Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “stem cell model of development”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed1994

Mechanisms involved in living systems organisation, especially the programming necessary to enable the construction of individuals in three dimensions.

The complexity of the organization of living systems escalates by orders of magnitude in the development, from single precursor cells, not only of the three-dimensional structures characterizing each species but also in the variations necessary to accommodate the 1 million or more separate and identifiable species on this planet. Although the genetic information controlling such information is currently considered to reside in cellular DNA, it is also held that such information is restricted to a linear form encoding specifically for protein. However, this not only fails to explain the co-ordination of the vast number of processes occurring in simple, single cell, organisms, but also the integration of cellular activities to serve the interest of the total system. In particular how can a homeobox containing only genes encoding specifically for proteins organize and implement the mechanisms necessary for three-dimensional development? This, and the organization and implementation of the massive amount of information necessary to execute the construction of such a wide range of species, each in its own unique and exquisite detail, calls for internal programming of a highly complex and sophisticated nature. It is proposed here that such a central computer-analog program does exist, housed in the molecular electronic structure of cellular nucleic acid, primarily in DNA: its possible nature is discussed. Since precursor cells contain only of the order of 10(-10) g of DNA, this proposal involves an increase in information storage efficiency comparable with that already achieved by silicon microprocessors over mechanical calculators.

Animals↗
PubMed2007

Use of T-cell antibodies for donor dosaging in a canine model of in utero hematopoietic stem cell transplantation.

AIM: Microchimerism following canine in utero hematopoietic stem cell transplantation (IUHSCT) development of T-cell dosing regimens. OBJECTIVE: To investigate the use of anti-T-cell antibodies for cell dosing of the donor graft in a canine model of IUHSCT. STUDY DESIGN: Canine IUHSCT was performed by ultrasound-guided intraperitoneal injection in days 35-38 of fetal canines with CD34(+) cells at doses of 4.5 x 10(8) to 1.3 x 10(9) cells/kg and T cells (CD3(+) CD5(+)) at doses of 8 x 10(6) to 8.8 x 10(8) cells/kg. Postnatal studies included tissue histology and polymerase chain reaction-based chimerism analysis. RESULTS: Term survival was 86-100%. Microchimerism (0-2%) was detected in five of eight recipients in multiple tissues. Histopathology revealed no evidence of graft-versus-host disease (GVHD). CONCLUSION: Canine IUHSCT is a useful model to investigate the role of donor T cells in engraftment and GVHD. IUHSCT at early gestational ages with high doses of donor T cells in the graft yields microchimerism in multiple tissues without GVHD.

Animals↗
PubMed2001

Computer modeling implicates stem cell overproduction in colon cancer initiation.

On the basis of our investigation of the premalignant crypt phenotype in familial adenomatous polyposis patients, the hypothesis is developed that tumor initiation in the colon is caused by crypt stem cell overproduction. A novel kinetic model for the colonic crypt was used to investigate how the earliest tissue abnormality (altered crypt labeling index) arises in these patients who have a mutant APC genotype. Only an increase in crypt stem cell number, not changes in the rate of cell cycle proliferation, differentiation, or apoptosis of the non-stem cell population, simulated this abnormality. This suggests that APC regulates the number of stem cells in the colonic crypt and when the cells become mutant, an expansion of the crypt stem cell population results.

Adenomatous Polyposis Coli↗
PubMed1998

Embryonic stem cells and embryoid bodies express lymphocyte costimulatory molecules.

Despite the importance of the costimulatory proteins B7-1 (CD80), B7-2 (CD86), and their counterreceptors CD28 and CTLA-4 (CD154) in the regulation of T cell proliferation in the adult immunological system, the initial appearance of these proteins during embryonic development has not been investigated. Using in vitro cultures of undifferentiated mouse embryonic stem (ES) cells and differentiating embryoid bodies as a model of very early embryonic development, we examined these cells for the presence of mRNA and protein corresponding to the B7 and CD28 families of costimulatory molecules. By flow cytometry, a stochastically regulated subpopulation of B7-1+ cells comprising 33% of total cells was detected in ES cell cultures, while negligible staining was found for B7-2, CTLA-4, and CD28. When ES cells were differentiated into embryoid bodies for 12 days, a CD45+ subpopulation of embryoid body cells were found to stain positively for B7-1, B7-2, and CD28. RT-PCR confirmed cell staining data by revealing amplification products corresponding to B7-1, B7-2, and CD28 in corresponding samples. Very low levels of CTLA-4 amplification products were found in all samples; however, surface staining of CTLA-4 was never detected. The functional capacity of ES cell B7-1 to bind its ligand was verified by the ability of the soluble fusion protein CTLA-4-Ig to bind ES cells and the ability of this reagent to block anti-B7-1 antibody binding in cell based competition assays. These results demonstrate that expression of costimulatory molecules arises very early during in vitro development and suggests that the early embryonic environment may utilize cellular signaling systems analogous to those seen in the immune system.

Abatacept↗
PubMed2001

Injection of allogeneic bone marrow cells into the portal vein of swine in utero.

The ability to safely manipulate the immune system of the developing fetus carries the hope of effective treatment strategies for certain congenital disorders that can be diagnosed during gestation. One possible intervention is the induction of specific transplantation tolerance to an adult donor who could provide tissue after birth without the need for immunosuppression. Although the introduction of allogeneic stem cells to a developing immune system has been shown to result in hematopoietic chimerism, donor-specific transplantation tolerance has not been demonstrated in a large animal model. In previous reports of in utero stem-cell transplantation, the cells were injected into the fetus by an intraperitoneal route. We sought to improve upon this technique of cell transplantation by developing a method for the safe delivery of allogeneic stem cells directly into the hepatic circulation of fetal swine. In the second phase of our study, we determined if adult allogeneic bone marrow cells delivered to the fetus by this intravascular route could result in result in hematopoietic chimerism and donor-specific transplantation tolerance. A method of successful intravascular injection was designed in which a laparotomy was performed on a sow at midgestation (50-55 days) to administer 1 cc of inoculum into the portal vein of each fetus using transuterine ultrasound guidance and a 25-gauge spinal needle. In one sow, 10 piglets were injected with saline to test safety, and 8 piglets were born. For transplantation of stem cells to the fetuses, donor bone marrow was harvested from a genetically defined miniature swine. In one sow the marrow was injected without T-cell depletion resulting in abortion. In the third sow, the marrow was depleted of T-cells to less than 0.01% using magnetic beads conjugated to anti-CD3 monoclonal antibodies. No chimerism was detected in these offspring. Only in the fourth sow where the T-cell depletion was reduced to about 1% of the cells in the inoculum did one animal demonstrate chimerism. This piglet showed reproducible blood chimerism (0.95% donor cells) detected by flow cytometry measurement of monoclonal antibodies to the donor MHC. In addition, this animal demonstrated hyporesponsiveness to donor lymphocytes in an MLR assay while reacting strongly to third-party stimulator cells. A split-thickness skin graft from the donor was accepted, and a third-party graft was rapidly rejected.

Animals↗
PubMed2005

The disparate role of BMP in stem cell biology.

Stem cells share several characteristics of cancer cells including loss of contact inhibition and immortality. Therefore, stem cells represent an excellent model system in which to define the molecular mechanisms underlying cancer development and progression. Several signal transduction pathways including leukemia inhibitory factor, Wnt and FGF have been demonstrated to function in stem cell self-renewal and differentiation. However, more recently bone morphogenetic proteins (BMPs) have emerged as key regulators of stem cell fate commitment. Intriguingly, BMPs have disparate roles in regulating the biology of embryonic stem (ES) cells compared with neural crest stem cells (NCSCs). Furthermore, although BMPs block neural differentiation of ES cells from both mouse and human, they contribute to self-renewal specifically in mouse ES cells. These observations strongly suggest that combinations of extracellular factors regulate stem cells, and that crosstalk between intracellular signaling pathways precisely defines stem cell fate commitment. In this review, we focus on the role of BMP signaling in mouse and human ES cells compared with NCSCs. We then discuss how the molecular effectors of BMP signaling may contribute to cancer, and thus represent potential targets for therapeutic intervention.

Animals↗
PubMed1993

Normal B lymphocyte differentiation.

Normal differentiation of B lineage cells has been the subject of intensive investigation over the past three decades. Current models of this process in humans are melded from the results of studies in a variety of organisms, including humans, mice and birds. Several recent developments have significantly reshaped and refined these models. The technique of homologous recombination in embryonic stem cells has allowed the production of mice with selectively disrupted genes that are important for B cell development in mice. At the same time, functional studies of human B cell differentiation, together with analysis of naturally occurring mutations that disrupt this process, have progressed rapidly. This has provided insight into the pathogenesis of lymphoproliferative and immunodeficiency diseases as well as a clearer view of normal developmental events. In this chapter we have reviewed human B cell differentiation with particular emphasis on newly emerging concepts. We also discussed CD5, a pan-T cell antigen that is expressed in low levels on a subpopulation of B cells implicated in the pathogenesis of chronic lymphocytic leukaemia (CLL). Finally, we discussed the issue of restricted variable region gene usage during B cell ontogeny and in CLL.

Animals↗
PubMed2002

Stem cells for myocardial regeneration.

Stem cells are being investigated for their potential use in regenerative medicine. A series of remarkable studies suggested that adult stem cells undergo novel patterns of development by a process referred to as transdifferentiation or plasticity. These observations fueled an exciting period of discovery and high expectations followed by controversy that emerged from data suggesting cell-cell fusion as an alternate interpretation for transdifferentiation. However, data supporting stem cell plasticity are extensive and cannot be easily dismissed. Myocardial regeneration is perhaps the most widely studied and debated example of stem cell plasticity. Early reports from animal and clinical investigations disagree on the extent of myocardial renewal in adults, but evidence indicates that cardiomyocytes are generated in what was previously considered a postmitotic organ. On the basis of postmortem microscopic analysis, it is proposed that renewal is achieved by stem cells that infiltrate normal and infarcted myocardium. To further understand the role of stem cells in regeneration, it is incumbent on us to develop instrumentation and technologies to monitor myocardial repair over time in large animal models. This may be achieved by tracking labeled stem cells as they migrate into myocardial infarctions. In addition, we must begin to identify the environmental cues that are needed for stem cell trafficking and we must define the genetic and cellular mechanisms that initiate transdifferentiation. Only then will we be able to regulate this process and begin to realize the full potential of stem cells in regenerative medicine.

Animals↗
PubMed1990

The BN acute myelocytic leukemia (BNML) (a rat model for studying human acute myelocytic leukemia (AML)).

Even if animal models have many properties in common with the human disease, as is the case for the BNML and human AML, they have their limitations with respect to the extrapolation to the clinical situation. This also holds for the BNML; thus, conclusions should only be drawn with great caution. Nevertheless, the studies in the BNML model have added considerably to the understanding of various processes that occur during the development of leukemia, e.g., the interaction of leukemic cells and normal hemopoietic stem cells in relation to the microenvironment. The methodology developed in the BNML model allows the quantification of the relative effectiveness of any given treatment with regard to the antileukemic activity compared with the toxicity for normal host tissues. Furthermore, the cell kinetic studies performed in the BNML as a consequence of timed sequential chemotherapy has been helpful in designing an approach to take advantage of this phenomenon in the treatment of acute leukemia. The comparison of the various treatment modalities, employed for the conditioning prior to bone marrow transplantation, made it possible to determine the relative effectiveness of the various approaches. The fractionation of total body irradiation for conditioning purposes was supposed to have a negligible effect with regard to a reduced antileukemic effect. Detailed studies that were conducted in the BNML model did not confirm this hypothesis indicating that (hyper-)fraction of TBI results in a reduced antileukemic effect. The in vitro purging studies in the BNML aimed at the elimination of residual leukemic cells in autologous bone marrow transplantation contributed to the introduction of this method in clinical practice. However, extended studies in the BNML model also indicated that the contribution of the residual leukemia cell in the patient contributed to a much greater extend to the recurrence of leukemia then did the residual cells in the autologous marrow graft. A major contribution of the BNML was achieved in the study of the area of so-called "minimal residual disease" (MRD). A number of so-far unknown aspects of relapsing leukemia could be identified and studied. A new concept of discriminating locally relapsing leukemia and a delayed occurrence of generalized spreading of leukemia formed the basis for the explanation of the observed heterogeneity in the distribution of leukemic cells during the remission and the subsequent relapse phase. In conclusion, it is obvious that proper comparison of the human disease as well as the counterpart in the animal model requires a detailed knowledge of both.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

Expression of the mouse gap junction gene Gjb3 is regulated by distinct mechanisms in embryonic stem cells and keratinocytes.

Connexins are the protein subunits of gap junction channels and are expressed in a highly regulated temporal and spatial pattern in embryonic development and adult life, with most cell types expressing more than one isoform. Connexin31 (Cx31) is encoded by the gene Gjb3 and expressed throughout mouse development n a complex pattern; in adult mice it becomes restricted to the granular layer of epidermis, testis, and placenta. In placenta, lack of Cx31 leads to transient dysmorphogenesis affecting embryonic survival. Here we have analyzed the structure of mouse Gjb3 as well as its transcriptional regulation by transient transfection of reporter gene constructs in HM1 mouse embryonic stem cells and a mouse keratinocytederived cell line, Hel37, as model systems for early development and skin, respectively. Like most connexin genes, Gjb3 is composed of two exons, the second of which contains the whole coding region and is separated from the first exon by an intron of 2.3 kb. Expression in keratinocytes is regulated by a basal promoter extending to 561 bp upstream of exon 1 in conjunction with a regulatory region between upstream positions 561 and 841. In contrast, expression of Gjb3 in embryonic stem cells depended on the basal promoter together with the intron. The enhancing effect of the intron was found only in embryonic stem cells and depended on its native position and the integrity of the splice sites. Thus, expression of Gjb3 in keratinocytes and embryonic stem cells is regulated by different cis-regulatory elements and differs in its requirements for the intron in situ.

Animals↗
PubMed1988

A case of angioimmunoblastic lymphadenopathy associated with a long spontaneous remission, retrobulbar neuritis, a clonal rearrangement of the T-cell receptor gamma chain gene and an unusual marrow infiltration.

A man with angioimmunoblastic lymphadenopathy entered a spontaneous remission that lasted 18 yr, ending in retrobulbar neuritis followed by a generalized relapse. After another remission was induced by prednisolone he developed marrow infiltration with a lymphoid cell of novel surface-marker phenotype. His lymph node cells demonstrated a clonal rearrangement of the T-cell receptor gamma chain (TcR gamma) genes whereas the TcR beta genes were heterogeneously rearranged. The marrow cells did not contain the rearranged TcR gamma gene. He died of pulmonary emboli 21 yr after his original presentation. We propose a model whereby the original event was the development of a lymphoid stem cell clone with no TcR gene rearrangement. Subsequently, a sub-clone bearing the TcR gamma gene rearrangement proliferated in the lymph nodes and further heterogeneous rearrangement of the TcR beta genes occurred within this subclone. Proliferation in the marrow of the original clone finally supervened.

Adult↗
PubMed2005

Single genetic mutations can account for melanocytic naevi.

BACKGROUND: The nature of melanocytic naevi is unknown notwithstanding their considerable significance for clinician and pathologist and despite the wealth of existing knowledge about melanocyte biology. OBJECTIVES: To investigate how far a simple mutational model can explain the clinical and pathological features of melanocytic naevi, in particular their pattern of onset and frequency. METHODS: I have constructed a model of the development of the adult melanocyte population from a single stem cell. The total cutaneous melanocyte population in a human adult is already known, as well as the range of spontaneous mutation rates at a given gene site. For each cycle of mitosis during the post stem-cell expansion of the melanocyte population, I calculate the accumulated number of cells likely to be mutated at a particular (although unknown) gene site. The results are interpreted in the light of a hypothesis that each of these mutant melanocytes will go on to form a melanocytic naevus. Comparisons are made with neurofibromas, occurring in type 1 neurofibromatosis and as sporadic lesions. RESULTS: A single genetic mutation in melanocyte precursors is found to be sufficient to explain the clinical and pathological features of melanocytic naevi. CONCLUSIONS: I propose that melanocytic naevi are a consequence of single spontaneous genetic mutations which inevitably occur during the development of the adult population of cutaneous melanocytes.

Cell Division↗
PubMed2005

Murine and human IL-7 activate STAT5 and induce proliferation of normal human pro-B cells.

The role of IL-7 in lymphoid development and T cell homeostasis has been extensively documented. However, the role of IL-7 in human B cell development remains unclear. We used a xenogeneic human cord blood stem cell/murine stromal cell culture to study the development of CD19+ B-lineage cells expressing the IL-7R. CD34+ cord blood stem cells were cultured on the MS-5 murine stromal cell line supplemented with human G-CSF and stem cell factor. Following an initial expansion of myeloid/monocytoid cells within the initial 2 wk, CD19+/pre-BCR- pro-B cells emerged, of which 25-50% expressed the IL-7R. FACS-purified CD19+/IL-7R+ cells were larger and, when replated on MS-5, underwent a dose-dependent proliferative response to exogenous human IL-7 (0.01-10.0 ng/ml). Furthermore, STAT5 phosphorylation was induced by the same concentrations of human IL-7. CD19+/IL-7R- cells were smaller and did not proliferate on MS-5 after stimulation with IL-7. In a search for cytokines that promote human B cell development in the cord blood stem cell/MS-5 culture, we made the unexpected finding that murine IL-7 plays a role. Murine IL-7 was detected in MS-5 supernatants by ELISA, recombinant murine IL-7 induced STAT5 phosphorylation in CD19+/IL-7R+ pro-B cells and human B-lineage acute lymphoblastic leukemias, and neutralizing anti-murine IL-7 inhibited development of CD19+ cells in the cord blood stem cell/MS-5 culture. Our results support a model wherein IL-7 transduces a replicative signal to normal human B-lineage cells that is complemented by additional stromal cell-derived signals essential for normal human B cell development.

Animals↗
PubMed2005

Muscle stem cells and regenerative myogenesis.

A population of myogenic progenitors termed satellite cells undertakes postnatal development and repair of skeletal muscle. Studies have indicated that atypical myogenic precursors can also participate in muscle regeneration. The source of this regenerative capacity has been attributed to "adult stem cells" that represent poorly understood multipotent cell lineages, believed to reside in all adult tissue populations. Here we review the origin and location of muscle satellite cells and stem cells, as well as the mechanisms by which they may be specified. We discuss how the experimental models utilized raise important questions regarding the validity of extrapolating these findings.

Animals↗
PubMed1987

In vitro chemoseparation of leukemic cells from murine bone marrow using VP16-213: importance of stem cell assays.

The use of chemopurified autologous bone marrow (BM) is being explored as a transplant source for patients with leukemia who do not have a HLA-matched donor. Because stem cell assays have not previously been found to predict engraftment after transplantation, the optimal drug(s) and drug concentrations have not been determined. To determine the effectiveness of the podophyllotoxin derivative, VP16, and the value of stem cell assays in chemopurification studies, a murine model using the C57B1/6 mouse and its syngeneic leukemia EL-4 was developed. Kill of committed (CFU-C) and pluripotent (CFU-S) hematopoietic stem cells and tumor (tCFU) stem cells after a 1-h exposure to VP16 was first determined. A marked kill differential of tCFU compared to that of the CFU-C/S populations was found, with no tCFU surviving at VP16 concentrations greater than 30 micrograms/ml. No kill differential of CFU-C versus CFU-S was seen at VP16 doses greater than 10 micrograms/ml. All mice transplanted with a mixture of 25 X 10(6) BM cells and 1 X 10(7) EL-4 cells treated in vitro with 40 micrograms/ml of VP16 died of their tumors. However by reducing the tumor burden to 1 X 10(6) EL-4 and 5 X 10(6) EL-4, nine of ten and four of six of the mice, respectively, survived 90+ days tumor free. On the basis of survival data, it was found that engraftment of VP16-treated BM was directly proportional to the product of the degree of CFU-S inhibition and BM cell inoculum, i.e., the number of viable CFU-S transplanted. The maximum VP16 concentration that led to predictable engraftment at BM doses less than 25 X 10(6) cells was 55 micrograms/ml. Thus, 15 mice were transplanted with 1 X 10(7) BM cells and 1 X 10(7) EL-4 cells, incubated with 55 micrograms/ml of VP16; 13 out of 15 survived tumor free for 90+ days. When VP16 was used as a BM chemopurification agent, up to 50% of contaminating tumor cells were eliminated from BM suspensions without affecting engraftment after transplantation. Because stem cell inhibition predicted engraftment, drug concentrations that maximized tumor cell kill could be chosen.

Animals↗
PubMed1995

Development of mouse models for cystic fibrosis.

Using gene targeting in embryonal stem cells it is now possible to create accurate genetic models of inherited human disease in the mouse. The value of an animal model of cystic fibrosis is in providing clarification of disease pathogenesis, genotype-phenotype correlation, the identification of other relevant genetic factors, and as the optimal test system for novel therapeutic intervention. Correction of the basic defect by a somatic gene therapy approach is an attractive approach to disease treatment. CF mouse models have been described which display the characteristic electrophysiological defect and thus both safety and efficacy can be monitored in these animals. Modulation of Cftr levels in transgenic animals and the results on disease phenotype give some indication of the level of gene expression necessary to give clinical effect.

Animals↗
PubMed2026

From stem cells to somites: Revealing genetic and exogenous factors of human embryogenesis.

Stem-cell-based human embryo models offer an ethically tractable platform for studying early human development. This study employs somitoids, three-dimensional models of human somitogenesis, to investigate how transcriptional programs and culture conditions influence somite formation and segmentation. We show that pre-differentiation culture medium impacts the developmental potential of induced pluripotent stem cells (iPSCs), with StemFit medium and Matrigel embedding outperforming mTeSR Plus medium in generating robust somite-like structures. Strikingly, these differences arise despite only subtle changes in transcriptomic and time-resolved proteomic profiles. P300-based proximity labeling also reveals a largely overlapping set of chromatin-associated regulators across iPSC conditions. In somitoids, enhancer-associated profiling highlights factors linked to somitogenesis, including MESP2 and TBX6. Knockout of three identified regulators, BPTF, RBPJ, and CITED2, demonstrate their essential roles in somite formation. Together, these findings highlight how culture conditions and enhancer-associated networks influence early human development and demonstrate somitoids as a scalable system for functional genomics.

Humans↗
PubMed2000

Expression of gangliosides in neuronal development of P19 embryonal carcinoma stem cells.

Gangliosides are constituents of the cell membrane and are known to have important functions in neuronal differentiation. We employed an embryonal carcinoma stem cell line P19 as an in vitro model to investigate the expression of gangliosides during neuronal development. After treatment with retinoic acid, these cells differentiate synchronously into neuron-like cells by a series of well-defined events of development. We examined several aspects of ganglioside metabolism, including the changes of ganglioside pattern, the activities and gene expression of several enzymes at different stages of differentiation, and the distribution of gangliosides in differentiating neurons. Undifferentiated P19 cells express mainly GM3 and GD3. After P19 cells were committed to differentiation, the synthesis of complex gangliosides was elevated more than 20-fold, coinciding with the stage of neurite outgrowth. During the maturation of differentiated cells, the expression of c-series gangliosides was downregulated concomitantly with upregulation of the expression of a- and b-series gangliosides. We also examined the distribution of gangliosides in differentiating neurons by confocal and transmission electron microscopy after cholera toxin B subunit and sialidase treatment. Confocal microscopic studies showed that gangliosides were distributed on the growth cones and exhibited a punctate localization on neurites and soma. Electron microscopic studies indicated that they also are enriched on the plasma membranes of neurites and the filopodia as well as on the lamellipodia of growth cones during the early stage of neurite outgrowth. Our data demonstrate that the expression of gangliosides in P19 cells during RA-induced neuronal differentiation resembles that of the in vivo development of the vertebrate brain, and hence validates it as an in vitro model for investigating the function of gangliosides in neuronal development.

Animals↗