Plasma CD93 concentration is a potential novel biomarker for coronary artery disease

Angiogenesis modulated by CD93 and its natural ligands IGFBP7 and MMRN2: a new target to facilitate solid tumor therapy by vasculature normalization

The tumor vasculature was different from the normal vasculature in both function and morphology, which caused hypoxia in the tumor microenvironment (TME). Previous anti-angiogenesis therapy had led to a modest improvement in cancer immunotherapy. However, antiangiogenic therapy only benefitted a few patients and caused many side effects. Therefore, there was still a need to develop a new approach to affect tumor vasculature formation. The CD93 receptor expressed on the surface of vascular endothelial cells (ECs) and its natural ligands, MMRN2 and IGFBP7, were now considered potential targets in the antiangiogenic treatment because recent studies had reported that anti-CD93 could normalize the tumor vasculature without impacting normal blood vessels. Here, we reviewed recent studies on the role of CD93, IGFBP7, and MMRN2 in angiogenesis. We focused on revealing the interaction between IGFBP7-CD93 and MMRN2-CD93 and the signaling cascaded impacted by CD93, IGFBP7, and MMRN2 during the angiogenesis process. We also reviewed retrospective studies on CD93, IGFBP7, and MMRN2 expression and their relationship with clinical factors. In conclusion, CD93 was a promising target for normalizing the tumor vasculature.

Role of CD93 in Health and Disease

CD93 (also known as complement protein 1 q subcomponent receptor C1qR1 or C1qRp), is a transmembrane glycoprotein encoded by a gene located on 20p11.21 and composed of 652 amino acids. CD93 can be present in two forms: soluble (sCD93) and membrane-bound (CD93). CD93 is mainly expressed on endothelial cells, where it plays a key role in promoting angiogenesis both in physiology and disease, such as age-related macular degeneration and tumor angiogenesis. In fact, CD93 is highly expressed in tumor-associated vessels and its presence correlates with a poor prognosis, poor immunotherapy response, immune cell infiltration and high tumor, node and metastasis (TNM) stage in many cancer types. CD93 is also expressed in hematopoietic stem cells, cytotrophoblast cells, platelets and many immune cells, i.e., monocytes, neutrophils, B cells and natural killer (NK) cells. Accordingly, CD93 is involved in modulating important inflammatory-associated diseases including systemic sclerosis and neuroinflammation. Finally, CD93 plays a role in cardiovascular disease development and progression. In this article, we reviewed the current literature regarding the role of CD93 in modulating angiogenesis, inflammation and tumor growth in order to understand where this glycoprotein could be a potential therapeutic target and could modify the outcome of the abovementioned pathologies.

Diagnostic and Prognostic Role of CD93 in Cardiovascular Disease: A Systematic Review

INTRODUCTION

Cluster of Differentiation (CD) 93 (also known as complement protein 1 q subcomponent receptor C1qR1 or C1qRp) is a transmembrane glycoprotein that can also be present in a soluble (sCD93) form. Recent studies have investigated the role of this protein in cardiovascular disease (CVD). The present systematic review aims to assess the associations between CD93 and cardiovascular (CV) risk factors and disease at both the proteomic and genomic levels.

METHODS

We conducted systematic searches in the PubMed, EMBASE, and Web of Science databases to identify all human studies since inception to February 2023 that investigated the role of CD93 in CV risk factors, CVD, and CV-associated outcomes. The data collection and analysis have been independently conducted by two reviewers. The search terms included: cardiovascular, heart failure, acute stroke, myocardial infarction, stroke, peripheral artery disease, cardiovascular death, MACE, hypertension, metabolic syndrome, hyperuricemia, diabetes, cd93, c1qr, C1qR1, complement protein 1 q subcomponent receptor.

RESULTS

A total of 182 references were identified, and 15 studies investigating the associations between CD93 protein levels or CD93 genetic polymorphisms and the development or prevalence of CV risk factors (i.e., hypertension, dyslipidemia, and obesity) and CVD (i.e., heart failure, coronary artery disease, and ischemic stroke) were included. Although promising, the quality and dimension of the analyzed studies do not allow for a definitive answer to the question of whether CD93 may hold diagnostic and prognostic value in CVD.

Synergistic regulation of microglia differentiation by CD93 and integrin β1 in the rat pneumococcal meningitis model

Streptococcus pneumoniae is the main bacterial pathogen of meningitis worldwide, which has a high mortality rate and survivors are prone to central nervous system (CNS) sequelae. In this regard, microglia activation has been associated with injury to the CNS. The aim of this study was to investigate the relationship between CD93, integrin β1, and microglia activation. In the rat pneumococcal meningitis model, we found significant increases of CD93 and integrin β1 expression and differentiation of M1 phenotype microglia. Furthermore, we showed in vitro siRNA-mediated downregulation of CD93 and integrin β1 expression after infecting highly aggressive proliferating immortalized (HAPI) microglia cells with S. pneumoniae. We observed differentiation of S. pneumonia-infected HAPI microglia cells to the M1 phenotype and significant release of soluble CD93 (sCD93) and integrin β1 expression. Complement C1q and metalloproteinases promoted sCD93 release. We also showed that downregulation of CD93 significantly reduced differentiation to M1 microglia and increased differentiation to M2 microglia. However, addition of recombinant CD93 may regulate microglia differentiation to the M1 phenotype. Furthermore, the downregulation of integrin β1 resulted in downregulation of the CD93 protein. In conclusion, interaction between integrin β1 and CD93 promotes differentiation of microglia to the M1 phenotype, increases the release of pro-inflammatory factors, and leads to nervous system injury in pneumococcal meningitis.

Molecular Characterization of Limited Ulcerative Colitis Reveals Novel Biology and Predictors of Disease Extension

BACKGROUND AND AIMS

Disease extent varies in ulcerative colitis (UC) from proctitis to left-sided colitis to pancolitis and is a major prognostic factor. When the extent of UC is limited there is often a sharp demarcation between macroscopically involved and uninvolved areas and what defines this or subsequent extension is unknown. We characterized the demarcation site molecularly and determined genes associated with subsequent disease extension.

METHODS

We performed RNA sequence analysis of biopsy specimens from UC patients with endoscopically and histologically confirmed limited disease, of which a subset later extended. Biopsy specimens were obtained from the endoscopically inflamed upper (proximal) limit of disease, immediately adjacent to the uninvolved colon, as well as at more proximal, endoscopically uninflamed colonic segments.

RESULTS

Differentially expressed genes were identified in the endoscopically inflamed biopsy specimens taken at each patient's most proximal diseased site relative to healthy controls. Expression of these genes in the more proximal biopsy specimens transitioned back to control levels abruptly or gradually, the latter pattern supporting the concept that disease exists beyond the endoscopic disease demarcation site. The gradually transitioning genes were associated with inflammation, angiogenesis, glucuronidation, and homeodomain pathways. A subset of these genes in inflamed biopsy specimens was found to predict disease extension better than clinical features and were responsive to biologic therapies. Network analysis revealed critical roles for interferon signaling in UC inflammation and poly(ADP-ribose) polymerase 14 (PARP14) was a predicted key driver gene of extension. Higher PARP14 protein levels were found in inflamed biopsy specimens of patients with limited UC that subsequently extended.

CONCLUSION

Molecular predictors of disease extension reveal novel strategies for disease prognostication and potential therapeutic targeting.

Soluble Complement Component 1q Receptor 1 (sCD93) Is Associated with Graft Function in Kidney Transplant Recipients

Cluster of differentiation 93 (CD93), also known as complement component 1q receptor 1 is a transmembrane glycoprotein expressed in endothelial and hematopoietic cells and associated with phagocytosis, cell adhesion, angiogenesis and inflammation. The extracellular part, soluble CD93 (sCD93), is released to body fluids in inflammation. Data on sCD93 in kidney diseases are limited. Our aim was to evaluate serum sCD93 in long-term kidney transplant recipients as a marker of inflammation and endothelial dysfunction that may be potentially useful in early recognition of graft dysfunction. Seventy-eight adult patients with functioning kidney graft and stable clinical state were examined at least one year after kidney transplantation. Serum sCD93 was measured by enzyme immunosorbent assay. Estimated glomerular filtration rate (eGFR) and albuminuria or proteinuria were assessed at baseline and over one-year follow-up. Increased sCD93 was associated with lower baseline eGFR independently of the confounders. Moreover, sCD93 was negatively associated with eGFR during one-year follow-up in simple analysis; however, this was not confirmed after adjustment for confounders. Baseline sCD93 was positively associated with baseline albuminuria and with increased proteinuria during the follow-up. Serum sCD93 was not correlated with other studied inflammatory markers (interleukin 6, C-reactive protein, procalcitonin and C3 and C4 complement components). To the best of our knowledge, this is the first report regarding the concentrations of sCD93 in kidney transplant recipients and one of the first reports showing the inverse association between sCD93 and renal function. Serum sCD93 should be further evaluated as a diagnostic and prognostic marker in renal transplantation.

CD93 has a crucial role in pathogenesis of psoriasis

BACKGROUND

Psoriasis is a chronic, immune-related disorder; inflammation, higher rate of epidermal proliferation, and angiogenesis are the main pathognomonic features. Cluster of differentiation 93 (CD93), an angiogenic element, plays a role in cell adhesion regulation and has a putative function in inflammation.

OBJECTIVE

To assess CD93 immunohistochemical expression in psoriatic skin and the association of CD93 single nucleotide polymorphisms (SNPs) rs2749817 to disease pathogenesis and severity.

METHODS

This case-control study was done on 50 patients with psoriasis vulgaris beside 50 age- and sex-matched healthy controls. Assessment of psoriasis severity was done by Psoriasis Area and Severity Index (PASI) score. 3 mm punch skin biopsies were taken from every participant, and hematoxylin and eosin staining and immunohistochemical staining for CD93 antibody were done. Assessment of CD93 rs2749817 gene polymorphism by the TaqMan allelic discrimination assay technique (real-time PCR) was done.

RESULTS

Immunohistochemical expression of CD93 showed membrano-cytoplasmic localization in both endothelial and inflammatory cells of cases and controls with significant more positivity in dermal endothelial and inflammatory cells of cases than controls (p = 0.001 and 0.014 respectively). Strong intensity was present in 18 of cases endothelial cells and 24 inflammatory cells with absence in controls (p =  0.001 for both) with significantly higher H-score and higher percent of positive cells (p  =  0.001 for both). The TC genotype was lower in patients compared to control (p-value = 0.006) and CC genotype which was present only in cases (p-value = 0.021).

CONCLUSION

Cluster of differentiation 93 has an essential role in psoriasis and an encouraging future therapy for psoriasis.

The relationship of indoxyl sulfate and p-cresyl sulfate with target cardiovascular proteins in hemodialysis patients

Protein-bound uremic toxins (Indoxyl sulfate [IS] and p-cresyl sulfate [PCS]) are both associated with cardiovascular (CV) and all-cause mortality in subjects with chronic kidney disease (CKD). Possible mechanisms have not been elucidated. In hemodialysis patients, we investigated the relationship between the free form of IS and PCS and 181 CV-related proteins. First, IS or PCS concentrations were checked, and high levels were associated with an increased risk of acute coronary syndrome (ACS) in 333 stable HD patients. CV proteins were further quantified by a proximity extension assay. We examined associations between the free form protein-bound uremic toxins and the quantified proteins with correction for multiple testing in the discovery process. In the second step, the independent association was evaluated by multivariable-adjusted models. We rank the CV proteins related to protein-bound uremic toxins by bootstrapped confidence intervals and ascending p-value. Six proteins (signaling lymphocytic activation molecule family member 5, complement component C1q receptor, C–C motif chemokine 15 [CCL15], bleomycin hydrolase, perlecan, and cluster of differentiation 166 antigen) were negatively associated with IS. Fibroblast growth factor 23 [FGF23] was the only CV protein positively associated with IS. Three proteins (complement component C1q receptor, CCL15, and interleukin-1 receptor-like 2) were negatively associated with PCS. Similar findings were obtained after adjusting for classical CV risk factors. However, only higher levels of FGF23 was related to increased risk of ACS. In conclusion, IS and PCS were associated with several CV-related proteins involved in endothelial barrier function, complement system, cell adhesion, phosphate homeostasis, and inflammation. Multiplex proteomics seems to be a promising way to discover novel pathophysiology of the uremic toxin.

Genetic variance and plasma concentration of CD93 is associated with cardiovascular mortality: Results from a 6.7‑year follow‑up of a healthy community‑living elderly population

Inflammation is one of the fundamental processes in numerous diseases. Cluster of differentiation (CD) 93, a glycoprotein, has been reported to be associated with a number of these diseases. There are reports indicating that a high plasma level of CD93 is associated with adverse events in ischaemic heart disease. Additionally, there are reports indicating different cardiovascular risks between different single nucleotide polymorphisms (SNPs) of CD93. Therefore, the present study aimed to determine whether the plasma concentration of CD93 and polymorphism of rs2749812 in CD93 were associated with clinical conditions and mortality in an elderly population. In 470 healthy elderly community-living individuals a novel clinical examination involving echocardiography and blood sampling was performed. The population was followed for 6.7 years. Plasma levels of CD93 and SNP analyses of rs2749812 of CD93 using PCR methodology were used. During the follow-up period, 106 (22.6%) all-cause and 61 (13.0%) cardiovascular deaths were registered. Those with the highest plasma concentration had markedly higher all-cause mortality. Evaluating the A/A, A/G and G/G genotypes, the G/G group exhibited significantly higher cardiovascular mortality (P=0.026), and an almost two-fold increased risk in a multivariate Cox regression model compared with the A/G genotype. Evaluation of subgroups with respect to sex, diabetes and hypertension revealed markedly increased cardiovascular risk in the G/G genotype in all subgroups. All results persisted in the multiple models used. In the present study, the glycoprotein CD93 was demonstrated to have prognostic cardiovascular information, with increased risk for those with a high plasma concentration. Furthermore, the G/G genotype of rs2749812 of CD93 has a significantly higher cardiovascular risk, as demonstrated here, and could therefore be regarded as a possible cardiovascular risk biomarker that might in the future be used to offer optimised cardiovascular patient handling. However, this was a small study, and more research is required.

Significance of Soluble CD93 in Type 2 Diabetes as a Biomarker for Diabetic Nephropathy: Integrated Results from Human and Rodent Studies

Cluster of differentiation 93 (CD93) is a glycoprotein expressed in activated endothelial cells. The extracellular portion of CD93 can be secreted as a soluble form (sCD93) under inflammatory conditions. As diabetic nephropathy (DN) is a well-known inflammatory disease, we hypothesized that sCD93 would be a new biomarker for DN. We prospectively enrolled 97 patients with type 2 diabetes and evaluated the association between serum sCD93 and DN prevalence. The association between CD93 and development of DN was investigated using human umbilical cord endothelial cells (HUVECs) in vitro and diabetic db/db mice in vivo. Subjects with higher sCD93 levels had a lower estimated glomerular filtration rate (eGFR). The sCD93 level was an independent determinant of both the albumin-to-creatinine ratio (ACR) and the eGFR. The risk of prevalent DN was higher in the high sCD93 group (adjusted odds ratio 7.212, 95% confidence interval 1.244-41.796, p = 0.028). In vitro, CD93 was highly expressed in HUVECs and both CD93 expression and secretion were upregulated after lipopolysaccharides (LPS) stimulation. In vivo, peritoneal and urine sCD93 levels and the renal glomerular expression of CD93 were significantly higher in the db/db mice than in the control db/m+ mice. These results suggest the potential of sCD93 as a candidate biomarker associated with DN.

C-type lectin family XIV members and angiogenesis

The growth and metastasis of tumors is dependent on angiogenesis. C-type lectins are carbohydrate-binding proteins with a diverse range of functions. The C-type lectin family XIV members are transmembrane glycoproteins, and all four members of this family have been reported to regulate angiogenesis, although the detailed mechanism of action has yet to be completely elucidated. They interact with extracellular matrix proteins and mediate cell-cell adhesion by their lectin-like domain. The aim of the present study was to summarize the available information on the function and mechanism of C-type lectin family XIV in angiogenesis and discuss their potential as targets for cancer therapy.

C-type lectin domain group 14 proteins in vascular biology, cancer and inflammation

The C‐type lectin domain (CTLD) group 14 family of transmembrane glycoproteins consist of thrombomodulin, CD93, CLEC14A and CD248 (endosialin or tumour endothelial marker‐1). These cell surface proteins exhibit similar ectodomain architecture and yet mediate a diverse range of cellular functions, including but not restricted to angiogenesis, inflammation and cell adhesion. Thrombomodulin, CD93 and CLEC14A can be expressed by endothelial cells, whereas CD248 is expressed by vasculature associated pericytes, activated fibroblasts and tumour cells among other cell types. In this article, we review the current literature of these family members including their expression profiles, interacting partners, as well as established and speculated functions. We focus primarily on their roles in the vasculature and inflammation as well as their contributions to tumour immunology. The CTLD group 14 family shares several characteristic features including their ability to be proteolytically cleaved and engagement of some shared extracellular matrix ligands. Each family member has strong links to tumour development and in particular CD93, CLEC14A and CD248 have been proposed as attractive candidate targets for cancer therapy.

Soluble CD93 is an apoptotic cell opsonin recognized by αx β2

Efferocytosis is essential for homeostasis and prevention of the inflammatory and autoimmune diseases resulting from apoptotic cell lysis. CD93 is a transmembrane glycoprotein previously implicated in efferocytosis, with mutations in CD93 predisposing patients to efferocytosis-associated diseases. CD93 is a cell surface protein, which is proteolytically shed under inflammatory conditions, but it is unknown how CD93 mediates efferocytosis or whether its efferocytic activity is mediated by the soluble or membrane-bound form. Herein, using cell lines and human monocytes and macrophages, we demonstrate that soluble CD93 (sCD93) potently opsonizes apoptotic cells but not a broad range of microorganisms, whereas membrane-bound CD93 has no phagocytic, efferocytic, or tethering activity. Using mass spectrometry, we identified α_x β₂ as the receptor that recognizes sCD93, and via deletion mutagenesis determined that sCD93 binds to apoptotic cells via its C-type lectin-like domain and to α_x β₂ by its EGF-like repeats. The bridging of apoptotic cells to α_x β₂ markedly enhanced efferocytosis by macrophages and was abrogated by α_x β₂ knockdown. Combined, these data elucidate the mechanism by which CD93 regulates efferocytosis and identifies a previously unreported opsonin-receptor system utilized by phagocytes for the efferocytic clearance of apoptotic cells.

Targeted proteomics reveals promising biomarkers of disease activity and organ involvement in antineutrophil cytoplasmic antibody-associated vasculitis

BACKGROUND

Targeted proteomics, which involves quantitative analysis of targeted proteins using selected reaction monitoring (SRM) mass spectrometry, has emerged as a new methodology for discovery of clinical biomarkers. In this study, we used targeted serum proteomics to identify circulating biomarkers for prediction of disease activity and organ involvement in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV).

METHODS

A large-scale SRM assay targeting 135 biomarker candidates was established using a triple-quadrupole mass spectrometer coupled with nanoflow liquid chromatography. Target proteins in serum samples from patients in the active and remission (6 months after treatment) stages were quantified using the established assays. Identified marker candidates were further validated by enzyme-linked immunosorbent assay using serum samples (n = 169) collected in a large-cohort Japanese study (the RemIT-JAV-RPGN study).

RESULTS

Our proteomic analysis identified the following proteins as biomarkers for discriminating patients with highly active AAV from those in remission or healthy control subjects: tenascin C (TNC), C-reactive protein (CRP), tissue inhibitor of metalloproteinase 1 (TIMP1), leucine-rich alpha-2-glycoprotein 1, S100A8/A9, CD93, matrix metalloproteinase 9, and transketolase (TKT). Of these, TIMP1 was the best-performing marker of disease activity, allowing distinction between mildly active AAV and remission. Moreover, in contrast to CRP, serum levels of TIMP1 in patients with active AAV were significantly higher than those in patients with infectious diseases. The serum levels of TKT and CD93 were higher in patients with renal involvement than in those without, and they predicted kidney outcome. The level of circulating TNC was elevated significantly in patients with lung infiltration. AAV severity was associated with markers reflecting organ involvement (TKT, CD93, and TNC) rather than inflammation. The eight markers and myeloperoxidase (MPO)-ANCA were clustered into three groups: MPO-ANCA, renal involvement (TKT and CD93), and inflammation (the other six markers).

CONCLUSIONS

We have identified promising biomarkers of disease activity, disease severity, and organ involvement in AAV with a targeted proteomics approach using serum samples obtained from a large-cohort Japanese study. Especially, our analysis demonstrated the effectiveness of TIMP1 as a marker of AAV activity. In addition, we identified TKT and CD93 as novel markers for evaluation of renal involvement and kidney outcome in AAV.

Soluble CD93 in Serum as a Marker of Allergic Inflammation

PURPOSE

CD93 is receiving renewed attention as a biomarker of inflammation. We aimed to evaluate the potential for serum sCD93 to serve as a novel biomarker for allergic inflammation.

MATERIALS AND METHODS

We enrolled 348 subjects with an allergic disease [allergic rhinitis (AR), chronic spontaneous urticaria (CSU), or bronchial asthma (BA)], including 14 steroid-naïve BA patients who were serially followed-up.

RESULTS

The serum sCD93 levels (ng/mL) in patients with exacerbated AR (mean±standard deviation, 153.1±58.4) were significantly higher than in patients without AR (132.2±49.0) or with stable AR (122.3±42.1). Serum sCD93 levels in exacerbated CSU (169.5±42.8) were also significantly higher than those in non-CSU (132.4±51.6) and stable CSU (122.8±36.2). This trend was also seen in BA. Serum levels in patients with ICS-naïve BA (161.4±53.1) were significantly higher than those in healthy controls without BA (112.2±30.8), low- and medium-dose ICS users. Serum sCD93 levels in high-dose ICS users (72.2±20.6) were significantly lower than those in low- and medium-dose users. The serum sCD93 levels in steroid-naïve patients with BA (195.1±72.7) decreased after ICS use for 4 weeks (134.4±42.8) and 8 weeks (100.7±13.4), serially.

CONCLUSION

Elevated serum sCD93 levels reflected exacerbated status of allergic diseases, including CSU, AR, and asthma. ICS use significantly diminished serum sCD93 levels in steroid-naïve patients with BA. This result may suggest sCD93 in serum as a therapeutic marker for allergic inflammation.

Soluble CD93 Is Involved in Metabolic Dysregulation but Does Not Influence Carotid Intima-Media Thickness

Type 2 diabetes and cardiovascular disease are complex disorders involving metabolic and inflammatory mechanisms. Here we investigated whether sCD93, a group XIV c-type lectin of the endosialin family, plays a role in metabolic dysregulation or carotid intima-media thickness (IMT). Although no association was observed between sCD93 and IMT, sCD93 levels were significantly lower in subjects with type 2 diabetes (n = 901, mean ± SD 156.6 ± 40.0 ng/mL) compared with subjects without diabetes (n = 2,470, 164.1 ± 44.8 ng/mL, P < 0.0001). Genetic variants associated with diabetes risk (DIAGRAM Consortium) did not influence sCD93 levels (individually or combined in a single nucleotide polymorphism score). In a prospective cohort, lower sCD93 levels preceded the development of diabetes. Consistent with this, a cd93-deficient mouse model (in addition to apoe deficiency) demonstrated no difference in atherosclerotic lesion development compared with apoe(-/-) cd93-sufficient littermates. However, cd93-deficient mice showed impaired glucose clearance and insulin sensitivity (compared with littermate controls) after eating a high-fat diet. The expression of cd93 was observed in pancreatic islets, and leaky vessels were apparent in cd93-deficient pancreases. We further demonstrated that stress-induced release of sCD93 is impaired by hyperglycemia. Therefore, we propose CD93 as an important component in glucometabolic regulation.

Soluble CD93 as a Novel Biomarker in Asthma Exacerbation

Asthma research is shifting from studying symptoms and lung functions to the narrow-focus cellular profiles protein analysis, biomarkers, and genetic markers. The transmembrane glycoprotein CD93 is involved in endothelial cell migration, angiogenesis, leukocytes extravasation, apoptosis, innate immunity and inflammation. Relationships between the serum level of soluble CD93 (sCD93) and acute myocardial infarction/premature MI/inflammatory arthritis/skin sclerosis have recently been reported. We hypothesized that sCD93 would be elevated during the acute phase of asthma. We measured the serum level of sCD93 in 57 patients with asthma exacerbation and 57 age-and gender-matched healthy controls. Additionally, sCD93 was reassessed at the time of discharge from the hospital. Clinical characteristics and peak expiratory flow (PEF) of the patients were assessed. The primary outcome was the comparison of serum level of sCD93 between asthmatics and healthy subjects. The sCD93 values ranged from 128 to 789 ng/mL in asthmatics (345.83±115.81) and from 31 to 289 ng/mL in control subjects (169.46±62.43). The difference between the 2 groups was statistically significant (P<0.001). The association between sCD93 and asthma remained significant after adjusting for age, sex, and BMI. The differences between asthmatics and controls remained significant on the last day of hospital stay. The association between sCD93 and PEF was not significant. In conclusion, the serum level of soluble CD93 is increased in patients with asthma exacerbation. It also showed that serum levels of sCD93 decreased with treatment of asthma attack. The clinical usefulness of determination of sCD93 as a biomarker of asthma requires further studies.

Sprouting angiogenesis is regulated by shedding of the C-type lectin family 14, member A (CLEC14A) ectodomain, catalyzed by rhomboid-like 2 protein (RHBDL2)

C-type lectin family 14, member A (CLEC14A), is a single-pass transmembrane glycoprotein that is overexpressed in tumor endothelial cells, and it promotes sprouting angiogenesis and modulates endothelial function via interactions with extracellular matrix proteins. Here, we show that CLEC14A is cleaved by rhomboid-like protein 2 (RHBDL2), one of 3 catalytic mammalian rhomboid-like (RHBDL) proteases, but that it is not cleaved by RHBDL1 or -3. Site-directed mutagenesis identified the precise site at which RHBDL2 cleaves CLEC14A, and targeted, small interfering RNAs that knockdown endogenous CLEC14A and RHBDL2 in human endothelial cells validated the specificity of CLEC14A shedding by RHBDL2. Loss of endogenous cleaved CLEC14A increased endothelial migration 2-fold, whereas that addition of recombinant cleaved CLEC14A inhibited the sprouting of human and murine endothelial cells 3-fold in several in vitro models. We assessed the in vivo role of cleaved CLEC14A in angiogenesis by using the rodent subcutaneous sponge implant model, and we found that CLEC14A protein inhibited vascular density by >50%. Finally, we show that cleaved CLEC14A binds to sprouting endothelial tip cells. Our data show that the ectodomain of CLEC14A regulates sprouting angiogenesis and suggests a role for RHBDL2 in endothelial function.-Noy, P. J., Swain, R. K., Khan, K., Lodhia, P., Bicknell, R. Sprouting angiogenesis is regulated by shedding of the C-type lectin family 14, member A (CLEC14A) ectodomain, catalyzed by rhomboid-like 2 protein (RHBDL2).

Effects of Controlled Cortical Impact on the Mouse Brain Vasculome

Perturbations in blood vessels play a critical role in the pathophysiology of brain injury and neurodegeneration. Here, we use a systematic genome-wide transcriptome screening approach to investigate the vasculome after brain trauma in mice. Mice were subjected to controlled cortical impact and brains were extracted for analysis at 24 h post-injury. The core of the traumatic lesion was removed and then cortical microvesels were isolated from nondirectly damaged ipsilateral cortex. Compared to contralateral cortex and normal cortex from sham-operated mice, we identified a wide spectrum of responses in the vasculome after trauma. Up-regulated pathways included those involved in regulation of inflammation and extracellular matrix processes. Decreased pathways included those involved in regulation of metabolism, mitochondrial function, and transport systems. These findings suggest that microvascular perturbations can be widespread and not necessarily localized to core areas of direct injury per se and may further provide a broader gene network context for existing knowledge regarding inflammation, metabolism, and blood-brain barrier alterations after brain trauma. Further efforts are warranted to map the vasculome with higher spatial and temporal resolution from acute to delayed phase post-trauma. Investigating the widespread network responses in the vasculome may reveal potential mechanisms, therapeutic targets, and biomarkers for traumatic brain injury.

Protein biomarkers for the prediction of cardiovascular disease in type 2 diabetes

AIMS/HYPOTHESIS

We selected the most informative protein biomarkers for the prediction of incident cardiovascular disease (CVD) in people with type 2 diabetes.

METHODS

In this nested case-control study we measured 42 candidate CVD biomarkers in 1,123 incident CVD cases and 1,187 controls with type 2 diabetes selected from five European centres. Combinations of biomarkers were selected using cross-validated logistic regression models. Model prediction was assessed using the area under the receiver operating characteristic curve (AUROC).

RESULTS

Sixteen biomarkers showed univariate associations with incident CVD. The most predictive subset selected by forward selection methods contained six biomarkers: N-terminal pro-B-type natriuretic peptide (OR 1.69 per 1 SD, 95% CI 1.47, 1.95), high-sensitivity troponin T (OR 1.29, 95% CI 1.11, 1.51), IL-6 (OR 1.13, 95% CI 1.02, 1.25), IL-15 (OR 1.15, 95% CI 1.01, 1.31), apolipoprotein C-III (OR 0.79, 95% CI 0.70, 0.88) and soluble receptor for AGE (OR 0.84, 95% CI 0.76, 0.94). The prediction of CVD beyond clinical covariates improved from an AUROC of 0.66 to 0.72 (AUROC for Framingham Risk Score covariates 0.59). In addition to the biomarkers, the most important clinical covariates for improving prediction beyond the Framingham covariates were estimated GFR, insulin therapy and HbA1c.

CONCLUSIONS/INTERPRETATION

We identified six protein biomarkers that in combination with clinical covariates improved the prediction of our model beyond the Framingham Score covariates. Biomarkers can contribute to improved prediction of CVD in diabetes but clinical data including measures of renal function and diabetes-specific factors not included in the Framingham Risk Score are also needed.

The characterization of a novel monoclonal antibody against CD93 unveils a new antiangiogenic target

The inhibition of tumor angiogenesis is one of the main challenges in cancer therapy. With the aim of developing monoclonal antibodies able to inhibit angiogenesis, we immunized mice with proliferating human umbilical vein endothelial cells. We generated a library of monoclonal antibodies able to recognize antigens expressed on endothelial cells and screened the antibodies for their ability to inhibit endothelial cell proliferation, migration, and sprouting in vitro. Here, we show that the antibody, designated as 4E1, is able to neutralize the formation of new vessels both in vitro and in vivo without affecting endothelial cell survival. By mass spectrometry we identified CD93 as the antigen bound by 4E1 and mapped the recognized epitope. CD93 is a transmembrane protein heavily glycosylated preferentially expressed in the vascular endothelium. CD93 silencing by lentiviral-mediated small hairpin RNA expression impairs human endothelial cell proliferation, migration, and sprouting. Altogether these findings reveal 4E1 as a novel antiangiogenic antibody and identify CD93 as a new target suitable for antiangiogenic therapy.

CD93 gene polymorphism is associated with disseminated colorectal cancer

PURPOSE

Cluster of differentiation 93 (CD93) is involved in apoptosis and inflammation and has a suggested role in angiogenesis, and all of which are involved in the development and dissemination of cancer. We evaluated the expression of CD93 and the association with two single nucleotide polymorphisms (SNPs), rs2749812 and rs2749817, as possible biomarkers in colorectal cancer (CRC).

METHODS

Tissue levels and plasma levels of CD93 were measured using an enzyme-linked immunosorbent assay (ELISA). Expression of CD93 was determined by immunohistochemistry, western blot and gene expression analysis. Genotype frequencies were established for the SNPs by real-time polymerase chain reaction (PCR), and the association with tumour stage and survival was analysed.

RESULTS

Total CD93 levels were 82% higher (P < 0.001) in tumours compared to matched normal tissues. Mean levels of soluble CD93 in plasma were 30% lower (P < 0.001) in the patients compared to the controls. The T/T genotype of SNP rs2749817 was more common in stage IV patients, with consequently higher risk of CRC death (T/T vs. C/C and C/T; hazard ratio (HR) = 1.73, 95% confidence interval (CI) = 1.11-2.67, P = 0.014), and was associated with a higher risk of CRC recurrence after radical operation (T/T vs. C/C and C/T; HR = 2.07, CI = 1.22-3.51, P = 0.007).

CONCLUSIONS

We showed that the T/T genotype of SNP rs2749817 is associated with disseminated cancer at diagnosis and an increased recurrence rate after radical operation. Patients with this genotype may benefit from early identification.

Unique properties of cluster of differentiation 93 in the umbilical cord blood of neonates

It has previously been reported by these authors that cluster of differentiation (CD) 93 is co-expressed on naive T-lymphocytes (CD4(+) CD45RA(+) cells) in neonatal umbilical cord blood cells (UCBCs) but not on normal adult peripheral blood cells (PBCs). In this study, expression of CD93 on other lymphocyte subsets and the concentration of soluble formed CD93 (sCD93) in serum or culture supernatants from neonatal umbilical cord blood (UCB) was examined. It was found that CD93 is also co-expressed on CD2(+) , CD16(+) , CD56(+) or CD25(+) cells in the lymphocyte population of neonatal UCBCs, but not on normal adult PBCs. The concentrations of sCD93 in serum and culture supernatants from neonatal UCB were significantly greater than those from normal adult peripheral blood. The concentrations of sCD93 in culture supernatants from neonatal UCBCs and normal adult PBCs treated with phorbol 12-myristate 13-acetate (PMA) were significantly enhanced compared with those without PMA treatment. The degree of enhancement of sCD93 by PMA in culture supernatants from neonatal UCBCs was significantly greater than that of normal adult PBCs and enhancement of sCD93 by PMA in the culture supernatants from neonatal UCBCs and normal adult PBCs was significantly suppressed by PKC inhibitor. Interestingly, the high concentration of serum sCD93 in neonates was significantly decreased in sera from infants at 1 month after birth. Expression of CD93 on the lymphocyte population of PBCs from infants at 1 month after birth was also significantly decreased, compared with that for neonatal UCBCs. These findings indicate that CD93 in neonatal UCB has unique properties as an immunological biomarker.

Soluble CD93 levels in patients with acute myocardial infarction and its implication on clinical outcome

Background

Inflammation plays a key role in the pathogenesis of acute myocardial infarction (MI). However, it is unclear whether marker of immune activation will provide prognostic information in these patients. We hypothesized that circulating levels of soluble CD93 (sCD93), a soluble form of transmembrane glycoprotein CD93, is increased in acute MI patients and its level would be associated with clinical outcomes in patients with acute MI.

Methods

We measured circulating levels of sCD93 in 120 patients with acute MI (63±13 yrs, M∶F = 85∶35) and in 120 age, sex-matched control subjects. In patients with acute MI, clinical characteristics, echocardiographic and laboratory findings were assessed at the time of initial enrollment. The primary outcome was defined as all-cause and cardiovascular death.

Results

Circulating sCD93 levels were significantly higher in patients with acute MI than in control subjects (552.1±293.7 vs. 429.8±114.2 ng/mL, p<0.0001). Upon in vitro inflammatory stimulation, increased CD93 shedding was demonstrated in acute MI patients but not in control subjects. During follow up period (median 208 days, 3-1058 days), the primary outcome occurred in 18 (15%) patients (9 cardiovascular deaths). Circulating levels of sCD93 were associated with all cause (p<0.0001) and cardiovascular (p<0.0001) mortality in patients with acute MI. Multivariate Cox regression analysis revealed that initial sCD93 level was found to be an independent predictor of all cause (p = 0.002) and cardiovascular mortality (p = 0.033) when controlled for age and left ventricular ejection fraction.

Conclusions

Circulating levels of sCD93 are elevated in patients with acute MI and their levels were associated with adverse clinical outcomes.

The epidermal growth factor-like domain of CD93 is a potent angiogenic factor

Human CD93, an epidermal growth factor (EGF)-like domain containing transmembrane protein, is predominantly expressed in the vascular endothelium. Studies have shown that AA4, the homolog of CD93 in mice, may mediate cell migration and angiogenesis in endothelial cells. Soluble CD93 has been detected in the plasma of healthy individuals. However, the role of soluble CD93 in the endothelium remains unclear. Recombinant soluble CD93 proteins with EGF-like domains (rCD93D123, with domains 1, 2, and 3; and rCD93D23, with domains 2 and 3) were generated to determine their functions in angiogenesis. We found that rCD93D23 was more potent than rCD93D123 in stimulating the proliferation and migration of human umbilical vein endothelial cells (HUVECs). Production of matrix-metalloproteinase 2 increased after the HUVECs were treated with rCD93D23. Further, in a tube formation assay, rCD93D23 induced cell differentiation of HUVECs through phosphoinositide 3-kinase/Akt/endothelial nitric oxide synthase and extracellular signal-regulated kinases-1/2 signaling. Moreover, rCD93D23 promoted blood vessel formation in a Matrigel-plug assay and an oxygen-induced retinopathy model in vivo. Our findings suggest that the soluble EGF-like domain containing CD93 protein is a novel angiogenic factor acting on the endothelium.

Membrane-associated CD93 regulates leukocyte migration and C1q-hemolytic activity during murine peritonitis

CD93 is emerging as a novel regulator of inflammation; however, its molecular function is unknown. CD93 exists as a membrane-associated glycoprotein on the surface of cells involved in the inflammatory cascade, including endothelial and myeloid cells. A soluble form (sCD93) is detectable in blood and is elevated with inflammation. In this study, we demonstrate heightened susceptibility to thioglycollate-induced peritonitis in CD93(-/-) mice. CD93(-/-) mice showed a 1.6-1.8-fold increase in leukocyte infiltration during thioglycollate-induced peritonitis between 3 and 24 h that returned to wild type levels by 96 h. Impaired vascular integrity in CD93(-/-) mice during peritonitis was demonstrated using fluorescence multiphoton intravital microscopy; however, no differences in cytokine or chemokine levels were detected with Luminex Multiplex or ELISA analysis. C1q-hemolytic activity in CD93(-/-) mice was decreased by 22% at time zero and by 46% 3 h after thioglycollate injection, suggesting a defect in the classical complement pathway. Leukocyte recruitment and C1q-hemolytic activity was restored to wild type levels when CD93 was expressed on either hematopoietic cells or nonhematopoietic cells in bone marrow chimeric mice. However, elevated levels of sCD93 in inflammatory fluid were observed only when CD93 was expressed on nonhematopoietic cells. Because cell-associated CD93 was sufficient to restore a normal inflammatory response, these data suggest that cell-associated CD93, and not sCD93, regulates leukocyte recruitment and complement activation during murine peritonitis.

The utility of collaborative biobanks for cardiovascular research

Differences between animal and human atherosclerosis have led to the requirement for clinical data, imaging information and biological material from large numbers of patients and healthy persons. Where such "biobanks" exist, they have been fruitful sources for genomewide association, diagnostic accuracy, ethnicity, and risk stratification cohort studies. In addition once established, they attract funding for future projects. Biobanks require a network of medical contributors, secure storage facilities, bioinformatics expertise, database managers, and ethical working practices to function optimally. There is the opportunity for collaboration between individual biobanks to further amplify the advantages afforded.