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

Expression of placental CD146 is dysregulated by prenatal alcohol exposure and contributes in cortical vasculature development and positioning of vessel-associated oligodendrocytes

Recent data showed that prenatal alcohol exposure (PAE) impairs the "placenta-brain" axis controlling fetal brain angiogenesis in human and preclinical models. Placental growth factor (PlGF) has been identified as a proangiogenic messenger between these two organs. CD146, a partner of the VEGFR-1/2 signalosome, is involved in placental angiogenesis and exists as a soluble circulating form. The aim of the present study was to investigate whether placental CD146 may contribute to brain vascular defects described in fetal alcohol spectrum disorder. At a physiological level, quantitative reverse transcription polymerase chain reaction experiments performed in human placenta showed that CD146 is expressed in developing villi and that membrane and soluble forms of CD146 are differentially expressed from the first trimester to term. In the mouse placenta, a similar expression pattern of CD146 was found. CD146 immunoreactivity was detected in the labyrinth zone and colocalized with CD31-positive endothelial cells. Significant amounts of soluble CD146 were quantified by ELISA in fetal blood, and the levels decreased after birth. In the fetal brain, the membrane form of CD146 was the majority and colocalized with microvessels. At a pathophysiological level, PAE induced marked dysregulation of CD146 expression. The soluble form of CD146 decreased in both placenta and fetal blood, whereas it increased in the fetal brain. Similarly, the expression of several members of the CD146 signalosome, such as VEGFR2 and PSEN, was differentially impaired between the two organs by PAE. At a functional level, targeted repression of placental CD146 by in utero electroporation (IUE) of CRISPR/Cas9 lentiviral plasmids resulted in (i) a decrease in cortical vessel density, (ii) a loss of radial vascular organization, and (iii) a reduced density of oligodendrocytes. Statistical analysis showed that the more the vasculature was impaired, the more the cortical oligodendrocyte density was reduced. Altogether, these data support that placental CD146 contributes to the proangiogenic "placenta-brain" axis and that placental CD146 dysfunction contributes to the cortical oligo-vascular development. Soluble CD146 would represent a promising placental biomarker candidate representative of alcohol-induced neurovascular defects in neonates, as recently suggested by PlGF (patents WO2016207253 and WO2018100143).

A Dietary Supplement Containing Fucoidan Preserves Endothelial Glycocalyx through ERK/MAPK Signaling and Protects against Damage Induced by CKD Serum

(1) Damage to the endothelial glycocalyx (eGC), a protective layer lining the endothelial luminal surface, is associated with chronic kidney disease (CKD), which leads to a worsening of cardiovascular outcomes in these patients. Currently, there are no targeted therapeutic approaches. Whether the dietary supplement Endocalyx^TM (ECX) protects against endothelial damage caused by uremic toxins is unknown. (2) We addressed this question by performing atomic force microscopy measurements on living endothelial cells. We examined the effect of ECX on eGC thickness at baseline and with pooled serum from hemodialysis patients. ECX was also successfully administered in vivo in mice, in which eGC was assessed using perfused boundary region measurements by intravital microscopy of cremasteric vessels. (3) Both ECX and fucoidan significantly improved baseline eGC thickness. Our data indicate that these effects are dependent on ERK/MAPK and PI3K signaling. After incubation with eGC damaging serum from dialysis patients, ECX increased eGC height. Intravital microscopy in mice revealed a relevant increase in baseline eGC dimensions after feeding with ECX. (4) We identified a dietary supplement containing glycocalyx substrates and fucoidan as potential mediators of eGC preservation in vitro and in vivo. Our findings suggest that fucoidan may be an essential component responsible for protecting the eGC in acute settings. Moreover, ECX might contribute to both protection and rebuilding of the eGC in the context of CKD.

CD146 at the Interface between Oxidative Stress and the Wnt Signaling Pathway in Systemic Sclerosis

CD146 involvement was recently described in skin fibrosis of systemic sclerosis through its regulation of the Wnt pathway. Because the interaction between Wnt and ROS signaling plays a major role in fibrosis, we hypothesized that in systemic sclerosis, CD146 may regulate Wnt/ROS crosstalk. Using a transcriptomic and western blot analysis performed on CD146 wild-type or knockout mouse embryonic fibroblasts, we showed a procanonical Wnt hallmark in the absence of CD146 that is reversed when CD146 expression is restored. We found an elevated ROS content in knockout cells and an increase in DNA oxidative damage in the skin sections of knockout mice compared with those of wild-type mice. We also showed that ROS increased CD146 and its noncanonical Wnt ligand, WNT5A, only in wild-type cells. In humans, fibroblasts from patients with systemic sclerosis presented higher ROS content and expressed CD146, whereas control fibroblasts did not. Moreover, CD146 and its ligand were upregulated by ROS in both human fibroblasts. The increase in bleomycin-induced WNT5A expression was abrogated when CD146 was silenced. We showed an interplay between Wnt and ROS signaling in systemic sclerosis, regulated by CD146, which promotes the noncanonical Wnt pathway and prevents ROS signaling, opening the way for innovative therapeutic strategies.

Soluble CD146 in the detection and grading of intravascular and tissue congestion in patients with acute dyspnoea: analysis of the prospective observational Lithuanian Echocardiography Study of Dyspnoea in Acute Settings (LEDA) cohort

OBJECTIVES

To evaluate the potential of soluble cluster of differentiation 146 (sCD146) in the detection and grading of congestion in patients with acute dyspnoea.

DESIGN

Subanalysis of the prospective observational Lithuanian Echocardiography Study of Dyspnoea in Acute Settings (LEDA) cohort.

SETTING

Two Lithuanian university centres.

PARTICIPANTS

Adult patients with acute dyspnoea admitted to the emergency department.

METHODS

Congestion was assessed using clinical and sonographic parameters. All patients underwent sCD146 and N-terminal pro-B-type natriuretic peptide (NT-proBNP) testing.

RESULTS

The median value of sCD146 concentration in the study cohort (n=437) was 405 (IQR 315-509) ng/mL. sCD146 was higher in patients with peripheral oedema than in those without (median (IQR) 472 (373-535) vs 400 (304-501) ng/mL, p=0.009) and with pulmonary rales than in those without (439 (335-528) vs 394 (296-484) ng/mL, p=0.001). We found a parallel increase of estimated right atrial pressure (eRAP) and sCD146 concentration: sCD146 was 337 (300-425), 404 (290-489) and 477 (363-572) ng/mL in patients with normal, moderately elevated and high eRAP, respectively (p=0.001). In patients with low NT-proBNP, high sCD146 distinguished a subgroup with a higher prevalence of oedema as compared with patients with low levels of both biomarkers (76.0% vs 41.0%, p=0.010). Moreover, high sCD146 indicated a higher prevalence of elevated eRAP, irrespective of NT-proBNP concentration (p<0.05).

CONCLUSION

sCD146 concentration reflects the degree of intravascular and tissue congestion assessed by clinical and echocardiographic indices, with this association maintained in patients with low NT-proBNP. Our data support the notion that NT-proBNP might represent heart stretch while sCD146 rather represents peripheral venous congestion.

Soluble CD146 is increased in preeclampsia and interacts with galectin-1 to regulate trophoblast migration through VEGFR2 receptor

OBJECTIVE

To explore the regulatory role of soluble CD146 (sCD146) and its interaction with galectin-1 (Gal1) in placenta-mediated complications of pregnancy.

DESIGN

Prospective pilot and experimental studies.

SETTING

University-affiliated hospital and academic research laboratory.

PATIENT(S)

One hundred fifteen women divided into three groups: 30 healthy, nonpregnant women, 50 women with normal pregnancies, and 35 with placenta-mediated pregnancy complications.

INTERVENTION(S)

Wound-healing experiments were conducted to study trophoblast migration.

MAIN OUTCOME MEASURE(S)

Quantification of sCD146 and Gal1 by enzyme-linked immunosorbent assay. Analysis of trophoblast migration by wound closure.

RESULT(S)

Concomitant detection of sCD146 and Gal1 showed lower sCD146 and higher Gal1 concentrations in women with normal pregnancies compared with nonpregnant women. In addition, follow-up of these women revealed a decrease in sCD146 associated with an increase in Gal1 throughout pregnancy. In contrast, in women with preeclampsia, we found significantly higher sCD146 concentrations compared with women with normal pregnancies and no modification of Gal1. We emphasize the opposing effects of sCD146 and Gal, since, unlike Gal1, sCD146 inhibits trophoblast migration. Moreover, the migratory effect of Gal1 was abrogated with the use of an anti-CD146 blocking antibody or the use of small interfering RNA to silence VEGFR2 expression. This suggests that trophoblast migration is mediated though the interaction of Gal1 with CD146, further activating the VEGFR2 signaling pathway. Significantly, sCD146 blocked the migratory effects of Gal1 on trophoblasts and inhibited its secretion, suggesting that sCD146 acts as a ligand trap.

CONCLUSION(S)

Soluble CD146 could be proposed as a biomarker in preeclampsia and a potential therapeutic target.

CLINICAL TRIAL REGISTRATION NUMBER

NCT 01736826.

Multiple variants of soluble CD146 are involved in Systemic Sclerosis: identification of a novel pro-fibrotic factor

OBJECTIVE

Systemic sclerosis (SSc) is an autoimmune disorder characterized by excessive fibrosis, immune dysfunction and vascular damages, in which expression of many growth factors is deregulated. CD146 was recently described as a major actor in SSc. As CD146 also exists as a circulating soluble form (sCD146) acting as a growth factor in numerous angiogenic- and inflammatory-related pathologies, we sought to identify the mechanisms underlying the generation of sCD146 and characterized the regulation and functions of the different identified variants in SSc.

METHODS

To this end, we performed in vitro experiments, including RNA-seq and antibody arrays, and in vivo experiments using animal models of SSc induced by bleomycin and of hindlimb ischemia.

RESULTS

Multiple forms of sCD146, generated by both shedding and alternative splicing of the primary transcript, were discovered. The shed form of sCD146 was generated from the cleavage of both long and short membrane isoforms of membrane CD146 through Adam10 and Tace metalloproteinases, respectively. In addition, two novel sCD146 splice variants, I5-13-sCD146 and I10-sCD146 were identified. Of interest, I5-13-sCD146 was significantly increased in sera of SSc patients, in particular in patients with pulmonary fibrosis, whereas I10-sCD146 was decreased. Further experiments revealed that shed sCD146 and I10-sCD146 displayed pro-angiogenic activity through FAK and PKCε signalling pathways, respectively, whereas I5-13-sCD146 displayed pro-fibrotic effects through wint1/β-catenin/wisp1 pathway.

CONCLUSION

Variants of sCD146, and in particular the novel I5-13-sCD146 splice variant, could thus constitute novel biomarkers and/or molecular targets for the diagnosis and treatment of SSc, but also of other angiogenesis- or fibrosis-related pathologies.

Thermosensitive Hydrogel Harboring CD146/IGF-1 Nanoparticles for Skeletal-Muscle Regeneration

In skeletal-muscle regeneration, it is critical to promote efferocytosis of immune cells and differentiation of satellite cells/postnatal muscle stem cells at the damaged sites. With the optimized poloxamer 407 composition gelled at body temperature, the drugs can be delivered locally. The purpose of this study is to develop a topical injection therapeutic agent for muscle regeneration, sarcopenia, and cachexia. Herein, we construct an injectable, in situ hydrogel system consisting of CD146, IGF-1, collagen I/III, and poloxamer 407, termed CIC gel. The secreted CD146 then binds to VEGFR2 on the muscle surface and effectively induces efferocytosis of neutrophils and macrophages. IGF-1 promotes satellite cell differentiation, and biocompatible collagen evades immune responses of the CIC gel. Consequently, these combined molecules activate muscle regeneration via autophagy and suppress muscle inflammation and apoptosis. Conclusively, we provide an applicable concept of the myogenesis-activating protein formulation, broadening the thermoreversible hydrogel to protein therapeutics for damaged muscle recovery.

The Role of the Adhesion Receptor CD146 and Its Soluble Form in Human Embryo Implantation and Pregnancy

CD146 is an adhesion molecule essentially located in the vascular system, which has been described to play an important role in angiogenesis. A soluble form of CD146, called sCD146, is detected in the bloodstream and is known as an angiogenic factor. During placental development, CD146 is selectively expressed in extravillous trophoblasts. A growing body of evidence shows that CD146 and, in particular, sCD146, regulate extravillous trophoblasts migration and invasion both in vitro and in vivo. Hereby, we review expression and functions of CD146/sCD146 in the obstetrical field, mainly in pregnancy and in embryo implantation. We emphasized the relevance of quantifying sCD146 in the plasma of pregnant women or in embryo supernatant in the case of in vitro fertilization (IVF) to predict pathological pregnancy such as preeclampsia or implantation defect. This review will also shed light on some major results that led us to define CD146/sCD146 as a biomarker of placental development and paves the way toward identification of new therapeutic targets during implantation and pregnancy.

Endothelial-Specific Deletion of CD146 Protects Against Experimental Glomerulonephritis in Mice

[Figure: see text].

Epithelial-Mesenchymal Transition in Asthma Airway Remodeling Is Regulated by the IL-33/CD146 Axis

Epithelial-mesenchymal transition (EMT) is essential in asthma airway remodeling. IL-33 from epithelial cells is involved in pulmonary fibrosis. CD146 has been extensively explored in cancer-associated EMT. Whether IL-33 regulates CD146 in the EMT process associated with asthma airway remodeling is still largely unknown. We hypothesized that EMT in airway remodeling was regulated by the IL-33/CD146 axis. House dust mite (HDM) extract increased the expression of IL-33 and CD146 in epithelial cells. Increased expression of CD146 in HDM-treated epithelial cells could be blocked with an ST2-neutralizing antibody. Moreover, HDM-induced EMT was dependent on the CD146 and TGF-β/SMAD-3 signaling pathways. IL-33 deficiency decreased CD146 expression and alleviated asthma severity. Similarly, CD146 deficiency mitigated EMT and airway remodeling in a murine model of chronic allergic airway inflammation. Furthermore, CD146 expression was significantly elevated in asthma patients. We concluded that IL-33 from HDM extract-treated alveolar epithelial cells stimulated CD146 expression, promoting EMT in airway remodeling in chronic allergic inflammation.

Assessment of successful percutaneous mitral commissurotomy by MRproANP and sCD146

Background

We studied the course of plasma concentrations of 4 cardiovascular biomarkers: natriuretic peptides (BNP, NT-proBNP; mid-regional (MR) pro-atrial NP); and soluble endothelial CD146 (sCD146), in patients with severe mitral valve stenosis undergoing percutaneous mitral commissurotomy (PMC) to identify potential markers of procedural success.

Methods

Biomarkers were tested in 40 patients the day before and the day after PMC. Success was defined as mitral valve area ≥ 1.5 cm²; or an increase of ≥0.5 cm2 in mitral valve area associated with echocardiographic mitral regurgitation <grade 3–4 post-PMC.

Results

Average age was 63.5 ± 12.7 years; 32(80%) were female. Before PMC, mean valve area was 1.1 ± 0.2 cm², mean gradient 9.1 ± 3.5 mmHg. PMC was successful in 30 (75%) and unsuccessful in 10 (25%). PMC yielded a significant reduction in MR-proANP and sCD146, driven by a significant reduction in these biomarkers in patients with successful procedure, whereas no reduction was observed in patients with unsuccessful procedure. A significant correlation was found between changes in plasma sCD146 and the relative change in mitral valve area. Elevated pre-procedural sPAP correlated with high sCD146, and accordingly, a significant correlation between the decrease in sPAP and sCD146 after PMC was shown.

Conclusions

MR-proANP and plasma sCD146 decreased significantly immediately after successful PMC. They appear to be markers of immediate success of PMC and of the hemodynamic improvement achieved by this procedure in patients with MS.

Trial registration

This study is part of the cohorts registered with ClinicalTrials.gov on June 16, 2011 under the number NCT01374880.

Soluble CD146, a cerebrospinal fluid marker for neuroinflammation, promotes blood-brain barrier dysfunction

The blood-brain barrier (BBB) dysfunction is an initial event of various neuroinflammatory diseases. However, the absence of reliable markers and mechanisms for BBB damage greatly limits the diagnosis and treatment of neuroinflammatory diseases. Soluble CD146 (sCD146) is mainly derived from vascular endothelial cells (ECs) and highly elevated in inflammatory settings. Based on a small cohort, our previous study showed that sCD146 is elevated in the cerebrospinal fluid (CSF) of multiple sclerosis (MS), which is accompanied with BBB damage. Nevertheless, whether sCD146 monitors and regulates the BBB dysfunction remains unknown.

Methods: Coupled serum and CSF samples from patients with or without neuroinflammatory diseases were collected via multicenter collaborations. sCD146 was measured by sandwich ELISA using anti-CD146 antibodies AA1 and AA98, both of which were generated in our laboratory. The correlations between sCD146 and other clinical parameters or inflammatory factors were analyzed by Spearman's correlation coefficient analysis. The role of sCD146 on BBB function was examined in an in vitro BBB model.

Results: Between July 20, 2011, and February 31, 2017, we collected coupled serum and CSF samples from 823 patients, of which 562 (68.3%) had neuroinflammatory diseases, 44 (5.3%) had remitting MS, and 217 (26.4%) had non-inflammatory neurological diseases (NIND). We found that sCD146 in CSF, but not in serum, is abnormally elevated in neuroinflammatory diseases (37.3 ± 13.3 ng/mL) compared with NIND (4.7 ± 2.9 ng/mL) and remitting MS (4.6 ± 3.5 ng/mL). Abnormally elevated CSF sCD146 is significantly correlated with the hyperpermeability-related clinical parameters of BBB and neuroinflammation-related factors. Moreover, CSF sCD146 shows higher sensitivity and specificity for evaluating BBB damage. Using an in vitro BBB model, we found that sCD146 impairs BBB function by promoting BBB permeability via an association with integrin αvβ1. Blocking integrin αvβ1 significantly attenuates sCD146-induced hyperpermeability of the BBB.

Conclusion: Our study provides convincing evidence that CSF sCD146 is a sensitive marker of BBB damage and neuroinflammation. Furthermore, sCD146 is actively involved in BBB dysfunction.

Soluble CD146 and B-type natriuretic peptide dissect overhydration into functional components of prognostic relevance in haemodialysis patients

Background

Accurate volume status evaluation and differentiation of cardiac and non-cardiac components of overhydration (OH) are fundaments of optimal haemodialysis (HD) management.

Methods

This study, by combining bioimpedance measurements, cardiovascular biomarkers and echocardiography, aimed at dissecting OH into its major functional components, and prospectively tested the association between cardiac and non-cardiac components of OH with mortality. In the first part, we validated soluble CD146 (sCD146) as a non-cardiac biomarker of systemic congestion in a cohort of 30 HD patients. In the second part, we performed a prospective 1-year follow-up study in an independent cohort of 144 HD patients.

Results

sCD146 incrementally increased after the short and long intervals after HD (+53 ng/mL, P = 0.006 and  +91 ng/mL, P < 0.001), correlated with OH as determined by bioimpedance and well-diagnosed OH (area under the receiver operating characteristics curve 0.72, P = 0.005). The prevalence of OH was lower for low-sCD146 and low-BNP patients (B-type natriuretic peptide, 29%) compared with subjects with either one or both biomarkers elevated (65-74%, P < 0.001). Notably, most low-BNP but high-sCD146 subjects were overhydrated. Systolic dysfunction was 2- to 3-fold more prevalent among high-BNP compared with low-BNP patients (44-68% versus 21-23%, chi-square P < 0.001), regardless of sCD146. One-year all-cause mortality was markedly higher in patients with high-BNP (P = 0.001) but not with high-sCD146. In multivariate analysis, systolic dysfunction and BNP, but not OH, were associated with lower survival.

Conclusions

The combination of BNP and sCD146 dissects OH into functional components of prognostic value. OH in HD patients is associated with higher mortality only if resulting from cardiac dysfunction.

Mesenchymal Stem Cell Functionalization for Enhanced Therapeutic Applications

IMPACT STATEMENT

Culture expansion of MSCs has detrimental effects on various cell characteristics and attributes (e.g., phenotypic changes and senescence), which, in addition to inherent interdonor variability, negatively impact the standardization and reproducibility of their therapeutic potential. The identification of innate distinct functional MSC subpopulations, as well as the description of ex vivo protocols aimed at maintaining phenotypes and enhancing specific functions have the potential to overcome these limitations. The incorporation of those approaches into cell-based therapy would significantly impact the field, as more reproducible clinical outcomes may be achieved.

Induction of Expression of CD271 and CD34 in Mesenchymal Stromal Cells Cultured as Spheroids

Cultured mesenchymal stromal cells (MSCs) are cells that can be used for tissue engineering or cell therapies owing to their multipotency and ability to secrete immunomodulatory and trophic molecules. Several studies suggest that MSCs can become pericytes when cocultured with endothelial cells (ECs) but failed to use pericyte markers not already expressed by MSCs. We hypothesized ECs could instruct MSCs to express the molecules CD271 or CD34, which are expressed by pericytes in situ but not by MSCs. CD271 is a marker of especial interest because it is associated with multipotency, a characteristic that wanes in MSCs as they are culture expanded. Consequently, surface expression of CD271 and CD34 was detected in roughly half of the MSCs cocultured with ECs as spheroids in the presence of insulin-like growth factor 1 (IGF-1). Conversely, expression of CD271 and CD34 was detected in a similar proportion of MSCs cultured under these conditions without ECs, and expression of these markers was low or absent when no IGF-1 was added. These findings indicate that specific culture conditions including IGF-1 can endow cultured MSCs with expression of CD271 and CD34, which may enhance the multipotency of these cells when they are used for therapeutic purposes.

Soluble CD146 is a predictive marker of pejorative evolution and of sunitinib efficacy in clear cell renal cell carcinoma

The objective of the study was to use CD146 mRNA to predict the evolution of patients with non-metastatic clear cell renal cell carcinoma (M0 ccRCC) towards metastatic disease, and to use soluble CD146 (sCD146) to anticipate relapses on reference treatments by sunitinib or bevacizumab in patients with metastatic ccRCC (M1).

Methods: A retrospective cohort of M0 patients was used to determine the prognostic role of intra-tumor CD146 mRNA. Prospective multi-center trials were used to define plasmatic sCD146 as a predictive marker of sunitinib or bevacizumab efficacy for M1 patients.

Results: High tumor levels of CD146 mRNA were linked to shorter disease-free survival (DFS) and overall survival (OS). ccRCC patients from prospective cohorts with plasmatic sCD146 variation <120% following the first cycle of sunitinib treatment had a longer progression-free survival (PFS) and OS. The plasmatic sCD146 variation did not correlate with PFS or OS for the bevacizumab-based treatment. In vitro, resistant cells to sunitinib expressed high levels of CD146 mRNA and protein in comparison to sensitive cells. Moreover, recombinant CD146 protected cells from the sunitinib-dependent decrease of cell viability.

Conclusion: CD146/sCD146 produced by tumor cells is a relevant biological marker of ccRCC aggressiveness and relapse on sunitinib treatment.

Therapeutic and Diagnostic Antibodies to CD146: Thirty Years of Research on Its Potential for Detection and Treatment of Tumors

CD146 (MCAM, MUC18, S-Endo1) is a transmembrane glycoprotein belonging to both CAM and mucin families. It exists as different splice variants and is cleaved from the membrane by metalloproteases to generate a soluble form. CD146 is expressed by numerous cancer cells as well as being one of the numerous proteins expressed by the vascular endothelium. It has also been identified on smooth muscle cells, pericytes, and some immune cells. This protein was initially described as an actor involved in tumor growth and metastatic dissemination processes. Some recent works highlighted the role of CD146 in angiogenesis. Interestingly, this knowledge allowed the development of therapeutic and diagnostic tools specifically targeting the different CD146 variants. The first anti-CD146 antibody designed to study the function of this molecule, MUC18, was described by the Pr. J.P. Jonhson in 1987. In this review, we will discuss the 30 following years of research focused on the detection, study, and blocking of this protein in physiological and pathological processes.

CD146 coordinates brain endothelial cell-pericyte communication for blood-brain barrier development

The blood-brain barrier (BBB) establishes a protective interface between the central neuronal system and peripheral blood circulation and is crucial for homeostasis of the CNS. BBB formation starts when the endothelial cells (ECs) invade the CNS and pericytes are recruited to the nascent vessels during embryogenesis. Despite the essential function of pericyte-EC interaction during BBB development, the molecular mechanisms coordinating the pericyte-EC behavior and communication remain incompletely understood. Here, we report a single cell receptor, CD146, that presents dynamic expression patterns in the cerebrovasculature at the stages of BBB induction and maturation, coordinates the interplay of ECs and pericytes, and orchestrates BBB development spatiotemporally. In mouse brain, CD146 is first expressed in the cerebrovascular ECs of immature capillaries without pericyte coverage; with increased coverage of pericytes, CD146 could only be detected in pericytes, but not in cerebrovascular ECs. Specific deletion of Cd146 in mice ECs resulted in reduced brain endothelial claudin-5 expression and BBB breakdown. By analyzing mice with specific deletion of Cd146 in pericytes, which have defects in pericyte coverage and BBB integrity, we demonstrate that CD146 functions as a coreceptor of PDGF receptor-β to mediate pericyte recruitment to cerebrovascular ECs. Moreover, we found that the attached pericytes in turn down-regulate endothelial CD146 by secreting TGF-β1 to promote further BBB maturation. These results reveal that the dynamic expression of CD146 controls the behavior of ECs and pericytes, thereby coordinating the formation of a mature and stable BBB.

Soluble CD146, an innovative and non-invasive biomarker of embryo selection for in vitro fertilization

Although progress was made in in vitro fertilization (IVF) techniques, the majority of embryos transferred fail to implant. Morphology embryo scoring is the standard procedure for most of IVF centres for choosing the best embryo, but remains limited since even the embryos classified as "top quality" may not implant. As it has been shown that i) CD146 is involved in embryo implantation and ii) membrane form is shed to generate soluble CD146 (sCD146), we propose that sCD146 in embryo supernatants may constitute a new biomarker of embryo selection. Immunocytochemical staining showed expression of CD146 in early embryo stages and sCD146 was detected by ELISA and Western-blot in embryo supernatants from D2. We retrospectively studied 126 couples who underwent IVF attempt. The embryo culture medium from each transferred embryo (n = 222) was collected for measurement of sCD146 by ELISA. Significantly higher sCD146 concentrations were present in embryo supernatants that did not implant (n = 185) as compared to those that successfully implanted (n = 37) (1310 +/- 1152 pg.mL-1 vs. 845+/- 1173 pg.mL-1, p = 0.024). Sensitivity analysis performed on single embryo transfers (n = 71) confirmed this association (p = 0.0054). The computed ROC curve established that the optimal sCD146 concentration for embryo implantation is under 1164 pg.mL-1 (sensitivity: 76%, specificity: 48%, PPV: 25% and NPV: 92%). Over this sCD146 threshold, the implantation rate was significantly lower (9% with sCD146 levels >1164 pg.ml-1 vs. 22% with sCD146 levels ≤ 1164 pg.mL-1, p = 0.01). Among the embryos preselected by morphologic scoring, sCD146 determination could allow a better selection of the embryo(s), thus improving the success of elective single embryo transfer. This study establishes the proof of concept for the use of sCD146 as a biomarker for IVF by excluding the embryo with the highest sCD146 level. A multicentre prospective study will now be necessary to further establish its use in clinical practice.

Soluble CD146 Is a Novel Marker of Systemic Congestion in Heart Failure Patients: An Experimental Mechanistic and Transcardiac Clinical Study

BACKGROUND

Soluble CD146 (sCD146), is an endothelial marker with similar diagnostic power as natriuretic peptides in decompensated heart failure (HF). While natriuretic peptides are released by the failing heart, sCD146 may be released by veins in response to stretch induced by systemic congestion in HF. This study investigated the source, effects of vascular stress on release and prognostic properties of sCD146 in HF.

METHODS

In a peripheral venous stress study, plasma concentrations of sCD146 and N-terminal probrain natriuretic-peptide (NT-proBNP) were measured in 44 HF patients at baseline and after 90 min of unilateral forearm venous congestion. In addition, sCD146 and NT-proBNP were measured in peripheral vein (PV) and coronary sinus (CS) blood samples of 137 HF patients and the transcardiac gradient was calculated. Those patients were followed for major adverse cardiovascular events (MACE) during 2 years.

RESULTS

The induction of venous stress was associated with a pronounced increase in circulating concentrations of sCD146 in the congested arm (+60 μg/L) compared to the control arm (+16 μg/L, P = 0.025), while no difference in NT-proBNP concentrations was seen. In contrast to positive transcardiac gradient for NT-proBNP, median sCD146 concentrations were lower in CS than in PV (396 vs 434, P &lt; 0.001), indicating a predominantly extracardiac source of sCD146. Finally, increased PV concentrations of sCD146 were associated with higher risk of MACE at 2 years.

CONCLUSIONS

Soluble CD146 is released from the peripheral vasculature in response to venous stretch and may reflect systemic congestion in chronic HF patients.

The gene expression profile of non-cultured, highly purified human adipose tissue pericytes: Transcriptomic evidence that pericytes are stem cells in human adipose tissue

Pericytes (PCs) are a subset of perivascular cells that can give rise to mesenchymal stromal cells (MSCs) when culture-expanded, and are postulated to give rise to MSC-like cells during tissue repair in vivo. PCs have been suggested to behave as stem cells (SCs) in situ in animal models, although evidence for this role in humans is lacking. Here, we analyzed the transcriptomes of highly purified, non-cultured adipose tissue (AT)-derived PCs (ATPCs) to detect gene expression changes that occur as they acquire MSC characteristics in vitro, and evaluated the hypothesis that human ATPCs exhibit a gene expression profile compatible with an AT SC phenotype. The results showed ATPCs are non-proliferative and express genes characteristic not only of PCs, but also of AT stem/progenitor cells. Additional analyses defined a gene expression signature for ATPCs, and revealed putative novel ATPC markers. Almost all AT stem/progenitor cell genes differentially expressed by ATPCs were not expressed by ATMSCs or culture-expanded ATPCs. Genes expressed by ATMSCs but not by ATPCs were also identified. These findings strengthen the hypothesis that PCs are SCs in vascularized tissues, highlight gene expression changes they undergo as they assume an MSC phenotype, and provide new insights into PC biology.

Does smoking, age or gender affect the protein phenotype of extracellular vesicles in plasma?

Extracellular vesicles (EVs) are involved in several diseases, which have formed the basis for the potential use of EV analyses in a clinical setting. The protein phenotype of EVs can provide information on the functionality of the vesicles and may be used for identification of disease-related biomarkers. With this extensive study of 161 healthy individuals it was elucidated that certain markers of plasma EVs are influenced by demographic variations such as gender, age and smoking status. When the purpose is to use EVs as a diagnostic tool, it should be emphasized how important it is to choose the correct demographic group when comparing marker levels of plasma EVs.

Inhibition of Transforming Growth Factor-β Receptor signaling promotes culture expansion of undifferentiated human Endometrial Mesenchymal Stem/stromal Cells

Human endometrial MSC (eMSC) are a novel source of MSC easily harvested from the highly regenerative uterine lining. We have developed protocols for eMSC isolation from single cell suspensions using magnetic bead-sorting using a perivascular marker antibody to SUSD2 and culture expansion in serum free medium (SFM). Similar to other MSC, eMSC spontaneously differentiate into fibroblasts during culture expansion decreasing their purity and efficacy. The aim of this study was to determine if A83-01, a TGF-β receptor inhibitor prevents eMSC differentiation in culture. SUSD2⁺ eMSC were cultured in SFM with bFGF/EGF in 5% O₂/5% CO₂. At passage 6, eMSC were incubated with or without A83-01 for 7 days, then analysed for MSC properties. A83-01 dose dependently promoted SUSD2⁺ eMSC proliferation and blocked apoptosis via the SMAD 2/3 pathway. Fewer A83-01 treated cells were autofluorescent or stained with β-galactosidase, indicating reduced senescence. A83-01-treated cells had higher cloning efficiency, differentiated into mesodermal lineages and expressed MSC phenotypic markers. These data suggest that A83-01 maintains SUSD2⁺ eMSC stemness, promoting proliferation by blocking senescence and apoptosis in late passage cultures through binding to TGF-β receptors. Small molecules such as A83-01 may enable the expansion of undifferentiated MSC for use in tissue engineering and cell-based therapies.

Cultured Human Adipose Tissue Pericytes and Mesenchymal Stromal Cells Display a Very Similar Gene Expression Profile

Mesenchymal stromal cells (MSCs) are cultured cells that can give rise to mature mesenchymal cells under appropriate conditions and secrete a number of biologically relevant molecules that may play an important role in regenerative medicine. Evidence indicates that pericytes (PCs) correspond to mesenchymal stem cells in vivo and can give rise to MSCs when cultured, but a comparison between the gene expression profiles of cultured PCs (cPCs) and MSCs is lacking. We have devised a novel methodology to isolate PCs from human adipose tissue and compared cPCs to MSCs obtained through traditional methods. Freshly isolated PCs expressed CD34, CD140b, and CD271 on their surface, but not CD146. Both MSCs and cPCs were able to differentiate along mesenchymal pathways in vitro, displayed an essentially identical surface immunophenotype, and exhibited the ability to suppress CD3(+) lymphocyte proliferation in vitro. Microarray expression data of cPCs and MSCs formed a single cluster among other cell types. Further analyses showed that the gene expression profiles of cPCs and MSCs are extremely similar, although MSCs differentially expressed endothelial cell (EC)-specific transcripts. These results confirm, using the power of transcriptomic analysis, that PCs give rise to MSCs and suggest that low levels of ECs may persist in MSC cultures established using traditional protocols.

The multifaceted role of CD146/MCAM in the promotion of melanoma progression

Human malignant melanoma is a common primary malignant cutaneous tumour derived from transformed epidermal melanocytes. Patients with melanoma have a high rate of mortality due to resistance to chemotherapeutic drugs, a major obstacle to a successful treatment. Several reports have suggested that CD146 plays an important role as a signalling molecule in human melanoma. This role includes CD146 as a participant in inflammation, differentiation, adhesion, tumourigenicity, metastasis, invasion and angiogenesis among other processes, which suggests that this molecule promotes the progression of human melanoma as a multifaceted regulator. In this article, we explore the effects and corresponding mechanisms with respect to the role of CD146/MUC18 in the promotion of human melanoma progression. Collectively, the studies indicated that targeting CD146, because it is a suitable marker of poor patient outcome, might be useful in the design of future strategies for the prevention and treatment of human melanoma.

Isolation of a circulating CD45-, CD34dim cell population and validation of their endothelial phenotype

Accurately detecting circulating endothelial cells (CECs) is important since their enumeration has been proposed as a biomarker to measure injury to the vascular endothelium. However, there is no single methodology for determining CECs in blood, making comparison across studies difficult. Many methods for detecting CECs rely on characteristic cell surface markers and cell viability indicators, but lack secondary validation. Here, a CEC population in healthy adult human subjects was identified by flow cytometry as CD45-, CD34dim that is comparable to a previously described CD45-, CD31bright population. In addition, nuclear staining with 7-aminoactinomycin D (7-AAD) was employed as a standard technique to exclude dead cells. Unexpectedly, the CD45-, CD34dim, 7-AAD- CECs lacked surface detectable CD146, a commonly used marker of CECs. Furthermore, light microscopy revealed this cell population to be composed primarily of large cells without a clearly defined nucleus. Nevertheless, immunostains still demonstrated the presence of the lectin Ulex europaeus and von Willebrand factor. Ultramicro analytical immunochemistry assays for the endothelial cell proteins CD31, CD34, CD62E, CD105, CD141, CD144 and vWF indicated these cells possess an endothelial phenotype. However, only a small amount of RNA, which was mostly degraded, could be isolated from these cells. Thus the majority of CECs in healthy individuals as defined by CD45-, CD34dim, and 7-AAD- have shed their CD146 surface marker and are senescent cells without an identifiable nucleus and lacking RNA of sufficient quantity and quality for transcriptomal analysis. This study highlights the importance of secondary validation of CEC identification.

Adhesion molecule CD146 and its soluble form correlate well with carotid atherosclerosis and plaque instability

AIMS

Intraplaque neovascularization and foam cell infiltration contribute to the development of unstable plaque, leading to thromboembolism and stroke. Cell adhesion molecules (CAMs) have been reported to be involved in the progression of atherosclerosis and plaque vulnerability. The aim of this study was to assess the association of adhesion molecule CD146 with carotid plaque instability.

METHODS

We collected forty atherosclerotic plaques from 40 patients undergoing carotid endarterectomy. The clinical information of each patient was obtained, and the plaque morphology and characteristics were examined by the ultrasound. The CD146 expressions of the plaques were graded by using semiquantitative scales. The serum level of soluble form of CD146 was detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

CD146 expression was mainly on the intraplaque blood vessels and infiltrated macrophages. The CD146 expression was strongly correlated with the matrix metalloproteinase-9(MMP-9)expressions (P < 0.001) in the plaques. Soluble CD146 (sCD146) was also elevated in patients with atherosclerotic plaques. There was significant correlation between the increased CD146 expression and sCD146 level (P = 0.0057). sCD146 correlated well with serum MMP-9 (P < 0.0044), IL-6 (P = 0.0044) and high sensitivity C-reactive protein (hsCRP) (P = 0.005).

CONCLUSIONS

Adhesion molecules CD146 and its soluble form strongly correlated with the development of inflammation of atherosclerosis and plaque instability. CD146 may be a promising biomarker for monitoring the development and instability of atherosclerotic plaque in patients with carotid diseases.

Cell-based approaches to joint surface repair: a research perspective

Repair of lesions of the articular cartilage lining the joints remains a major clinical challenge. Surgical interventions include osteochondral autograft transfer and microfracture. They can provide some relief of symptoms to patients, but generally fail to durably repair the cartilage. Autologous chondrocyte implantation has thus far shown the most promise for the durable repair of cartilage, with long-term follow-up studies indicating improved structural and functional outcomes. However, disadvantages of this technique include the need for additional surgery, availability of sufficient chondrocytes for implantation, and maintenance of their phenotype during culture-expansion. Mesenchymal stem cells offer an attractive alternative cell-source for cartilage repair, due to their ease of isolation and amenability to ex vivo expansion while retaining stem cell properties. Preclinical and clinical studies have demonstrated the potential of mesenchymal stem cells to promote articular cartilage repair, but have also highlighted several key challenges. Most notably, the quality and durability of the repair tissue, its resistance to endochondral ossification, and its effective integration with the surrounding host tissue. In addition, challenges exist related to the heterogeneity of mesenchymal stem cell preparations and their quality-control, as well as optimising the delivery method. Finally, as our knowledge of the cellular and molecular mechanisms underlying articular cartilage repair increases, promising studies are emerging employing bioactive scaffolds or therapeutics that elicit an effective tissue repair response through activation and mobilisation of endogenous stem and progenitor cells.

Effect of chronic intermittent hypoxia on triglyceride uptake in different tissues

Chronic intermittent hypoxia (CIH) inhibits plasma lipoprotein clearance and adipose lipoprotein lipase (LPL) activity in association with upregulation of an LPL inhibitor angiopoietin-like protein 4 (Angptl4). We hypothesize that CIH inhibits triglyceride (TG) uptake via Angptl4 and that an anti-Angptl4-neutralizing antibody would abolish the effects of CIH. Male C57BL/6J mice were exposed to four weeks of CIH or intermittent air (IA) while treated with Ab (30 mg/kg ip once a week). TG clearance was assessed by [H(3)]triolein administration retroorbitally. CIH delayed TG clearance and suppressed TG uptake and LPL activity in all white adipose tissue depots, brown adipose tissue, and lungs, whereas heart, liver, and spleen were not affected. CD146+ CD11b- pulmonary microvascular endothelial cells were responsible for TG uptake in the lungs and its inhibition by CIH. Antibody to Angptl4 decreased plasma TG levels and increased TG clearance and uptake into adipose tissue and lungs in both control and CIH mice to a similar extent, but did not reverse the effects of CIH. The antibody reversed the effects of CIH on LPL in adipose tissue and lungs. In conclusion, CIH inactivates LPL by upregulating Angptl4, but inhibition of TG uptake occurs predominantly via an Angptl4/LPL-independent mechanism.

Identification of soluble CD146 as a regulator of trophoblast migration: potential role in placental vascular development

Both vasculogenesis and angiogenesis occur during normal placental vascular development. Additionally, the placenta undergoes a process of vascular mimicry (pseudo-vasculogenesis) where the placental extravillous trophoblast (EVT) that invade the spiral arteries convert from an epithelial to an endothelial phenotype during normal pregnancy. As soluble CD146 (sCD146) constitutes a new physiological factor with angiogenic properties, we hypothesized that it could be involved in the regulation of placental vascular development by acting on EVT. Using placental villous explants, we demonstrated that sCD146 inhibits EVT outgrowth. Consistently, we showed that sCD146 inhibits the ability of EVT cells (HTR8/SVneo) to migrate, invade and form tubes in Matrigel, without affecting their proliferation or apoptosis. The involvement of sCD146 in human pregnancy was investigated by evaluation of sCD146 levels in 50 pregnant women. We observed physiological down-regulation of sCD146 throughout pregnancy. These results prompted us to investigate the effect of prolonged sCD146 administration in a rat model of pregnancy. Repeated systemic sCD146 injections after coupling caused a significant decrease of pregnancy rate and number of embryos. Histological studies performed on placenta evidenced a reduced migration of glycogen cells (analogous to EVT in rat) in sCD146-treated rats. We propose that in human, sCD146 could represent both an attractive biomarker of placental vascular development and a therapeutic target in pregnancy complications associated with pathological angiogenesis.

Soluble form of the endothelial adhesion molecule CD146 binds preferentially CD16+ monocytes

The cell adhesion molecule CD146 is normally located at the endothelial cell-to-cell junction and colocalizes with actin cytoskeleton. The soluble form of CD146 (sCD146) has been identified in the endothelial cell supernatant and in normal human plasma, and is increased in pathologic conditions with altered endothelial function. Soluble CD146 binding to monocytes promotes their transendothelial migration, which represents a central step in the development of atherosclerotic plaque. Since peripheral blood monocytes are characterized by a phenotypic and functional heterogeneity, with different transendothelial migration capacity, we hypothesized that monocyte subsets differently bind sCD146. Based on surface CD14 and CD16 expression monocytes were distinguished by flow cytometry (FACS) into three subsets: CD14++/CD16-, CD14++/CD16+ and CD14+/CD16+. CD16+ monocytes have been found to possess higher transendothelial migration ability. FACS analysis on blood monocytes from 30 healthy subjects revealed that higher percentages of CD14++/CD16+ (median, first and third quartile: 2.26, 1.62-3.87) and of CD14+/CD16+ (2.59, 1.28-4.80) were positive for CD146 (both p < 0.01), in comparison to CD14++/CD16- (0.66, 0.47-1.01). Moreover, in vitro treatment of ficoll separated monocytes with recombinant CD146 showed that both CD16+ subsets increased their percentage of CD146-positive events compared to CD16- monocytes (p < 0.01). Soluble CD146 levels were evaluated by ELISA in plasma samples of subjects from our study group and showed a correlation with percentage of CD146-positive CD14+/CD16+ monocyte subset. In this work we have demonstrated that monocyte subsets behave differently with regard to their sCD146 binding activity; because binding of CD146 influences transendothelial migration of monocytes, modulation of monocyte-CD146 interaction may represent a potential target to limit atherosclerotic plaque development.

CD146 expression on primary nonhematopoietic bone marrow stem cells is correlated with in situ localization

Nonhematopoietic bone marrow mesenchymal stem cells (BM-MSCs) are of central importance for bone marrow stroma and the hematopoietic environment. However, the exact phenotype and anatomical distribution of specified MSC populations in the marrow are unknown. We characterized the phenotype of primary human BM-MSCs and found that all assayable colony-forming units-fibroblast (CFU-Fs) were highly and exclusively enriched not only in the lin⁻/CD271⁺/CD45⁻/CD146⁺ stem-cell fraction, but also in lin⁻/CD271⁺/CD45⁻/CD146(⁻/low) cells. Both populations, regardless of CD146 expression, shared a similar phenotype and genotype, gave rise to typical cultured stromal cells, and formed bone and hematopoietic stroma in vivo. Interestingly, CD146 was up-regulated in normoxia and down-regulated in hypoxia. This was correlated with in situ localization differences, with CD146 coexpressing reticular cells located in perivascular regions, whereas bone-lining MSCs expressed CD271 alone. In both regions, CD34⁺ hematopoietic stem/progenitor cells were located in close proximity to MSCs. These novel findings show that the expression of CD146 differentiates between perivascular versus endosteal localization of non-hematopoietic BM-MSC populations, which may be useful for the study of the hematopoietic environment.

Up-regulation of MUC18 in airway epithelial cells by IL-13: implications in bacterial adherence

Airway bacterial infections are a major problem in lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. Increased Th2 cytokines, such as IL-13, are observed in lung diseases and may contribute to bacterial infections. How Th2 cytokines affect bacterial infection remains unknown. MUC18, an adhesion molecule shown to be involved in the pathogenesis of malignant melanoma, has been recently identified in airway epithelial cells of patients with COPD. We investigated MUC18 regulation by IL-13 and the role of MUC18 in bacterial adherence to epithelial cells. Human airway tissues, brushed bronchial epithelial cells from normal subjects and subjects with asthma, and epithelial cell lines (e.g., HEK293 cells) were used to study the regulation of MUC18 by IL-13 and the involvement of MUC18 in bacterial (e.g., Mycoplasma pneumoniae [Mp] and nontypeable Haemophilus influenzae [NTHi]) adherence to epithelial cells. Asthmatic bronchial epithelium expressed higher levels of MUC18 than normal bronchial epithelium. IL-13 increased MUC18 in cultured bronchial epithelial cells from normal subjects and particularly from subjects with asthma. IL-13-induced MUC18 expression may be modulated in part through transcription factor specificity protein 1. Overexpression of human MUC18 in HEK293 cells increased cell-associated Mp and NTHi levels. Moreover, MUC18 was shown to directly interact with Mp and NTHi. These results for the first time show that an allergic airway milieu (e.g., IL-13) increases MUC18 expression, which may contribute to increased bacterial infection/colonization in asthma and other lung diseases.