Identification of CD146 as a component of the endothelial junction involved in the control of cell-cell cohesion

Extending the chinchilla middle ear epithelial model for mucin gene investigation

OBJECTIVES

To investigate the expression of recently identified human mucin genes in an in vivo model of the chinchilla middle ear epithelium (CMEE).

METHODS

CMEE was harvested, RNA was extracted and primers were designed for RT-PCR to assess for expression of mucin genes Muc6, Muc17 and Muc18. Further sequencing of these genes was also accomplished.

RESULTS

Mucin genes Muc6, Muc17 and Muc18 was assessed and found to be identical to the expression in human and mouse MEE.

CONCLUSION

This study further characterizes mucin gene expression in the CMEE and provides additional sequence data for chinchilla middle ear genes. The concordance of this gene expression data to that of both the human and mouse models further demonstrates the utility of this animal model in OM investigations.

Human CD133-derived bone marrow stromal cells establish ectopic hematopoietic microenvironments in immunodeficient mice

Cultured adherent bone marrow stromal cells (BMSCs) are capable of forming ectopic hematopoietic microenvironments (HMEs) in immunodeficient mice. However, the cell surface phenotype of the native bone marrow stem/progenitor cell that gives rise to BMSCs that support hematopoiesis remains poorly defined. We recently reported the derivation of human BMSC-like cells (CD133BMSCs) by magnetic cell sorting against Prominin-1 (CD133), an epitope expressed by embryonic, fetal, and adult stem cells. Here we demonstrate that CD133BMSCs are capable of forming ectopic HMEs. Cultured adherent CD133BMSCs derived from sorted CD133-positive cells lacked CD133 expression, but were uniformly positive for CD146, an epitope recently described to identify self-renewing osteoprogenitor cells that could transfer the HME. CD133BMSCs were genetically-tagged by lentivirus, expanded, and seeded into HA/TCP/fibrin constructs that were implanted subcutaneously. After 60days, CD133BMSCs produced human osteocytes, osteoblasts, adipocytes, and reticular cells that supported murine hematopoiesis. CD133BMSCs that were not transduced with lentivirus also formed HMEs. Control constructs seeded with human dermal fibroblasts formed connective tissue, but failed to form HMEs. Our data indicate that CD133 expression identifies a native human bone marrow stem/progenitor cell that gives rise to BMSCs capable of forming the HME.

Epileptic seizures increase circulating endothelial cells in peripheral blood as early indicators of cerebral vascular damage

Circulating endothelial cells (CECs) are nonhematopoetic mononuclear cells in peripheral blood that are dislodged from injured vessels during cardiovascular disease, systemic vascular disease, and inflammation. Their occurrence during cerebrovascular insults has not been previously described. Epileptic seizures cause the long-term loss of cerebrovascular endothelial dilator function. We hypothesized that seizures cause endothelial sloughing from cerebral vessels and the appearance of brain-derived CECs (BCECs), possible early indicators of cerebral vascular damage. Epileptic seizures were induced by bicuculline in newborn pigs; venous blood was then sampled during a 4-h period. CECs were identified in the fraction of peripheral blood mononuclear cells by the expression of endothelial antigens (CD146, CD31, and endothelial nitric oxide synthase) and by Ulex europeaus lectin binding. In control animals, few CECs were detected. Seizures caused a time-dependent increase in CECs 2-4 h after seizure onset. Seizure-induced CECs coexpress glucose transporter-1, a blood-brain barrier-specific glucose transporter, indicating that these cells originate in the brain vasculature and are thus BCECs. Seizure-induced BCECs cultured in EC media exhibited low proliferative potential and abnormal cell contacts. BCEC appearance during seizures was blocked by a CO-releasing molecule (CORM-A1) or cobalt protoporphyrin (heme oxygenase-1 inducer), which prevented apoptosis in cerebral arterioles and the loss of cerebral vascular endothelial function during the late postictal period. These findings suggest that seizure-induced BCECs are injured ECs dislodged from cerebral microvessels during seizures. The correlation between the appearance of BCECs in peripheral blood, apoptosis in cerebral vessels, and the loss of postictal cerebral vascular function suggests that BCECs are early indicators of late cerebral vascular damage.

CD146 short isoform increases the proangiogenic potential of endothelial progenitor cells in vitro and in vivo

RATIONALE

CD146, a transmembrane immunoglobulin mainly expressed at the intercellular junction of endothelial cells, is involved in cell-cell cohesion, paracellular permeability, monocyte transmigration and angiogenesis. CD146 exists as 2 isoforms, short (sh) and long (lg), but which isoform is involved remains undefined.

OBJECTIVE

The recently described role of CD146 in angiogenesis prompted us to investigate which isoform was involved in this process in human late endothelial progenitors (EPCs), with the objective of increasing their proangiogenic potential.

METHODS AND RESULTS

Immunofluorescence experiments showed that, in subconfluent EPCs, shCD146 was localized in the nucleus and at the migrating edges of the membrane, whereas lgCD146 was intracellular. In confluent cells, shCD146 was redistributed at the apical membrane and lgCD146 was directed toward the junction. In contrast to lgCD146, shCD146 was overexpressed in EPCs as compared to mature endothelial cells and upregulated by vascular endothelial growth factor and SDF-1 (stromal cell-derived factor 1). Study of the properties of both isoforms in vitro provided evidence that shCD146 was involved in EPC adhesion to activated endothelium, migration, and proliferation, with a paracrine secretion of interleukin-8 or angiopoietin 2, whereas lgCD146 was implicated in stabilization of capillary-like structures in Matrigel and transendothelial permeability. In an animal model of hindlimb ischemia, transplantation of shCD146-modified EPCs selectively promoted both EPC engraftment and blood flow.

CONCLUSIONS

Altogether, these findings establish that CD146 isoforms display distinct functions in vessels regeneration. Selective improvement of therapeutic angiogenesis by shCD146 overexpression suggests a potential interest of shCD146-transduced EPCs for the treatment of peripheral ischemic disease.

PAX3 expression in normal skin melanocytes and melanocytic lesions (naevi and melanomas)

BACKGROUND

Cutaneous Malignant Melanoma is an aggressive form of skin cancer, arising in cutaneous melanocytes. The transcription factor PAX3 regulates melanocyte specification from neural crest cells during development but expression in differentiated melanocytes is uncertain. By contrast it is frequently found in melanomas and naevi and is a marker for melanoma staging and detection. In this study we analysed the expression of PAX3 across the spectrum of melanocytic cells, from normal melanocytes to cells of benign and malignant lesions to better assess its function in these various tissues. Pax3 and PAX3 (italicized) refer to the mouse and human gene, respectively; whereas Pax3 and PAX3 (non-italicized) refer to the corresponding mouse and human protein.

METHODOLOGY AND PRINCIPAL FINDINGS

PAX3 expression was analysed by immunohistochemistry and qRT-PCR. Immunofluorescence was used for co-expression with differentiation, migration and survival markers. As expected PAX3 expression was observed in naevi and melanoma cells. It was also found in melanocytes of normal skin where it co-expressed with melanocyte markers, MITF and MLANA. Co-expression with its downstream target, antiapoptotic factor BCL2L1 confirms PAX3 as a cell survival regulator. PAX3 was also co-expressed with melanoma cell migration marker MCAM in dermal naevi and melanoma cell nests, but this downstream target of PAX3 was not present in normal epidermal melanocytes, suggesting differential roles for PAX3 in normal epidermal melanocytes and melanoma cells. Most interestingly, a proportion of PAX3-positive epidermal melanocytes in normal skin show HES1 and Ki67 co-expression, indicating their less differentiated proliferative phenotype.

CONCLUSIONS AND SIGNIFICANCE

Our results suggest that a previously identified role for PAX3, that of regulator of an undifferentiated plastic state, may operate in melanocytes of normal skin. This role, possibly required for cellular response to environmental stimuli, may contribute to formation and development of melanocytic lesions in which PAX3 expression is prominent.

Soluble CD146 displays angiogenic properties and promotes neovascularization in experimental hind-limb ischemia

CD146, an endothelial molecule involved in permeability and monocyte transmigration, has recently been reported to promote vessel growth. As CD146 is also detectable as a soluble form (sCD146), we hypothesized that sCD146 could stimulate angiogenesis. Experiments of Matrigel plugs in vivo showed that sCD146 displayed chemotactic activity on endogenous endothelial cells, and exogenously injected late endothelial progenitor cells (EPCs). Recruited endothelial cells participated in formation of vascular-like structures. In vitro, sCD146 enhanced angiogenic properties of EPCs, with an increased cell migration, proliferation, and capacity to establish capillary-like structures. Effects were additive with those of vascular endothelial growth factor (VEGF), and sCD146 enhanced VEGFR2 expression and VEGF secretion. Consistent with a proangiogenic role, gene expression profiling of sCD146-stimulated EPCs revealed an up-regulation of endothelial nitric oxide synthase, urokinase plasminogen activator, matrix metalloproteinase 2, and VEGFR2. Silencing membrane-bound CD146 inhibited responses. The potential therapeutic interest of sCD146 was tested in a model of hind limb ischemia. Local injections of sCD146 significantly reduced auto-amputation, tissue necrosis, fibrosis, inflammation, and increased blood flow. Together, these findings establish that sCD146 displays chemotactic and angiogenic properties and promotes efficient neovascularization in vivo. Recombinant human sCD146 might thus support novel strategies for therapeutic angiogenesis in ischemic diseases.

Outgrowth endothelial cells: sources, characteristics and potential applications in tissue engineering and regenerative medicine

Endothelial progenitor cells from peripheral blood or cord blood are attracting increasing interest as a potential cell source for cellular therapies aiming to enhance the neovascularization of tissue engineered constructs or ischemic tissues. The present review focus on a specific population contained in endothelial progenitor cell cultures designated as outgrowth endothelial cells (OEC) or endothelial colony forming cells from peripheral blood or cord blood. Special attention will be paid to what is currently known in terms of the origin and the cell biological or functional characteristics of OEC. Furthermore, we will discuss current concepts, how OEC might be integrated in complex tissue engineered constructs based on biomaterial or co-cultures, with special emphasis on their potential application in bone tissue engineering and related vascularization strategies.

Soluble CD146 is generated by ectodomain shedding of membrane CD146 in a calcium-induced, matrix metalloprotease-dependent process

CD146 is a cell adhesion molecule localized at the endothelial junction and is involved in the control of cell-cell cohesion. In this study, we showed that calcium influx in human microvascular lung endothelial cells results in the loss of surface CD146 and the release of soluble CD146. This calcium-induced CD146 shedding could be prevented with inhibitors of matrix metalloproteases indicating a central role of matrix metalloproteases in this process. We also investigated if CD146 shedding influences vascular permeability. Endothelial cell monolayers cultured on filter membranes showed an increased permeability for albumin when stimulated with ionomycin. This calcium-induced increase in permeability was inhibited when CD146 shedding was prevented by a matrix metalloprotease inhibitor. Our data indicate that surface CD146 plays a central role in the regulation of vascular permeability and demonstrate that CD146 and matrix metalloproteases are potential targets to modify endothelial barrier function.

Development of microfluidics as endothelial progenitor cell capture technology for cardiovascular tissue engineering and diagnostic medicine

We have developed a unique microfluidic platform capable of capturing circulating endothelial progenitor cells (EPCs) by understanding surface chemistries and adhesion profiles. The surface of a variable-shear-stress microfluidic device was conjugated with 6 different antibodies [anti-CD34, -CD31, -vascular endothelial growth factor receptor-2 (VEGFR-2), -CD146, -CD45, and -von Willebrand factor (vWF)] designed to match the surface antigens on ovine peripheral blood-derived EPCs. Microfluidic analysis showed a shear-stress-dependent decrease in EPC adhesion on attached surface antigens. EPCs exhibited increased adhesion to antibodies against CD34, VEGFR-2, CD31, and CD146 compared to CD45, consistent with their endothelial cell-specific surface profile, when exposed to a minimum shear stress of 1.47 dyn/cm(2). Bone-marrow-derived mesenchymal stem cells and artery-derived endothelial and smooth muscle cells were used to demonstrate the specificity of the EPC microfluidic device. Coated hematopoietic specific-surface (CD45) and granular vWF antibodies, as well as uncoated bare glass and substrate (1% BSA), were utilized as controls. Microfluidic devices have been developed as an EPC capture platform using immobilized antibodies targeted as EPC surface antigens. This EPC chip may provide a new and effective tool for addressing challenges in cardiovascular disease and tissue engineering.

CD146 and its soluble form regulate monocyte transendothelial migration

OBJECTIVES

During inflammation, cell adhesion molecules are modulated or redistributed for leukocyte transmigration. Among molecules at the interendothelial junction, CD146 is involved in cell-cell cohesion and permeability, but its role in monocyte transmigration is unknown.

METHODS AND RESULTS

TNF enhanced CD146 expression at the junction and apical membrane of human umbilical veins endothelial cells (HUVECs) through CD146 synthesis and intracellular store redistribution. In addition, TNF increased the release of a soluble form (sCD146) through a metalloproteinase-dependent mechanism. The redistribution of CD146 to the junction led us to investigate its role in monocyte transmigration using THP1 and freshly isolated monocytes. Evidence that CD146 contributes to monocyte transmigration was provided by inhibition experiments using anti-CD146 antibodies and CD146 siRNA in HUVECs. In addition, sCD146 specifically bound both monocytes and HUVECs and dose-dependently increased monocyte transmigration. Assessment of sCD146 binding on immobilized CD146 failed to evidence any homophilic interaction. Together, our data suggest endothelial CD146 binds heterophilically with a yet unknown ligand on monocytes.

CONCLUSIONS

Our results demonstrate that CD146 is regulated by the inflammatory cytokine TNF and that CD146 and sCD146 are both involved in monocyte transendothelial migration during inflammation.

CD146 expression is associated with a poor prognosis in human breast tumors and with enhanced motility in breast cancer cell lines

Introduction

Metastasis is a complex process involving loss of adhesion, migration, invasion and proliferation of cancer cells. Cell adhesion molecules play a pivotal role in this phenomenon by regulating cell–cell and cell–matrix interactions. CD146 (MCAM) is associated with an advanced tumor stage in melanoma, prostate cancer and ovarian cancer. Studies of CD146 expression and function in breast cancer remain scarce except for a report concluding that CD146 could act as a tumor suppressor in breast carcinogenesis.

Methods

To resolve these apparent discrepancies in the role of CD146 in tumor cells, we looked at the association of CD146 expression with histoclinical features in human primary breast cancers using DNA and tissue microarrays. By flow cytometry, we characterized CD146 expression on different breast cancer cell lines. Using siRNA or shRNA technology, we studied functional consequences of CD146 downmodulation of MDA-MB-231 cells in migration assays. Wild-type, mock-transfected and downmodulated transfected cells were profiled using whole-genome DNA microarrays to identify genes whose expression was modified by CD146 downregulation.

Results

Microarray studies revealed the association of higher levels of CD146 with histoclinical features that belong to the basal cluster of human tumors. Expression of CD146 protein on epithelial cells was detected in a small subset of cancers with histoclinical features of basal tumors. CD146⁺ cell lines displayed a mesenchymal phenotype. Downmodulation of CD146 expression in the MDA-MB-231 cell line resulted in downmodulation of vimentin, as well as of a set of genes that include both genes associated with a poor prognosis in a variety of cancers and genes known to promote cell motility. In vitro functional assays revealed decreased migration abilities associated with decreased CD146 expression.

Conclusions

In addition to its expression in the vascular compartment, CD146 is expressed on a subset of epithelial cells in malignant breast. CD146 may directly or indirectly contribute to tumor aggressiveness by promoting malignant cell motility. Changes in molecular signatures following downmodulation of CD146 expression suggest that CD146 downmodulation is associated with the reversal of several biological characteristics associated with epithelial to mesenchymal transition, and the phenomenon associated with the metastatic process.

Increased expression of VEGF and CD146 in patients with inflammatory bowel disease

BACKGROUND

Angiogenesis has been suggested as an integral part of inflammatory bowel disease pathology. Vascular endothelial growth factor has long been considered to play a central, specific role in angiogenesis. Endothelial junction adhesion molecules, such as CD146, have recently been suggested to play a potent role in angiogenesis. CD34 is expressed on vascular endothelium, and it has been reported to be upregulated on endothelium in IBD. We investigated the expression of tissue vascular endothelial growth factor, CD34 and CD146 in the inflamed mucosa of patients with active inflammatory bowel disease compared with no inflamed mucosa of healthy controls.

METHODS

Forty-two IBD patients [23 ulcerative colitis, 19 Crohn's disease] and ten healthy controls were included in the study. In colonoscopically obtained biopsies, CD34, CD146 and vascular endothelial growth factor expression were evaluated by immunohistochemistry.

RESULTS

Vascular endothelial growth factor was detected in the mucosa of all groups, and its expression was significantly higher in both Crohn's disease and ulcerative colitis compared with controls (p<0.05). Immunohistochemical staining for CD146 in the inflamed mucosa was significantly higher in both Crohn's disease and ulcerative colitis compared with controls (p=0.002). A trend of higher CD34 expression in Crohn's disease and ulcerative colitis compared with controls was also found, but the difference among the three groups was not statistically significant (p=0.09).

CONCLUSIONS

Inflamed mucosa of patients with active Crohn's disease and ulcerative colitis showed a markedly enhanced expression of VEGF and CD146, than normal mucosa of controls, indicating a possible role of angiogenesis in the pathogenesis of inflammatory bowel disease.

Multipotent mesenchymal stromal cells obtained from diverse human tissues share functional properties and gene-expression profile with CD146+ perivascular cells and fibroblasts

OBJECTIVE

The relationship of multipotent mesenchymal stromal cells (MSC) with pericytes and fibroblasts has not been established thus far, although they share many markers of primitive marrow stromal cells and the osteogenic, adipogenic, and chondrogenic differentiation potentials.

MATERIALS AND METHODS

We compared MSCs from adult or fetal tissues, MSC differentiated in vitro, fibroblasts and cultures of retinal pericytes obtained either by separation with anti-CD146 or adhesion. The characterizations included morphological, immunophenotypic, gene-expression profile, and differentiation potential.

RESULTS

Osteogenic, adipocytic, and chondrocytic differentiation was demonstrated for MSC, retinal perivascular cells, and fibroblasts. Cell morphology and the phenotypes defined by 22 markers were very similar. Analysis of the global gene expression obtained by serial analysis of gene expression for 17 libraries and by reverse transcription polymerase chain reaction of 39 selected genes from 31 different cell cultures, revealed similarities among MSC, retinal perivascular cells, and hepatic stellate cells. Despite this overall similarity, there was a heterogeneous expression of genes related to angiogenesis, in MSC derived from veins, artery, perivascular cells, and fibroblasts. Evaluation of typical pericyte and MSC transcripts, such as NG2, CD146, CD271, and CD140B on CD146 selected perivascular cells and MSC by real-time polymerase chain reaction confirm the relationship between these two cell types. Furthermore, the inverse correlation between fibroblast-specific protein-1 and CD146 transcripts observed on pericytes, MSC, and fibroblasts highlight their potential use as markers of this differentiation pathway.

CONCLUSION

Our results indicate that human MSC and pericytes are similar cells located in the wall of the vasculature, where they function as cell sources for repair and tissue maintenance, whereas fibroblasts are more differentiated cells with more restricted differentiation potential.

Transendothelial migration of leukocytes is promoted by plasma from a subgroup of immune thrombocytopenic purpura patients with small-vessel ischemic brain disease

We previously described a subgroup of immune thrombocytopenic purpura (ITP) patients presenting with recurring transient ischemic attack-like symptoms and progressive cognitive impairment due to small vessel disease (SVD) seen in the brain. They presented minimal bleeding despite thrombocytopenia, and platelet activation was elevated compared to classic ITP. On the hypothesis that the blood-brain barrier (BBB) is compromised in this subgroup, we investigated the effect of plasma from SVD-ITP patients on the transendothelial migration of leukocytes (TEML). Brain microvascular endothelial cells (BMVEC) were grown to confluence on 6.5-microm pore filters and plasma from 10 healthy controls, 20 classic ITP, and 5 SVD-ITP were added and incubated 24 hr. Then 1 x 10(5) monocytes (U937) were added and the number migrated through the EC monolayer after 6 hr was measured by flow cytometry. The effect on TEML of danazol was also assessed. We found that plasma from SVD-ITP but not classic ITP induced 10-fold rise in EC activation marker CD62E and a sevenfold increase in TEML, to 38.5% +/- 12.5% of cells migrated, compared to normal controls (5.6% +/- 1.2%) or classic ITP (6.1% +/- 0.2%), P < 0.001. Preincubation of U937 with endothelial microparticles (EMP) increased TEML by 20.0% +/- 6.4% with SVD-ITP plasma, significantly more than with classic ITP or control plasmas, P = 0.003. Pretreatment of cultures with danazol (100 microg/mL) inhibited TEML by 25% in all wells tested, whether or not EMP were added. In summary, SVD-ITP plasma activates EC and augments TEML, suggesting plasma-mediated BBB dysfunction in this syndrome. Danazol modestly but significantly inhibited TEML.

Dilation-dependent activation of platelets and prothrombin in human thoracic ascending aortic aneurysm

OBJECTIVE

The purpose of this study was to investigate whether thoracic ascending aortic aneurysm (TAAA) induces platelet activation as mural thrombus participates in aortic dilatation in abdominal aortic aneurysm and TAAA are associated with rheological factors favoring coagulation activation.

METHODS AND RESULTS

We studied the relation between coagulation activation and aortic diameter in Marfan patients (MFS) with various aortic diameters (n=52). We then studied patients presenting large aneurysms associated with bicuspid aortic valve (BAV) and degenerative form. Lastly, we used immunochemistry and biochemistry to investigate prothrombin/thrombin retention within the aortic wall. Microparticles, sGPV, tissue factor, and TAT complexes were increased in plasma from MFS with large aneurysms (>or=45 mm) compared to MFS with limited aortic dilatation (<45 mm). Similar elevations were observed in all patients with large aortic aneurysms, regardless of the etiology, the site of maximal aortic dilation, associated valvulopathy, risk factors, or treatments. P-selectin and platelet-bound fibrinogen were also increased, demonstrating platelet activation in large aneurysms. Significant increase in sCD146 plasma concentration suggested alteration of endothelium.

CONCLUSIONS

Platelet activation occurs in patients with large aneurysms of the ascending aorta, is dependent on aortic dilation, and is associated with thrombin generation, part of which appears to be retained in mucoid degeneration areas.

Peripheral blood endothelial progenitors as potential reservoirs of Kaposi's sarcoma-associated herpesvirus

Background

The cellular reservoirs of Kaposi's sarcoma-associated herpesvirus (KSHV) and the exact nature of the putative KSHV-infected circulating precursor of spindle cells of Kaposi's sarcoma (KS) still remain poorly defined. Because KS spindle cells are thought to be of endothelial origin, and because mature endothelial cells do not sustain persistent KSHV-infection, our attention was focalized on circulating hematopoietic precursors able to differentiate into endothelial lineage.

Methods and Findings

Late endothelial progenitor cells (late-EPCs) were cultured from the peripheral blood mononuclear cells of 16 patients with classic KS. The presence and load of KSHV genomes were analyzed by real-time polymerase chain reaction in DNA extracted from cells and supernatants of late-EPC cultures obtained from 7 patients. Endothelial colonies cultured from the peripheral blood of KS patients were found to satisfy all requisites to be defined late-EPCs: they appeared from the CD14-negative fraction of adherent cells after 11–26 days of culture, could be serially expanded in vitro, expressed high levels of endothelial antigens but lacked leukocyte markers. Late-EPC cultures were found to harbor KSHV-DNA at variable levels and to retain the virus after multiple passages in cells as well as in supernatants, suggesting that a quote of KSHV lytic infection may spontaneously occur. Lytic phase induction or hypoxia could amplify virus release in supernatants.

Conclusion

Our results suggest that circulating endothelial progenitors from KS patients are KSHV-infected and support viral productive replication and may therefore represent potential virus reservoirs and putative precursors of KS spindle cells.

Murine CD146 is widely expressed on endothelial cells and is recognized by the monoclonal antibody ME-9F1

The endothelium plays an important role in the exchange of molecules, but also of immune cells between blood and the underlying tissue. The endothelial molecule S-Endo 1 antigen (CD146) is preferentially located at endothelial junctions and has been claimed to support endothelial integrity. In this study we show that the monoclonal antibody ME-9F1 recognizes the extracellular portion of murine CD146. Making use of ME-9F1 we found CD146 highly expressed and widely spread on endothelial cells in the analyzed murine tissues. In contrast to humans that express CD146 also on T cells or follicular dendritic cells, murine CD146 albeit at low levels was only found on a subset of NK1.1+ cells. The antibody against murine CD146 is useful for immunomagnetic sorting of primary endothelial cells not only from the liver but from various other organs. In vitro, no evidence was seen that the formation and integrity of endothelial monolayers or the transendothelial migration of T cells was affected by antibody binding to CD146 or by crosslinking of the antigen. This makes the antibody ME-9F1 an excellent tool especially for the ex vivo isolation of murine endothelial cells intended to be used in functional studies.

Dual role of melanoma cell adhesion molecule (MCAM)/CD146 in lymphocyte endothelium interaction: MCAM/CD146 promotes rolling via microvilli induction in lymphocyte and is an endothelial adhesion receptor

The melanoma cell adhesion molecule (MCAM)/CD146 is expressed as two isoforms differing by their cytoplasmic domain (MCAM long (MCAM-l) and MCAM short (MCAM-s)). MCAM being expressed by endothelial cells and activated T cells, we analyzed its involvement in lymphocyte trafficking. The NK cell line NKL1 was transfected by MCAM isoforms and submitted to adhesion on both the endothelial cell monolayer and recombinant molecules under shear stress. MCAM-l transfection reduced rolling velocity and increased NKL1 adhesion on the endothelial cell monolayer and VCAM-1. Scanning electron microscopy revealed that MCAM-l induced microvilli formation and extension. In contrast, MCAM short or mock transfection had no effect on adhesion of NKL1 cells and microvilli formation. As shown by mutagenesis, serine 32 of the MCAM-l cytoplasmic tail, belonging to a putative protein kinase C phosphorylation site, was necessary for MCAM-l-actin cytoskeleton interaction and microvilli induction. Accordingly, chelerythrine chloride, a protein kinase C inhibitor, abolished MCAM-l-induced microvilli and rolling of MCAM-l-transfected NKL1 cells. Inhibition of adhesion under shear stress by anti-MCAM Abs suggested that both lymphoid MCAM-l and endothelial MCAM were also directly involved in lymphocyte endothelium interaction. MCAM-l-transfected NKL1 and activated CD4 T cells adhered to rMCAM under shear stress whereas anti-MCAM Ab treatment inhibited this process. Taken together, these data establish that MCAM is involved in the initial steps of lymphocyte endothelium interaction. By promoting the rolling on the inflammation marker VCAM-1 via microvilli induction and displaying adhesion receptor activity involving possible homophilic MCAM-l-MCAM-l interactions, MCAM might be involved in the recruitment of activated T cells to inflammation sites.

Cell adhesion molecule DM-GRASP presented as nanopatterns to neurons regulates attachment and neurite growth

Adhesion and neurite formation of neurons and neuroblastoma cells critically depends on the lateral spacing of the cell adhesion molecule DM-GRASP offered as nanostructured substrate.

A unique population of effector memory lymphocytes identified by CD146 having a distinct immunophenotypic and genomic profile

Background

CD146 is a well described homotypic adhesion molecule found on endothelial cells and a limited number of other cell types. In cells from the peripheral circulation, CD146 has also been reported to be on activated lymphocytes in vitro and in vivo. The function associated with CD146 expression on lymphoid cells is unknown and very little information is available concerning the nature of CD146+ lymphocytes. In the current study, lymphocytes from healthy donors were characterized based upon the presence or absence of CD146 expression.

Results

CD146 was expressed on a low percentage of circulating T lymphocytes, B lymphocytes, and NK cells in healthy individuals. CD146 expression can be induced and upregulated in vitro on both B cells and T cells, but does not correlate with the expression of other markers of T cell activation. CD146 positive T cells do not represent clonal expansions as determined with the use of anti Vβ reagents. Data suggest that CD146 positive cells have enhanced adherence to endothelial monolayers in vitro. Gene profiling and immunophenotyping studies between CD146+ and CD146- T cells revealed several striking genotypic distinctions such as the upregulation of IL-8 and phenotypic differences including the paucity of CCR7 and CD45RA among CD146 positive T cells, consistent with effector memory function. A number of genes involved in cell adhesion, signal transduction, and cell communication are dramatically upregulated in CD146+ T cells compared to CD146- T cells.

Conclusion

CD146 appears to identify small, unique populations of T as well as B lymphocytes in the circulation. The T cells have immunophenotypic characteristics of effector memory lymphocytes. The characteristics of these CD146+ lymphocytes in the circulation, together with the known functions in cell adhesion of CD146 on endothelial cells, suggests that these lymphocytes may represent a small subpopulation of cells primed to adhere to the endothelium and possibly extravasate to sites of inflammation.

Elevation of serum adiponectin and CD146 levels in diabetic nephropathy

OBJECTIVE

The present study was undertaken to measure serum levels of adiponectin and CD146, an endothelial cell injury marker, and to clarify the property of adiponectin and CD146 in patients with diabetic nephropathy.

DESIGN

A total of 280 diabetic patients, and 49 control subjects were enrolled. Serum levels of adiponectin and CD146 were measured by ELISA.

RESULTS

Serum adiponectin levels were relatively low in the diabetic patients as compared to the control subjects. Inversely, serum adiponectin levels were significantly greater in those with stages IV and V of diabetic nephropathy than the control subjects. Serum CD146 levels were gradually increased according to the progression of diabetic nephropathy, and that in the stages IIIb-V was significantly greater than that in the control group. Serum adiponectin positively correlated with serum creatinine and negatively correlated with 1/creatinine. Similar results were obtained with serum CD146 levels. However, there was no relationship between serum adiponectin and CD146 levels.

CONCLUSION

These results indicate that serum adiponectin levels seem to reduce in the diabetic patients, and finally increase in end stage of diabetic nephropathy. In contrast, serum CD146 may closely associate with development of micro- and macrovascular complications in diabetic patients. Further study is required to elucidate the exact role of adiponectin and CD146 in the development of vascular complication in end stage of diabetic nephropathy.

Endothelial adherens and tight junctions in vascular homeostasis, inflammation and angiogenesis

Endothelial cells lining the vessel wall are connected by adherens, tight and gap junctions. These junctional complexes are related to those found at epithelial junctions but with notable changes in terms of specific molecules and organization. Endothelial junctional proteins play important roles in tissue integrity but also in vascular permeability, leukocyte extravasation and angiogenesis. In this review, we will focus on specific mechanisms of endothelial tight and adherens junctions.

Improved identification of endothelial erosion by simultaneous detection of endothelial cells (CD31/CD34) and platelets (CD42b)

Loss of endothelial cells (ECs) with ensuing exposure of thrombogenic subendothelial surface is a common cause of thromboembolic complications in atherosclerotic arteries. Thus, endothelial denudation has emerged as a major contributor to the pathogenesis of atherosclerosis and its complications. Despite ongoing efforts in elucidating the pathogenesis of endothelial erosions in human atherosclerotic arteries, the mechanisms of erosion have remained enigmatic, partly due to lack of well-established methods for its identification. Here the authors point out plausible pitfalls in the current methodology and provide an improved immunohistochemical method for identifying endothelial erosion; i.e., immunofluorescence double staining with antibodies against CD42b and CD31/CD34. This method enables reliable detection of ECs and platelets in the same staining by allowing detection of "pseudoendothelium" caused by CD31 staining of a thin platelet layer covering sites of endothelial erosion. As erosion with a luminal platelet thrombus is likely to represent an in vivo erosion, and erosion without platelets an ex vivo artefact, the method makes it possible to exclude artefactual erosions resulting from sample processing. The novel immunostaining protocol presented here allows more reliable detection of endothelial erosions and so may facilitate studies on the mechanisms involved in the pathogenesis of plaque erosion and acute coronary syndromes.

Expression and distribution of MUC18 in human uveal melanoma

The immunoglobulin superfamily protein MUC18 is involved in transendothelial migration and signal transduction, and is expressed in malignancies including cutaneous melanoma. Recent in vitro studies showed evidence of increased MUC18 protein in some uveal melanoma cell lines with an increased potential for invasion. We assessed seven uveal and three metastasis-derived melanoma cell lines for the expression of MUC18 mRNA and protein by RT-PCR, and immunoblotting and immunocytochemistry, respectively. We also examined the expression and distribution of MUC18 in paraffin sections of primary uveal melanomas (n = 23; 5/23 spindle; 18/23 mixed and epithelioid) and normal eyes (n = 3) using a polyclonal goat anti-human antibody to MUC18 visualized with peroxidase and Vector NovaRED. Distribution and intensity of immunostaining was graded semi-quantitatively (grade 0 to 3) by 2 independent observers. All cell lines expressed MUC18 mRNA and protein ( approximately 130 kDa), and showed punctate cell membrane MUC18 immunostaining. Primary melanomas displayed heterogeneous cell membrane and cytoplasmic MUC18, with moderate to strong immunolabelling (> or =grade 2) in approximately 70% of tumours. Vasculature in tumours and in retina and choroid of all melanoma-affected and normal eyes showed intense MUC18 immunostaining. These observations further suggest a role for MUC18 in uveal melanoma growth; moreover, interactions between MUC18-positive melanoma cells and vasculature may be important for the hematogenous spread of cells during metastases.

Human hepatic stem cells from fetal and postnatal donors

Human hepatic stem cells (hHpSCs), which are pluripotent precursors of hepatoblasts and thence of hepatocytic and biliary epithelia, are located in ductal plates in fetal livers and in Canals of Hering in adult livers. They can be isolated by immunoselection for epithelial cell adhesion molecule–positive (EpCAM+) cells, and they constitute ∼0.5–2.5% of liver parenchyma of all donor ages. The self-renewal capacity of hHpSCs is indicated by phenotypic stability after expansion for >150 population doublings in a serum-free, defined medium and with a doubling time of ∼36 h. Survival and proliferation of hHpSCs require paracrine signaling by hepatic stellate cells and/or angioblasts that coisolate with them. The hHpSCs are ∼9 μm in diameter, express cytokeratins 8, 18, and 19, CD133/1, telomerase, CD44H, claudin 3, and albumin (weakly). They are negative for α-fetoprotein (AFP), intercellular adhesion molecule (ICAM) 1, and for markers of adult liver cells (cytochrome P450s), hemopoietic cells (CD45), and mesenchymal cells (vascular endothelial growth factor receptor and desmin). If transferred to STO feeders, hHpSCs give rise to hepatoblasts, which are recognizable by cordlike colony morphology and up-regulation of AFP, P4503A7, and ICAM1. Transplantation of freshly isolated EpCAM+ cells or of hHpSCs expanded in culture into NOD/SCID mice results in mature liver tissue expressing human-specific proteins. The hHpSCs are candidates for liver cell therapies.

Mascot file parsing and quantification (MFPaQ), a new software to parse, validate, and quantify proteomics data generated by ICAT and SILAC mass spectrometric analyses: application to the proteomics study of membrane proteins from primary human endothelial cells

Proteomics strategies based on nanoflow (nano-) LC-MS/MS allow the identification of hundreds to thousands of proteins in complex mixtures. When combined with protein isotopic labeling, quantitative comparison of the proteome from different samples can be achieved using these approaches. However, bioinformatics analysis of the data remains a bottleneck in large scale quantitative proteomics studies. Here we present a new software named Mascot File Parsing and Quantification (MFPaQ) that easily processes the results of the Mascot search engine and performs protein quantification in the case of isotopic labeling experiments using either the ICAT or SILAC (stable isotope labeling with amino acids in cell culture) method. This new tool provides a convenient interface to retrieve Mascot protein lists; sort them according to Mascot scoring or to user-defined criteria based on the number, the score, and the rank of identified peptides; and to validate the results. Moreover the software extracts quantitative data from raw files obtained by nano-LC-MS/MS, calculates peptide ratios, and generates a non-redundant list of proteins identified in a multisearch experiment with their calculated averaged and normalized ratio. Here we apply this software to the proteomics analysis of membrane proteins from primary human endothelial cells (ECs), a cell type involved in many physiological and pathological processes including chronic inflammatory diseases such as rheumatoid arthritis. We analyzed the EC membrane proteome and set up methods for quantitative analysis of this proteome by ICAT labeling. EC microsomal proteins were fractionated and analyzed by nano-LC-MS/MS, and database searches were performed with Mascot. Data validation and clustering of proteins were performed with MFPaQ, which allowed identification of more than 600 unique proteins. The software was also successfully used in a quantitative differential proteomics analysis of the EC membrane proteome after stimulation with a combination of proinflammatory mediators (tumor necrosis factor-alpha, interferon-gamma, and lymphotoxin alpha/beta) that resulted in the identification of a full spectrum of EC membrane proteins regulated by inflammation.

Visualization of CD146 dimerization and its regulation in living cells

Our previous study showed that the adhesion molecule CD146 as a biomarker is over-expressed on activated endothelium during angiogenesis, which was induced by tumor conditional medium and inhibited by anti-CD146 monoclonal antibody (mAb AA98). However, the CD146 molecular organization on the cells is unknown. Here, using immunoprecipitation, we found that the dimerization of CD146 occurs in both normal and tumor cells. However, the dimer/monomer ratio was higher in tumor cells than in normal cells. Moreover, we found that CD146 dimerization was up-regulated by tumor conditional medium through the NF-kappa B pathway and down-regulated by mAb AA98. To further confirm that CD146 dimerization occurs in living cells, we used fluorescence resonance energy transfer (FRET) with melanoma Mel888 cells co-expressing CFP/YFP-tagged CD146 fusion proteins. By acceptor photobleaching, we observed a strong FRET signal produced by these two fluorescence-tagged proteins. The FRET efficiency reached 20.1%. Our data provide the first evidence that CD146 dimerization occurs in living cells and is regulated within the tumor microenvironment, implying that dimerization of CD146 may be associated with malignancy.

Glomerulus-specific mRNA transcripts and proteins identified through kidney expressed sequence tag database analysis

The kidney glomerulus plays a crucial role in blood filtration but the molecular composition and physiology of the glomerulus is not well understood. We previously constructed and large-scale sequenced four mouse glomerular expressed sequence tag (EST) libraries from newborn and adult mouse glomeruli. Here, we compared glomerular EST profiles with whole kidney EST profiles, thereby identifying 497 transcripts corresponding to UniGene clusters that were glomerulus-enriched, that is expressed more abundantly in glomeruli than in whole kidney. These include several known protein-coding glomerulus-specific transcripts critical for glomerulus development and function, but also a large number of gene transcripts, which have not previously been shown to be expressed in the glomerulus, or implicated in glomerular functions. We used in situ hybridization to demonstrate glomerulus-specific RNA expression for six novel glomerular genes and the public Human Protein Atlas to verify glomerular protein expression for another two. The higher mRNA abundance for the eight genes in glomeruli compared with whole kidney was also verified by Taqman quantitative polymerase chain reaction. We surmise that the further characterization of these genes and proteins will increase our understanding of glomerular development and physiology.

sVE-cadherin and sCD146 serum levels in patients with multiple myeloma

The role of angiogenesis in multiple myeloma (MM) pathogenesis is well established. Angiogenesis is linked to the functional state of endothelial junctions that are modulated by the growth and activation of endothelial cells. CD146 and vascular endothelial-cadherin (VE-cadherin) are cell adhesion molecules localized at the endothelial junction. The aim of the study was to assess sVE-cadherin and sCD146 serum levels in MM patients. Forty-six untreated patients with MM were included in this study. In addition, 23 of 46 patients were analyzed again in partial remission after initial chemotherapy. Twenty-two samples from healthy volunteers were evaluated as the control. There was no significant difference in sCD146 level between MM patients and the control (511 +/- 177.2 vs. 460.9 +/- 156.9 ng/ml respectively). In untreated MM patients, sVE-cadherin level was significantly higher than in the control (1.36 +/- 0.55 vs. 0.63 +/- 0.56 ng/ml respectively; P < 0.05). In untreated MM patients, sVE-cadherin level was significantly higher than in MM patients in partial remission (1.36 +/- 0.55 vs. 0.5 +/- 0.33 respectively; P < 0.05). sVE-cadherin but not sCD146 serum level was increased in untreated MM patients and decreases after chemotherapy in patients in partial remission. VE-cadherin may reflect intensity of angiogenesis in MM and may be useful in prognosis of response to treatment.

Cell-cell adhesion in lung endothelium

Homotypic cell-cell adhesion is essential for tissue and organ development, remodeling, regeneration, and physiological function. Whereas a significant number of homotypic cell-cell adhesion molecules have been identified, much more is known about those concentrated in epithelia than in endothelia. Among the endothelial cell-cell adhesion molecules, very little is known that is specific to endothelium in the pulmonary and bronchial circulations. This review focuses primarily on homotypic cell-cell adhesion molecules that are or are likely to be important in lung endothelium.

M-CAM expression as marker of poor prognosis in epithelial ovarian cancer

Currently available clinico-pathologic criteria provide an imperfect assessment of outcome for patients with advanced epithelial ovarian cancer (EOC). Identification of prognostic factors related to tumor biology might improve this assessment. We investigated the prognostic significance of the melanoma cell adhesion molecule (M-CAM) in EOC. Using the same antibody, M-CAM expression was tested by Western blotting in protein extracts and by immunohistochemestry in tissue microarrays generated from 133 consecutively resected, well characterized EOC samples. Fisher test, Kaplan-Meier method and Cox proportional hazards analysis were used to relate M-CAM expression to clinico-pathological variables and to time to progression (TTP) and overall survival (OS). In vitro biochemical analysis showed a progressively increased M-CAM expression from normal to malignant cells. M-CAM protein, detected immunohistochemically, was significantly associated with advanced tumor stage, serous and undifferentiated histotype, extent of residual disease and p53 accumulation. Presence or absence of M-CAM significantly divided patients according to their TTP (median, 22 vs. 79 months, respectively; log-rank p = 0.001) and OS (median, 42 vs. 131 months, respectively; log-rank p = 0.0003). In the subgroup of advanced stage patients who achieved complete response after front-line treatment, M-CAM expression and absence of residual disease were significantly associated with shorter TTP (p = 0.003, HR 5.25, 95% Cl 1.79-15.41 and p = 0.011, HR 3.77, 95% Cl 1.36-10.49 respectively) at the multivariate level. In the same sub-group of patients, M-CAM expression remained the only parameter significantly associated with OS (p = 0.005, HR 3.35, 95% Cl 1.42-6.88). M-CAM is a marker of early relapse and poorer outcome in EOC. In particular, M-CAM expression identifies a subgroup of front-line therapy-responding patients who undergo dramatic relapses, thus helping to better select patients who might benefit from new/alternative therapeutic modalities.

Circulating endothelial cells in cardiovascular disease

Quantification of circulating endothelial cells (CECs) in peripheral blood is developing as a novel and reproducible method of assessing endothelial damage/dysfunction. The CECs are thought to be mature cells that have detached from the intimal monolayer in response to endothelial injury and are a different cell population to endothelial progenitor cells (EPCs). The EPCs are nonleukocytes derived from the bone marrow that are believed to have proliferative potential and may be important in vascular regeneration. Currently accepted methods of CEC quantification include the use of immunomagnetic bead separation (with cell counting under fluorescence microscopy) and flow cytometry. Several recent studies have shown increased numbers of CECs in cardiovascular disease and its risk factors, such as unstable angina, acute myocardial infarction, stroke, diabetes mellitus, and critical limb ischemia, but no change in stable intermittent claudication, essential hypertension, or atrial fibrillation. Furthermore, CEC quantification at 48 h after acute myocardial infarction has been shown to be an accurate predictor of major adverse coronary events and death at both 1 month and 1 year. This article presents an overview of the pathophysiology of CECs in the setting of cardiovascular disease and a brief comparison with EPCs.

A dileucine motif targets MCAM-l cell adhesion molecule to the basolateral membrane in MDCK cells

Melanoma cell adhesion molecule (MCAM), an adhesion molecule belonging to the Ig superfamily, is an endothelial marker and is expressed in different epithelia. MCAM is expressed as two isoforms differing by their cytoplasmic domain: MCAM-l and MCAM-s (long and short). In order to identify the respective role of each MCAM isoform, we analyzed MCAM isoform targeting in polarized epithelial Madin-Darby canine kidney (MDCK) cells using MCAM-GFP chimeras. Confocal microscopy revealed that MCAM-s and MCAM-l were addressed to the apical and basolateral membranes, respectively. Transfection of MCAM-l mutants established that a single dileucine motif (41-42) of the cytoplasmic domain was required for MCAM-l basolateral targeting in MDCK cells. Although double labelling experiments showed that MCAM-l is not a component of adherens junctions and focal adhesions, its expression on basolateral membranes suggests that MCAM-l is involved in epithelium insuring.

Retention of a differentiated endothelial phenotype by outgrowth endothelial cells isolated from human peripheral blood and expanded in long-term cultures

Rapid adequate vascularization by autologous human endothelial cells remains a limiting step in the treatment of ischemic tissues and the generation of new tissues. We have expanded outgrowth endothelial cells (OEC) from human peripheral blood and investigated their phenotypic stability in long-term cultures. Our goal has been to obtain suitable numbers of autologous endothelial cells for pro-angiogenic cell therapies. Mononuclear cells were isolated from human peripheral blood. During culture, cells were characterized for several endothelial and stem cell markers in mono- or in co-culture with mature endothelial cells. In cultures from peripheral blood, we observed cells with a variable ability to assume a differentiated endothelial phenotype. Most of the cells showed markers reported for endothelial progenitor cells or hemangioblasts (CD31, KDR, VE-cadherin, CD34, CD117, CD45) but failed to develop a differentiated phenotype. Caveolin-1 was not detectable in these cells by reverse transcription/polymerase chain reaction (RT-PCR) or immunofluorescence. Another cell type arising from the same cultures expressed a differentiated phenotype and was designated as an OEC. This subset as an OEC was expanded in long-term cultures and analyzed by immunofluorescence, flow-cytometry, and RT-PCR for a stable endothelial phenotype. OEC showed several markers of a differentiated endothelium, such as high levels of caveolin-1 throughout all tested passages, and the ability to form angiogenic sprouts in vitro. Thus, OEC in long-term expansion cultures from blood mononuclear cells are phenotypically highly stable, a feature that is an important prerequisite for using OEC from peripheral blood for autologous endothelial cell therapies.

Circulating endothelial cells: a novel marker of endothelial damage

Circulating endothelial cells (CECs) were first described over 30 years ago in smears of peripheral blood. Since then, more sophisticated techniques for CEC isolation have become available. In particular, immunomagnetic isolation and fluorescence-activated cell sorting (FACS) have been employed with success. We provide a short historical perspective and a comprehensive review on the subject. We review isolation and enumeration of CECs with an emphasis on CD146-driven immunomagnetic isolation and FACS. We describe, in great detail, advantages and pitfalls of both approaches and compare their specificity. Moreover, we provide a comprehensive list of clinical studies in this field and describe the possible clinical use of CECs. We also describe the phenotype of these cells and list typical surface markers. In addition, we review the phenotype of CECs and discuss mechanisms of detachment. We speculate about potential interactions between CECs and other cell subsets. We also describe other serum markers of endothelial damage and compare CECs with these markers. Finally, we highlight differences between circulating endothelial cells and endothelial progenitor cells. In summary, CECs must now be regarded as a sensitive and specific marker of endothelial damage. We emphasize that use of CECs in a clinical setting is on the horizon and pathogenetic clues may also be obtained.

Differential CD146 expression on circulating versus tissue endothelial cells in rectal cancer patients: implications for circulating endothelial and progenitor cells as biomarkers for antiangiogenic therapy

PURPOSE

Circulating endothelial cells (CECs) and progenitor cells are currently evaluated as potential biomarkers of antiangiogenic therapy. CD146 is considered a panendothelial-specific marker, but its utility as a CEC marker in cancer patients remains unclear.

PATIENTS AND METHODS

We analyzed the expression of CD146 on mononuclear blood cells, primary tissue endothelial cells, and malignant and normal tissues by flow cytometric and immunohistochemical analyses. Furthermore, we measured the circulation kinetics of CD146+ cells before, and then 3 and 12 days after vascular endothelial growth factor (VEGF) antibody blockade by bevacizumab infusion in rectal cancer patients enrolled in a phase I trial.

RESULTS

In the peripheral blood of these cancer patients, over 90% of the CD146+ cells were CD45+ hematopoietic cells. CD146 expression was primarily detected on a subset of CD3+CD4+ lymphocytes, and was undetectable on CD34+CD133+CD45(dim) progenitor cells or CD31(bright)CD45- viable CECs. In contradistinction, CD146 was detectable in tissues on both cellular components of tumor vessel wall: CD31(bright)CD45- endothelial cells and alpha-SMA+ pericytes. Unlike viable CECs and progenitor cells, CD146+ cell concentration in the peripheral blood of cancer patients did not decrease during VEGF blockade.

CONCLUSION

CD146 is fairly homogeneously expressed on vascular endothelium but not on viable CECs or progenitor cells. The vast majority of CD146+ blood cells are lymphocytes, and VEGF blockade by bevacizumab did not significantly change their number in rectal cancer patients. These results underscore the need for further characterization and identification of new markers for CEC subpopulations for their development as biomarkers of antiangiogenic therapy.

Isolation and enumeration of circulating endothelial cells by immunomagnetic isolation: proposal of a definition and a consensus protocol

BACKGROUND

Circulating endothelial cells (CECs) have been identified as markers of vascular damage in a variety of disorders, such as myocardial infarction, vasculitis, and transplantation. CD146-driven immunomagnetic isolation has gained widespread use, but the technique is hampered by the lack of a definition of CECs and the absence of a consensus for their enumeration.

AIM

To evaluate several variables influencing immunomagnetic isolation of CECs, formulate a definition for CECs and propose a consensus protocol for their enumeration.

METHODS

We devised a protocol based on CD146-driven immunomagnetic isolation and a subsequent confirmatory step with Ulex-Europaeus-Lectin-1 staining. In a multi-center effort, we evaluated the preanalytical and analytical phases of this protocol. We evaluated the effects of storage, anticoagulation and density centrifugation, and compiled previous experience with this technique.

RESULTS

Our protocol permitted unequivocal identification of CECs with acceptable reproducibility. There was an effect of storage time in that median cell numbers declined to only 87.5% of their baseline values during 24 h of storage at 4 degrees C. Recovery was lower with citrate than with ethylene-diamine tetra-acetic acid after 4 h of storage; density centrifugation was also associated with lower recovery. We provide a comprehensive list of technical recommendations and potential pitfalls. Finally, based on our experience with this protocol and a recent consensus workshop, we formulated a working definition for CECs.

CONCLUSION

Our work represents an important step toward consensus regarding the CECs. Our recommendations represent the experience of three major centers and should now be scrutinized by others in the field.

Endothelial cell activation and neovascularization are prominent in dermatomyositis

Background

While vascular and immune abnormalities are common in juvenile and adult dermatomyositis (DM), the molecular changes that contribute to these abnormalities are not clear. Therefore, we investigated pathways that facilitate new blood vessel formation and dendritic cell migration in dermatomyositis.

Methods

Muscle biopsies from subjects with DM (9 children and 6 adults) and non-myositis controls (6 children and 7 adults) were investigated by immunohistochemistry using antibodies that recognize existing (anti-CD146) and newly formed blood vessels (anti-αVβ3) and mature dendritic cells (anti-DC-LAMP). Blood vessel quantification was performed by digitalized image analysis. Additional muscle biopsies from subjects with adult DM and non-myositis controls were used for global gene expression profiling experiments.

Results

A significant increase in neovascularization was found in muscle biopsies of DM patients; neovascularization (αVβ3 positive capillaries and vessels per muscle fiber) was much higher in juvenile than in adult DM patients (control vs juvenile DM: Mean ± SE: 0.06 ± 0.01 vs 0.6 ± 0.05; p < 0.0001 and control vs adult DM: Mean ± SE: 0.60 ± 0.1 vs 0.75 ± 0.1; p = 0.051). Gene expression analysis demonstrated that genes that participate not only in angiogenesis but also in leukocyte trafficking and the complement cascade were highly up regulated in DM muscle in comparison to age matched controls. DC-LAMP positive dendritic cells were highly enriched at perivascular inflammatory sites in juvenile and adult DM patients along with molecules that facilitate dendritic cell transmigration and reverse transmigration (CD142 and CD31).

Conclusion

These results suggest active neovascularization and endothelial cell activation in both juvenile and adult DM. It is likely that close association of monocytes with endothelial cells initiate rapid dendritic cell maturation and an autoimmune response in DM.

Increased expression of CD146, a new marker of the endothelial junction in active inflammatory bowel disease

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC), the 2 major forms of inflammatory bowel diseases (IBD), have been associated with disturbances in vascular physiology, including permeability and angiogenesis, that are in part regulated by the endothelial intercellular junctions. These junctions are composed of several adhesion molecules including the platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31) and the more recently described CD146 (S-Endo1 Ag, MUC18).

AIM

To study the expression of tissue and soluble form of CD146 in patients with CD or UC in relation to disease activity and location. This study was made in comparison with the soluble form of CD31 (sCD31).

RESULTS

In active disease, a high expression of CD146 was observed on endothelial cells in intestinal biopsies from both CD and UC. In addition, we observed a decrease of sCD146 in relation to active disease and extensive location of CD and UC. Lower levels of sCD31 were also detected in active and extensive location of UC, but no difference could be observed in CD.

CONCLUSION

sCD146 is a novel marker of the endothelial intercellular junction that reflects endothelial remodeling more effectively than soluble CD31. Further studies are warranted to determine whether sCD146 will provide a serological assay reflecting alterations in vascular permeability and vessel proliferation in the inflamed IBD intestine.