in neonates or adults. These results have been encouraging, and bring personalized tissue engineering for prenatal treatment of genetic disorders closer to the clinic.

Trisomy 21 mid-trimester amniotic fluid induced pluripotent stem cells maintain genetic signatures during reprogramming: implications for disease modeling and cryobanking

Trisomy 21 is the most common chromosomal abnormality and is associated primarily with cardiovascular, hematological, and neurological complications. A robust patient-derived cellular model is necessary to investigate the pathophysiology of the syndrome because current animal models are limited and access to tissues from affected individuals is ethically challenging. We aimed to derive induced pluripotent stem cells (iPSCs) from trisomy 21 human mid-trimester amniotic fluid stem cells (AFSCs) and describe their hematopoietic and neurological characteristics. Human AFSCs collected from women undergoing prenatal diagnosis were selected for c-KIT(+) and transduced with a Cre-lox-inducible polycistronic lentiviral vector encoding SOX2, OCT4, KLF-4, and c-MYC (50,000 cells at a multiplicity of infection (MOI) 1-5 for 72 h). The embryonic stem cell (ESC)-like properties of the AFSC-derived iPSCs were established in vitro by embryoid body formation and in vivo by teratoma formation in RAG2(-/-), γ-chain(-/-), C2(-/-) immunodeficient mice. Reprogrammed cells retained their cytogenetic signatures and differentiated into specialized hematopoietic and neural precursors detected by morphological assessment, immunostaining, and RT-PCR. Additionally, the iPSCs expressed all pluripotency markers upon multiple rounds of freeze-thawing. These findings are important in establishing a patient-specific cellular platform of trisomy 21 to study the pathophysiology of the aneuploidy and for future drug discovery.

5' isomiR variation is of functional and evolutionary importance

We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3′ and/or 5′ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5′ differences and in support of this we report that a 5′ isomiR-9–1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5′ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes.

Unravelling the pluripotency paradox in fetal and placental mesenchymal stem cells: Oct-4 expression and the case of The Emperor's New Clothes

Mesenchymal stem cells (MSC) from fetal-placental tissues have translational advantages over their adult counterparts, and have variably been reported to express pluripotency markers. OCT-4 expression in fetal-placental MSC has been documented in some studies, paradoxically without tumourogenicity in vivo. It is possible that OCT-4 expression is insufficient to induce true "stemness", but this issue is important for the translational safety of fetal-derived MSC. To clarify this, we undertook a systematic literature review on OCT-4 in fetal or adnexal MSC to show that most studies report OCT-4 message or protein expression, but no study provides definitive evidence of true OCT-4A expression. Discrepant findings were attributable not to different culture conditions, tissue sources, or gestational ages but instead to techniques used. In assessing OCT-4 as a pluripotency marker, we highlight the challenges in detecting the correct OCT-4 isoform (OCT-4A) associated with pluripotency. Although specific detection of OCT-4A mRNA is achievable, it appears unlikely that any antibody can reliably distinguish between OCT-4A and the pseudogene OCT-4B. Finally, using five robust techniques we demonstrate that fetal derived-MSC do not express OCT-4A (or by default OCT-4B). Reports suggesting OCT-4 expression in fetal-derived MSC warrant reassessment, paying attention to gene and protein isoforms, pseudogenes, and antibody choice as well as primer design. Critical examination of the OCT-4 literature leads us to suggest that OCT-4 expression in fetal MSC may be a case of "The Emperor's New Clothes" with early reports of (false) positive expression amplified in subsequent studies without critical attention to emerging refinements in knowledge and methodology.

Potential of human fetal chorionic stem cells for the treatment of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a genetic bone pathology with prenatal onset, characterized by brittle bones in response to abnormal collagen composition. There is presently no cure for OI. We previously showed that human first trimester fetal blood mesenchymal stem cells (MSCs) transplanted into a murine OI model (oim mice) improved the phenotype. However, the clinical use of fetal MSC is constrained by their limited number and low availability. In contrast, human fetal early chorionic stem cells (e-CSC) can be used without ethical restrictions and isolated in high numbers from the placenta during ongoing pregnancy. Here, we show that intraperitoneal injection of e-CSC in oim neonates reduced fractures, increased bone ductility and bone volume (BV), increased the numbers of hypertrophic chondrocytes, and upregulated endogenous genes involved in endochondral and intramembranous ossification. Exogenous cells preferentially homed to long bone epiphyses, expressed osteoblast genes, and produced collagen COL1A2. Together, our data suggest that exogenous cells decrease bone brittleness and BV by directly differentiating to osteoblasts and indirectly stimulating host chondrogenesis and osteogenesis. In conclusion, the placenta is a practical source of stem cells for the treatment of OI.

Human fetal and adult bone marrow-derived mesenchymal stem cells use different signaling pathways for the initiation of chondrogenesis

Cartilage injuries and osteoarthritis are leading causes of disability in developed countries. The regeneration of damaged articular cartilage using cell transplantation or tissue engineering holds much promise but requires the identification of an appropriate cell source with a high proliferative propensity and consistent chondrogenic capacity. Human fetal mesenchymal stem cells (MSCs) have been isolated from a range of perinatal tissues, including first-trimester bone marrow, and have demonstrated enhanced expansion and differentiation potential. However, their ability to form mature chondrocytes for use in cartilage tissue engineering has not been clearly established. Here, we compare the chondrogenic potential of human MSCs isolated from fetal and adult bone marrow and show distinct differences in their responsiveness to specific growth factors. Transforming growth factor beta 3 (TGFβ3) induced chondrogenesis in adult but not fetal MSCs. In contrast, bone morphogenetic protein 2 (BMP2) induced chondrogenesis in fetal but not adult MSCs. When fetal MSCs co-stimulated with BMP2 and TGFβ3 were used for cartilage tissue engineering, they generated tissue with type II collagen and proteoglycan content comparable to adult MSCs treated with TGFβ3 alone. Investigation of the TGFβ/BMP signaling pathway showed that TGFβ3 induced phosphorylation of SMAD3 in adult but not fetal MSCs. These findings demonstrate that the initiation of chondrogenesis is modulated by distinct signaling mechanisms in fetal and adult MSCs. This study establishes the feasibility of using fetal MSCs in cartilage repair applications and proposes their potential as an in vitro system for modeling chondrogenic differentiation and skeletal development studies.

Molecular signature of human amniotic fluid stem cells during fetal development

Mid-gestation c-KIT(+) amniotic fluid stem cells (AFSC) have an intermediate phenotype between embryonic and adult stem cells and are easy to reprogram to pluripotency. We previously showed that 1st trimester AFSC can be reprogrammed to functional pluripotency in a transgene-free approach. Despite both parental populations sharing a common phenotype, expressing CD29, CD44, CD73, CD90, CD105, SSEA4 and OCT4, 2nd trimester AFSC, contrary to 1st trimester cells, do not express NANOG, SSEA3, TRA-1-60 and TRA-1-81, and have slower growth kinetics. Here, we used the Illumina Beadstudio microarray platform to analyse the transcriptome of 1st and 2nd trimester AFSC and show a unique 1st trimester AFSC-specific gene expression signature consisting of 366 genes and a larger set of 603 genes common with hESC compared to 496 genes overlapping between 2nd trimester AFSC and hESC. We conclude that both populations are related but distinct to each other as well as to hESC.

Induced pluripotent stem (iPS) cells from human fetal stem cells (hFSCs)

INTRODUCTION

(1) Human embryonic stem (ES) cells are pluripotent but are difficult to be used for therapy because of immunological, oncological and ethical barriers. (2) Pluripotent cells exist in vivo, i.e., germ cells and epiblast cells but cannot be isolated without sacrificing the developing embryo. (3) Reprogramming to pluripotency is possible from adult cells using ectopic expression of OKSM and other integrative and non-integrative techniques. (4) Hurdles to overcome include i.e stability of the phenotype in relation to epigenetic memory.

SOURCES OF DATA

We reviewed the literature related to reprogramming, pluripotency and fetal stem cells.

AREAS OF AGREEMENT

(1) Fetal stem cells present some advantageous characteristics compared with their neonatal and postnatal counterparts, with regards to cell size, growth kinetics, and differentiation potential, as well as in vivo tissue repair capacity. (2) Amniotic fluid stem cells are more easily reprogrammed to pluripotency than adult fibroblast. (3) The parental population is heterogeneous and present an intermediate phenotype between ES and adult somatic stem cells, expressing markers of both.

AREAS OF CONTROVERSY

(1) It is unclear whether induced pluripotent stem (iPS) derived from amniotic fluid stem cells are fully or partially reprogrammed. (2) Optimal protocols to ensure highest efficiency and phenotype stability remains to be determined. (3) The "level" of reprogramming, fully vs partial, of iPS derived from amniotic fluid stem cells remain to be determined.

GROWING POINTS

Banking of fully reprogrammed cells may be important both for (1) autologous and allogenic applications in medicine, and (2) disease modeling.

Placenta as a reservoir of stem cells: an underutilized resource?

INTRODUCTION

Both embryonic and adult tissues are sources of stem cells with therapeutic potential but with some limitations in the clinical practice such as ethical considerations, difficulty in obtaining and tumorigenicity. As an alternative, the placenta is a foetal tissue that can be obtained during gestation and at term, and it represents a reservoir of stem cells with various potential.

SOURCES OF DATA

We reviewed the relevant literature concerning the main stem cells that populate the placenta.

AREAS OF AGREEMENT

Recently, the placenta has become useful source of stem cells that offer advantages in terms of proliferation and plasticity when compared with adult cells and permit to overcome the ethical and safety concern inherent in embryonic stem cells. In addition, the placenta has the advantage of containing epithelia, haematopoietic and mesenchymal stem cells. These stem cells possess immunosuppressive properties and have the capacity of suppress in vivo inflammatory responses.

AREAS OF CONTROVERSY

Some studies describe a subpopulation of placenta stem cells expressing pluripotency markers, but for other studies, it is not clear whether pluripotent stem cells are present during gestation beyond the first few weeks. Particularly, the expression of some pluripotency markers such as SSEA-3, TRA-1-60 and TRA-1-81 has been reported by us, but not by others.

GROWING POINTS

Placenta stem cells could be of great importance after delivery for banking for autologous and allogeneic applications. The beneficial effects of these cells may be due to secretion of bioactive molecules that act through paracrine actions promoting beneficial effects.

AREAS TIMELY FOR DEVELOPING RESEARCH

Understanding the role of placenta stem cells during pregnancy and their paracrine actions could help in the study of some diseases that affect the placenta during pregnancy.

Ontological differences in first compared to third trimester human fetal placental chorionic stem cells

Human mesenchymal stromal/stem cells (MSC) isolated from fetal tissues hold promise for use in tissue engineering applications and cell-based therapies, but their collection is restricted ethically and technically. In contrast, the placenta is a potential source of readily-obtainable stem cells throughout pregnancy. In fetal tissues, early gestational stem cells are known to have advantageous characteristics over neonatal and adult stem cells. Accordingly, we investigated whether early fetal placental chorionic stem cells (e-CSC) were physiologically superior to their late gestation fetal chorionic counterparts (l-CSC). We showed that e-CSC shared a common phenotype with l-CSC, differentiating down the osteogenic, adipogenic and neurogenic pathways, and containing a subset of cells endogenously expressing NANOG, SOX2, c-MYC, and KLF4, as well as an array of genes expressed in pluripotent stem cells and primordial germ cells, including CD24, NANOG, SSEA4, SSEA3, TRA-1-60, TRA-1-81, STELLA, FRAGILIS, NANOS3, DAZL and SSEA1. However, we showed that e-CSC have characteristics of an earlier state of stemness compared to l-CSC, such as smaller size, faster kinetics, uniquely expressing OCT4A variant 1 and showing higher levels of expression of NANOG, SOX2, c-MYC and KLF4 than l-CSC. Furthermore e-CSC, but not l-CSC, formed embryoid bodies containing cells from the three germ layer lineages. Finally, we showed that e-CSC demonstrate higher tissue repair in vivo; when transplanted in the osteogenesis imperfecta mice, e-CSC, but not l-CSC increased bone quality and plasticity; and when applied to a skin wound, e-CSC, but not l-CSC, accelerated healing compared to controls. Our results provide insight into the ontogeny of the stemness phenotype during fetal development and suggest that the more primitive characteristics of early compared to late gestation fetal chorionic stem cells may be translationally advantageous.

Upregulating CXCR4 in human fetal mesenchymal stem cells enhances engraftment and bone mechanics in a mouse model of osteogenesis imperfecta

Stem cells have considerable potential to repair damaged organs and tissues. We previously showed that prenatal transplantation of human first trimester fetal blood mesenchymal stem cells (hfMSCs) in a mouse model of osteogenesis imperfecta (oim mice) led to a phenotypic improvement, with a marked decrease in fracture rate. Donor cells differentiated into mature osteoblasts, producing bone proteins and minerals, including collagen type Iα2, which is absent in nontransplanted mice. This led to modifications of the bone matrix and subsequent decrease of bone brittleness, indicating that grafted cells directly contribute to improvement of bone mechanical properties. Nevertheless, the therapeutic effect was incomplete, attributing to the limited level of engraftment in bone. In this study, we show that although migration of hfMSCs to bone and bone marrow is CXCR4-SDF1 (SDF1 is stromal-derived factor) dependent, only a small number of cells present CXCR4 on the cell surface despite high levels of internal CXCR4. Priming with SDF1, however, upregulates CXCR4 to increase the CXCR4(+) cell fraction, improving chemotaxis in vitro and enhancing engraftment in vivo at least threefold in both oim and wild-type bone and bone marrow. Higher engraftment in oim bones was associated with decreased bone brittleness. This strategy represents a step to improve the therapeutic benefits of fetal cell therapy toward being curative.

The effects of culture on genomic imprinting profiles in human embryonic and fetal mesenchymal stem cells

Human embryonic stem (hES) cells and fetal mesenchymal stem cells (fMSC) offer great potential for regenerative therapy strategies. It is therefore important to characterise the properties of these cells in vitro. One major way the environment impacts on cellular physiology is through changes to epigenetic mechanisms. Genes subject to epigenetic regulation via genomic imprinting have been characterised extensively. The integrity of imprinted gene expression therefore provides a measurable index for epigenetic stability. Allelic expression of 26 imprinted genes and DNA methylation at associated differentially methylated regions (DMRs) was measured in fMSC and hES cell lines. Both cell types exhibited monoallelic expression of 13 imprinted genes, biallelic expression of six imprinted genes, and there were seven genes that differed in allelic expression between cell lines. fMSCs exhibited the differential DNA methylation patterns associated with imprinted expression. This was unexpected given that gene expression of several imprinted genes was biallelic. However, in hES cells, differential methylation was perturbed. These atypical methylation patterns did not correlate with allelic expression. Our results suggest that regardless of stem cell origin, in vitro culture affects the integrity of imprinted gene expression in human cells. We identify biallelic and variably expressed genes that may inform on overall epigenetic stability. As differential methylation did not correlate with imprinted expression changes we propose that other epigenetic effectors are adversely influenced by the in vitro environment. Since DMR integrity was maintained in fMSC but not hES cells, we postulate that specific hES cell derivation and culturing practices result in changes in methylation at DMRs.

Biological characteristics of stem cells from foetal, cord blood and extraembryonic tissues

Foetal stem cells (FSCs) can be isolated during gestation from many different tissues such as blood, liver and bone marrow as well as from a variety of extraembryonic tissues such as amniotic fluid and placenta. Strong evidence suggests that these cells differ on many biological aspects such as growth kinetics, morphology, immunophenotype, differentiation potential and engraftment capacity in vivo. Despite these differences, FSCs appear to be more primitive and have greater multi-potentiality than their adult counterparts. For example, foetal blood haemopoietic stem cells proliferate more rapidly than those found in cord blood or adult bone marrow. These features have led to FSCs being investigated for pre- and post-natal cell therapy and regenerative medicine applications. The cells have been used in pre-clinical studies to treat a wide range of diseases such as skeletal dysplasia, diaphragmatic hernia and respiratory failure, white matter damage, renal pathologies as well as cancers. Their intermediate state between adult and embryonic stem cells also makes them an ideal candidate for reprogramming to the pluripotent status.

Comparative osteogenic transcription profiling of various fetal and adult mesenchymal stem cell sources

Human mesenchymal stem cells (MSC) from adult and fetal tissues are promising candidates for cell therapy but there is a need to identify the optimal source for bone regeneration. We have previously characterized MSC populations in first trimester fetal blood, liver, and bone marrow and we now evaluate their osteogenic differentiation potential in comparison to adult bone marrow MSC. Using quantitative real-time RT-PCR, we demonstrated that 16 osteogenic-specific genes (OC, ON, BSP, OP, Col1, PCE, Met2A, OPG, PHOS1, SORT, ALP, BMP2, CBFA1, OSX, NOG, IGFII) were expressed in both fetal and adult MSC under basal conditions and were up-regulated under osteogenic conditions both in vivo and during an in vitro 21-day time-course. However, under basal conditions, fetal MSC had higher levels of osteogenic gene expression than adult MSC. Upon osteogenic differentiation, fetal MSC produced more calcium in vitro and reached higher levels of osteogenic gene up-regulation in vivo and in vitro. Second, we observed a hierarchy within fetal samples, with fetal bone marrow MSC having greater osteogenic potential than fetal blood MSC, which in turn had greater osteogenic potential than fetal liver MSC. Finally, we found that the level of gene expression under basal conditions was positively correlated with both calcium secretion and gene expression after 21 days in osteogenic conditions. Our findings suggest that stem cell therapy for bone dysplasias such as osteogenesis imperfecta may benefit from preferentially using first trimester fetal blood or bone marrow MSC over fetal liver or adult bone marrow MSC.

Transplantation of human fetal mesenchymal stem cells improves glomerulopathy in a collagen type I alpha 2-deficient mouse

Fetal mesenchymal stem cell (fetal MSC) therapy has potential to treat genetic diseases with early onset, including those affecting the kidney and urinary tract. A collagen type I alpha 2-deficient mouse has a deletion in the alpha2 chain of the procollagen type I gene, resulting in the synthesis of abnormal alpha1(I)(3) homotrimers, which replace normal alpha 1(I)2 alpha 2(I)1 heterotrimers and a glomerulopathy. We first confirmed that col1 alpha 2-deficient homozygous mice show abnormal collagen deposition in the glomeruli, which increases in frequency and severity with postnatal age. Intrauterine transplantation of human MSCs from first trimester fetal blood led postnatally to a reduction of abnormal homotrimeric collagen type I deposition in the glomeruli of 4-12 week-old col1 alpha 2-deficient mice. Using bioluminescence imaging, in situ hybridization and immunohistochemistry in transplanted col1 alpha 2-deficient mice, we showed that the damaged kidneys preferentially recruited donor cells in glomeruli, around mesangial cells. Real-time RT-PCR demonstrated that this effect was seen at an engraftment level of 1% of total cells in the kidney, albeit higher in glomeruli. We conclude that intrauterine transplantation of human fetal MSCs improves renal glomerulopathy in a collagen type I-deficient mouse model. These data support the feasibility of prenatal treatment for hereditary renal diseases.

A biomarker-based mathematical model to predict bone-forming potency of human synovial and periosteal mesenchymal stem cells

OBJECTIVE

To develop a biomarker-based model to predict osteogenic potency of human mesenchymal stem cells (MSCs) from synovial membrane and periosteum.

METHODS

MSC populations were derived from adult synovium and periosteum. Phenotype analysis was performed by fluorescence-activated cell sorting and real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Telomere lengths were determined by Southern blot analysis. In vitro osteogenesis was assessed quantitatively by measurements of alkaline phosphatase activity and calcium deposits. To investigate bone formation in vivo, MSCs were seeded onto osteoinductive scaffolds and implanted subcutaneously in nude mice. Bone was assessed by histology, and the human origin investigated by in situ hybridization for human Alu genomic repeats. Quantitation was achieved by histomorphometry and real-time RT-PCR for human osteocalcin. Analysis at the single-cell level was performed with clonal populations obtained by limiting dilution. Multiple regressions were used to explore the incremental predictive value of the markers.

RESULTS

Periosteal MSCs had significantly greater osteogenic potency than did synovial MSCs inherent to the single cell. Bone was largely of human origin in vivo. Within the same tissue type, there was variability between different donors. To identify predictors of osteogenic potency, we measured the expression levels of osteoblast lineage genes in synovial and periosteal clonal MSCs prior to osteogenic treatment. We identified biomarkers that correlated with osteogenic outcome and developed a mathematical model based on type I collagen and osteoprotegerin expression that predicts the bone-forming potency of MSC preparations, independent of donor-related variables and tissue source.

CONCLUSION

Our findings indicate that our quality-control mathematical model estimates the bone-forming potency of MSC preparations for bone repair.

Stem cell differentiation and expansion for clinical applications of tissue engineering

This invited review discusses the latest advances stem cell biology, tissue engineering and the transition from bench to bedside. An overview is presented as to which the best cell source might be for cell therapy and tissue engineering applications, best biomaterials currently available and the challenges the field faces to translate basic research into therapies for a large number of human diseases.

Osterix induces osteogenic gene expression but not differentiation in primary human fetal mesenchymal stem cells

The transcription factor osterix (Osx) is a key regulator of osteoblast differentiation and induces bone formation in embryonic but not adult stem cells. We investigated the effect of up-regulating Osx on an intermediate stem cell type, first trimester fetal mesenchymal stem cells (MSCs), which are more expandable than adult MSCs. Human fetal (hf ) MSCs were transduced with a lentiviral vector encoding human Osx. In undifferentiating MSCs cultures, forced expression of Osx stimulated osteopontin and alkaline phosphatase expression. However, Osx did not up-regulate osteocalcin, a late marker of osteoblast differentiation or result in extracellular calcium crystals, indicating that Osx does not directly mediate terminal differentiation in primary hfMSCs. To understand the downstream effects of Osx expression in primary hfMSCs, we next investigated the regulatory relationship between Osx, and the transcription factors Dlx5, Runx2, and Msx2. Osx induced Dlx5 but did not affect Runx2 and Msx2, whereas stealth ribonucleic acid interference of Osx inhibited Dlx5 without affecting expression of Runx2 and Msx2. In conclusion, Osx regulates osteogenic gene expression in hfMSCs but is insufficient to induce terminal osteogenic differentiation.

Fetal stem cells: betwixt and between

Fetal stem cells can be isolated not only from fetal blood and hemopoietic organs in early pregnancy, but from a variety of somatic organs as well as amniotic fluid and placenta throughout gestation. Fetal blood is a rich source of hemopoietic stem cells, which proliferate more rapidly than those in cord blood or adult bone marrow. First-trimester fetal blood, liver, and bone marrow also contain a population of mesenchymal stem cells, which appear to be more primitive with greater multipotentiality than their adult counterparts. Fetal stem cells may thus represent an intermediate cell type in the current debate focusing on dichotomized adult versus embryonic stem cells, and thus prove advantageous as a source for downstream cell therapy applications. They have also been implicated in fetomaternal trafficking in pregnancy, and in long-term microchimerism in postreproductive women.

Widespread distribution and muscle differentiation of human fetal mesenchymal stem cells after intrauterine transplantation in dystrophic mdx mouse

Duchenne muscular dystrophy (DMD) is a common X-linked disease resulting from the absence of dystrophin in muscle. Affected boys suffer from incurable progressive muscle weakness, leading to premature death. Stem cell transplantation may be curative, but is hampered by the need for systemic delivery and immune rejection. To address these barriers to stem cell therapy in DMD, we investigated a fetal-to-fetal transplantation strategy. We investigated intramuscular, intravascular, and intraperitoneal delivery of human fetal mesenchymal stem cells (hfMSCs) into embryonic day (E) 14-16 MF1 mice to determine the most appropriate route for systemic delivery. Intramuscular injections resulted in local engraftment, whereas both intraperitoneal and intravascular delivery led to systemic spread. However, intravascular delivery led to unexpected demise of transplanted mice. Transplantation of hfMSCs into E14-16 mdx mice resulted in widespread long-term engraftment (19 weeks) in multiple organs, with a predilection for muscle compared with nonmuscle tissues (0.71% vs. 0.15%, p < .01), and evidence of myogenic differentiation of hfMSCs in skeletal and myocardial muscle. This is the first report of intrauterine transplantation of ontologically relevant hfMSCs into fully immunocompetent dystrophic fetal mice, with systemic spread across endothelial barriers leading to widespread long-term engraftment in multiple organ compartments. Although the low-level of chimerism achieved is not curative for DMD, this approach may be useful in other severe mesenchymal or enzyme deficiency syndromes, where low-level protein expression may ameliorate disease pathology.

Human first-trimester fetal MSC express pluripotency markers and grow faster and have longer telomeres than adult MSC

The biological properties of stem cells are key to the success of cell therapy, for which MSC are promising candidates. Although most therapeutic applications to date have used adult bone marrow MSC, increasing evidence suggests that MSC from neonatal and mid-gestational fetal tissues are more plastic and grow faster. Fetal stem cells have been isolated earlier in development, from first-trimester blood and hemopoietic organs, raising the question of whether they are biologically closer to embryonic stem cells and thus have advantages over adult bone marrow MSC. In this study, we show that human first-trimester fetal blood, liver, and bone marrow MSC but not adult MSC express the pluripotency stem cell markers Oct-4, Nanog, Rex-1, SSEA-3, SSEA-4, Tra-1-60, and Tra-1-81. In addition, fetal MSC, irrespective of source, had longer telomeres (p < .001), had greater telomerase activity (p < .01), and expressed more human telomerase reverse transcriptase (p < .01). Fetal MSC were also more readily expandable and senesced later in culture than their adult counterparts (p < .01). Compared with adult MSC, first-trimester fetal tissues constitute a source of MSC with characteristics that appear advantageous for cell therapy.

Splicing speckles are not reservoirs of RNA polymerase II, but contain an inactive form, phosphorylated on serine2 residues of the C-terminal domain

"Splicing speckles" are major nuclear domains rich in components of the splicing machinery and polyA(+) RNA. Although speckles contain little detectable transcriptional activity, they are found preferentially associated with specific mRNA-coding genes and gene-rich R bands, and they accumulate some unspliced pre-mRNAs. RNA polymerase II transcribes mRNAs and is required for splicing, with some reports suggesting that the inactive complexes are stored in splicing speckles. Using ultrathin cryosections to improve optical resolution and preserve nuclear structure, we find that all forms of polymerase II are present, but not enriched, within speckles. Inhibition of polymerase activity shows that speckles do not act as major storage sites for inactive polymerase II complexes but that they contain a stable pool of polymerase II phosphorylated on serine(2) residues of the C-terminal domain, which is transcriptionally inactive and may have roles in spliceosome assembly or posttranscriptional splicing of pre-mRNAs. Paraspeckle domains lie adjacent to speckles, but little is known about their protein content or putative roles in the expression of the speckle-associated genes. We find that paraspeckles are transcriptionally inactive but contain polymerase II, which remains stably associated upon transcriptional inhibition, when paraspeckles reorganize around nucleoli in the form of caps.

Fixation-induced redistribution of hyperphosphorylated RNA polymerase II in the nucleus of human cells

RNA polymerase II (pol II) transcribes the most varied group of genes and is present in hypo- and hyperphosphorylated forms, with residues Ser(2) and Ser(5) of the C-terminal domain (CTD) of the largest subunit as main targets of phosphorylation. The elongating (active) form is phosphorylated on Ser(2) and can be specifically recognized with the H5 antibody. It has been found in different nuclear distributions: in discrete sites throughout the nucleoplasm, consistent with a role in transcription, and/or concentrated in "splicing speckles", a nuclear compartment mostly devoid of transcriptional activity. Here, we assess the effects of cell fixation and permeabilization on the distribution of polymerase II and correlate its distribution with the preservation of cellular ultrastructure. We show that phospho-Ser(2) polymerase II can redistribute to, or be differentially retained in, "speckles" in conditions that do not preserve cellular ultrastructure. The fixation protocols that disrupt polymerase II distribution also cause partial or total loss of TATA-binding protein, Sm antigen and PML staining in PML bodies, and have no noticeable effect in the labeling of SC35 in "splicing speckles" or coilin in Cajal bodies. When nuclear ultrastructure is preserved, phospho-Ser(2) polymerase II is found in discrete sites throughout the nucleoplasm, without visible enrichment within splicing speckles. A minor proportion of the total amount of the phospho-Ser(2) form is present in these domains.

Targeting of human eNOS promoter to the Hprt locus of mice leads to tissue-restricted transgene expression

Phenotypic heterogeneity of the endothelium arises from cell type-specific differences in gene expression. An understanding of the mechanisms that underlie differential gene expression would provide important insight into the molecular basis of vascular diversity. In standard transgenic assays, multiple copies of heterologous DNA cassettes are randomly integrated into the mouse genome, resulting in significant line-to-line variation in expression. To overcome these limitations, we have targeted a single copy of a transgene that contains 1,600 bp of the human endothelial nitric oxide synthase (eNOS) promoter coupled to the LacZ reporter gene to the X-linked hypoxanthine phosphoribosyltransferase (Hprt) locus of mice by homologous recombination. The transgene was inserted in either of the orientations relative to that of the Hprt gene. In mice derived from multiple embryonic stem (ES) cell clones, the expression pattern was limited to a subset of endothelial cells, cardiomyocytes, and vascular smooth muscle cells. These findings suggest that Hprt locus targeting is a feasible tool for studying endothelial cell-restricted gene regulation.

Characterization of the mouse von Willebrand factor promoter

Expression of the von Willebrand factor (vWF) gene is restricted to the endothelial and megakaryocyte lineages. Within the endothelium, expression of vWF varies between different vascular beds. We have previously shown that the human vWF promoter spanning a region between -2182 (relative to the start site of transcription) and the end of the first intron contains information for environmentally responsive, vascular bed-specific expression in the heart, skeletal muscle, and brain. In the present study, we cloned the mouse vWF (mvWF) promoter and studied its function in cultured endothelial cells and transgenic mice. In transient transfection assays, the mvWF gene was found to be regulated by distinct mechanisms in different endothelial cell subtypes. In independent lines of transgenic mice, an mvWF promoter fragment containing DNA sequences between -2645 and the end of the first intron directed endothelial cell-specific expression in the microvascular beds of the heart, brain, and skeletal muscle as well as the endothelial lining of the aorta. In 1 line of mice, reporter gene activity was also detected in bone marrow megakaryocytes. Taken together, these findings suggest that both the mouse and human vWF promoters are regulated by vascular bed-specific mechanisms.

Mice selected for differences in sensitivity to a benzodiazepine receptor inverse agonist vary in intermale aggression

Brain gamma-aminobutyric acid (GABA) levels are involved in intermale aggression in mice. It was therefore expected that animals genetically selected for their sensitivity to the convulsive effects of methyl beta-carboline-3-carboxylate (beta-CCM; BS, beta-CCM sensitive, and BR, beta-CCM resistant), a benzodiazepine (BZ) inverse agonist that specifically binds to the BZ site on the GABA-A receptor complex, would differ in their levels of aggressive behavior. Using two different aggression tests, in two independent experiments, we showed that BS mice are more aggressive than BR animals. The precise mechanisms underlying the observed line differences in beta-CCM sensitivity and aggression remain to be determined.

A vascular bed-specific pathway

The endothelial nitric oxide synthase (eNOS) gene is induced by a variety of extracellular signals under both in vitro and in vivo conditions. To gain insight into the mechanisms underlying environmental regulation of eNos expression, transgenic mice were generated with the 1,600-bp 5' flanking region of the human eNos promoter coupled to the coding region of the LacZ gene. In multiple independent lines of mice, transgene expression was detected within the endothelium of the brain, heart, skeletal muscle, and aorta. beta-galactosidase activity was consistently absent in the vascular beds of the liver, kidney, and spleen. In stable transfection assays of murine endothelial progenitor cells, the 1,600-bp promoter region was selectively induced by conditioned media from cardiac myocytes, skeletal myocytes, and brain astrocytes. Cardiac myocyte-mediated induction was partly abrogated by neutralizing anti-platelet-derived growth factor (PDGF) antibodies. In addition, promoter activity was upregulated by PDGF-AB. Analysis of promoter deletions revealed that a PDGF response element lies between -744 and -1,600 relative to the start site of transcription, whereas a PDGF-independent cardiac myocyte response element is present within the first 166 bp of the 5' flanking region. Taken together, these results suggest that the eNos gene is regulated in the cardiac endothelium by both a PDGF-dependent and PDGF-independent microvascular bed-specific signaling pathway.

Neuronal and behavioral differences between Mus musculus domesticus (C57BL/6JBy) and Mus musculus castaneus (CAST/Ei)

Previous studies have demonstrated that classical inbred strains of laboratory mice do not exhibit large genetic distances when simple sequence repeats (SSRs) are used to test for their polymorphisms whereas mice from wild origin exhibit high polymorphisms (more than 90%) for these sequence when compared with classical inbred strains of laboratory mice. The difference between Mus musculus castaneus and C57BL/6J reaches 98% and F1s male and female are fertile. These two properties pave the way for gene mapping derivating segregating generations between these strains. The phenotypical characteristics of Mus musculus castaneus have not been investigated, unfortunately. The first screening of Mus musculus castaneus and C57BL/6By was carried out for sensorial and motor development, spontaneous behavior in new environment, paw preference, maternal behavior, aggression in two different situations and time to learn escape in a water maze. Morphometry of hippocampus and weight of the male reproductive organs for measures that have been reported to be correlated with several of the examined behavior are also reported. The authors tested also reactivity to one drug (beta-CCM) revealing seizure proneness. The two strains differ for 69% of the reported measures. Comparison to other strains for the same measures obtained in the laboratory for identical tests with mice reared in identical situations provided the mean to compare Mus musculus castaneus with a large set of more or less traditional mice. This strain has the most extreme position for 80% of the comparisons.

A mutation in the connexin 50 (Cx50) gene is a candidate for the No2 mouse cataract

PURPOSE

The No2 cataractous mouse mutant displays a bilateral, congenital, hereditary nuclear opacity of the ocular lens. The aim of this work was to identify and subsequently screen an optimal candidate gene for a mutation correlated and consistent with the observed phenotype.

METHODS

The No2 cataract was mapped in relation to genes and microsatellite markers by crossing to the wild mouse strain Mus spretus and then backcrossing to the inbred strain C3H/ HeH. The Cx50 (MP70) protein coding region and flanking sequences were amplified from normal parental as well as heterozygous and homozygous mutant genomic DNAs. These PCR products were then sequenced directly. Sequence data was corroborated by restriction analysis of PCR products.

RESULTS

Mapping of the No2 cataract placed it in the vicinity of Gja8, the gene encoding connexin 50 (MP70), a major component of lens fiber gap junctions. Amplification and subsequent sequencing of the Cx50 protein coding regions revealed a single A-->C transversion within codon 47. This sequence change resulted in the creation of an HhaI restriction endonuclease restriction site, allowing for corroboration of the sequence data via restriction analysis using this enzyme. The sequence alteration is also predicted to result in the nonconservative substitution of alanine (Ala) for the normally encoded aspartic acid (Asp) at this position within the polypeptide.

CONCLUSIONS

The identified mutation in Gja8 is both correlated and consistent with the cataract observed in the No2 mouse mutant, making it an ideal candidate for the cataract. This study provides the first evidence that a mutation in a lens connexin can result in congenital hereditary cataract, highlighting the importance of lens connexins in maintaining lens transparency.

Intermale aggression, GAD activity in the olfactory bulbs and Y chromosome effect in seven inbred mouse strains

The capacity to attack a passive standard opponent in a resident-intruder test and the GAD activity in the olfactory bulbs were measured in 140 male mice from seven different inbred mouse strains. The effect of the non-pseudo autosomal region of the Y-chromosome (YNPAR) on these two phenotypes has also been investigated using a quartet of reciprocal strains congenic for the YNPAR. A strong negative correlation was found between the two variables but the YNPAR is not involved. This result suggests that males of more attacking strains have a lower olfactory threshold, making the olfactory discrimination of the opponent easier and its identification as a stranger more efficient.

Olfaction, GABAergic neurotransmission in the olfactory bulb, and intermale aggression in mice: modulation by steroids

A model to explain individual differences in mice for the propensity to attack male conspecifics is proposed. In the first part of the paper, the relation between olfaction and intermale aggression is discussed emphasizing the importance of olfactory cues provided by the opponent and their subsequent processing by the attacking male. The physiological role of GABA in the olfactory pathway is presented in the second part of the paper. The third part investigates the possible modulating action of steroids on the GABA-A receptor complex, intermale aggression, and olfaction. We hypothesize that at least part of the individual differences in the propensity to attack may be explained by a differential olfactory recognition and discrimination of the opponent as a stranger through a differential processing threshold of the olfactory cues provided by the urine of the opponent. A possible modulation of this threshold by steroids, especially testosterone, is also discussed.

Intermale aggression and dark/light preference in ten inbred mouse strains

The capacity of males to attack a passive standard opponent in a resident-intruder test and the preferences in a dark/light choice situation were measured in 200 male mice from 10 different inbred mouse strains. Large strain differences were found for all variables recorded, i.e., the proportion of attacking males, the time spent in the brightly lit box, and the number of transitions between the lit and the dark boxes. A strong negative correlation was found between the first two variables. This result suggests that males of more attacking strains have a higher level of anxiety but do not differ for their level of activity. An involvement of GABA as mediating factor is suggested.

Hippocampal morphology in the inbred mouse strains NZB and CBA/H and their reciprocal congenics for the nonpseudoautosomal region of the Y chromosome

The effects of the nonpseudoautosomal region of the Y chromosome (YNPAR) on hippocampal morphology have been investigated in the inbred mouse strains NZB/BINJ and CBA/H, using comparisons between the two parentals and their respective congenics N.H-YNPAR and H.N-YNPAR. Results obtained depend upon the hippocampal variable measured. YNPAR had no effect on the sizes of the stratum oriens, hilus, or mossy fiber terminal fields (both suprapyramidal and intra- and infrapyramidal). However, in interaction with the strain background, it affected the strata lacunosum-moleculare, radiatum, and pyramidale. Possible relationships among gene(s), mossy fiber terminal fields, and intermale aggression are discussed.

Intermale aggression tested in two procedures, using four inbred strains of mice and their reciprocal congenics: Y chromosomal implications

Indications of a role for the nonpseudoautosomal region of the Y chromosome (YNPAR) in intermale attack behavior have been demonstrated by Maxson's group using C57BL/10 (B10) and DBA/1 (D1) inbred mouse strains and their reciprocal congenics. Carlier and Roubertoux' group, using CBA/H (H) and NZB/B1NJ (N) mice, did not find such a YNPAR effect. For the two research groups, however, not only were the parental strains different, but also the rearing conditions and testing methods. The divergent conclusions drawn may therefore have been due either to genetic variation or to environment-related variables. We carried out two experiments to investigate these alternatives. The N and H strains were raised and tested according to the experimental design used by Maxson's group (homogeneous set test) and the D1 and B10 strains were raised and tested according to the experimental design of Carlier and Roubertoux' group (standard opponent test). Considering all studies together, the YNPAR effect appeared in both sets of mice only when using the homogeneous set test. This raises the question of what environmentally related variables are involved in the YNPAR effect on intermale attack. One strong hypothesis is that the different types of opponents in each experimental design send differing olfactory signals, which, in turn, differentially affect the capacity to elicit intermale attack behavior.

Y chromosomal effects on hippocampal mossy fiber distributions in mice selected for aggression

The influence of the non-pseudoautosomal region of the Y chromosome (YNPAR) on the sizes of the hippocampal intra- and infrapyramidal mossy fiber (IIPMF) terminal fields were examined in wild house mice. For this purpose selection lines for short attack latency (SAL), long attack latency (LAL), and their respective congenics for the YNPAR were used. We found an incremental effect of the (non-aggressive) LAL YNPAR, combined with an additive effect of the line background on the sizes of the IIPMF terminal fields. In contrast, only the line background affected attack latency. The implications of this finding for the previously observed correlation between the size of the IIPMF and aggression in male house mice are discussed.