Engineered whole cut meat-like tissue by the assembly of cell fibers using tendon-gel integrated bioprinting

With the current interest in cultured meat, mammalian cell-based meat has mostly been unstructured. There is thus still a high demand for artificial steak-like meat. We demonstrate in vitro construction of engineered steak-like tissue assembled of three types of bovine cell fibers (muscle, fat, and vessel). Because actual meat is an aligned assembly of the fibers connected to the tendon for the actions of contraction and relaxation, tendon-gel integrated bioprinting was developed to construct tendon-like gels. In this study, a total of 72 fibers comprising 42 muscles, 28 adipose tissues, and 2 blood capillaries were constructed by tendon-gel integrated bioprinting and manually assembled to fabricate steak-like meat with a diameter of 5 mm and a length of 10 mm inspired by a meat cut. The developed tendon-gel integrated bioprinting here could be a promising technology for the fabrication of the desired types of steak-like cultured meats.

Estrogen-inducible sFRP5 inhibits early B-lymphopoiesis in vivo, but not during pregnancy

Mammals have evolved to protect their offspring during early fetal development. Elaborated mechanisms induce tolerance in the maternal immune system for the fetus. Female hormones, mainly estrogen, play a role in suppressing maternal lymphopoiesis. However, the molecular mechanisms involved in the maternal immune tolerance are largely unknown. Here, we show that estrogen-induced soluble Frizzled-related proteins (sFRPs), and particularly sFRP5, suppress B-lymphopoiesis in vivo in transgenic mice. Mice overexpressing sFRP5 had fewer B-lymphocytes in the peripheral blood and spleen. High levels of sFRP5 inhibited early B-cell differentiation in the bone marrow (BM), resulting in the accumulation of cells with a common lymphoid progenitor (CLP) phenotype. Conversely, sFRP5 deficiency reduced the number of hematopoietic stem cells (HSCs) and primitive lymphoid progenitors in the BM, particularly when estrogen was administered. Furthermore, a significant reduction in CLPs and B-lineage-committed progenitors was observed in the BM of sfrp5-null pregnant females. We concluded that, although high sFRP5 expression inhibits B-lymphopoiesis in vivo, physiologically, it contributes to the preservation of very primitive lymphopoietic progenitors, including HSCs, under high estrogen levels. Thus, sFRP5 regulates early lympho-hematopoiesis in the maternal BM, but the maternal-fetal immune tolerance still involves other molecular mechanisms that remain to be uncovered.

Adult-specific systemic over-expression reveals novel in vivo effects of the soluble forms of ActRIIA, ActRIIB and BMPRII

Bone morphogenetic proteins (BMPs)/growth differentiation factors (GDFs), which belong to the TGF-beta superfamily, are pleiotropic factors that play a role in regulating the embryonic development and postnatal homeostasis of various organs and tissues by controlling cellular differentiation, proliferation and apoptosis. Conventional transgenic and knockout (KO) mouse approaches have provided only limited information regarding the in vivo functions of BMP signaling in adult animals due to the effects on prenatal development and the difficulty in manipulating multiligand signals simultaneously. We recently produced transgenic chimeric mice(Tg chimeras) in which the soluble IgG1-Fc fusion protein of three BMP type II receptors (ActRIIA, ActRIIB, BMPRII) was highly circulated (281-709 μg/ml), specifically in adult mouse blood. Since each BMP receptor can bind to multiple BMP ligands, these Tg chimeras should be useful to investigate the effects of trapping multiple BMP ligands. Remarkably, some phenotypes were unexpected based on previous studies, such as KO mouse analyses, presumably representing the effects of the multiple ligand trapping. These phenotypes included increased red blood cells (RBCs) and decreased viability in adults. In a further study, we focused on the phenotype of increased RBCs and found that extramedullary hematopoiesis in the spleen, not in the bone marrow, was increased using histological and flow cytometric analyses. Although it remains to be elucidated whether the transgene products affect the tissues directly or indirectly, our data provide novel and important insight into the biological functions of the soluble IgG1-Fc fusion protein of three BMP type II receptors in adults, and our approach should have broad applications to research on other ligand receptor families and studies involving mouse models.

Targeted deletion of the tybe IIb Na(+)-dependent Pi-co-transporter, NaPi-IIb, results in early embryonic lethality

NaPi-IIb encodes a Na(+)-dependent Pi co-transporter, which is expressed in various adult tissues and mediates transport of extracellular Pi ions coupling with Na(+) ion. To define the role of NaPi-IIbin vivo, NaPi-IIb gene deficient mice were generated utilizing targeted mutagenesis, yielding viable, heterozygous NaPi-IIb mice. In contrast, homozygous NaPi-IIb mice died in utero soon after implantation, indicating that NaPi-IIb was essential for early embryonic development. In situ hybridization revealed NaPi-IIb mRNA expression in the parietal endoderm, followed by the visceral endoderm, at a time point prior to establishment of a functioning chorio-allantoic placenta. At the time point of functional placenta development, the main site of NaPi-IIb production resided in the labyrinthine zone, where embryonic and maternal circulations were in closest contact. Expression patterns of NaPi-IIb suggest that NaPi-IIb plays an important role in Pi absorption from maternal circulation.

R-Spondin proteins: a novel link to beta-catenin activation

The R-spondin (Rspo) protein family is a recently described group of four distinct human secreted proteins. Reported activities for Rspo proteins include essential roles in vertebrate development and their ligand-type activities overlap substantially with those of the canonical Wnt ligands in that both Rspo and canonical Wnt signaling result in the activation of beta-catenin. In a general functional screen for human secreted proteins using transgenic mouse models, we identified human R-spondin1 (hRspo1) protein as a potent and specific mitogen for the gastrointestinal epithelium and demonstrated a potential therapeutic application for the protein in mouse models of cancer therapy-induced mucositis. In contrast to previous studies, our data indicated only partial overlap between Wnt and Rspo ligand activities, suggesting that there may be independent receptor/signaling pathways for Rspo proteins that intersect those of Wnt at the level of beta-catenin. Here we summarize the current reported data on the Rspo family and discuss these results in terms of alternate mechanisms of action. We have extended our observations on the potential therapeutic application of Rspo proteins by showing that all four human Rspo family members are capable of inducing epithelial proliferation and report the first non-vertebrate Rspo family member.

Generation of Chromosome-Specific Monoclonal Antibodies Using In Vitro-Differentiated Transchromosomic Mouse Embryonic Stem Cells

Monoclonal antibodies (MoAbs) recognizing lineage- and stage-specific human cell-surface antigens are valuable reagents for the characterization and isolation of various specialized cell populations derived from human embryonic stem cells (hESCs). In this report, we examined the use of in vitro differentiated transchromosomic mouse embryonic stem cells (TC-ESCs) as immunogens to obtain MoAbs against human cell-surface antigens. Immunization of a neural-cell population derived from differentiating human chromosome 4 and 11 TC-ESCs resulted in two chromosome-specific MoAbs, h4-neural1 and h11-neural1, respectively. The staining profiles of differentiated TC-ESCs and human embryonic carcinoma cells with these MoAbs were similar to the expression profile of nestin, a well-characterized intracellular marker for neural progenitor cells. We also described the successful purification and identification of the gene for h4-neural1 antigen (CD133, 4p15.32) with immunoaffinity chromatography. This procedure may have significant utility in generating MoAbs useful for understanding the mechanism that regulates the in vitro differentiation of hESCs.

Mitogenic influence of human R-spondin1 on the intestinal epithelium

Several described growth factors influence the proliferation and regeneration of the intestinal epithelium. Using a transgenic mouse model, we identified a human gene, R-spondin1, with potent and specific proliferative effects on intestinal crypt cells. Human R-spondin1 (hRSpo1) is a thrombospondin domain-containing protein expressed in enteroendocrine cells as well as in epithelial cells in various tissues. Upon injection into mice, the protein induced rapid onset of crypt cell proliferation involving beta-catenin stabilization, possibly by a process that is distinct from the canonical Wnt-mediated signaling pathway. The protein also displayed efficacy in a model of chemotherapy-induced intestinal mucositis and may have therapeutic application in gastrointestinal diseases.

Vitamin D receptor-independent FGF23 actions in regulating phosphate and vitamin D metabolism

FGF23 suppresses both serum phosphate and 1,25-dihydroxyvitamin D [1,25D] levels in vivo. Because 1,25D itself is a potent regulator of phosphate metabolism, it has remained unclear whether FGF23-induced changes in phosphate metabolism were caused by a 1,25D-independent mechanism. To address this issue, we intravenously administered recombinant FGF23 to vitamin D receptor (VDR) null (KO) mice as a rapid bolus injection and evaluated the early effects of FGF23. Administration of recombinant FGF23 further decreased the serum phosphate level in VDR KO mice, accompanied by a reduction in renal sodium-phosphate cotransporter type IIa (NaPi2a) protein abundance and a reduced renal 25-hydroxyvitamin D-1alpha-hydroxylase (1alphaOHase) mRNA level. Thus FGF23-induced changes in NaPi2a and 1alphaOHase expression are independent of the 1,25D/VDR system. However, 24-hydroxylase (24OHase) mRNA expression remained undetectable by the treatment with FGF23. We also analyzed the regulatory mechanism for FGF23 expression. The serum FGF23 level was almost undetectable in VDR KO mice, whereas dietary calcium supplementation significantly increased circulatory levels of FGF23 and its mRNA abundance in bone. This finding indicates that calcium is another determinant of FGF23 production that occurs independently of the VDR-mediated mechanism. In contrast, dietary phosphate supplementation failed to induce FGF23 expression in the absence of VDR, whereas marked elevation in circulatory FGF23 was observed in wild-type mice fed with a high-phosphate diet. Taken together, FGF23 works, at least in part, in a VDR-independent manner, and FGF23 production is also regulated by multiple mechanisms involving VDR-independent pathways.

A novel transgenic chimaeric mouse system for the rapid functional evaluation of genes encoding secreted proteins

A major challenge of the post-genomic era is the functional characterization of anonymous open reading frames (ORFs) identified by the Human Genome Project. In this context, there is a strong requirement for the development of technologies that enhance our ability to analyze gene functions at the level of the whole organism. Here, we describe a rapid and efficient procedure to generate transgenic chimaeric mice that continuously secrete a foreign protein into the systemic circulation. The transgene units were inserted into the genomic site adjacent to the endogenous immunoglobulin (Ig) κ locus by homologous recombination, using a modified mouse embryonic stem (ES) cell line that exhibits a high frequency of homologous recombination at the Igκ region. The resultant ES clones were injected into embryos derived from a B-cell-deficient host strain, thus producing chimaerism-independent, B-cell-specific transgene expression. This feature of the system eliminates the time-consuming breeding typically implemented in standard transgenic strategies and allows for evaluating the effect of ectopic transgene expression directly in the resulting chimaeric mice. To demonstrate the utility of this system we showed high-level protein expression in the sera and severe phenotypes in human EPO (hEPO) and murine thrombopoietin (mTPO) transgenic chimaeras.

A new model mouse for Duchenne muscular dystrophy produced by 2.4 Mb deletion of dystrophin gene using Cre-loxP recombination system

Duchenne muscular dystrophy (DMD) is caused by mutation in the 2.4-Mb dystrophin (DMD) gene . This gene encodes a number of tissue-specific isoforms of dystrophin generated by transcription from at least seven promoters and also by alternative splicing. We deleted entire genomic region of the DMD gene on mouse chromosome X using a Cre-loxP recombination system. Introduction of a loxP site in dystrophin's first and last exon by homologous recombination in mouse embryonic stem (ES) cells generated "DMD-floxed" (flanked by loxP sites) ES cells, which we subjected to Cre-mediated excision leading to establishment of "DMD-null" ES cell lines. The DMD-null mice produced from the DMD-null ES cells were viable but displayed severe muscular hypertrophy and dystrophy. In addition to the muscular impairment, the DMD-null mouse exhibited some behavioral abnormality and male sterility. The DMD-floxed mice produced from the DMD-floxed ES cells were viable, phenotypically normal, and were born with the expected Mendelian frequency, despite the absence of brain (cortical)-type dystrophin (Dp427c) expression. Since production of multiple dystrophin isoforms due to alternative splicing or exon skipping is totally prevented in the DMD-null mouse, these new mutants will provide an improved model system for functional studies of dystrophin and its isoforms.

Human artificial chromosome (HAC) vector provides long-term therapeutic transgene expression in normal human primary fibroblasts

Human artificial chromosomes (HACs) segregating freely from host chromosomes are potentially useful to ensure both safety and duration of gene expression in therapeutic gene delivery. However, low transfer efficiency of intact HACs to the cells has hampered the studies using normal human primary cells, the major targets for ex vivo gene therapy. To elucidate the potential of HACs to be vectors for gene therapy, we studied the introduction of the HAC vector, which is reduced in size and devoid of most expressed genes, into normal primary human fibroblasts (hPFs) with microcell-mediated chromosome transfer (MMCT). We demonstrated the generation of cytogenetically normal hPFs harboring the structurally defined and extra HAC vector. This introduced HAC vector was retained stably in hPFs without translocation of the HAC on host chromosomes. We also achieved the long-term production of human erythropoietin for at least 12 weeks in them. These results revealed the ability of HACs as novel options to circumvent issues of conventional vectors for gene therapy.

Sequential targeting of the genes encoding immunoglobulin-μ and prion protein in cattle

Gene targeting is accomplished using embryonic stem cells in the mouse but has been successful, only using primary somatic cells followed by embryonic cloning, in other species. Gene targeting in somatic cells versus embryonic stem cells is a challenge; consequently, there are few reported successes and none include the targeting of transcriptionally silent genes or double targeting to produce homozygotes. Here, we report a sequential gene targeting system for primary fibroblast cells that we used to knock out both alleles of a silent gene, the bovine gene encoding immunoglobulin-mu (IGHM), and produce both heterozygous and homozygous knockout calves. We also carried out sequential knockout targeting of both alleles of a gene that is active in fibroblasts, encoding the bovine prion protein (PRNP), in the same genetic line to produce doubly homozygous knockout fetuses. The sequential gene targeting system we used alleviates the need for germline transmission for complex genetic modifications and should be broadly applicable to gene functional analysis and to biomedical and agricultural applications.

Targeted ablation of Fgf23 demonstrates an essential physiological role of FGF23 in phosphate and vitamin D metabolism

Inorganic phosphate is essential for ECM mineralization and also as a constituent of important molecules in cellular metabolism. Investigations of several hypophosphatemic diseases indicated that a hormone-like molecule probably regulates serum phosphate concentration. FGF23 has recently been recognized as playing important pathophysiological roles in several hypophosphatemic diseases. We present here the evidence that FGF23 is a physiological regulator of serum phosphate and 1,25-dihydroxyvitamin D (1,25[OH]2D) by generating FGF23-null mice. Disruption of the Fgf23 gene did not result in embryonic lethality, although homozygous mice showed severe growth retardation with abnormal bone phenotype and markedly short life span. The Fgf23(-/-) mice displayed significantly high serum phosphate with increased renal phosphate reabsorption. They also showed an elevation in serum 1,25(OH)2D that was due to the enhanced expression of renal 25-hydroxyvitamin D-1alpha-hydroxylase (1alpha-OHase) from 10 days of age. These phenotypes could not be explained by currently known regulators of mineral homeostasis, indicating that FGF23 is essential for normal phosphate and vitamin D metabolism.

The structure and function of a soybean beta-glucan-elicitor-binding protein

beta-Glucan elicitor (GE), released from the cell wall of the phytopathogenic fungus Phytophthora megasperma by soybean glucanases, causes defense reactions in soybean. A GE-binding protein (GEBP) was purified from the membrane fraction of soybean root cells, and its cDNA was isolated. Expression of the cDNA clone in tobacco suspension cultured cells and in Escherichia coli conferred GE-binding activity to both. An antibody against the recombinant protein was found to inhibit the GE binding with the soybean cotyledon membrane fraction as well as the resulting accumulation of phytoalexin. Immunolocalization assays indicated that the GEBPs are located in the plasma membrane of root cells. These results suggest that the cDNA encodes a GE receptor and may mediate the signaling of the elicitor.

Inhibition of the endothelin-converting enzyme by pepsin digests of food proteins

Inhibitory activities toward the endothelin-converting enzyme (ECE) were detected in pepsin digests of bonito pyrolic appendix and beef. After Sep-Pak C18 fractionation, this activity from bonito and beef was recovered in the 50% and 25% ethanol fractions, respectively. Activities were also recovered in the ultrafiltrate (< 5000 Da), and disappeared after a pronase treatment. Therefore, these inhibitory activities may have peptidic properties.

A novel protein secretion factor from a Vibrio species which operates in Escherichia coli

A DNA fragment specific to a Vibrio species was found to promote extracellular secretion of proteins, when cloned into Escherichia coli. Cells harboring a plasmid carrying this fragment secreted significant amounts of periplasmic beta-lactamase and alkaline phosphatase into the medium, however most cytoplasmic beta-galactosidase was retained within the cell. The DNA sequence essential for this property was found to be a gene encoding 76 amino acids, which was designated as the 'PAS factor'. Highly expressed PAS factor is harmful to the cell, this may be due to a disruption of the membrane structure and/or function.

Pharmacological effects of recombinant human granulocyte colony-stimulating factor modified by polyethylene glycol on anticancer drug-induced neutropenia in mice

1. To clarify the pharmacological effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) conjugated to polyethylene glycol (PEG), its effects on the number of circulating neutrophils in mice made neutropenic by cyclophosphamide (CPA) or 5-fluorouracil (5-FU) were compared with rhG-CSF lacking PEG. 2. In normal mice, PEG-conjugated rhG-CSF (PEG-rhG-CSF, 10 micrograms protein/kg) induced an increase in neutrophils which lasted for 72 h after injection whereas the effect of rhG-CSF (10 micrograms protein/kg) disappeared by 24 h after injection. 3. In CPA or 5-FU-induced neutropenic mice, PEG-rhG-CSF inhibited neutropenia or accelerated recovery from neutropenia and its potency was higher than that of rhG-CSF. 4. These results indicate that PEG-rhG-CSF has a longer duration of action than rhG-CSF and is more effective in the recovery from neutropenia.

Chemical modification of recombinant human granulocyte colony-stimulating factor by polyethylene glycol increases its biological activity in vivo

Recombinant human granulocyte colony-stimulating factor (rHuG-CSF) produced in Escherichia coli was chemically modified by polyethylene glycol (PEG) of molecular weights 4,500 or 10,000. The neutrophils observed at 32 hours after intravenous injection of the rHuG-CSF modified with PEG (4,500) or PEG (10,000) to mice were, respectively, 2.5 times and 5 times more than that observed after the injection of the unmodified rHuG-CSF. These results show that the covalent attachment of PEG to rHuG-CSF enhanced its pharmacological activity in vivo and that the modification with the larger PEG molecule is more effective to enhance the in vivo activity of rHuG-CSF.

Order of binding of substrate to valyl-tRNA synthetase from Bacillus stearothermophilus in amino acid activation reaction

Amino acid activation reaction with valyl-tRNA synthetase (EC 6.1.1.9) from Bacillus stearothermophilus was studied kinetically by measuring ATP-PPi exchange to find the order of the binding of substrate to the enzyme. The effects of the concentration of the substrates (L-valine and ATP) and two dead-end inhibitors (L-valinol and adenosine) on the reaction rate were analyzed. The results indicate that L-valine and ATP are bound to the enzyme in a random sequence. This conclusion is consistent with the one previously suggested by static binding experiments.

Fluorometric study on the interaction of amino acids and ATP with valyl-tRNA synthetase from Bacillus stearothermophilus

Interactions of several amino acids and nucleotides with valyl-tRNA synthetase [EC 6.1.1.9] (VRS) from Bacillus stearothermophilus were investigated using as a probe the ligand-induced quenching of protein fluorescence (lambda ex = 295 nm, lambda em = 340 nm) of VRS. L-Valine, L-threonine, L-isoleucine, L-glutamic acid, L-leucine, and D-valine caused fluorescence quenching. Among them, L-threonine had a Kd value comparable to that for the cognate substrate, L-valine, but the other amino acids were bound more weakly as estimated by the fluorescence titration method. L-Alanine, L-histidine, and L-serine did not cause any fluorescence change. Among the nucleotides tested (ATP, ADP, AMP, GTP, ITP, CTP, and UTP), only ATP caused the fluorescence change. In the presence of an excess amount of ATP, only L-valine and L-threonine, among the tested amino acids, induced the fluorescence quenching, and the binding of L-valine was greatly favored under this condition. This is consistent with the results of the ATP-PP1 exchange reaction by VRS, in which only L-valine and L-threonine, of these 9 amino acids tested, could serve as substrates, and the Km value for L-valine was much smaller than that for L-threonine. Thus the binding of ATP to VRS enhances the substrate specificity of VRS towards amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)