Mouse Leukemia Inhibitory Factor Research Articles

Treatment with low-dose aspirin increased the level LIF and integrin β3 expression in mice during the implantation window

Embryo implantation is the group of processes by which the developing blastocyst adheres to, and embeds into, the receptive endometrium. Changes in the expression of molecules on the cell surface have been seen in the conversion of the endometrial surface from a non-receptive to a receptive state. Cell adhesion molecules like integrins, or soluble factors such as Leukemia inhibitory factor (LIF) have been identified to play an important role during the implantation period. Studies have suggested that low-dose aspirin (<100 mg/d) treatment can improve implantation rate, ovarian responsiveness, and pregnant rates in IVF patients. The mechanism of this increased implantation rate is unclear, and in this study we hypothesised that the expression of integrin β3 or LIF may be altered, during implantation window, by treatment with low-dose aspirin. Female mice were treated with 0.9 mg/ml aspirin daily for 15 days and then were mated. The protein or mRNA levels of LIF and integrin β3 in the endmetrium were determined on the day 4 post-coitus using immuno-fluorescence and RT-PCR. We found the expression of LIF or integrin β3 was significantly increased in the endometrium of mice that were treated with low dose of aspirin by immuno-fluorescence. In addition, the mRNA level of LIF or integrin β3 on the endometrium of aspirin treated mice was also significantly increased compared to untreated mice. We conclude that low dose aspirin alters the expression of endometrial LIF and integrin β3 and that these changes may increase endometrial receptivity.

145 PAX2 OVEREXPRESSION IN EMBRYOID BODIES INDUCES UPREGULATION OF INTEGRIN α 8 AND AQUAPORIN-1 INVOLVED IN KIDNEY DEVELOPMENT

You have accessJournal of UrologyStem Cell Research1 Apr 2010145 PAX2 OVEREXPRESSION IN EMBRYOID BODIES INDUCES UPREGULATION OF INTEGRIN α8 AND AQUAPORIN-1 INVOLVED IN KIDNEY DEVELOPMENT Akihiro Nakane, Ryuichi Nishinakamura, Kentaro Mizuno, Yoshiyuki Kojima, Tetsuji Maruyama, Yutaro Hayashi, and Kenjiro Kohri Akihiro NakaneAkihiro Nakane Nagoya, Japan More articles by this author , Ryuichi NishinakamuraRyuichi Nishinakamura Kumamoto, Japan More articles by this author , Kentaro MizunoKentaro Mizuno Nagoya, Japan More articles by this author , Yoshiyuki KojimaYoshiyuki Kojima Nagoya, Japan More articles by this author , Tetsuji MaruyamaTetsuji Maruyama Nagoya, Japan More articles by this author , Yutaro HayashiYutaro Hayashi Nagoya, Japan More articles by this author , and Kenjiro KohriKenjiro Kohri Nagoya, Japan More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.198AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Transcription factor Pax2 is essential for kidney development in mice, and overexpression of Pax2 in chick embryos leads to ectopic formation of nephric structures. We have generated embryonic stem (ES) cell lines that repress Pax2 expression in a tetracycline-dependent manner and examined their differentiation potential by embryoid body (EB) formation. METHODS MGZRTcH2 cells, in which gene expression can be controlled by the Tet-off system, were maintained on 0.1% gelatin-coated tissue culture plates in Glasgow minimal essential medium, 10% fetal bovine serum, and 103 units/ml mouse leukemia inhibitory factor at 37°C with 5% CO2. MGZRTcH2 cells were electroporated with the Pax2-containing exchange vector. Eight days after electroporation, Pax2-recombinant clones were picked up and recombination was confirmed by Southern blot analysis. ES cells were cultured in the same medium without LIF to induce EB formation by the hanging drop culture method. EBs were analyzed by reverse transcription-PCR and immunocytochemistry. RESULTS RT-PCR analysis was performed in the parental ES cell line, EBs and clones containing Tet-inducible Pax2. In the presence of Tet (Tet+), gene expression patterns were similar to those in parental cells. In the absence of tetracycline, aquaporin-1 (Aqp1) and integrin α8 were upregulated when cells were induced to form EBs. EBs derived from these cell lines expressed Pax2 and subsequently integrin f¿8 and Aqp1, both of which are possibly involved in kidney development. We further examined expression changes at the protein level. EBs from ES clones containing Tet-inducible Pax2 were cultured with or without tetracycline, and stained with anti-AQP1 and anti-Pax2 antibodies. Pax2 protein was detected only in the absence of Tet. AQP1 protein was also upregulated in the absence of Tet. Considering the slow induction kinetics, our data suggest that Pax2 and additional factors induced in EBs synergistically regulate the two targets. CONCLUSIONS ES cell lines with inducible Pax2 expression will also be useful for dissecting genetic cascades functioning in the development of various organs, including the kidney. © 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e59 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Akihiro Nakane Nagoya, Japan More articles by this author Ryuichi Nishinakamura Kumamoto, Japan More articles by this author Kentaro Mizuno Nagoya, Japan More articles by this author Yoshiyuki Kojima Nagoya, Japan More articles by this author Tetsuji Maruyama Nagoya, Japan More articles by this author Yutaro Hayashi Nagoya, Japan More articles by this author Kenjiro Kohri Nagoya, Japan More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

CNS-targeted LIF Expression Improves Therapeutic Efficacy and Limits Autoimmune-mediated Demyelination in a Model of Multiple Sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) with an inflammatory and a neurodegenerative component. The neuropoietic cytokine leukemia inhibitory factor (LIF) is expressed in MS lesions, but its effect on lesion development is far from understood. LIF is an interesting candidate for MS therapy, as it has neuroprotective properties and may also promote the survival of myelinating oligodendrocytes (OLGs). However, therapeutic administration of LIF is complicated by its limited ability to cross the blood-brain barrier and its pleiotropic actions outside the CNS. In this study, lentiviral vectors (LVs) were used to achieve stable expression and secretion of LIF in the CNS of adult mice. CNS-targeted expression of LIF significantly reduced demyelination in a murine model of MS. In addition, local expression of LIF ameliorated clinical symptoms with enhanced efficacy compared to systemic treatment with recombinant protein. These findings demonstrate that gene therapeutic administration of LIF is a promising approach to limit lesion burden and clinical symptoms in neuroinflammatory disease.

Heart failure causes cholinergic transdifferentiation of cardiac sympathetic nerves via gp130-signaling cytokines in rodents

Although several cytokines and neurotrophic factors induce sympathetic neurons to transdifferentiate into cholinergic neurons in vitro, the physiological and pathophysiological roles of this remain unknown. During congestive heart failure (CHF), sympathetic neural tone is upregulated, but there is a paradoxical reduction in norepinephrine synthesis and reuptake in the cardiac sympathetic nervous system (SNS). Here we examined whether cholinergic transdifferentiation can occur in the cardiac SNS in rodent models of CHF and investigated the underlying molecular mechanism(s) using genetically modified mice. We used Dahl salt-sensitive rats to model CHF and found that, upon CHF induction, the cardiac SNS clearly acquired cholinergic characteristics. Of the various cholinergic differentiation factors, leukemia inhibitory factor (LIF) and cardiotrophin-1 were strongly upregulated in the ventricles of rats with CHF. Further, LIF and cardiotrophin-1 secreted from cultured failing rat cardiomyocytes induced cholinergic transdifferentiation in cultured sympathetic neurons, and this process was reversed by siRNAs targeting Lif and cardiotrophin-1. Consistent with the data in rats, heart-specific overexpression of LIF in mice caused cholinergic transdifferentiation in the cardiac SNS. Further, SNS-specific targeting of the gene encoding the gp130 subunit of the receptor for LIF and cardiotrophin-1 in mice prevented CHF-induced cholinergic transdifferentiation. Cholinergic transdifferentiation was also observed in the cardiac SNS of autopsied patients with CHF. Thus, CHF causes target-dependent cholinergic transdifferentiation of the cardiac SNS via gp130-signaling cytokines secreted from the failing myocardium.

Mice Overexpressing Murine Oncostatin M (OSM) Exhibit Changes in Hematopoietic and Other Organs that Are Distinct from Those of Mice Overexpressing Human OSM or Bovine OSM

Oncostatin M (OSM) and leukemia inhibitory factor (LIF) belong to the interleukin-6 family of cytokines. The authors' previous in vitro work demonstrated that in mouse cells mouse OSM (mOSM) signals through a heterodimeric receptor complex incorporating the mOSM-specific receptor mOSMRbeta while human OSM (hOSM) and bovine OSM (bOSM) use the mouse LIF receptor mLIFRbeta rather than mOSMRbeta. These in vitro data suggest that prior studies in mouse systems with hOSM or bOSM (the usual molecules used in early studies) reflect LIF rather than OSM biology. The current work assessed whether or not this divergence in actions among these three OSMs also occurs in vivo in mouse models. Adult female (C57BL/6J x DBA/2J) F(1) mice were engineered to stably overexpress mOSM, hOSM, or bOSM by retrovirus-mediated gene transfer (n = 10 or more per group). After 4 weeks, molecular and hematologic profiles and anatomic phenotypes in multiple organs were assessed by standard techniques. Animals overexpressing either hOSM or bOSM had an identical phenotype resembling that associated with LIF activation, including significant hematologic abnormalities (anemia, neutrophilia, lymphopenia, eosinopenia, and thrombocytosis); weight loss; profound enlargement (lymph node, spleen) and/or structural reorganization (lymph node, spleen, thymus) of lymphoid organs; and severe osteosclerosis. In contrast, mice overexpressing mOSM did not develop hematologic changes, weight loss, or osteosclerosis and exhibited more modest and anatomically distinct restructuring of lymphoid organs. These data indicate that activities imputed to OSM and the mOSMRbeta signaling pathway using in vitro and in vivo mouse experimental systems are unique to mOSM.

Neuroinflammation facilitates LIF entry into brain: role of TNF

Leukemia inhibitory factor (LIF) is a proinflammatory cytokine mediating a variety of central nervous system (CNS) responses to inflammatory stimuli. During lipopolysaccharide (LPS)-induced inflammation, blood concentrations of LIF increase, correlating with lethality of sepsis. Circulating LIF crosses the blood-brain barrier (BBB) by a saturable transport system. Here we determine how this transport system is regulated in neuroinflammation. Using transport assays that quantify the influx rate and volume of distribution of LIF in mice, we show that LPS facilitated the permeation of LIF from the blood to the brain without compromising the paracellular permeability of the BBB as determined by coadministration of fluorescein. Concurrently, gp130 (shared by the interleukin-6 family of cytokines), but not gp190 (the specific receptor for LIF) or cilliary neutrophic factor (CNTF-Ralpha, a unique receptor for cilliary neurotrophic factor that also uses gp130 and gp190), showed increased levels of mRNA and protein expression in cerebral microvessels from the LPS-treated mice. The upregulation of gp130 by LPS was at least partially mediated by vascular tumor necrosis factor receptor (TNFR)1 and TNFR2. This was shown by elevated TNFR1 and TNFR2 mRNA and protein in cerebral microvessels after LPS and by the absence of the LPS effect on gp130 in knockout mice lacking these receptors. The results show that neuroinflammation by LPS induces endothelial signaling and enhances cytokine transport across the BBB.

Effect of Bushenantai recipe on the expression of endometrial LIF in mice with embryonic implantation dysfunction

In order to observe the effect of Bushenantai recipe on the expression of endometrial leukemia-inhibitory factor (LIF) in mice with embryonic implantation dysfunction (EID), 120 Kunming mice post coition were randomized into three groups: normal control group, model group and traditional Chinese medicine group (TCM group) (n=40 in each group). Uterus was collected on the pregnancy day (Pd) 4, 5, 6 after an intravenous injection of Evan's blue. The endometrium was dyed by Evan's blue and the mean points of response were observed on Pd 5. The expression of LIF mRNA and protein was detected by RT-PCR and immunohistochemistry respectively and analyzed statistically by image system. The results showed that the number of implantation sites in model group was remarkably less than in normal control group and TCM group. There was no significant difference between normal control group and TCM group. The expression of LIF mRNA and protein in model group was delayed. Bushenantai recipe could increase the expression of LIF mRNA and protein in endometria of mice with EID. It was suggested that Bushenantai recipe could improve embryo implantation of mice with EID by promoting the endometrial LIF expression and endometrial decidualization.

Identification of Novel Direct Stat3 Target Genes for Control of Growth and Differentiation

Signal transducer and activator of transcription 3 (Stat3) is a key regulator of gene expression in response to signaling of the glycoprotein 130 (gp130) family cytokines, including interleukin 6, oncostatin M, and leukemia inhibitory factor. Many efforts have been made to identify Stat3 target genes and to understand the mechanism of how Stat3 regulates gene expression. Using the microarray technique, hundreds of genes have been documented to be potential Stat3 target genes in different cell types. However, only a small fraction of these genes have been proven to be true direct Stat3 target genes. Here we report the identification of novel direct Stat3 target genes using a genome-wide screening procedure based on the chromatin immunoprecipitation method. These novel Stat3 target genes are involved in a diverse array of biological processes such as oncogenesis, cell growth, and differentiation. We show that Stat3 can act as both a repressor and activator on its direct target genes. We further show that most of the novel Stat3 direct target genes are dependent on Stat3 for their transcriptional regulation. In addition, using a physiological cell system, we demonstrate that Stat3 is required for the transcriptional regulation of two of the newly identified direct Stat3 target genes important for muscle differentiation.

Reconstitution of high affinity leukaemia inhibitory factor (LIF) receptors in haemopoietic cells transfected with the cloned human LIF receptor.

cDNA clones encoding the human leukaemia inhibitory factor (hLIF) receptor were isolated by screening a placental cDNA expression library in COS-7 cells with 125I-hLIF. The cloned LIF receptor is a member of the haemopoietin receptor family and comprises a signal sequence (44 amino acids), an extracellular region of two haemopoietin receptor domains and three fibronectin type III domains (789 amino acids), a transmembrane domain (26 amino acids) and a cytoplasmic domain (238 amino acids). The LIF receptor is expressed in COS-7 cells as a 190 kDa glycoprotein that specifically binds human LIF with low affinity, but does not bind mouse LIF. Clones encoding a soluble form of the homologous mouse LIF receptor have been isolated, suggesting complex interactions between the various forms of LIF ligand and receptor in vivo. The LIF receptor is most related to the gp130 signal-transducing component of the IL-6 receptor, a feature that may provide a molecular basis for the intertwined biologies of LIF and IL-6 in the absence of obvious structural similarly between the ligands. Mouse B9 plasmacytoma cells transfected with the human LIF receptor display novel high affinity LIF receptors that are presumed to consist of transfected receptors in association with endogenous mouse high affinity-converting subunits. Unlike the low affinity human LIF receptor, the mixed species high affinity receptor is capable of binding mouse LIF.

An unusual cytokine:Ig-domain interaction revealed in the crystal structure of leukemia inhibitory factor (LIF) in complex with the LIF receptor.

Leukemia inhibitory factor (LIF) receptor is a cell surface receptor that mediates the actions of LIF and other IL-6 type cytokines through the formation of high-affinity signaling complexes with gp130. Here we present the crystal structure of a complex of mouse LIF receptor with human LIF at 4.0 A resolution. The structure is, to date, the largest cytokine receptor fragment determined by x-ray crystallography. The binding of LIF to its receptor via the central Ig-like domain is unlike other cytokine receptor complexes that bind ligand predominantly through their cytokine-binding modules. This structure, in combination with previous crystallographic studies, also provides a structural template to understand the formation and orientation of the high-affinity signaling complex between LIF, LIF receptor, and gp130.

Effects of human versus mouse leukemia inhibitory factor on the in vitro development of bovine embryos

Leukemia inhibitory factor (LIF) is a cytokine that shows conflicting effects on in vitro produced (IVP) bovine embryos. Bovine LIF (bLIF) has been cloned and used in culture, but there is no commercially available bLIF. Thus, researchers use human LIF (hLIF) to supplement the culture medium for bovine embryos because of its greater sequence homology compared to murine LIF (mLIF). We compared the effects of mLIF and hLIF on the development of bovine embryos in culture with the effects described for bLIF. Oocytes were matured and fertilized in vitro and cultured in modified synthetic oviduct fluid with BSA. On Day 6 post-insemination, morulae were cultured for 48 h in the presence of: (1) mLIF, 100 ng ml −1; (2) hLIF, 100 ng ml −1; or (3) no LIF. Reduced blastocyst rates were observed on Day 8 for hLIF at the middle and expanded stages, while mLIF had no effect. In contrast, Day 8 blastocysts showed decreased cell counts both in terms of inner cell mass (ICM) and ICM/total cell proportions in the presence of mLIF, while hLIF had no effect. No changes were seen in trophectoderm (TE) and total cell counts. The increased hatching rates and TE cell counts previously described for bLIF, together with the disparate effects exhibited by hLIF and mLIF during blastocyst formation indicate these compounds are inappropriate to replace bLIF. We recommend that heterospecific LIF should not be used to supplement the culture medium for bovine embryo or embryonic stem cells.

Cell Cycle and Developmental Regulations of Replication Factors in Mouse Embryonic Stem Cells

Embryonic stem (ES) cells can grow rapidly and permanently while maintaining their differentiation capacity. To gain insight into how the cell cycle progression of undifferentiated murine ES cells is regulated, we have examined the expression patterns of various replication and cell cycle regulators. Most factors including cyclins, Cdc6, and geminin are rather constitutively expressed during the cell cycle of ES cells. Furthermore, the transcript levels of almost all the cell cycle regulators we investigated except for p21 and p27 are higher in undifferentiated ES cells than in murine embryonic fibroblasts (MEFs), and the increased stability of mRNA in ES cells may be partially responsible for this at least with some of the factors. More strikingly, the transcriptional levels of these factors are strongly correlated with the acetylated state of histone H3 at their promoter regions. However, the methylation state of histone or CpG methylation of the promoter region is not generally correlated significantly with the expression pattern of these factors in both cell types. On the protein level, Cdc6, ASK, cyclin A2, and cyclin B1 are extremely abundant in ES cells compared with MEFs. Furthermore, they are rapidly down-regulated upon induction of differentiation of ES cells. The significance of these findings is discussed in relation to the unusual proliferative properties of ES cells in an undifferentiated state.

Chicken leukemia inhibitory factor maintains chicken embryonic stem cells in the undifferentiated state.

Mouse embryonic stem (ES) cells can be maintained in an undifferentiated state in the presence of leukemia inhibitory factor (LIF), a member of the interleukin-6 cytokine family. In other mammals, this is not possible with LIF alone. Chicken ES-like cells (blastodermal cells) have only been cultured with mouse LIF because chicken LIF was not available. However the culture system is imperfect and chicken ES-like cells equivalent to mouse ES cells were not observed. In the present study, we cloned the cDNA-encoding chicken LIF using mRNA subtraction and RACE methodology. The chicken LIF cDNA encodes a protein with approximately 40% sequence identity to mouse LIF. It has 211 amino acids including a putative N-terminal signal peptide of 24 residues. Chicken blastodermal cells were cultured in the presence of bacterially expressed chicken LIF or mouse LIF. The expression of alkaline phosphatase and embryonal carcinoma cell monoclonal antibody-1 and stage-specific embryonic antigen-1 and the activation of STAT3 were examined, all of which are indices of the undifferentiated state. Exposure in the blastodermal cells to recombinant chicken LIF but not to mouse LIF maintained the expression of these various markers. After 9 days of incubation, the blastodermal cells formed cystic embryoid bodies in the presence of mouse LIF but not in the presence of recombinant chicken LIF. We conclude that chicken LIF is able to maintain chicken ES cell cultures in the undifferentiated state.

Studies using the estrogen receptor alpha knockout uterus demonstrate that implantation but not decidualization-associated signaling is estrogen dependent.

Ovarian hormonal signaling is essential for proper functioning of the uterus in the establishment of pregnancy. Previous studies have demonstrated that decidualization, a stromal transformation that occurs in response to embryo implantation, can be elicited in the uterus of estrogen receptor alpha knockout (alphaERKO) mice in the absence of the estrogen dependence normally seen in wild-type (WT) mice for this response. While the alphaERKO stromal compartment demonstrated the necessary decidual response, embryo implantation is a process initiated in the epithelial layer, a uterine component that lacks estrogen responsiveness in the alphaERKO. To determine if the alphaERKO uterus would be competent for implantation, donor embryos were transferred into the uterine lumen of WT and alphaERKO females that had been ovariectomized and treated with exogenous estradiol and progesterone to mimic early pregnancy. No implantation occurred in the alphaERKO, while implantation sites containing live embryos were seen in similarly treated WT uteri, indicating that functional estrogen receptor alpha (ERalpha) is required for implantation. Previous observations of estrogen-independent decidualization in the alphaERKO prompted investigation of the mechanism leading to estrogen independence of this process. The disruption of progesterone receptor (PR), Hoxa10, Cox2, or LIF in transgenic mice results in the loss of decidualization response. Therefore, the expression of these genes was studied in WT and alphaERKO uteri by comparing expression following vehicle, progesterone alone (P), or estradiol priming followed by progesterone with nidatory estradiol (E+Pe) and by comparing expression following the above hormonal manipulations in addition to luminal infusion of oil used previously as decidualization-initiating stimulus. The whole-uterus level of PR and Hoxa10 mRNAs did not vary; however, the PR protein was induced in the stroma 24 h after oil infusion. Interestingly, in the WT, this induction was most apparent in samples receiving E+Pe, while in the alphaERKO samples, the induction occurred independent of any hormone priming. Cox2 protein and mRNA increased in both WT and alphaERKO samples 2 h after oil infusion in all three of the treatment groups. In the WT samples, Cox2 levels remained elevated 24 h after oil infusion only in the E+Pe treatment group; however, the elevated Cox2 was seen in samples taken 24 h after oil infusion in all three alphaERKO treatment groups. The alphaERKO uterine tissue appeared to sustain more extensive damage when examined 24 h after oil infusion. Severe trauma, such as crushing of the uterine tissue, has previously been shown to remove the requirement for nidatory estradiol for deciduomas to develop, indicating that the greater susceptibility of alphaERKO uterine tissue to damage from intraluminal oil infusion is contributing to decidualization in the absence of ERalpha. Leukemia inhibitory factor (LIF) mRNA was also induced following estradiol treatment in the WT, but also following oil infusion in WT samples that were not treated with estradiol. In contrast, estradiol does not induce LIF mRNA in the alphaERKO, but oil infusion leads to a robust increase in LIF in all alphaERKO sample groups. LIF binds and activates its membrane receptor, which initiates responses including the phosphorylation and nuclear translocation of Stat3 transcription factor. Thus, Stat3 phosphorylation was studied in WT and alphaERKO samples and found to be induced following oil infusion in all samples. Together, these and previous observations illustrate that estrogen is essential for epithelial proliferation and embryo implantation and that estrogen is dispensable for stromal decidualization in the alphaERKO, as the essential genes and signals required for the response are still induced.

Leukemia inhibitory factor enhances bone formation in calvarial bone defect.

For bone defect reconstruction, locally administered cytokine plasmid was examined. Leukemia inhibitory factor (LIF) can bind to the osteoblast cell surface and induce bone formation both in vitro and in vivo. The authors investigated the local mouse LIF complementary deoxyribonucleic acid (cDNA) plasmid in the pcDNA 3 expression vector, which is promoted by cytomegalovirus and is stabilized by bovine growth hormone polyadenylation, with a gelatin sponge carrier. A total of 150 male Wistar rats were used. They were divided into three groups. Group 1 (N = 30) was treated with the gelatin carrier of the pcDNA 3 vector, group 2 (N = 90) was treated with three different doses of LIF cDNA (0.1, 1, and 10 micrograms) in the pcDNA 3-vector plasmid along with the gelatin carrier, and group 3 (N = 30) was treated with recombinant human bone morphogenetic protein -2. Ten animals in each group were euthanized at 1, 3, and 5 weeks postoperatively. Animals treated with LIF cDNA showed significantly enhanced bone mineral density (p < 0.05), as confirmed by dual-energy X-ray absorptiometry (DEXA), in 3 weeks compared with the control vehicle. By 3 weeks, the number of fibroblast-like cells and collagen fibers decreased, whereas the osteoblast-like cells increased inversely, as revealed during histological examination. LIF messenger ribonucleic acid demonstrated by in situ hybridization was observed most markedly in osteocytes of the LIF cDNA-treated group. Also, LIF peptide was detected in the same cell type by immunohistochemistry. Locally administered LIF cDNA plasmid in a gelatin carrier can increase bone density significantly, with subsequent bone formation, probably via osteocyte activation.

STIMULATION OF OSTEOCLAST DIFFERENTIATION IN VITRO BY MOUSE ONCOSTATIN M, LEUKAEMIA INHIBITORY FACTOR, CARDIOTROPHIN-1 AND INTERLEUKIN 6: SYNERGY WITH DEXAMETHASONE

The role of oncostatin M in bone metabolism is not clearly defined, and the actions of mouse oncostatin M (mOSM) on osteoclast development has not been previously determined. We therefore examined the ability of recombinant mOSM to stimulate osteoclast formation and activity using cocultures of murine calvaria and bone marrow cells, and compared the responses to other members of the interleukin 6 family of cytokines including mouse leukaemia inhibitory factor (LIF), cardiotrophin-1 (CT-1) and IL-6. Mouse OSM, LIF and CT-1 strongly induced the formation of tartrate resistant acid phosphatase positive (TRAP+) multinucleated cells (MNC) in a dose-dependent fashion. OSM, LIF or CT-1 also elevated the number and size of resorptive pits when cocultures were added to smooth cortical bone slices, indicating enhancement of osteoclast activity. The activity of OSM was reduced by indomethacin (10−8–10−6M), whereas addition of dexamethasone (DEX) at 10−7–10−5M synergistically enhanced OSM-induced numbers of TRAP+MNC. DEX (10−7M) costimulation also synergistically enhanced TRAP+cell numbers of LIF, and CT-1 treated cocultures. IL-6 had no activity alone, but further enhanced TRAP+cell formation in mOSM or DEX (10−7M) treated cocultures. When added to mouse calvarial osteoblast cultures, mOSM induced secretion of IL-6 protein and elevation of mRNA whereas LIF or CT-1 did not. IL-6 mRNA levels and protein secretion were reduced in osteoblasts by costimulation with DEX. These results show that mouse OSM, LIF and CT-1 induce osteoclast differentiation and activation, that DEX synergizes with each in this activity, and that mouse OSM induces responses in osteoblasts that are not shown by LIF or CT-1. Collectively these data suggest an important role of these cytokines in osteoporosis caused by high levels of corticosteroid.

Chimeric cytokine receptor can transduce expansion signals in interleukin 6 receptor alpha (IL-6Ralpha)-, IL-11Ralpha-, and gp130-low to -negative primitive hematopoietic progenitors.

We generated transgenic mice expressing chimeric receptors, which comprise extracellular domains of the human granulocyte-macrophage colony-stimulating factor (hGM-CSF) receptor and transmembrane and cytoplasmic domains of the mouse leukemia inhibitory factor receptor. In suspension cultures of lineage-negative (Lin(-)), 5-fluorouracil-resistant bone marrow cells of the transgenic mice, a combination of hGM-CSF and stem cell factor (SCF) induced exponential expansions of mixed colony-forming unit. The combination of hGM-CSF and SCF was effective on enriched, Lin(-)Sca-1(+)c-kit(+) progenitors and increased either mixed colony-forming unit or cobblestone area-forming cells. In case of stimulation with hGM-CSF and SCF, interleukin-6 (IL-6) and SCF, or IL-11 and SCF, the most efficient expansion was achieved with hGM-CSF and SCF. When Lin(-)Sca-1(+)c-kit(+)CD34(-) further enriched progenitors were clone sorted and individually incubated in the presence of SCF, hGM-CSF stimulated a larger number of cells than did IL-6, IL-6 and soluble IL-6 receptor (IL-6R), or IL-11. These data suggest the presence of IL-6Ralpha-, IL-11Ralpha-, and gp130-low to -negative primitive hematopoietic progenitors. Such primitive progenitors are equipped with signal transduction molecules and can expand when these chimeric receptors are genetically introduced into the cells and stimulated with hGM-CSF in the presence of SCF.

Cloning and characterization of a specific receptor for mouse oncostatin M.

Oncostatin M (OSM) is a member of a family of cytokines that includes ciliary neurotrophic factor, interleukin-6, interleukin-11, cardiotrophin-1, and leukemia inhibitory factor (LIF). The receptors for these cytokines consist of a common signaling subunit, gp130, to which other subunits are added to modify ligand specificity. We report here the isolation and characterization of a cDNA encoding a subunit of the mouse OSM receptor. In NIH 3T3 cells (which endogenously express gp130, LIF receptor beta [LIFRbeta], and the protein product, c12, of the cDNA described here), mouse LIF, human LIF, and human OSM signaled through receptors containing the LIFRbeta and gp130 but not through the mouse OSM receptor. Mouse OSM, however, signaled only through a c12-gp130 complex; it did not use the LIF receptor. Binding studies demonstrated that mouse OSM associated directly with either the c12 protein or gp130. These data highlight the species-specific differences in receptor utilization and signal transduction between mouse and human OSM. In mouse cells, only mouse OSM is capable of activating the mouse OSM receptor; human OSM instead activates the LIF receptor. Therefore, these data suggest that all previous studies with human OSM in mouse systems did not elucidate the biology of OSM but, rather, reflected the biological actions of LIF.

Measurement of leukemia inhibitory factor in biological fluids by radioimmunoassay.

Leukemia inhibitory factor (LIF) exhibits multiple biological activities in various tissues, and we have shown that LIF activates POMC gene transcription in response to immune signals. As higher serum levels of LIF have been reported in septicemia, we measured LIF values in biological fluids by RIA. Immunoreactive LIF was detected in 303 of 428 human serum samples. Circulating LIF detection rates were 69% in acute inflammatory diseases, 83% in chronic inflammatory diseases, 61% in noninflammatory diseases, and 90% in cancer patients. Serum concentrations of human LIF was higher in patients with inflammatory disease than in noninflammatory disease (0.80 +/- 0.10 vs. 0.53 +/- 0.02 ng/mL; P < 0.05) or in cancer patients (0.44 +/- 0.06; P < 0.05). Higher serum human LIF levels were found in septicemia (0.78 +/- 0.14 ng/mL), pneumonia (0.80 +/- 0.10 ng/mL), acute bronchitis (0.88 +/- 0.09 ng/mL), other infections (1.01 +/- 0.17 ng/mL), and systemic lupus erythematosus (SLE; 0.79 +/- 0.06 ng/mL). In 7 septicemia patients, Gram-negative infection was associated with higher LIF levels (1.06 +/- 0.16 ng/mL) than was Gram-positive infection (0.58 +/- 0.14 ng/mL). In patients with acute inflammatory disease, serum LIF levels decreased within several days after hospitalization. To test circulating mouse (m) LIF changes in response to inflammatory stress, lipopolysaccharide (LPS) was injected ip to mice. LPS increased serum mLIF values concordantly with ACTH levels. After i.p. injection of 80 microg LPS, serum mLIF increased by 144% (P < 0.05), 173% (P < 0.05), and 134% at 30, 90, and 120 min respectively. In vitro, however, LPS did not increase ACTH and mLIF secretion from dispersed mouse primary pituitary cells. These results suggest that LIF is an important participant in the pathogenesis of the acute inflammatory response. The elevated serum LIF levels observed in inflammation do not appear to originate from the pituitary.

Structure of the mouse leukaemia inhibitory factor receptor gene: regulated expression of mRNA encoding a soluble receptor isoform from an alternative 5' untranslated region.

The low-affinity leukaemia inhibitory factor receptor (LIF-R) is a component of cell-surface receptor complexes for the multifunctional cytokines leukaemia inhibitory factor, ciliary neurotrophic factor, oncostatin M and cardiotrophin-1. Both soluble and transmembrane forms of the protein have been described and several LIF-R mRNAs have been reported previously. In order to determine the coding potential of LIF-R mRNAs we have isolated and characterized the mouse LIF-R gene. mRNA encoding soluble LIF-R (sLIF-R) is formed by inclusion of an exon in which polyadenylation signals are provided by a B2 repeat. This exon is located centrally within the LIF-R gene but is excluded from the transmembrane LIF-R mRNA by alternative splicing. The transmembrane receptor is encoded by 19 exons distributed over 38 kb. Two distinct 5' non-coding exons have been identified, indicating the existence of alternative promoters. One of these is G/C rich and possesses a consensus initiator sequence as well as potential Sp1 binding sites. Expression of exon 1 from this promoter occurs in a wide variety of tissues, whereas expression of the alternative 5' untranslated region (exon 1a) is normally restricted to liver, the principal source of sLIF-R. During pregnancy expression of exon 1a becomes detectable also in the uterus. Expression of exon 1a increases dramatically during gestation and is accompanied by a similar quantitative rise in expression of sLIF-R mRNA. These findings establish that expression of LIF-R is under complex transcriptional control and indicate that regulated expression of the soluble cytokine receptor isoform may be due principally to an increase in the activity of a dedicated promoter.