Use of Serum MicroRNAs as Biomarker for Hepatobiliary Diseases in Dogs

Background

Current biochemical indicators cannot discriminate between parenchymal, biliary, vascular, and neoplastic hepatobiliary diseases. MicroRNAs are promising new biomarkers for hepatobiliary disease in humans and dogs.

Objective

To measure serum concentrations of an established group of microRNAs in dogs and to investigate their concentrations in various types of hepatobiliary diseases.

Animals

Forty‐six client‐owned dogs with an established diagnosis of hepatobiliary disease and stored serum samples and eleven client‐owned healthy control Labrador Retrievers.

Methods

Retrospective study. Medical records of dogs with parenchymal, biliary, vascular, or neoplastic hepatobiliary diseases and control dogs were reviewed. Concentrations of miR‐21, miR‐122, miR‐126, miR‐148a, miR‐200c, and miR‐222 were quantified in serum by real‐time polymerase chain reaction.

Results

No different microRNA concentrations were found in the adenoma and congenital portosystemic shunt groups. In all other diseases, miR‐122 concentrations were elevated with the highest concentration in the mucocele group (267‐fold, CI: 40–1,768, P < .001). In dogs with biliary diseases, miR‐21 and miR‐222 were only increased in dogs with mucoceles (26‐fold, CI: 5–141, P = .005 and 13‐fold, CI: 2–70, P = .025, respectively). Uniquely increased microRNAs were found in the hepatocellular carcinoma group (miR‐200c, 35‐fold increase, CI: 3–382, P = .035) and the chronic hepatitis group (miR‐126, 22‐fold increase, CI: 5–91, P = .002).

Conclusions and Clinical Importance

A microRNA panel consisting of miR‐21, miR‐122, miR‐126, miR‐200c, and miR‐222 can distinguish between parenchymal, biliary, and neoplastic hepatobiliary diseases. Serum microRNA profiling is a promising new tool that might be a valuable addition to conventional diagnostics to help diagnose various hepatobiliary diseases in dogs.

Presentation of chemokine SDF-1 alpha by fibronectin mediates directed migration of T cells

The role of chemokine-matrix interactions in integrin-dependent T-cell migration was examined to address the critical question of how chemokines provide directional information. The chemokine SDF-1 alpha binds fibronectin (Fn) with a low nanomolar K(d) (equilibrium dissociation constant). SDF-1 alpha presented by Fn induced directed migration. Spatial concentration gradients of chemokine were not required to maintain directed migration. Fn-presented chemokine induced the polarization of cells, including the redistribution of the SDF-1 alpha receptor, to the basal surface and leading edge of the cell. A new model for directed migration is proposed in which the co-presentation of an adhesive matrix and chemokine provides the necessary positional information independent of a soluble spatial gradient. (Blood. 2000;96:2682-2690)

Infection by porcine endogenous retrovirus after islet xenotransplantation in SCID mice

Animal donors such as pigs could provide an alternative source of organs for transplantation. However, the promise of xenotransplantation is offset by the possible public health risk of a cross-species infection. All pigs contain several copies of porcine endogenous retroviruses (PERV), and at least three variants of PERV can infect human cell lines in vitro in co-culture, infectivity and pseudotyping experiments. Thus, if xenotransplantation of pig tissues results in PERV viral replication, there is a risk of spreading and adaptation of this retrovirus to the human host. C-type retroviruses related to PERV are associated with malignancies of haematopoietic lineage cells in their natural hosts. Here we show that pig pancreatic islets produce PERV and can infect human cells in culture. After transplantation into NOD/SCID (non-obese diabetic, severe combined immunodeficiency) mice, we detect ongoing viral expression and several tissue compartments become infected. This is the first evidence that PERV is transcriptionally active and infectious cross-species in vivo after transplantation of pig tissues. These results show that a concern for PERV infection risk associated with pig islet xenotransplantation in immunosuppressed human patients may be justified.

The macrophage receptor MARCO

MARCO (macrophage receptor with collagenous structure) belongs to the class A scavenger receptor molecules. The structure and function of the molecule is described. Although it is expressed on subsets of macrophages, it can be upregulated on other macrophages after bacterial infection. The strategic position of MARCO-expressing cells in lymphoid organs suggests an important role for this bacteria-binding molecule in removal of pathogens.

Progression and regression of atherosclerosis in APOE3-Leiden transgenic mice: an immunohistochemical study

Apolipoprotein E3-Leiden (APOE3-Leiden) transgenic mice develop hyperlipidemia and are highly susceptible to diet-induced atherosclerosis. We have studied the progression and regression of atherosclerosis using immunohistochemistry. Female transgenic mice were fed a moderate fat diet to study atherosclerosis over a longer time period. Fatty streaks arose in the intima and consisted of lipid filled macrophages which differed in origin. All macrophages expressed the macrophage scavenger receptor while two thirds expressed sialoadhesin and were positive for an antibody recognizing marginal zone macrophages (MOMA-1). All macrophages were negative for the scavenger receptor MARCO and 50% were positive for CD4. Small fatty streaks contained CD-3 positive T-lymphocytes which were for more than 70% CD4-positive. ICAM-1 was positive both in atherosclerotic and control mice. In early plaques, fibrosis was observed on the luminal and medial site of the foam cells while smooth muscle cells were only observed in the fibrous cap. To study regression, we used a high fat, high cholesterol diet to rapidly induce atherosclerosis (14 weeks). The animals were then fed normal chow. Subsequently, atherosclerosis was assayed over time (4, 8, 16 weeks). Cholesterol levels dropped in 4 weeks to control levels. The animals did not show a significantly decrease in plaque size over time. but the percentage macrophages was significantly smaller in the animals after 4 weeks. In conclusion, the APOE3-Leiden mouse is a useful model to study the progression and regression of atherosclerosis.

Role of macrophage scavenger receptors in hepatic granuloma formation in mice

In mice homozygous for the gene mutation for type I and type II macrophage scavenger receptors (MSR-A), MSR-A-/-, the formation of hepatic granulomas caused by a single intravenous injection of heat-killed Corynebacterium parvum was delayed significantly for 10 days after injection, compared with granuloma formation in wild-type (MSR-A+/+) mice. In the early stage of granuloma formation, numbers of macrophages and their precursor cells were significantly reduced in MSR-A-/- mice compared with MSR-A+/+ mice. In contrast to MSR-A+/+ mice, no expression of monocyte chemoattractant protein-1, tumor necrosis factor-alpha, and interferon-gamma mRNA was observed in MSR-A-/- mice by 3 days after injection. Also in MSR-A-/- mice, uptake of C. parvum by Kupffer cells and monocyte-derived macrophages in the early stage of granuloma formation was lower and elimination of C. parvum from the liver was slower than in MSR-A+/+ mice. In the livers of MSR-A+/+ mice, macrophages and sinusoidal endothelial cells possessed MSR-A, but this was not seen in the livers of MSR-A-/- mice. In both MSR-A-/- and MSR-A+/+ mice, expression of other scavenger receptors was demonstrated. These data suggest that MSR-A deficiency impairs the uptake and elimination of C. parvum by macrophages and delays hepatic granuloma formation, particularly in the early stage.

Regulation and functional involvement of macrophage scavenger receptor MARCO in clearance of bacteria in vivo

The scavenger receptors expressed by macrophages are thought to play an important role in the immune response against bacteria by mediating binding and phagocytosis. A novel member of the class A scavenger receptor family, macrophage receptor with collagenous structure (MARCO), has recently been identified. In this study we have generated a panel of mAbs with specificities for different domains of this receptor. Two of those reacting with the C-terminal cysteine-rich domain block ligand binding of MARCO. The in vivo expression of this murine receptor is normally restricted to distinct populations of macrophages in the spleen and lymph nodes. During bacillus Calmette-Guérin (BCG) infection, during bacterial sepsis, or after the injection of purified LPS, however, the expression of MARCO is rapidly induced on macrophages in other tissues, including Kupffer cells in the liver. Using the mouse macrophage cell line J774.2, it was shown that LPS stimulation up-regulates surface expression of MARCO in a dose- and time-dependent fashion. The proinflammatory cytokines IL-1, IL-6, TNF-alpha, and IFN-gamma had little or no effect. Using inhibitory mAbs, the relevance of MARCO for the clearance of circulating bacteria in vivo was determined. Although the overall elimination of live Escherichia coli and Staphylococcus aureus from the blood did not appear to be affected by treatment with these Abs, the capturing of heat-killed bacteria by macrophages in the marginal zone areas of the spleen was clearly inhibited. This study suggests a role for MARCO in the host antibacterial defense.

Signal-regulatory protein is selectively expressed by myeloid and neuronal cells

Signal-regulatory proteins (SIRP) are transmembrane glycoproteins with three extracellular Ig-like domains, closely related to Ag receptors Ig, TCR, and MHC, and a cytoplasmic domain with two immunoreceptor with tyrosine-based inhibition motifs that can interact with src homology 2 domain-containing phosphatases. SIRP have previously been shown to inhibit signaling through receptor tyrosine kinases, but their physiologic function is unknown. Here we demonstrate by expression cloning that the mAbs ED9, ED17, and MRC-OX41 recognize rat SIRP. In addition, we show for the first time that rat SIRP is selectively expressed by myeloid cells (macrophages, monocytes, granulocytes, dendritic cells) and neurons. Moreover, SIRP ligation induces nitric oxide production by macrophages. This implicates SIRP as a putative recognition/signaling receptor in both immune and nervous systems.

Role of macrophage scavenger receptors in diet-induced atherosclerosis in mice

To clarify the role of type I and type II macrophage scavenger receptors (MSR-A) in the progression of diet-induced atherosclerosis, we generated mice lacking both MSR-A and low-density lipoprotein receptor (LDLR). After 4 or 12 weeks of a high-fat diet, the sizes of atherosclerotic lesions in MSR-A/LDLR double knockout mice were significantly reduced (p < 0.05) compared with those in LDLR single knockout mice. However, atherosclerotic lesions mainly composed of foamy macrophages were still observed in double knockout mice. Formation of atherosclerotic lesions in double knockout mice was partially explained by the participation of scavenger receptors other than MSR-A such as MARCO, CD36, and macrosialin/CD68. These receptors were clearly demonstrated in the atherosclerotic lesions in double knockout mice as well as LDLR single knockout mice by immunohistochemistry or by reverse transcriptase-polymerase chain reaction. Because the very low density lipoprotein (VLDL) fraction was elevated in the double and single knockout mice, we further examined the possibility that VLDL may participate in foam cell formation in atherosclerotic lesions. When incubated with VLDL isolated from LDLR-deficient mice, cholesterol ester accumulation and foamy transformation occurred in MSR-A-deficient macrophages as well as in normal macrophages. These data indicate that MSR-A plays an essential role in the development of diet-induced atherosclerosis. It also appears that other scavenger receptors, such as MARCO, CD36, and macrosialin/CD68, as well as uptake of VLDL are involved in foam cell formation during atherogenesis in MSR-A/LDLR double knockout mice.

The role of the mouse macrophage scavenger receptor in myelin phagocytosis

Myelin phagocytosis during Wallerian degeneration and immune-mediated demyelination depends on the action of mononuclear cells of the monocyte/macrophage system. The present study investigated the role of the macrophage scavenger receptor, a trimeric membrane glycoprotein, in myelin uptake by macrophages. Two in vitro models of myelin phagocytosis were used: an organ culture model of mouse peripheral nerves exposed to cocultured macrophages and a quantitative flow cytometric assay. Different concentrations of the monoclonal rat anti-mouse scavenger receptor antibody (2F8) were applied to these systems to selectively block the macrophage scavenger receptor. Concentration-dependent effects on macrophage migration and myelin uptake were seen when the macrophage scavenger receptor was blocked by the antibody 2F8. Low concentrations reduced myelin phagocytosis by the invading macrophages; higher concentrations completely abolished macrophage invasion of the nerves. Using a quantitative flow cytometric assay it was also shown that the 2F8 antibody inhibits phagocytosis of myelin in a dose-dependent manner. These data indicate that the macrophage scavenger receptor is involved in myelin phagocytosis by macrophages.

Extracellular matrix proteins expressed by human adult astrocytes in vivo and in vitro: an astrocyte surface protein containing the CS1 domain contributes to binding of lymphoblasts

Primary cultures of human astrocytes, expressing glial fibrillary acidic protein (GFAP), were obtained from postmortem brain tissue samples. These cultured astrocytes produced an extracellular matrix (ECM), containing laminin (Ln) and fibronectin (Fn), as shown with specific antibodies. The perinuclear staining observed in these cells indicated that these proteins were de novo synthesized. Monoclonal antibody (mAb) 90.45, which recognizes the CS1 sequence found in an alternatively spliced form of Fn, also stained cultured astrocytes. Immunohistochemical analysis of normal human brain tissue showed positive staining for the CS1 domain, both on protoplasmic and fibrous astrocytes located in the gray and white matter. In contrast to cultured astrocytes, no immunoreactivity for Ln or Fn was found on astrocytes in normal human brain tissue. These in situ data indicate that the CS1 domain expressed by astrocytes is not part of a splicing variant of Fn. Western blot analysis confirmed that the CS1 domain expressed by cultured human astrocytes is part of an astrocyte protein which is different from human Fn. The CS1 domain is a known ligand for the adhesion receptor alpha4beta1 (VLA-4). We found that the human lymphoma cell lines Jurkat and Ramos, which express alpha4beta1, bound to cultured human astrocytes, and that this interaction could be partly blocked by mAb 90.45 or a synthetic CS1 peptide. Thus, the novel CS1-containing surface protein expressed by astrocytes in vitro and in vivo, contributes to binding of lymphoblasts, and therefore may be a relevant adhesion molecule for the recruitment of alpha4-integrin expressing leukocytes into the central nervous system (CNS).

Macrophage phagocytosis of myelin in vitro determined by flow cytometry: phagocytosis is mediated by CR3 and induces production of tumor necrosis factor-alpha and nitric oxide

Demyelination of axons in the central nervous system (CNS) during multiple sclerosis (MS) and its animal model experimental allergic encephalomyelitis (EAE) is a result of phagocytosis and digestion by macrophages (M phi) and the local release of inflammatory mediators like tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO). We have investigated the process of myelin phagocytosis by M phi in vitro using flow cytometric analysis. The binding and uptake of CNS-derived myelin was dose dependent, was abolished in the presence of EDTA and was enhanced after opsonization with complement. The phagocytosis of opsonized myelin could be inhibited by antibodies directed against complement receptor type 3 (CR3). Furthermore, CR3 also contributes to phagocytosis of non-opsonized myelin, e.g. under serum-free conditions. The phagocytosis of CNS-derived myelin induced the production of substantial amounts of TNF-alpha and NO by the M phi. Our results indicate an important role for CR3 in myelin phagocytosis. The induction of TNF-alpha and NO which accompanies this phagocytosis may further contribute to the overall process of demyelination during MS or EAE.

CD66 nonspecific cross-reacting antigens are involved in neutrophil adherence to cytokine-activated endothelial cells

Neutrophil adherence to cytokine-activated endothelial cell (EC) monolayers depends on the expression of the endothelial leukocyte adhesion molecule-1 (ELAM-1). The ligand for ELAM-1 is the sialylated Lewis-x antigen (SLe(x)) structure. The selectin LAM-1 (or LECAM-1) has been described as one of the SLe(x)-presenting glycoproteins involved in neutrophil binding to ELAM-1. Other presenter molecules have not yet been described. Our data demonstrate that the carcinoembryonic antigen (CEA)-like surface molecules on neutrophils--known as the nonspecific cross-reacting antigens (NCAs)--are involved in neutrophil adherence to monolayers of IL-1-beta-activated EC. The NCAs are recognized by CD66 (NCA-160 and NCA-90) and CD67 (NCA-95). Because NCA-95 and NCA-90 have previously been found to be phosphatidylinositol (PI)-linked, paroxysmal nocturnal hemoglobinuria (PNH) neutrophils (which lack PI-linked surface proteins) were tested as well. PNH neutrophils showed a diminished binding to activated EC. CD66 (on PNH cells still recognizing the transmembrane NCA-160 form) still inhibited the adherence of PNH cells to IL-1-beta-activated EC, but to a limited extent. Soluble CEA(-related) antigens inhibited normal neutrophil adherence as well, whereas neutrophil transmigration was unaffected. Sialidase-treatment as well as CD66 preclearing abolished the inhibitory capacity of the CEA(-related) antigens. The binding of soluble CEA antigens to IL-1-beta-pretreated EC was blocked by anti-ELAM-1. These soluble antigens, as well as the neutrophil NCA-160 and NCA-90, both recognized by CD66 antibodies, presented the SLe(x) determinant. Together, these findings indicate that the CD66 antigens (i.e., NCA-160/NCA-90) function as presenter molecules of the SLe(x) oligosaccharide structures on neutrophils that bind to ELAM-1 on EC.