Self-renewal and differentiation of mouse embryonic stem cells as measured by Oct 4 gene expression: effects of lif, serum-free medium, retinoic acid, and dbcAMP

Neonatal lung-derived SSEA-1+ cells exhibited distinct stem/progenitor characteristics and organoid developmental potential

Stem/progenitor cells, because of their self-renewal and multiple cell type differentiation abilities, have good potential in regenerative medicine. We previously reported a lung epithelial cell population that expressed the stem cell marker SSEA-1 was abundant in neonatal but scarce in adult mice. In the current study, neonatal and adult mouse-derived pulmonary SSEA-1⁺ cells were isolated for further characterization. The results showed that neonatal-derived pulmonary SSEA-1⁺ cells highly expressed lung development-associated genes and had enhanced organoid generation ability compared with the adult cells. Neonatal pulmonary SSEA-1⁺ cells generated airway-like and alveolar-like organoids, suggesting multilineage cell differentiation ability. Organoid generation of neonatal but not adult pulmonary SSEA-1⁺ cells was enhanced by fibroblast growth factor 7 (FGF 7). Furthermore, neonatal pulmonary SSEA-1⁺ cells colonized and developed in decellularized and injured lungs. These results suggest the potential of lung-derived neonatal-stage SSEA-1⁺ cells with enhanced stem/progenitor activity and shed light on future lung engineering applications.

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Pulmonary SSEA-1⁺ cells are abundant in neonatal and scarce in adult stages

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The stem/progenitor activity of pulmonary SSEA-1⁺ cells is enhanced in neonatal stage

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Neonatal pulmonary SSEA-1⁺ cells developed into airway- and alveolar-like organoids

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FGF7 regulates alveolar epithelium development of neonatal pulmonary SSEA-1⁺ cells

Effects of vitamin A and retinoic acid on mouse embryonic stem cells and their differentiating progeny

Embryonic development is controlled by retinoids, and one approach that has been used to investigate the mechanisms for retinoid actions in developmental processes has been to study the effects of adding retinoids to cultures of pluripotent embryonic stem cells (ESC). To date, most in vitro retinoid research has been directed at deciphering the actions of all-trans retinoic acid (atRA). atRA is a derivative of all-trans retinol (a.k.a. vitamin A, VA), which mammals can generate via an enzyme-catalyzed pathway. atRA's effects on development result from its (1) activation of receptor complexes (RARs and RXRs) in the nucleus which then bind to and activate RA response elements (RAREs) in genes and (2) its interactions with processes that are initiated in the cytoplasm. While much work has focused on the impact of atRA on cell differentiation, VA, itself, has been shown to exert effects on the maintenance of ESC identity that are not dependent upon classic RA-signaling pathways. In this chapter, we present results from our laboratory and others using well-documented approaches for investigating the effects of retinoids on the differentiation of ESC in vitro and introduce a novel method that uses chemically-defined growth conditions. The merits of each approach are discussed.

Expression of the Embryonic Transcription Factor Oct4 in Canine Neoplasms: A Potential Marker for Stem Cell Subpopulations in Neoplasia

Neoplastic cells and stem cells share several phenotypic characteristics. Recently, numerous studies have identified adult stem cells that have been hypothesized to be the cellular origin for cancer in several tissues. Oct4 has been consistently associated with pluripotent or stemlike cells, and it is hypothesized that Oct4 is necessary for the maintenance of pluripotency. We hypothesize that Oct4-positive cells are present in all canine neoplasms and that these subpopulations of neoplastic cells might represent “cancer stem” cells. To test this hypothesis, 83 canine neoplasms representing 21 neoplastic diseases were evaluated for Oct4 expression using immunohistochemistry. The results of this study showed that all tumors included in this study contained a subpopulation of Oct4-positive cells, although the proportion of Oct4-positive cells and the intensity of immunoreactivity varied both within and between tumor types. Subpopulations of Oct4-positive cells identified in these tumors are likely to represent “cancer stem” cells and therefore might be responsible for the maintenance and propagation of the tumors. If these cells represent cancer stem cells, and are therefore responsible for the maintenance and growth of the neoplastic cellular population, then these cells should serve as relevant therapeutic targets and offer the greatest potential for curative treatment.

Ox-LDL modifies the behaviour of bone marrow stem cells and impairs their endothelial differentiation via inhibition of Akt phosphorylation

This study was to investigate the effect of oxidized low-density lipoprotein (ox-LDL) on the behaviour of bone marrow stem cells and their endothelial differentiation as well as the underlying mechanisms. Adult rat bone marrow multipotent progenitor cells (MAPCs) were incubated with ox-LDL for up to 2 weeks. Ox-LDL treatment resulted in a time- and dose-dependent reduction of MAPC population in culture through a combination of decreased cell proliferation and increased apoptosis. The expression of stem cell marker Oct-4 was significantly suppressed in MAPCs by ox-LDL in a dose- and time-dependant manner. Endothelial differentiation of MAPCs was substantially inhibited by ox-LDL with markedly decreased expression of endothelial markers vWF, Flk-1 and CD31, as well as impaired in vitro vascular structure formation. Ox-LDL-induced apoptosis and inhibition of Oct-4 expression, cell proliferation and endothelial differentiation of MAPCs were associated with significant inhibition of Akt phosphorylation. Akt overexpression in MAPCs transfected with a constitutively active Akt completely reversed the effects of ox-LDL on MAPCs including enhanced apoptosis, decreased cell proliferation, suppressed Oct-4 expression and endothelial differentiation as well as in vitro vascular structure formation. In conclusion, ox-LDL promotes apoptosis and inhibits Oct-4 expression and self-renewal of MAPCs, and impairs their endothelial differentiation via suppression of Akt signalling.

Propagation of embryonic stem cells in stirred suspension without serum

Embryonic stem cells (ESCs) with their unlimited capacity for self-renewal and ability to differentiate along multiple cell lineages are a superb starting material for biotechnology applications and cellular therapies. However, realization of the potential of ESCs requires the development of scalable systems for their production in large quantities and in a regulated manner. Here, we describe a methodology for the expansion of mouse ESCs (mESCs) as pluripotent aggregates in a stirred suspension bioreactor and in medium without serum. Initially, the culture of feeder cell-independent mESCs in dishes was adapted to serum-free conditions. Also, we explored whether spinner flasks equipped with a triangle-shaped impeller and baffles support the culture of mESC aggregates. Serum-free culture in these vessels resulted in an almost 20-fold increase in the live mESC concentration over 4 days without significant loss of cell viability. Even after consecutive passages, mESCs retained high expression of pluripotency markers Oct3/4, Rex1 and SSEA-1. More importantly, when differentiation was induced these cells adopted fates of all three germ layers namely neuroectoderm, cardiac mesoderm and definitive endoderm. These findings demonstrate that stem cells can be propagated under serum-free conditions in a scalable stirred-suspension culture without loss of their pluripotency.

Co-localization of angiotensin-converting enzyme 2-, octomer-4- and CD34-positive cells in rabbit atherosclerotic plaques

Angiotensin‐converting enzyme 2 (ACE2) is a novel enzyme with possible implications in the treatment of blood pressure disorders. Recent evidence suggests that an upregulation of ACE2 can be stimulated by all‐trans retinoic acid (at‐RA); however, at‐RA also affects regulation of the stem‐cell marker octomer‐4 (Oct‐4) and thus cellular differentiation. We have previously shown that smooth muscle cells and macrophages present within rabbit atherosclerotic plaques are positive for ACE2, Oct‐4 and the haematopoietic stem‐cell marker CD34. Thus, to provide evidence that possible at‐RA treatment could affect both plaque cellular biology (via effects on cellular differentiation) and blood pressure (via ACE2), it is vital to show that cells with atherosclerotic plaques co‐express all three markers. Thus, we sought to provide evidence that a subset of cells within atherosclerotic plaques is positive for ACE2, Oct‐4 and CD34. We used New Zealand White rabbits that were fed a control diet supplemented with 0.5% cholesterol plus 1% methionine for 4 weeks and then allowed to consume a normal diet for 10 weeks. Immunohistochemistry was performed by standard techniques. We report that ACE2, Oct‐4 and CD34 were all present within atherosclerotic plaques. Although macrophages were positive for all three markers, spindle‐shaped cells in the media did not show all three markers. The endothelium overlying normal arterial wall showed positive Oct‐4 and ACE2 immunoreactivity, but CD34 immunoreactivity was patchy, indicating that such cells might not have fully differentiated. It is concluded that cells in atherosclerotic plaques express co‐express ACE2, Oct‐4 and CD34. Further studies aimed at establishing the effects of all‐trans retinoic acid on blood pressure and atherosclerotic cell differentiation are warranted.

Generation of novel adipocyte monolayer cultures from embryonic stem cells

Here we show a simplified and improved method to produce large quantities of evenly distributed monolayer cultures that display major characteristics of adipocytes. These cultures are applicable for quantitative analysis for biochemical and molecular events in adipogenesis during development and may provide a useful system for high-throughput drug screening assays of antiobesity drugs. In our method, we treated embryoid bodies (EBs) with all-trans retinoic acid (ATRA) for 3 days, 1 day after they attached to the gelatin-coated culture plates without further transfer. The cells were maintained in insulin and trioiodothyronine (T(3))-containing medium until day 12, when they were dispersed by enzymatic digestion and replated onto multiple culture plates. Two days later, adipocyte induction factors were added for 6 days and examined 6 days later. The amount of lipid droplet-laden adipocytes in the culture reached approximately 80%, with a nearly five-fold increase in GPDH activity. The cells expressed high levels of adipose-specific proteins (adipocyte markers), including PPARgamma2, ALBP, LPL, HSL, perilipin, and DGAT1. The adipocytes are functionally active, as evidenced by their response to lipolytic agents, such as forskolin, Bt2-cAMP, and isoproterenol, with more than 20-fold increases in glycerol release.

Self-renewal and differentiation of mouse embryonic stem cells as measured by Oct4 expression: the role of the cAMP/PKA pathway

In this study we examined the role of the cAMP/protein kinase A (PKA) pathway in affecting IOUD2 ES cell self-renewal and differentiation, Oct4 expression, and cell proliferation. Forskolin, the adenylate cyclase agonist, alone had no effect on ES cell self-renewal. However, when cells were treated with the differentiation-inducing agent retinoic acid, forskolin significantly promoted ES cell self-renewal. Effectively, forskolin rescued cells from a pathway of differentiation. Culturing ES cells in the presence of the phosphodiesterase inhibitor IBMX had no effect on ES cell self-renewal but did increase cell proliferation. In the presence of 100 muM IBMX without LIF, 10 muM forskolin significantly increased ES cell self-renewal. The cell permeable cAMP analog 8-Br-cAMP (1 and 5 mM) promoted ES cell differentiation in the presence of LIF, while in the absence of LIF, it promoted ES cell self-renewal. The effect of the PKA specific inhibitors H89 and KT5720 on Oct4 expression was, again, LIF-dependent. In the presence of LIF, these inhibitors decreased Oct4 expression, while they increased Oct4 expression in the absence of LIF. In general, ES cells maintained on a self-renewal pathway through the presence of LIF show little effect from altered cAMP signaling except at higher levels. However, in strict contrast, when ES cell are on a differentiation pathway through exposure to retinoic acid or the removal of LIF, altering cAMP levels can rescue the self-renewal process promoting Oct4 expression. This study clearly shows that the cAMP/PKA pathway plays a role in ES cell self-renewal pathways.

Trophic factor induction of human umbilical cord blood cells in vitro and in vivo

The mononuclear fraction of human umbilical cord blood (HUCBmnf) is a mixed cell population that multiple research groups have shown contains cells that can express neural proteins. In these studies, we have examined the ability of the HUCBmnf to express neural antigens after in vitro exposure to defined media supplemented with a cocktail of growth and neurotrophic factors. It is our hypothesis that by treating the HUCBmnf with these developmentally-relevant factors, we can expand the population, enhance the expression of neural antigens and increase cell survival upon transplantation. Prior to growth factor treatment in culture, expression of stem cell antigens is greater in the non-adherent HUCBmnf cells compared to the adherent cells (p < 0.05). Furthermore, treatment of the non-adherent cells with growth factors, increases BrdU incorporation, especially after 14 days in vitro (DIV). In HUCBmnf-embryonic mouse striata co-culture, a small number of growth factor treated HUCBmnf cells were able to integrate into the growing neural network and express immature (nestin and TuJ1) and mature (GFAP and MAP2) neural markers. Treated HUCBmnf cells implanted in the subventricular zone predominantly expressed GFAP although some grafted HUCBmnf cells were MAP2 positive. While short-term treatment of HUCBmnf cells with growth and neurotrophic factors enhanced proliferative capacity in vitro and survival of the cells in vivo, the treatment regimen employed was not enough to ensure long-term survival of HUCBmnf-derived neurons necessary for cell replacement therapies for neurodegenerative diseases.

Interplay of leukemia inhibitory factor and retinoic acid on neural differentiation of mouse embryonic stem cells

Embryonic stem (ES) cells have great potential for cell replacement in neurodegenerative disorders. Implantation of these cells into the brain, however, requires their prior differentiation. We examined the interplay between leukemia inhibitory factor (LIF) and retinoic acid (RA) on neural differentiation of mouse ES (mES) cells. Mouse embryonic stem cells were allowed to form cell aggregates, the so-called embryoid bodies (EBs), in the absence or presence of LIF. In the absence of LIF, mES cells downregulated the expression of the undifferentiated mES cell marker Oct-3/4, and increased mRNA levels of two neural precursor markers, Sox-1 and Nestin, as well as the neuronal marker beta-tubulin III. This neuronal differentiation was enhanced by treating EBs with RA. Moreover, RA irreversibly increased the number of postmitotic neurons in culture, as shown by the reduction of proliferating mES cells and the increase in beta-tubulin III-positive cells 6 days after RA removal, which in turn affected mES cell viability. The addition of LIF during EBs formation, however, blocked completely this neuronal differentiation. Our findings also showed that pre-differentiation of mES cells in vitro avoided the teratocarcinoma formation observed when proliferating mES cells were grafted into the brain. In addition, mES cells pre-differentiated with RA in culture showed a reduction in proliferation and the presence of neural phenotypes after grafting. In conclusion, the present results indicate that RA enhances neuronal differentiation of mES cells in the absence of LIF, although it compromises cell viability and transplantation.

wnt3a but not wnt11 supports self-renewal of embryonic stem cells

wnt proteins (wnts) promote both differentiation of midbrain dopaminergic cells and self-renewal of haematopoietic stem cells. Mouse embryonic stem (ES) cells can be maintained and self-renew on mouse feeder cell layers or in media containing leukemia inhibitory factor (LIF). However, the effects of wnts on ES cells self-renewal and differentiation are not clearly understood. In the present study, we found that conditioned medium prepared from L cells expressing wnt3a can replace feeder cell layers and medium containing LIF in maintaining ES cells in the proliferation without differentiation (self-renewal) state. By contrast, conditioned medium from NIH3T3 cells expressing wnt11 did not. Alkaline phosphatase staining and compact colony formation were used as criteria of cells being in the undifferentiated state. ES cells maintained in medium conditioned by Wnt3a expressing cells underwent freezing and thawing while maintaining properties seen with LIF maintained ES cells. Purified wnt3a did not maintain self-renewal of ES cells for prolonged intervals. Thus, other factors in the medium conditioned by wnt3a expressing cells may have contributed to maintenance of ES cells in a self-renewal state. Pluripotency of ES cells was determined with the use of embryoid bodies in vitro. PD98059, a MEK specific inhibitor, promoted the growth of undifferentiated ES cells maintained in conditioned medium from wnt3a expressing cells. By contrast, the P38 MAPK inhibitor SB230580 did not, suggesting a role for the MEK pathway in self-renewal and differentiation of ES cells maintained in the wnt3a cell conditioned medium. Thus, our results show that conditioned medium from wnt3a but not wnt11 expressing cells can maintain ES cells in self-renewal and in a pluripotent state.