Dysfunctional Sars-CoV-2-M protein-specific cytotoxic T lymphocytes in patients recovering from severe COVID-19

Although the importance of virus-specific cytotoxic T lymphocytes (CTL) in virus clearance is evident in COVID-19, the characteristics of virus-specific CTLs related to disease severity have not been fully explored. Here we show that the phenotype of virus-specific CTLs against immunoprevalent epitopes in COVID-19 convalescents might differ according to the course of the disease. We establish a cellular screening method that uses artificial antigen presenting cells, expressing HLA-A^*24:02, the costimulatory molecule 4-1BBL, SARS-CoV-2 structural proteins S, M, and N and non-structural proteins ORF3a and nsp6/ORF1a. The screen implicates SARS-CoV-2 M protein as a frequent target of IFNγ secreting CD8⁺ T cells, and identifies M_198-206 as an immunoprevalent epitope in our cohort of HLA-A^*24:02 positive convalescent COVID-19 patients recovering from mild, moderate and severe disease. Further exploration of M_198-206-specific CD8⁺ T cells with single cell RNA sequencing reveals public TCRs in virus-specific CD8⁺ T cells, and shows an exhausted phenotype with less differentiated status in cells from the severe group compared to cells from the moderate group. In summary, this study describes a method to identify T cell epitopes, indicate that dysfunction of virus-specific CTLs might be an important determinant of clinical outcomes.

Photoacoustic in vivo 3D imaging of tumor using a highly tumor-targeting probe under high-threshold conditions

Three-dimensional (3D) representation of a tumor with respect to its size, shape, location, and boundaries is still a challenge in photoacoustic (PA) imaging using artificial contrast agents as probes. We carried out PA imaging of tumors in mice using 800RS-PMPC, which was obtained by coupling of 800RS, a near-infrared cyanine dye, with PMPC, a highly selective tumor-targeting methacrylate polymer having phosphorylcholine side chains, as a probe. The conjugate 800RS-PMPC forms compact nanoparticles (dDLS = 14.3 nm), retains the biocompatibility of the parent polymer (PMPC) and exhibits unprecedented PA performance. When applied to mice bearing a 6 × 3 × 3 mm3 tumor buried 6 mm beneath the skin, the probe 800RS-PMPC selectively accumulates in the tumor and emits PA signals that are strong enough to be unambiguously distinguished from noise signals of endogenous blood/hemoglobin. The PA image thus obtained under high-threshold conditions allows 3D characterization of the tumor in terms of its size, shape, location, and boundaries.

Biological reduction of nitroimidazole-functionalized gold nanorods for photoacoustic imaging of tumor hypoxia

Tumor-selective accumulation of gold nanorods (GNR) has been demonstrated for visualization of tumor hypoxia by photoacoustic imaging. We prepared GNRs with hypoxia-targeting nitroimidazole units (G-NI) on their surface. Biological experiments revealed that G-NI produced a strong photoacoustic signal in hypoxic tumor cells and tissues.

Tumor-selective accumulation of gold nanorods (GNR) has been demonstrated for visualization of tumor hypoxia by photoacoustic imaging.

IgA regulates the composition and metabolic function of gut microbiota by promoting symbiosis between bacteria

Immunoglobulin A (IgA) promotes health by regulating the composition and function of gut microbiota, but the molecular requirements for such homeostatic IgA function remain unknown. We found that a heavily glycosylated monoclonal IgA recognizing ovalbumin coats Bacteroides thetaiotaomicron (B. theta), a prominent gut symbiont of the phylum Bacteroidetes. In vivo, IgA alters the expression of polysaccharide utilization loci (PUL), including a functionally uncharacterized molecular family provisionally named Mucus-Associated Functional Factor (MAFF). In both mice and humans, MAFF is detected predominantly in mucus-resident bacteria, and its expression requires the presence of complex microbiota. Expression of the MAFF system facilitates symbiosis with other members of the phylum Firmicutes and promotes protection from a chemically induced model of colitis. Our data reveal a novel mechanism by which IgA promotes symbiosis and colonic homeostasis.

Aggregate Formation of Oligonucleotides that Assist Molecular Imaging for Tracking of the Oxygen Status in Tumor Tissue

The use of DNA aggregates could be a promising strategy for the molecular imaging of biological functions. Herein, phosphorescent oligodeoxynucleotides were designed with the aim of visualizing oxygen fluctuation in tumor cells. DNA-ruthenium conjugates (DRCs) that consisted of oligodeoxynucleotides, a phosphorescent ruthenium complex, a pyrene unit for high oxygen responsiveness, and a nitroimidazole unit as a tumor-targeting unit were prepared. In general, oligonucleotides have low cell permeability because of their own negative charges; however, the DRC formed aggregates in aqueous solution due to the hydrophobic pyrene and nitroimidazole groups, and smoothly penetrated the cellular membrane to accumulate in tumor cells in a hypoxia-selective manner. The oxygen-dependent phosphorescence of DRC in cells was also observed. In vivo experiments revealed that aggregates of DRC accumulated in hypoxic tumor tissue that was transplanted into the left leg of mice, and showed that oxygen fluctuations in tumor tissue could be monitored by tracking of the phosphorescence emission of DRC.

Dioxetane formation and chemiluminescent emission upon the combination of a vinylphenol derivative with naphthalene endoperoxide

We designed a chemiluminescent system using nanoparticles.

TWEAK/Fn14 pathway promotes a T helper 2-type chronic colitis with fibrosis in mice

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK), a TNF superfamily member, induces damage of the epithelial cells (ECs) and production of inflammatory mediaters through its receptor Fn14 in a model of acute colitis. In our current study of chronic colitis induced by repeated rectal injection of a hapten, we found that inflammation, fibrosis, and T helper 2 (Th2)-type immunity were significantly reduced in Fn14 gene knockout (KO) mice when compared with wild-type (WT) control mice. Expression of thymic stromal lymphopoietin (TSLP) was lower in Fn14 KO colon ECs than in WT ECs. TWEAK potentiates the induction of TSLP by interleukin-13 (IL-13) in colon explants from WT but not in Fn14 KO tissue. TSLP receptor KO mice exhibit milder chronic colitis, similar to that in Fn14 KO mice. TWEAK and IL-13 synergistically promote fibroblast proliferation. Thus we propose an IL-13-TWEAK/Fn14-TSLP axis as a key mechanism underlying chronic colitis with fibrosis.

TWEAK/Fn14 pathway promotes chronic colitis and fibrosis mediated by IL-13-TSLP axis (P3244)

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a cytokine of the TNF ligand superfamily that is constitutively expressed by many immune cell types including monocytes/macrophages, DC, neutrophils, natural killer cells, and also T cells. The only known signaling receptor for TWEAK, FGF-inducible molecule 14 (Fn14), is a highly inducible molecule in epithelial cells (EC), endothelial cells, and other mesenchymal cell types wherein TWEAK signals through Fn14 to promote the canonical and noncanonical NF-κB, MAPK and potentially other pathways. We previously reported that TWEAK promoted colitis in mice by enhancing production of inflammatory mediators by EC. TWEAK also induced EC damage in the presence of IL-13, which is known as a pathogenic profibrotic T helper 2-type cytokine. In our current study of chronic colitis induced by repeated rectal injection of a hapten, we found that inflammation, fibrosis, and T helper 2-type immunity were significantly reduced in Fn14 knockout (KO) mice when compared with wild type (WT) control mice. Expression of thymic stromal lymphopoietin (TSLP) was lower in Fn14 KO colon EC than in WT EC. TWEAK/Fn14 was required for the induction by IL-13 of TSLP in colon explants. TWEAK and IL-13 synergistically promote embryonic fibroblast proliferation. Thus we propose an IL-13-TWEAK/ Fn14-TSLP axis as a key mechanism underlying chronic colitis with fibrosis.

The protective role of the transmembrane thioredoxin-related protein TMX in inflammatory liver injury

AIMS

Accumulating evidence indicates that oxidative stress is associated with inflammation, and the cellular redox status can determine the sensitivity and the final outcome in response to inflammatory stimuli. To control the redox balance, mammalian cells contain a variety of oxidoreductases belonging to the thioredoxin superfamily. The large number of these enzymes suggests a complex mechanism of redox regulation in mammals, but the precise function of each family member awaits further investigations.

RESULTS

We generated mice deficient in transmembrane thioredoxin-related protein (TMX), a transmembrane oxidoreductase in the endoplasmic reticulum (ER). When exposed to lipopolysaccharide (LPS) and d-(+)-galactosamine (GalN) to induce inflammatory liver injury, mutant mice were highly susceptible to the toxicants and developed severe liver damage. LPS-induced production of inflammatory mediators was equivalent in both wild-type and TMX(-/-) mice, whereas neutralization of the proinflammatory cytokine tumor necrosis factor-α suppressed the toxic effects of LPS/GalN in the mutant mice. Liver transcriptional profiles revealed enhanced activation of the p53-signaling pathway in the TMX(-/-) mice after LPS/GalN treatment. Furthermore, TMX deficiency also caused increased sensitivity to thioacetamide, which exerts its hepatotoxicity through the generation of reactive oxygen species.

INNOVATION

The present study is the first to address the role of the oxidoreductase TMX in inflammatory liver injury. The phenotype of mice deficient in TMX suggests a functional link between redox regulation in the ER and susceptibility to oxidative tissue damage.

CONCLUSION

We conclude that TMX plays a major role in host defense under the type of inflammatory conditions associated with oxidative stress.

Interleukin-13 damages intestinal mucosa via TWEAK and Fn14 in mice-a pathway associated with ulcerative colitis

BACKGROUND & AIMS

TWEAK, a member of the tumor necrosis factor (TNF) superfamily, promotes intestinal epithelial cell injury and signals through the receptor Fn14 following irradiation-induced tissue damage and during development of colitis in mice. Interleukin (IL)-13, an effector of tissue damage in similar models, has been associated with the pathogenesis of ulcerative colitis (UC). We investigated interactions between TWEAK and IL-13 following mucosal damage in mice.

METHODS

We compared patterns of gene expression in intestinal tissues from wild-type and TWEAK knockout mice following γ-irradiation. Intestinal explants from these mice were used to detect cell damage induced by IL-13 and TNF-α. Levels of messenger RNA for IL-13, TWEAK, and Fn14 were measured in mucosal samples from patients with UC.

RESULTS

Based on gene expression analysis, TWEAK mediates γ-irradiation-induced epithelial cell cycle arrest and apoptosis. However, TWEAK alone did not induce damage or apoptosis of primary intestinal epithelial cells. On the other hand, exogenous IL-13 activated caspase-3 in naïve intestinal explants; this process required TWEAK, Fn14, and secretion of endogenous TNF-α which was mediated by ADAM17. Conversely, activation of caspase by exogenous TNF-α required IL-13, TWEAK, and Fn14. In mucosa from patients with UC, messenger RNA levels of IL-13, TWEAK, and Fn14 increased with level of disease severity.

CONCLUSIONS

IL-13-induced damage of intestinal epithelial cells requires TWEAK, its receptor (Fn14), and TNF-α. IL-13, TNF-α, TWEAK, and Fn14 could perpetuate and aggravate intestinal inflammation in patients with UC.

Thioredoxin binding protein 2 modulates natural killer T cell-dependent innate immunity in the liver: possible link to lipid metabolism

Thioredoxin binding protein 2 (TBP2) plays a regulatory role in lipid metabolism and immune regulation. We previously reported the effect of TBP2 loss-of-function on lipid metabolism using TBP2 knockout (TBP2KO) mice. In this study, we employed TBP2 transgenic (TBP2TG) mice to analyze the in vivo effect of TBP2 gain-of-function. We revealed a decrease in the percentage of hepatic natural killer T (NKT) cells in TBP2KO mice and an increase in the percentage of hepatic NKT cells in TBP2TG mice. The TBP2KO mice were resistant to concanavalin A (ConA)-induced hepatitis, but they were highly susceptible to other types of hepatitis. TBP2 modulates lipid metabolism as well as NKT cell activity. Moreover, TBP2 expression was increased significantly in klotho-deficient mice, which exhibit a syndrome resembling aging human phenotypes. TBP2 may play multiple roles in lipid metabolism, innate immunity, and aging.

Direct association of thioredoxin-1 (TRX) with macrophage migration inhibitory factor (MIF): regulatory role of TRX on MIF internalization and signaling

Thioredoxin-1 (TRX) is a small (14 kDa) multifunctional protein with the redox-active site Cys-Gly-Pro-Cys. Macrophage migration inhibitory factor (MIF) is a 12 kDa cytokine belonging to the TRX family. Historically, when we purified TRX from the supernatant of ATL-2 cells, a 12 kDa protein was identified along with TRX, which was later proved to be MIF. Here, we show that TRX and MIF form a complex in the cell and the culture supernatant of ATL-2 cells. Using a BIAcore assay, we confirmed that TRX has a specific affinity with MIF. We also found that extracellular MIF was more effectively internalized into the ATL-2 cells expressing TRX on the cell surface, than the Jurkat T cells which do not express surface TRX. Moreover, anti-TRX antibody blocked the MIF internalization, suggesting that the cell surface TRX is involved in MIF internalization into the cells. Furthermore, anti-TRX antibody inhibited MIF-mediated enhancement of TNF-alpha production from macrophage RAW264.7 cells. These results suggest that the cell surface TRX serves as one of the MIF binding molecules or MIF receptor component and inhibits MIF-mediated inflammatory signals.

Physical and functional interaction of transmembrane thioredoxin-related protein with major histocompatibility complex class I heavy chain: redox-based protein quality control and its potential relevance to immune responses

In the endoplasmic reticulum (ER), a variety of oxidoreductases classified in the thioredoxin superfamily have been found to catalyze the formation and rearrangement of disulfide bonds. However, the precise function and specificity of the individual thioredoxin family proteins remain to be elucidated. Here, we characterize a transmembrane thioredoxin-related protein (TMX), a membrane-bound oxidoreductase in the ER. TMX exists in a predominantly reduced form and associates with the molecular chaperon calnexin, which can mediate substrate binding. To determine the target molecules for TMX, we apply a substrate-trapping approach based on the reaction mechanism of thiol-disulfide exchange, identifying major histocompatibility complex (MHC) class I heavy chain (HC) as a candidate substrate. Unlike the classical ER oxidoreductases such as protein disulfide isomerase and ERp57, TMX seems not to be essential for normal assembly of MHC class I molecules. However, we show that TMX-class I HC interaction is enhanced during tunicamycin-induced ER stress, and TMX prevents the ER-to-cytosol retrotranslocation of misfolded class I HC targeted for proteasomal degradation. These results suggest a specific role for TMX and its mechanism of action in redox-based ER quality control.

Thioredoxin and thioredoxin binding protein 2 in the liver

Thioredoxin (TRX) is a 12-kDa protein with redox-active dithiol in the active site -Cys-Gly-Pro-Cys- and constitutes a major thiol reducing system. TRX protects cells from stress-induced damage through antioxidative, antiapoptotic, and anti-inflammatory effect. In animal models, thioacetamide (TAA)-induced acute hepatitis and TAA-induced liver fibrosis was attenuated in TRX transgenic (TRXTG) mice. Plasma level of TRX is a good marker for hepatitis and nonalcoholic steatohepatitis (NASH) in human patients. Recently, we identified TRX binding protein 2 (TBP2) in a yeast two-hybrid screening. TBP2 regulates both the expression and reducing activity of TRX as well as cell growth. TBP2 knockout (TBP2KO) mice showed disorder in lipid metabolism. TBP2 plays a multiple role on cell growth and lipid and glucose metabolism. Thus, TRX and TBP2 play important roles in the pathophysiology of liver diseases, including NASH, indicating that ratio of TRX and TBP2 expression could be a novel marker of liver diseases like NASH.

Dendritic cells derived from TBP-2-deficient mice are defective in inducing T cell responses

Thioredoxin-binding protein-2 (TBP-2), also known as vitamin D3-up-regulated protein 1 (VDUP1), was identified as an endogenous molecule interacting with thioredoxin (TRX). Here, we show that dendritic cells (DC) derived from TBP-2-deficient mice are defective in the function of T cell activation. To compare TBP-2(-/-) DC function with wild-type (WT) DC, we stimulated DC with lipopolysaccharide (LPS). Although TBP-2(-/-) DC and WT DC expressed comparable levels of MHC class II and costimulatory molecules such as CD40, CD80 and CD86, the IL-12p40, IL-12p70 and IL-6 productions of TBP-2(-/-) DC were attenuated. In a mixed leukocyte reaction (MLR), the concentrations of IL-2, IFN-gamma, IL-4 and IL-10 in the culture supernatant of MLR with TBP-2(-/-) DC were significantly lower than those in the cultures with WT DC. In MLR also, as with LPS stimulation, IL-12p40 and IL-12p70 production from TBP-2(-/-) DC was less than that from WT DC. Proliferation of T cells cultured with TBP-2(-/-) DC was poorer than that with WT DC. In vivo delayed-type hypersensitivity responses in TBP-2(-/-) mice immunized with ovalbumin were significantly reduced compared to WT mice. These results indicate that TBP-2 plays a crucial role in DC to induce T cell responses.

Fatty acid methyl ester (FAME) technology for monitoring biological foaming in activated sludge: full scale plant verification

Fatty acid methyl ester (FAME) technology was evaluated as a monitoring tool for quantification of Gordonia amarae in activated sludge systems. The fatty acid, 19:1 alcohol, which was identified as a unique fatty acid in G. amarae was not only confirmed to be present in foaming plant samples, but the quantity of the signature peak correlated closely with the degree of foaming. Foaming potential experiment provided a range of critical foaming levels that corresponded to G. amarae population. This range of critical Gordonia levels was correlated to the threshold signature FAME amount. Six full-scale wastewater treatment plants were selected based on a survey to participate in our full-scale study to evaluate the potential application of the FAME technique as the Gordonia monitoring tool. Greater amounts of signature FAME were extracted from the mixed liquor samples obtained from treatment plants experiencing Gordonia foaming problems. The amounts of signature FAME correlated well with the conventional filamentous counting technique. These results demonstrated that the relative abundance of the signature FAMEs can be used to quantitatively monitor the abundance of foam-causing microorganism in activated sludge.

Lipid raft-mediated uptake of cysteine-modified thioredoxin-1: apoptosis enhancement by inhibiting the endogenous thioredoxin-1

Thioredoxin-1 (TRX) plays important roles in cellular signaling by controlling the redox state of cysteine residues in target proteins. TRX is released in response to oxidative stress and shows various biologic functions from the extracellular environment. However, the mechanism by which extracellular TRX transduces the signal into the cells remains unclear. Here we report that the cysteine modification at the active site of TRX promotes the internalization of TRX into the cells. TRX-C35S, in which the cysteine at residue 35 of the active site was replaced with serine, was internalized more effectively than wild-type TRX in human T-cell leukemia virus-transformed T cells. TRX-C35S bound rapidly to the cell surface and was internalized into the cells dependent on lipid rafts in the plasma membrane. This process was inhibited by wild-type TRX, reducing reagents such as dithiothreitol, and methyl-beta-cyclodextrin, which disrupts lipid rafts. Moreover, the internalized TRX-C35S binds to endogenous TRX, resulting in the generation of intracellular reactive oxygen species (ROS) and enhanced cis-diamine-dichloroplatinum (II) (CDDP)-induced apoptosis via a ROS-mediated pathway involving apoptosis signal-regulating kinase-1 (ASK-1) activation. These findings suggest that the cysteine at the active site of TRX plays a key role in the internalization and signal transduction of extracellular TRX into the cells.

Redox regulation of mast cell histamine release in thioredoxin-1 (TRX) transgenic mice

Thioredoxin-1 (TRX) is a stress-inducible redox-regulatory protein with antioxidative and anti-inflammatory effects. Here we show that the release of histamine from mast cells elicited by cross-linking of high-affinity receptor for IgE (FcepsilonRI) was significantly suppressed in TRX transgenic (TRX-tg) mice compared to wild type (WT) mice. Intracellular reactive oxygen species (ROS) of mast cells stimulated by IgE and antigen was also reduced in TRX-tg mice compared to WT mice. Whereas there was no difference in the production of cytokines (IL-6 and TNF-alpha) from mast cells in response to 2,4-dinitrophenylated bovine serum albumin (DNP-BSA) stimulation in TRX-tg and WT mice. Immunological status of TRX-tg mice inclined to T helper (Th) 2 dominant in primary immune response, although there was no difference in the population of dendritic cells (DCs) and regulatory T cells. We conclude that the histamine release from mast cells in TRX-tg mice is suppressed by inhibition of ROS generation. As ROS are involved in mast cell activation and facilitate mediator release, TRX may be a key signaling molecule regulating the early events in the IgE signaling in mast cells and the allergic inflammation.

Thioredoxin-1 Ameliorates Myosin-Induced Autoimmune Myocarditis by Suppressing Chemokine Expressions and Leukocyte Chemotaxis in Mice

Background— Cardiac myosin–induced myocarditis is an experimental autoimmune myocarditis (EAM) model used to investigate autoimmunological mechanisms in inflammatory heart diseases and resembles fulminant myocarditis in humans. We investigated the therapeutic role of thioredoxin-1 (TRX-1), a redox-regulatory protein with antioxidant and antiinflammatory effects, in murine EAM.

Methods and Results— EAM was generated in 5-week-old male BALB/c mice by immunization with porcine cardiac myosin at days 0 and 7. Recombinant human TRX-1 (rhTRX-1), C32S/C35S mutant rhTRX-1, or saline was administered intraperitoneally every second day from day 0 to 20. In addition, rabbit anti-mouse TRX-1 serum or normal rabbit serum was administered intraperitoneally on days −1, 2, and 6. Animals were euthanized on day 21. Histological analysis of the heart showed that TRX-1 significantly reduced the severity of EAM, whereas mutant TRX-1 failed to have such an effect, and anti–TRX-1 antibody enhanced the disease markedly. Immunohistochemical analysis showed that TRX-1 significantly suppressed cardiac macrophage inflammatory protein (MIP)-1α, MIP-2, and 8-hydroxydeoxyguanosine expression and macrophage infiltration into the heart in EAM. Although serum levels of MIP-1α were not suppressed by TRX-1 until day 21, both an in vitro chemotaxis chamber assay and an in vivo air pouch model showed that TRX-1 significantly suppressed MIP-1α– or MIP-2–induced leukocyte chemotaxis. However, real-time reverse transcription–polymerase chain reaction showed that TRX-1 failed to decrease chemokine receptor expression increased in the bone marrow cells of EAM mice.

Conclusions— TRX-1 attenuates EAM by suppressing chemokine expressions and leukocyte chemotaxis in mice.

TMX, a human transmembrane oxidoreductase of the thioredoxin family: the possible role in disulfide-linked protein folding in the endoplasmic reticulum

Various proteins sharing thioredoxin (Trx)-like active site sequences (Cys-Xxx-Xxx-Cys) have been found and classified in the Trx superfamily. Among them, transmembrane Trx-related protein (TMX) was recently identified as a novel protein possessing an atypical active site sequence, Cys-Pro-Ala-Cys. In the present study, we describe the properties of this membranous Trx-related molecule. Endogenous TMX was detected as a protein of approximately 30 kDa with a cleavable signal peptide. TMX was enriched in membrane fractions and exhibited a similar subcellular distribution with calnexin localized in the endoplasmic reticulum (ER). The examination of membrane topology of TMX suggested that the N-terminal region containing the Trx-like domain was present in the ER lumen, where protein disulfide isomerase (PDI) was found to assist protein folding. Recombinant TMX showed PDI-like activity to refold scrambled RNase. These results indicate the possibility that TMX can modify certain molecules with its oxidoreductase activity and be involved in the redox regulation in the ER.

Cysteine-dependent immune regulation by TRX and MIF/GIF family proteins

Thioredoxin (TRX) superfamily proteins that contain a conserved redox-active site -Cys-Xa.a.-Xa.a.-Cys- includes proinflammatory cytokine, macrophage migration inhibiting factor (MIF) and the immune regulatory cytokine, glycosylation inhibiting factor (GIF) in which Cys-60 is cysteinylated. In this report, we have analyzed the functional interaction between TRX and MIF/GIF. The stable Jurkat T cell line transfected with human TRX gene (TRX-transfectant) was highly resistant to hydrogen peroxide-induced apoptosis, but not the cell line transfected with vector (mock-transfectant). The expression level of MIF/GIF protein of TRX-transfectant was lower than that of mock-transfectant. Conversely, the expression level of intracellular TRX protein in CD4(+)-T cells derived from MIF -/- mice were significantly higher than that from background BALB/c mice. These findings collectively suggest that oxidative stress-induced apoptosis on T lymphocytes might be protected by the reciprocal regulation of TRX and MIF/GIF expression.

Evidence for stanniocalcin gene expression in mammalian bone

Stanniocalcin (STC) acts as a regulator of calcium and phosphate homeostasis in an endocrine manner in bony fish. Recently, complementary DNAs encoding human and mouse STC have been characterized, and the messenger RNA (mRNA) expression was identified in various tissues, such as kidney, small intestine, prostate, thyroid, and ovary. Because previous studies concerning the effects of fish STC on mammalian bone have been discussed, there is a good possibility that mammalian STC is a local factor in bone. Here, we demonstrated STC mRNA expression in neonatal mouse calvaria, the primary cultured mouse osteoblast-rich fractions, and human and mouse osteoblastic cell lines. We also mapped the cellular distribution of the STC mRNA in femur and calvaria in developing mice. Several transcripts with a major 4-kb band were detected in all samples. The cellular distribution of the mRNA expression corresponded closely to osteoblasts in both femur and calvaria. Significant labeling of the STC mRNA was also identified in chondrocytes but not in osteoclasts and other bone marrow elements. These results are the first evidence that hormone may be actually expressed in osteoblasts and chondrocytes, and they strongly implicate the involvement of local STC in both endochondral and membrane bone as an autocrine/paracrine factor.