gp38k (CHI3L1) is a novel adhesion and migration factor for vascular cells

Chitinase-3-like protein-1 (YKL-40) as a marker of endothelial dysfunction in obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is a highly prevalent disorder affecting 15-24% of adults and triples the risk for hypertension independent of other risk factors. The exact mechanisms of endothelial dysfunction and variable susceptibility to hypertension in OSA are not entirely clear. No biomarker to date has been found to be associated with hypertension in OSA. Chitinase-3-like protein-1(YKL-40) is a circulating moiety with roles in injury, repair and angiogenesis that is dysregulated in atherosclerosis and correlates with increased cardiovascular morbidity and mortality. We sought to determine the role of YKL-40, as a biomarker, for endothelial dysfunction and hypertension in OSA.

METHODS

All subjects underwent polysomnography for suspected sleep-disordered breathing. Endothelial-dependent vasodilatory capacity was assessed using flow-mediated vasodilation (FMD). YKL-40 was measured in plasma using ELISA methodology.

RESULTS

We studied 95 subjects in four groups according to OSA and hypertension status. FMD was markedly impaired in hypertensive OSA (8.0% ± 0.5 vasodilation) compared to normotensive OSA (13.5% ± 0.5, P <0.0001) and non-OSA with hypertension (10.5% ± 0.8, P <0.01) and without hypertension (16.1% ± 1.0, P <0.0001). YKL-40 was significantly elevated only in hypertensive OSA compared to other three groups and had a negative correlation with FMD (r=-0.37, P = 0.0008). Receiver operating characteristic (ROC) curve analysis for YKL-40 in predicting endothelial dysfunction had a sensitivity of 71% and a specificity of 64% with AUC = 0.68, 0.57 to 0.80, P = 0.004.

CONCLUSIONS

Elevated circulating levels of YKL-40 are observed in only hypertensive OSA and have a significant negative correlation with endothelial function. This specificity suggests YKL-40 could be a potential biomarker for endothelial dysfunction in OSA.

YKL-40 in allogeneic hematopoietic cell transplantation after AML and myelodysplastic syndrome

YKL-40, also called chitinase-3-like-1 protein, is an inflammatory biomarker that has been associated with disease severity in inflammatory and malignant diseases, including AML, multiple myeloma and lymphomas. The objective of the current study was to assess the prognostic value of pretransplant recipient and donor plasma YKL-40 concentrations in patients with AML (n=624) or myelodysplastic syndrome (n=157) treated with allogeneic hematopoietic cell transplantation (HCT). In recipients, the plasma YKL-40 concentrations were increased when the HCT-comorbidity index was ⩾5 (P=0.028). There were no significant associations between plasma YKL-40 concentrations in recipients and any outcome measures. In donors with YKL-40 plasma concentrations above the age-adjusted 95th percentile, a trend toward increased grade II-IV acute GvHD in recipients was observed (adjusted hazard ratio 1.39 (95% confidence interval 1.00-1.94), P=0.050), with no significant associations with overall survival, treatment-related mortality or relapse. In conclusion, our study shows that YKL-40 does not aid risk stratification of patients undergoing allogeneic HCT, but suggests that YKL-40 may aid donor selection when multiple, otherwise equal, donors are available.

Glycoprotein YKL-40: a novel biomarker of chronic graft-vs-host disease activity and severity?

AIM

To investigate whether increased YKL-40 levels positively correlate with graft-vs-host disease (cGVHD) activity and severity and if YKL-40 could serve as a disease biomarker.

METHODS

This case-control study was conducted at the University Hospital Centre Zagreb from July 2013 to October 2015. 56 patients treated with hematopoietic stem cell transplantation (HSCT) were included: 35 patients with cGVHD and 21 without cGVHD. There was no difference between groups in age, sex, median time from transplant to study enrollment, intensity of conditioning, type of donor, or source of stem cells. Blood samples were collected at study enrollment and YKL-40 levels were measured with ELISA. Disease activity was estimated using Clinician's Impression of Activity and Intensity of Immunosuppression scales and disease severity using Global National Institutes of Health (NIH) score.

RESULTS

YKL-40 levels were significantly higher in cGVHD patients than in controls (P=0.003). The difference remained significant when patients with myelofibrosis were excluded from the analysis (P=0.017). YKL-40 level significantly positively correlated with disease severity (P<0.001; correlation coefficient 0.455), and activity estimated using Clinician's Impression of Activity (P=0.016; correlation coefficient 0.412) but not using Intensity of Immunosuppression (P=0.085; correlation coefficient 0.296).

CONCLUSION

YKL-40 could be considered a biomarker of cGVHD severity and activity. However, validation in a larger group of patients is warranted, as well as longitudinal testing of YKL-40 levels in patients at risk of developing cGVHD.

Role of inflammatory marker YKL-40 in the diagnosis, prognosis and cause of cardiovascular and liver diseases

This review summarizes present evidence for the role of YKL-40 in the diagnosis, prognosis and cause of cardiovascular and alcoholic liver disease. The question of whether YKL-40 is merely a marker or a causal factor in the development of cardiovascular and liver disease is addressed, with emphasis on the Mendelian randomization design. The Mendelian randomization approach uses genetic variants associated with lifelong high plasma YKL-40 levels that are largely unconfounded and not prone to reverse causation. Thus, the approach mimics a controlled double-blind randomized trial, but it uses genetic variants rather than a drug and placebo, and like a blinded trial, it allows inference about causality. Moreover, the review also covers background on the molecular biology and functions of YKL-40, YKL-40 levels in healthy individuals and reference range, and the role of YKL-40 as a biomarker of cardiovascular and alcoholic liver disease. YKL-40 is a plasma protein named after its three N-terminal amino acids, Y (tyrosine), K (lysine) and L (leucine), and its molecular weight of 40 kDa. It is produced by local inflammatory cells in inflamed tissues, such as lipid-laden macrophages inside the vessel wall and perhaps also hepatic stellate cells. Observational studies show that plasma YKL-40 levels are elevated in patients with cardiovascular and liver disease and are associated with disease severity and prognosis. Furthermore, elevated plasma YKL-40 levels in apparently healthy individuals are associated with a 2-fold increased risk of future ischemic stroke and venous thromboembolism, but not with myocardial infarction, suggesting that YKL-40 could play a role in the formation of embolisms rather than atherosclerosis per se. Further, elevated YKL-40 levels combined with excessive alcohol consumption are associated with 10-years risk of alcoholic liver cirrhosis of up to 7%, suggesting that YKL-40 can be used as a strong noninvasive marker of predicting alcoholic liver cirrhosis. Importantly, in Mendelian randomization studies, genetically elevated plasma YKL-40 levels were not associated with risk of cardiovascular and alcoholic liver disease, thus suggesting that plasma YKL-40 does not play a causal role in the development of these diseases. Despite this, plasma YKL-40 levels may play a role in disease progression after diagnosis, and inhibition of YKL-40 activity might be a novel therapy in some cardiovascular and liver diseases.

YKL-40/chitinase-3-like protein 1 is associated with poor prognosis and promotes cell growth and migration of cholangiocarcinoma

YKL-40, a chitinase-like glycoprotein, is expressed at a high level in cancer patients. Its exact function is unknown and is the subject of current investigation. Here, we report the correlation of plasma YKL-40 levels with clinicopathological features of cholangiocarcinoma (CCA), a lethal bile duct cancer, particularly prevalent in Northeastern Thailand. Statistical analysis of plasma YKL-40 concentrations in 57 CCA patients and 41 normal healthy subjects gave a median value of 169.5 ng/mL for CCA patients compared with 46.9 ng/mL for the control subjects (P < 0.0001). There was no significant association of plasma YKL-40 levels with patient age, tumor grade, or histology type. However, Kaplan-Meier analysis suggested that the elevated plasma YKL-40 level was particularly associated with short survival in CCA patients (P = 0.038). Immunohistochemical examination of 34 CCA tissues revealed low expression of YKL-40 in CCA cells, but high expression in adjacent intratumoral stroma, liver, and connective tissues. Univariate analysis showed significant association of the intratumoral YKL-40 expression in CCA tissues with the non-papillary type CCA. Addition of rYKL-40 in the culture medium and transient expression of YKL-40 in CCA cell lines were shown to promote the growth and migration of the tumor cells, and that YKL-40 interacted with a cell-surface receptor involved in the Akt/Erk-mediated pathway. In conclusion, our results support the proposal of YKL-40 as a new candidate prognostic biomarker for cancer diseases.

Site-Specific Secretome Map Evidences VSMC-Related Markers of Coronary Atherosclerosis Grade and Extent in the Hypercholesterolemic Swine

A major drawback in coronary atherosclerosis (ATS) research is the difficulty of investigating early phase of plaque growth and related features in the clinical context. In this study, secreted proteins from atherosclerotic coronary arteries in a hypercholesterolemic swine model were characterized by a proteomics approach and their expression was correlated to site-specific ATS stage and extent. A wide coronary artery map of secreted proteins has been obtained in high fat (HF) diet induced ATS swine model and a significantly different expression of many proteins related to vascular smooth muscle cell (VSMC) activation/migration has been identified. Significant associations with ATS stage of HF coronary lesions were found for several VSMC-derived proteins and validated for chitinase 3 like protein 1 (CHI3L1) by tissue immunoexpression. A direct correlation (R(2) = 0.85) was evidenced with intima to media thickness ratio values and ELISA confirmed the higher blood concentrations of CHI3L1 in HF cases. These findings confirmed the pivotal role of VSMCs in coronary plaque development and demonstrated a strong site-specific relation between VSMC-secreted CHI3L1 and lesion grade, suggesting that this protein could be proposed as a useful biomarker for diagnosing and staging of atherosclerotic lesions in coronary artery disease.

Plasma YKL-40 during pregnancy and gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is characterised by hyperglycaemia during pregnancy. The clinical circumstances involved in the development of GDM leaves the patient at a high risk of the subsequent development of type 2 diabetes. Plasma levels of the inflammation marker YKL-40 are elevated in type 2 diabetes and correlate with fasting plasma glucose levels and insulin resistance in patients with type 2 diabetes. With the present study we aimed to determine if pregnancy (and associated insulin resistance) with or without GDM affects plasma YKL-40 levels. Plasma from women diagnosed with GDM and healthy normal glucose-tolerant pregnant women (non-GDM) was obtained at the third trimester of pregnancy and again 3-4 months following delivery, and levels of YKL-40 and interleukin 6 (IL-6; known to regulate YKL-40) were measured. Plasma YKL-40 levels were similarly low during pregnancy in both groups and increased significantly after delivery, but remained lower in the GDM group compared with the non-GDM group postpartum. In contrast, plasma IL-6 levels were not affected by pregnancy or diagnosis of GDM, Nevertheless, YKL-40 levels were associated with IL-6 levels in the non-GDM group (but not in the GDM group). Pregnancy seems to be associated with a temporary reduction in circulating YKL-40, which increases after delivery, but to a much lesser extent in women with GDM than in non-GDM women.

Serum YKL-40 for monitoring myocardial ischemia after revascularization in patients with stable coronary artery disease

AIM

The aim was to investigate the inflammatory biomarker YKL-40 as a monitor of myocardial ischemia in patients with coronary artery disease (CAD).

METHODS

A total of 311 patients with stable CAD were included. Blood samples were taken at baseline, the day after coronary angiography and/or after percutaneous coronary intervention and after 6 months.

RESULTS

A total of 148 (48%) patients were revascularized and 163 patients underwent only coronary angiography. In the entire population, serum YKL-40 increased significantly from baseline to 6 months (p = 0.05). This tendency was seen in nonrevascularized patients (p = 0.06), but not in revascularized patients (p = 0.46). Serum YKL-40 increased approximately 25% the day after the invasive procedure (p < 0.001) and then decreased significantly to nearly baseline after 6 months (p = 0.002).

CONCLUSION

Serum YKL-40 is a potential promising biomarker of disease progression but not of myocardial ischemia in patients with stable CAD.

YKL-40 level in gingival crevicular fluid from patients with periodontitis and type 2 diabetes

OBJECTIVE

YKL-40 is a chitin-binding glycoprotein, the level of which increases in inflammatory diseases, diabetes mellitus (DM), cardiovascular diseases, and tumors. Gingival crevicular fluid (GCF) contains many proteins and markers of periodontitis. The purpose of this study was to investigate YKL-40 level in GCF from patients with periodontitis and DM and the association between YKL-40 level and chronic periodontitis (CP) or DM.

SUBJECTS AND METHODS

The subjects were 121 patients with DM, CP, DM and periodontitis (DM-P), and healthy subjects (H). GCF was collected using paper strips after the sites for GCF collection were clinically evaluated for probing depth (PD), gingival index (GI), and bleeding on probing (BOP). YKL-40 in GCF was identified by Western blotting, and its level was determined by ELISA.

RESULTS

YKL-40 was contained in GCF samples from H, DM, CP, and DM-P sites, and its levels (amount and concentration) in CP and DM-P were significantly higher than those in H and DM. GCF YKL-40 level significantly correlated with PD and GI, and its level in BOP-positive sites was significantly higher than that in BOP-negative ones.

CONCLUSIONS

GCF YKL-40 level was elevated in periodontitis, but not DM. YKL-40 in GCF may be an inflammatory marker for periodontitis.

RelB/p50 complexes regulate cytokine-induced YKL-40 expression

The secreted protein, YKL-40, has been proposed as a biomarker of a variety of human diseases characterized by ongoing inflammation, including chronic neurologic pathologies such as multiple sclerosis and Alzheimer's disease. However, inflammatory mediators and the molecular mechanism responsible for enhanced expression of YKL-40 remained elusive. Using several mouse models of inflammation, we now show that YKL-40 expression correlated with increased expression of both IL-1 and IL-6. Furthermore, IL-1 together with IL-6 or the IL-6 family cytokine, oncostatin M, synergistically upregulated YKL-40 expression in both primary human and mouse astrocytes in vitro. The robust cytokine-driven expression of YKL-40 in astrocytes required both STAT3 and NF-κB binding elements of the YKL-40 promoter. In addition, YKL-40 expression was enhanced by constitutively active STAT3 and inhibited by dominant-negative IκBα. Surprisingly, cytokine-driven expression of YKL-40 in astrocytes was independent of the p65 subunit of NF-κB and instead required subunits RelB and p50. Mechanistically, we show that IL-1-induced RelB/p50 complex formation was further promoted by oncostatin M and that these complexes directly bound to the YKL-40 promoter. Moreover, we found that expression of RelB was strongly upregulated during inflammation in vivo and by IL-1 in astrocytes in vitro. We propose that IL-1 and the IL-6 family of cytokines regulate YKL-40 expression during sterile inflammation via both STAT3 and RelB/p50 complexes. These results suggest that IL-1 may regulate the expression of specific anti-inflammatory genes in nonlymphoid tissues via the canonical activation of the RelB/p50 complexes.

Proteins from the 18 glycosyl hydrolase family are associated with kidney dysfunction in patients with diabetes type 2

OBJECTIVES

To investigate chitotriosidase (CHIT1) activity and chitinase-3-like protein 1 (YKL-40) concentration in plasma of type 2 diabetic patients and evaluate their relationship with kidney dysfunction.

MATERIALS AND METHODS

94 diabetic subjects and 33 controls were enrolled in the study. Plasma CHIT1 activity and YKL-40 concentration were measured along with routine laboratory parameters.

RESULTS

Levels of CHIT1 and YKL-40 in plasma of type 2 diabetic patients increased progressively with the degree of albuminuria. CHIT1 discriminated normoalbuminuric subjects from those with abnormal albuminuria better than YKL-40.

CONCLUSIONS

CHIT1represent a supportive biomarker connected with development of diabetic vascular complications, especially kidney dysfunction.

Circulating YKL-40 level, but not CHI3L1 gene variants, is associated with atherosclerosis-related quantitative traits and the risk of peripheral artery disease

YKL-40, a pleotropic cytokine, is emerging as a risk factor and a prognostic predictor of atherosclerotic cardiovascular disease. We attempted to elucidate the genetic, clinical and biochemical correlates of circulating YKL-40 level and, by combining it with CHI3L1 gene variants, with the risk and long-term mortality of peripheral artery disease (PAD). Plasma YKL-40 concentrations were measured in 612 Taiwanese individuals who had no clinically overt systemic disease. Clinical parameters, CHI3L1 gene promoter variants and 18 biomarker levels were analyzed. Eighty-six PAD patients were further enrolled for analysis. Significant associations were found between CHI3L1 genotypes/haplotypes and YKL-40 levels for the health examination subjects (smallest p = 8.36 × 10-7 for rs4950928 and smallest p = 1.72 × 10-10 for haplotype TGG) and also for PAD patients. For the health examination subjects, circulating YKL-40 level, but not CHI3L1 gene variants, were positively associated with age, smoking, and circulating levels of triglyceride, lipocalin 2 and multiple inflammatory biomarkers and negatively associated with low-density-lipoprotein cholesterol levels. Circulating YKL-40 level is also significantly associated with the risk of PAD (p = 3.3 × 10-23). Circulating YKL40 level, but not CHI3L1 gene promoter variants, is associated with the risk of PAD in Taiwanese. The association of YKL-40 levels with multiple quantitative traits relating to the risk of PAD may provide a molecular basis linking YKL-40 to atherosclerotic cardiovascular disease.

Serum YKL-40: a potential biomarker for psoriasis or endothelial dysfunction in psoriasis?

Psoriasis is a disease that can contribute to a risk of atherosclerosis. In several studies, impaired endothelial dysfunction (ED) is correlated with psoriasis. Serum YKL-40 is a new inflammatory biomarker of vascular damage, like ED and cardiovascular diseases. The aim of the study was to compare relevance of serum YKL-40 levels in psoriasis patients and healthy subjects according to ED diagnosis and identifiable cardiovascular risk factors. Sixty (31 female, 29 male) patients with plaque psoriasis, and 30 (18 female, 12 male) healthy controls were selected according to whether they had at least one or no identifiable risk factors for cardiovascular disease. All subjects were evaluated ultrasonographically for endothelial function and diagnosed as with or without ED and all groups compared for serum YKL-40 levels. YKL-40 levels of psoriatic patients with ED were higher than healthy controls with ED (P = <0.05). There were no statistical differences in between subjects without ED. YKL-40 levels of patients over age of 40 were higher than younger ones (P < 0.05). But in healthy controls, there were no differences. In comparison of cardiovascular risk-positive (RP) patients and RP healthy subjects, YKL-40 levels were higher in RP patients (P = <0.05). The elevation of plasma YKL-40 in psoriasis can be associated not only with inflammation of the disease, but also with ED. YKL-40 can be used as a marker for predicting and preventing cardiovascular diseases in RP psoriatic patients with age above 40.

miR-24 limits aortic vascular inflammation and murine abdominal aneurysm development

Identification and treatment of abdominal aortic aneurysm (AAA) remain among the most prominent challenges in vascular medicine. MicroRNAs (miRNAs) are crucial regulators of cardiovascular pathology and represent intriguing targets to limit AAA expansion. Here we show, by using two established murine models of AAA disease along with human aortic tissue and plasma analysis, that miR-24 is a key regulator of vascular inflammation and AAA pathology. In vivo and in vitro studies reveal chitinase 3-like 1 (Chi3l1) to be a major target and effector under the control of miR-24, regulating cytokine synthesis in macrophages as well as their survival, promoting aortic smooth muscle cell migration and cytokine production, and stimulating adhesion molecule expression in vascular endothelial cells. We further show that modulation of miR-24 alters AAA progression in animal models, and that miR-24 and CHI3L1 represent novel plasma biomarkers of AAA disease progression in humans.

Abdominal aortic aneurysm (AAA) is a potentially fatal and often asymptomatic disease whose causes remain unclear. Here the authors show that a microRNA, miR-24, and its target, the glycoprotein chitinase 3-like 1, represent key regulators of AAA development.

Elevation in circulating YKL-40 concentration in patients with cerebrovascular disease

YKL-40 is a novel inflammatory protein. Elevated serum levels of YKL-40 have been reported in patients with atherosclerosis and other cardiovascular diseases, but the circulating profile of YKL-40 in patients with cerebrovascular disease has been less investigated. This prospective observational study aimed to determine serum levels of YKL-40 in patients with different subtypes and severities of cerebrovascular disease. Eighty patients with acute ischemic stroke, 30 patients with acute hemorrhagic stroke, 15 patients with transient ischemic attack (TIA) and 18 age- and gender-matched healthy control subjects were recruited. Blood was sampled. Serum levels of YKL-40 were measured by ELISA. In healthy control subjects, serum levels of YKL-40 were 45.09 ± 31.41 ng/ml, significantly lower than those in patients with acute ischemic stroke (178.58 ± 127.78 ng/ml), hemorrhagic stroke (105.32 ± 87.35 ng/ml) and TIA (148.09 ± 108 ng/ml) respectively (P<0.05). When the 80 acute ischemic stroke cases were stratified into four Oxfordshire Community Stroke subtypes, serum levels of YKL-40 were significantly higher in patients with total anterior (n=16), partial anterior (n=25) and posterior (n=12) circulation infarctions respectively than those with lacunar (n=27) infarction (P<0.05). Moreover, 63 of 80 patients with acute ischemic stroke survived. Circulating levels of YKL-40 in these stroke survivors were associated with the United States National Institutes of Health Stroke Scale (NIHSS) scores of neurological deficit. In summary, serum levels of YKL-40 were elevated in patients with cerebrovascular disease in lesion subtype- and severity-dependent manners. These observations suggest a potential for YKL-40 as a diagnostic/prognostic biomarker for cerebrovascular disease.

Plasma levels of the proinflammatory chitin-binding glycoprotein YKL-40, variation in the chitinase 3-like 1 gene (CHI3L1), and incident cardiovascular events

Background

YKL‐40, encoded by the chitinase 3‐like 1 (CHI3L1) gene, is a chitinase‐like protein involved in innate immune function hypothesized to play a role in the progression of atherosclerosis that may have differential roles in myocardial infarction (MI), as compared to stroke.

Methods and Results

In a nested case‐control study conducted within a prospective cohort of 23 294 initially healthy women of European ancestry, we (1) measured plasma concentration of YKL‐40 among 359 participants who subsequently developed cardiovascular events and among 359 age‐, smoking‐, and hormone replacement therapy–matched participants who remained free of disease during 17 years of follow‐up, (2) compared effects of YKL‐40 on vascular risk to that associated with 3 alternative inflammatory biomarkers (high‐sensitivity C‐reactive protein) ([hsCRP], soluble intracellular adhesion molecule 1, and fibrinogen), and (3) evaluated the role of 41 single‐nucleotide polymorphisms (SNPs) in the chitinase 3‐like 1 gene (CHI3L1) as determinants of YKL‐40 levels and incident vascular events. YKL‐40 levels were higher in women with hypertension, diabetes, and obesity and correlated modestly with high‐density lipoprotein cholesterol, triglycerides, and hsCRP, but not with low‐density lipoprotein cholesterol. Baseline YKL‐40 level was significantly associated with incident thromboembolic stroke with a magnitude of effect (a 40% per quartile increase in odds ratio [OR], P=0.019) comparable to that of hsCRP (a 52% per quartile increase in OR, P=0.006). By contrast, no significant association was observed between YKL‐40 and incident MI. Genetic variation in CHI3L1 was strongly associated with YKL‐40 levels; however, in this sample set, we did not observe a statistically significant association between genotype and future vascular events.

Conclusions

Among initially healthy U.S. women, plasma levels of the proinflammatory chitenase‐like protein, YKL‐40, were influenced by environmental as well as genetic factors and predicted incident thromboembolic stroke, but not MI, a differential effect consistent with limited previous data.

Increased plasma YKL-40/chitinase-3-like-protein-1 is associated with endothelial dysfunction in obstructive sleep apnea

Purpose

Obstructive sleep apnea (OSA) is a common disorder affecting 15–24% of the adults and is associated with increased risk of hypertension and atherosclerosis. The exact mechanisms underlying hypertension in OSA are not entirely clear. YKL-40/Chitinase-3-like protein-1 is a circulating moiety with roles in injury, repair and angiogenesis that is dysregulated in atherosclerosis and a number of other diseases. We sought to determine the role of YKL-40 in endothelial dysfunction and hypertension in OSA.

Methods

We studies 23 normotensive OSA (N-OSA) and 14 hypertensive OSA (H-OSA) without diabetes and apparent cardiovascular disease. Endothelial-dependent nitric oxide-mediated vasodilatory capacity was assessed by flow-mediated vasodilation (FMD). YKL-40, vascular endothelial growth factor (VEGF) and the soluble form of VEGF receptor-1or sFlt-1 were measured in plasma using ELISA methodology.

Results

N-OSA subjects aged 49.1±2.3 years and H-OSA aged 51.3±1.9 years with BMI 36.1±1.6 and 37.6±1.9 kg/m², respectively. The apnea-hypopnea index (AHI) was 41±5 events/hr in N-OSA and 46±6 in H-OSA with comparable degree of oxygen desaturations during sleep. FMD was markedly impaired in H-OSA (8.3%±0.8) compared to N-OSA (13.2%±0.6, P<0.0001). Plasma YKL-40 was significantly elevated in H-OSA (55.2±7.9 ng/ml vs. 35.6±4.2 ng/ml in N-OSA, P = 0.02) and had an inverse relationship with FMD (r = −0.52, P = 0.013). There was a significant positive correlation between sFlt-1/VEGF, a measure of decreased VEGF availability, and YKL-40 (r = 0.42, P = 0.04).

Conclusion

The levels of plasma YKL-40 were elevated in H-OSA group and inversely correlated with the endothelial-dependent vasodilatory capacity whereas there was a positive correlation between sFlt-1/VEGF and YKL-40. These findings suggest that YKL-40 is dysregulated, in part, due to perturbation of VEGF signaling, and may contribute to endothelial dysfunction and hypertension in OSA.

Simulating tumor microenvironment: changes in protein expression in an in vitro co-culture system

BACKGROUND

The role of the microenvironment during the initiation and progression of carcinogenesis is thought to be of critical importance, both for the enhanced understanding of fundamental cancer biology as well as for improving molecular diagnostics and therapeutics. The aim of this study was to establish an in vitro model based on a co-culture of healthy human fibroblasts (HFs) and human osteosarcoma cells (MG-63s) to simulate the microenvironment including tumor and healthy cells.

METHODS

The HFs and MG-63s were in vitro co-cultured for a period of time ranging from 24 h to 7 days. Cell morphology and organization were studied using phase contrast microscopy while the expression of Human Cartilage Glycoprotein 39 (YKL-40), Vascular Endothelial Growth Factor (VEGF) and Matrix Metalloprotease 1 (MMP1) was investigated by Real Time PCR and Western Blotting.

RESULTS

The results showed a characteristic disposition of tumor and healthy co-cultured cells in columns which are not visible in tumor and healthy cells grown singularly. The expression of YKL-40, VEGF and MMP1 significantly changed in co-cultured cells compared to HFs and MG-63s separately cultured.

CONCLUSIONS

We concluded that the tumor microenvironment has an influence on the protein expression of the healthy surrounding tissues and the process of tumorigenicity.

Antibody directed against human YKL-40 increases tumor volume in a human melanoma xenograft model in scid mice

Induced overexpression of the secretory protein YKL-40 promotes tumor growth in xenograft experiments. We investigated if targeting YKL-40 with a monoclonal antibody could inhibit tumor growth. YKL-40 expressing human melanoma cells (LOX) were injected subcutenously in Balb/c scid mice. Animals were treated with intraperitoneal injections of anti-YKL-40, isoptype control or PBS. Non-YKL-40 expressing human pancreatic carcinoma cell line PaCa 5061 served as additional control. MR imaging was used for evaluation of tumor growth. Two days after the first injections of anti-YKL-40, tumor volume had increased significantly compared with controls, whereas no effects were observed for control tumors from PaCa 5061 cells lacking YKL-40 expression. After 18 days, mean tumor size of the mice receiving repeated anti-YKL-40 injections was 1.82 g, >4 times higher than mean tumor size of the controls (0.42 g). The effect of anti-YKL-40 on the increase of tumor volume started within hours after injection and was dose dependent. Intratumoral hemorrhage was observed in the treated animals. The strong effect on tumor size indicates important roles for YKL-40 in melanoma growth and argues for a careful evaluation of antibody therapy directed against YKL-40.

Serum YKL-40 levels and chitotriosidase activity in patients with beta-thalassemia major

BACKGROUND

YKL-40 association with human disease has been the object of many years of investigation. β-thalassemia patients are affected by hepatic siderosis, which determines a fibrotic process and tissue remodelling. Chitotriosidase has been found to be increased in thalassemic patients returning to normal in patients submitted to bone marrow transplantation. YKL-40 is associated with macrophage activation in liver and in other tissues. The aim of the study was to analyse the level of serum YKL-40 and plasma chitotriosidase activity of patients with beta-thalassemia to assess whether their expression correlates with liver disease and degree of liver siderosis.

METHODS

Expression of YKL-40 and chitotriosidase as a marker of inflammation in 69 thalassemic patients were evaluated. We sought to investigate whether these two chitinases could be considered as a significant biomarker to evaluate therapy effectiveness.

RESULTS

Surprisingly we found normal value of YKL-40. We, also, analysed chitotriosidase activity in the same patients that was slightly increased as a consequence of macrophage activation.

CONCLUSIONS

These data would suggest a good treatment for these patients.

Role of tumor associated macrophages in tumor angiogenesis and lymphangiogenesis

Tumor angiogenesis is an essential process for supplying rapidly growing malignant tissues with essential nutrients and oxygen. An angiogenic switch allows tumor cells to survive and grow, and provides them access to vasculature resulting in metastatic disease. Monocyte-derived macrophages recruited and reprogrammed by tumor cells serve as a major source of angiogenic factors boosting the angiogenic switch. Tumor endothelium releases angiopoietin-2 and further facilitates recruitment of TIE2 receptor expressing monocytes (TEM) into tumor sites. Tumor-associated macrophages (TAM) sense hypoxia in avascular areas of tumors, and react by production of angiogenic factors such as VEGFA. VEGFA stimulates chemotaxis of endothelial cells (EC) and macrophages. In some tumors, TAM appeared to be a major source of MMP9. Elevated expression of MMP9 by TAM mediates extracellular matrix (ECM) degradation and the release of bioactive VEGFA. Other angiogenic factors released by TAM include basic fibroblast growth factor (bFGF), thymidine phosphorylase (TP), urokinase-type plasminogen activator (uPA), and adrenomedullin (ADM). The same factors used by macrophages for the induction of angiogenesis [like vascular endothelial growth factor A (VEGF-A) and MMP9] support lymphangiogenesis. TAM can express LYVE-1, one of the established markers of lymphatic endothelium. TAM support tumor lymphangiogenesis not only by secretion of pro-lymphangiogenic factors but also by trans-differentiation into lymphatic EC. New pro-angiogenic factor YKL-40 belongs to a family of mammalian chitinase-like proteins (CLP) that act as cytokines or growth factors. Human CLP family comprises YKL-40, YKL-39, and SI-CLP. Production of all three CLP in macrophages is antagonistically regulated by cytokines. It was recently established that YKL-40 induces angiogenesis in vitro and in animal tumor models. YKL-40-neutralizing monoclonal antibody blocks tumor angiogenesis and progression. The role of YKL-39 and SI-CLP in tumor angiogenesis and lymphangiogenesis remains to be investigated.

Cells from the skin of patients with systemic sclerosis secrete chitinase 3-like protein 1

Background

The chitinase-like protein, Chi3L1, is associated with increased fibrotic activity as well as inflammatory processes. The capacity of skin cells from systemic sclerosis (SSc) patients to produce Chi3L1, and the stimulation of its synthesis by cytokines or growth factors known to be associated with SSc, was investigated.

Methods

Cells were isolated from forearm and/or abdomen skin biopsies taken from SSc patients and normal individuals and stimulated with cytokines and growth factors to assess Chi3L1 expression. Chi3L1-expressing cells were characterized by immunohistochemical staining.

Results

Chi3L1 was not secreted by skin cells from normal individuals nor was its synthesis induced by any of the cytokines or growth factors investigated. In contrast, Chi3L1 secretion was induced by OSM or IL-1 in cells from all forearm biopsies of SSc patients, and endogenous secretion in the absence of cytokines was detected in several specimens. Patients with Chi3L1-producing cells at both the arm and abdomen had a disease duration of less than 3 years. Endogenous Chi3L1 production was not a property of the major fibroblast population nor of myofibroblasts, but rather was related to the presence of stem-like cells not present in normal skin. Other cells, however, contributed to the upregulation of Chi3L1 by OSM.

Conclusions

The emergence of cells primed to respond to OSM with increased Chi3L1 production appears to be associated with pathological processes active in SSc.

General significance

The presence of progenitor cells expressing the chilectin Chi3L1 in SSc skin appears to play a role in the initiation of the disease process.

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Cells isolated from the skin of scleroderma patients secrete Chi3L1.

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Chi3L1 production is stimulated by oncostatin M or interleukin 1.

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Patients with Chi3L1 producing cells have disease duration of < 3 years.

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Chi3L1 production is a property of stem-like cells not present in normal skin.

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Other cells contribute to Chi3L1 upregulation by oncostatin M.

Evaluation of CHI3L-1 and CHIT-1 expression in differentiated and polarized macrophages

Chitinase 3-like protein 1 (CHI3L-1) and chitotriosidase (CHIT-1) are members of the chitinase family. CHI3L-1 is a newly recognized protein that is secreted by activated macrophages and neutrophils and expressed in a broad spectrum of inflammatory conditions and cancers. In human plasma, CHIT-1 activity has been proposed as a biochemical marker of macrophage activation. Although CHI3L-1 expression in inflammation is under examination, little is known regarding its regulation during macrophages' full maturation and polarization. In this study, we compared CHI3L-1 and CHIT-1 modulation during monocyte to macrophage transition and polarization. Gene expression analysis was investigated by real-time PCR. We found that during the maturation of monocytes into macrophages, the expression of both CHI3L-1 and CHIT-1 increased exponentially over time. Additionally, we observed a different regulation of CHI3L-1 and CHIT-1 in undifferentiated monocytes under stimulation with lipopolysaccharide, interferon-γ, and interleukin-4, at the same concentration used to polarize macrophages. Our finding suggests that in the immune response, the role of CHI3L-1 and CHIT-1 is not restricted to innate immunity, but they are also protagonists in acquired immunity.

YKL-40 expression could be a poor prognostic marker in the breast cancer tissue

YKL-40 is a glycoprotein involved in cellular growth, migration, and the inflammatory process. Elevation in serum levels of YKL-40 has been associated with worse prognosis in various cancers, including breast cancer. Given that the clinical significance of YKL-40 expression in breast cancer tissue is unclear, we aimed to determine the prognostic value of YKL-40 expression in breast cancer tissue using immunohistochemistry. We performed tissue microarray (TMA) analysis of 425 breast cancer tissues collected during operation. Immunohistochemical staining was performed to measure expression of YKL-40 and several breast cancer biomarkers, such as aldehyde dehyadrogenase1, TGF-beta, and Gli-1 as well as hormonal receptor and Her-2/neu status. Statistical analysis of the relationship of YKL-40 expression with clinicopathological characteristics was performed for 390 TMA samples. YKL-40 was expressed to varying degrees in 84.9% of breast cancer tissues. YKL-40 expression was correlated with estrogen receptor and progesterone receptor negativity and was positively correlated with TGF-beta and Gli-1 expression. Strong YKL-40 expression was associated with a larger proportion of Her-2/neu-enriched and basal-like tumors. The results of this study demonstrate that YKL-40 expression in breast cancer tissues is associated with hormone receptor negativity and Her-2/neu-enriched molecular subtypes of breast cancer, and therefore could be considered a poor prognostic predictor.

YKL-40 acts as an angiogenic factor to promote tumor angiogenesis

A secreted glycoprotein YKL-40 also named chitinase-3-like-1 is normally expressed by multiple cell types such as macrophages, chondrocytes, and vascular smooth muscle cells. However, a prominently high level of YKL-40 was found in a wide spectrum of human diseases including cancers and chronic inflammatory diseases where it was strongly expressed by cancerous cells and infiltrating macrophages. Here, we summarized recent important findings of YKL-40 derived from cancerous cells and smooth muscle cells during tumor angiogenesis and development. YKL-40 is a potent angiogenic factor capable of stimulating tumor vascularization mediated by endothelial cells and maintaining vascular integrity supported by smooth muscle cells. In addition, YKL-40 induces FAK-MAPK signaling and up-regulates VEGF receptor 2 in endothelial cells; but a neutralizing antibody (mAY) against YKL-40 inhibits its angiogenic activity. While YKL-40 is essential for angiogenesis, little is known about its functional role in tumor-associated macrophage (TAM)-mediated tumor development. Therefore, significant efforts are urgently needed to identify pathophysiological function of YKL-40 in the dynamic interaction between tumor cells and TAMs in the tumor microenvironment, which may offer substantial mechanistic insights into tumor angiogenesis and metastasis, and also point to a therapeutic target for treatment of cancers and other diseases.

Plasma YKL-40 and CHI3L1 in systemic inflammation and sepsis-experience from two prospective cohorts

YKL-40, derived from the CHI3L1 gene, has been associated with outcome of infectious and inflammatory diseases. We hypothesized that plasma YKL-40 concentrations and CHI3L1 genotype could be used as prognostic biomarkers in the assessment of systemic inflammatory response syndrome (SIRS) and sepsis. The objective of the study was to assess the prognostic value of plasma YKL-40 and CHI3L1 genotype in patients with SIRS and sepsis. Plasma YKL-40 and CHI3L1 genotype (rs4950928) were analyzed at time of admission to intensive care units (ICU), in two prospective cohorts of consecutive SIRS patients (cohort 1, n=272; cohort 2, n=502). The plasma YKL-40 cut-off for predicting survival was determined in cohort 1 by receiver operator characteristic analyses and validated in cohort 2. In cohort 1 patients with plasma YKL-40 ≤505ng/ml (area under the curve 0.64 (95% confidence interval (CI) 0.57-0.70), p<0.001, sensitivity 53%, specificity 76%) had superior day 90 survival (81% vs. 55%, p<0.001, hazard ratio (HR) 2.29 (95% CI 1.29-4.07)). In the second cohort plasma YKL-40 ≤505ng/ml was also associated with superior survival (61% vs. 38%, p<0.001, HR 1.43 (1.03-1.99)). CHI3L1 minor allele homozygosity was associated with low plasma YKL-40 at time of admission (p=0.002) and no variation (p=0.462) in concentrations throughout the first 14 days in the ICU, but this was not associated with better survival. In conclusion patients with SIRS and sepsis, plasma YKL-40 ≤505ng/ml at time of ICU admission was associated with better survival. However, this association was not observed for patients homozygous for the low expressing YKL-40 CHI3L1 allele.

Elevated serum YKL-40 level predicts myocardial reperfusion and in-hospital MACE in patients with STEMI

BACKGROUND

Macrophages in atherosclerotic plaques secrete YKL-40, a new biomarker of acute and chronic inflammation in patients with stable CAD. We hypothesized that YKL-40 may be a specific marker reflecting the burden of localized inflammation in myocardium and a predictor in patients with STEMI. In this study, we investigated the relationship of YKL-40 to in-hospital major adverse cardiac events (MACE), reperfusion parameters and its predictors in patients with STEMI.

METHODS

In total, 80 patients with STEMI and no history of prior coronary artery disease (CAD), who underwent primary percutaneous coronary intervention (p-PCI), were enrolled consecutively. In addition, 30 patients with normal coronary arteries (NCA) were enrolled as a control group. Cardiac biomarker levels including creatinine kinase-MB fraction (CK-MB), troponin-I, admission glucose and inflammatory markers including leukocytes and YKL-40 levels were measured as admission values.

RESULTS

In our study, YKL-40 levels correlated to high-sensitivity CRP levels (r = 0.333, p = 0.003), TIMI risk score (r = 0.445, p < 0.001), age (r = 0.477, p < 0.001), pain to balloon time (r = 0.432, p < 0.001), leukocyte and neutrophil count (r = 0.386, p < 0.001 and r = 0.430, p < 0.001, respectively), hemoglobin (r = - 0.345, p = 0.002), admission and fasting blood glucose (r = 0.388, p < 0.001 and r = 0.427, p < 0.001), creatinine levels (r = 0.395, p < 0.001) and myocardial blush grade (r = - 0.334, p = 0.004). When the patients were divided into two groups determined by presence or absence of MACE, the patients with MACE had significantly higher levels of YKL-40 in comparison to the patients without MACE and the control group (194 ± 104, 114 ± 61 and 110 ± 53 μg/L, p < 0.001, respectively). In multivariate logistic regression analysis in STEMI patients, only YKL-40 level (OR: 1.011, 95%CI: 1.002-1.019, p = 0.011) and leukocyte count (OR: 1.264, 95%CI: 1.037-1.540, p = 0.020) were the independent predictors for MACE. Sensitivity and specificity of YKL-40 to predict MACE, when 125 μg/l was accepted as a cut-off value, were 84% and 70%, respectively.

CONCLUSION

We found that serum YKL-40 is related to older age, increased admission glucose levels, leukocyte counts and decreased hemoglobin levels; YKL-40 level and leukocyte count independently predicted MACE.

Potential biomarkers of insulin resistance and atherosclerosis in type 2 diabetes mellitus patients with coronary artery disease

Type 2 diabetes mellitus patients with coronary artery disease have become a major public health concern. The occurrence of insulin resistance accompanied with endothelial dysfunction worsens the state of atherosclerosis in type 2 diabetes mellitus patients. The combination of insulin resistance and endothelial dysfunction leads to coronary artery disease and ischemic heart disease complications. A recognized biological marker, high-sensitivity C-reactive protein, has been used widely to assess the progression of atherosclerosis and inflammation. Along with coronary arterial damage and inflammatory processes, high-sensitivity C-reactive protein is considered as an essential atherosclerosis marker in patients with cardiovascular disease, but not as an insulin resistance marker in type 2 diabetes mellitus patients. A new biological marker that can act as a reliable indicator of both the exact state of insulin resistance and atherosclerosis is required to facilitate optimal health management of diabetic patients. Malfunctioning of insulin mechanism and endothelial dysfunction leads to innate immune activation and released several biological markers into circulation. This review examines potential biological markers, YKL-40, alpha-hydroxybutyrate, soluble CD36, leptin, resistin, interleukin-18, retinol binding protein-4, and chemerin, as they may play significant roles in insulin resistance and atherosclerosis in type 2 diabetes mellitus patients with coronary artery disease.

Serum YKL-40 predicts long-term mortality in patients with stable coronary disease: a prognostic study within the CLARICOR trial

OBJECTIVE

We investigated whether the inflammatory biomarker YKL-40 could improve the long-term prediction of death made by common risk factors plus high-sensitivity C-reactive protein (hs-CRP) and N-terminal-pro-B natriuretic peptide (NT-proBNP) in patients with stable coronary artery disease (CAD).

BACKGROUND

Non-hospitalized CAD patients are usually followed in general practice. There is a need for identify biomarkers which could help to foresee the prognoses of these patients. Elevated serum YKL-40 is a short-term predictor for myocardial infarction, cardiovascular mortality and all-cause mortality in patients with stable CAD.

METHODS

Serum YKL-40, hs-CRP, and NT-proBNP were measured in 4265 (97.6%) of the 4372 patients with stable CAD included in the CLARICOR trial, and death was registered in a 6-years follow-up period.

RESULTS

The median serum YKL-40 was 110 μg/L [IQR=93], hs-CRP 2.8 mg/L [IQR=4.74], and NT-proBNP 203 ng/L [IQR=407]. During 6 years follow-up period 923 (21.1%) patients died. After adjustment for type of intervention, risk factors (age, sex, hypertension, diabetes, smoking status, and previous myocardial infarction) and medical treatment (diuretics, digoxin, and statin) serum YKL-40 (transformed as ln(max(82, YKL-40/μg/L)) was significantly associated with all-cause mortality [hazard ratio (HR)=1.55, 95% CI=1.39-1.73, p<0.001]. After additional adjustment for ln(hs-CRP) and ln(NT-proBNP) this was still true [HR=1.38, 95% CI=1.21-1.53, p<0.001].

CONCLUSIONS

Serum YKL-40 is a predictor of long-term mortality in patients with stable CAD independent of common risk factors and ln(hs-CRP) and ln(NT-proBNP). Serum YKL-40 can be used for prognostication in these patients.

Subtype-specific response to bevacizumab is reflected in the metabolome and transcriptome of breast cancer xenografts

Antiangiogenic therapy with bevacizumab has shown varying results in breast cancer clinical trials. Identifying robust biomarkers for selecting patients who may benefit from such treatment and for monitoring response is important for the future use of bevacizumab. Two established xenograft models representing basal-like and luminal-like breast cancer were used to study bevacizumab treatment response on the metabolic and gene expression levels. Tumor samples were obtained from mice treated with bevacizumab, doxorubicin or a combination of the two drugs, and high resolution magic angle spinning magnetic resonance spectroscopy and gene expression microarray analysis was performed. Combination treatment with bevacizumab showed the strongest growth inhibiting effect in basal-like tumors, and this was reflected by a significant change in the metabolomic and transcriptomic profiles. In the luminal-like xenografts, addition of bevacizumab did not improve the effect of doxorubicin. On the global transcriptomic level, the largest gene expression changes were observed for the most efficient treatment in both models. Glycerophosphocholine showed opposite response in the treated xenografts compared with untreated controls; lower in basal-like and higher in luminal-like tumors. Comparing combination therapy with doxorubicin monotherapy in basal-like xenografts, 14 genes showed significant differential expression, including very low density lipoprotein receptor (VLDLR) and hemoglobin, theta 1 (HBQ1). Bevacizumab-treated tumors were associated with a more hypoxic phenotype, while no evidence was found for associations between bevacizumab treatment and vascular invasion or tumor grade. This study underlines the importance of characterizing biological differences between subtypes of breast cancer to identify personalized biomarkers for improved patient stratification and evaluation of response to therapy.

The diagnostic and prognostic value of serum YKL-40 in endometrial cancer

PURPOSE

To evaluate the diagnostic and prognostic value of serum YKL-40 in endometrial cancer (EC).

METHODS

Serum YKL-40 levels were detected and compared in 34 of the 50 cases with EC before surgery, in 22 of the 34 with EC after surgery, in 30 cases with uterine myoma, and in 30 healthy women as normal controls. Receiver operating characteristics (ROC) curves were adopted for diagnosis and calculation of area under each ROC curve in EC. The progression-free survival (PFS) and overall survival (OS) between YKL-40 positive and negative patients were compared in the follow-up.

RESULTS

The mean pre-operative serum YKL-40 values were significantly higher than that in the uterine myoma cases and in the healthy women (P = 0.000). The mean post-operative serum YKL-40 in the 22 EC cases was significantly lower than pre-operative serum YKL-40 levels in these cases (P = 0.000). There were critical differences between the area under ROC curve for YKL-40 and CA125 (P = 0.053). The PFS and OS for the YKL-40-positive patients were significantly shorter than those for the YKL-40-negative patients.

CONCLUSION

Preliminary investigations have shown that serum YKL-40 level may have a definite clinical value in the diagnosis and prognosis of EC.

YKL-40 is elevated in patients with peripheral arterial disease and diabetes or pre-diabetes

OBJECTIVE

YKL-40 is secreted by macrophages in atherosclerotic lesions and involved in plaque rupture. YKL-40 is elevated in coronary artery disease, and predicts cardiovascular mortality. Experimental in vivo and in vitro data suggest a role of YKL-40 in tissue remodeling. A disease modulating potency of YKL-40 was not investigated in peripheral arterial disease (PAD).

METHODS

We measured YKL-40 in 460 subjects: 316 PAD: 71 normal glucose metabolism (PAD-NGM), 90 pre-diabetes (PAD-PREDM) and 155 diabetes (PAD-DM); 20 diabetes with atherosclerosis but without PAD (AS-DM); 85 diabetes without macro-vascular complications (DM) and 39 healthy controls (CO).

RESULTS

YKL-40 is higher in PAD vs. CO (median [25-75 percentile]: 103 [69-159] vs. 43 [30-80]ng/ml; p<0.001). In addition, YKL-40 is elevated in DM (p<0.001), PAD-NGM (p=0.001), PAD-PREDM (p<0.001), PAD-DM (p<0.001) and AS-DM (p=0.002) compared to CO. Among PAD, YKL-40 is increased in PAD-PREDM (p=0.001) and PAD-DM (p=0.01) vs. PAD-NGM. By multivariate regression YKL-40 is significantly associated with age (beta=0.272), triglycerides (beta=0.216), aspartate-amino-transferase (beta=0.177) and c-reactive-protein (beta=0.178). Underpinning its role YKL-40 was found to be associated with micro-/macroalbuminuria (p=0.014/p=008)--a strong remodeling inducer. In addition, YKL-40 was elevated in existence of mediasclerosis (p=0.008), a remodeling process.

CONCLUSION

We are first to show that YKL-40 is higher in subjects with peripheral arterial disease. YKL-40 was higher in PAD patients with pre-/diabetes. In addition, YKL-40 was associated with the "severity" of generalized atherosclerosis estimated by affected vascular beds. All our findings point towards a role of YKL-40 in the progression/prognosis of patients with PAD and concomitant diabetes.

Role of YKL-40 in bronchial smooth muscle remodeling in asthma

RATIONALE

Bronchial remodeling, including increased bronchial smooth muscle (BSM) mass, contributes to bronchial obstruction in asthma. However, its mechanisms are complex and remain controversial. Recently, a role of the chitinase 3-like 1 protein (YKL-40) has been evoked in asthma. Indeed, YKL-40 concentration was increased in asthmatic serum, and correlated with asthma severity and subepithelial membrane thickness. Nevertheless, the role of YKL-40 on BSM cells remains to be investigated.

OBJECTIVES

To evaluate whether YKL-40 altered the physiologic properties of BSM cells in asthma in vitro and ex vivo.

METHODS

We enrolled 40 subjects with asthma, 13 nonsmokers, and 16 smokers. BSM cells were derived from bronchial specimens obtained by either fiberoptic bronchoscopy or lobectomy. We assessed cell proliferation using BrdU, flow cytometry, and cell count; signaling intermediates using Western blot; cell migration using inserts, wound healing, and phalloidin staining; and cell synthesis using ELISA and Western blot. The involvement of protease activated receptor (PAR)-2 was evaluated using blocking antibody and dedicated lentiviral small hairpin RNA. We also determined the BSM area and the YKL-40 staining ex vivo using immunohistochemistry on biopsies from subjects with asthma and control subjects.

MEASUREMENTS AND MAIN RESULTS

We demonstrated that YKL-40 increased BSM cell proliferation and migration through PAR-2-, AKT-, ERK-, and p38-dependent mechanisms. The increased cell migration was higher in BSM cells of subjects with asthma than that of control subjects. Furthermore, YKL-40 epithelial expression was positively correlated with BSM mass in asthma.

CONCLUSIONS

This study indicates that YKL-40 promotes BSM cell proliferation and migration through a PAR-2-dependent mechanism.

Increased immunohistochemical expression of YKL-40 in the spleen of patients with portal hypertension

YKL-40 has been identified as a growth factor in connective tissue cells and also a migration factor in vascular smooth muscle cells. To a large extent, the increase of serum YKL-40 is attributed to liver fibrosis and asthma. However, the relationship of the expression and clinical/prognostic significance of YKL-40 to the splenomegaly of patients with portal hypertension is unclear. In the present study, the expression of YKL-40 was studied by immunohistochemistry in 48 splenomegaly tissue samples from patients with portal hypertension and in 14 normal spleen specimens. All specimens were quickly stored at -80°C after resection. Primary antibodies YKL-40 (1:150 dilution, rabbit polyclonal IgG) and MMP-9 (1:200 dilution, rabbit monoclonal IgG) and antirabbit immunoglobulins (HRP K4010) were used in this study. The relationship of clinicopathologic features with YKL-40 is presented. The expression of YKL-40 indicated by increased immunochemical reactivity was significantly up-regulated in splenomegaly tissues compared to normal spleen tissues. Overexpression of YKL-40 was found in 68.8% of splenomegaly tissues and was significantly associated with Child-Pugh classification (P = 0.000), free portal pressure (correlation coefficient = 0.499, P < 0.01) and spleen fibrosis (correlation coefficient = 0.857, P < 0.01). Further study showed a significant correlation between YKL-40 and MMP-9 (correlation coefficient = -0.839, P < 0.01), indicating that YKL-40 might be an accelerator of spleen tissue remodeling by inhibiting the expression of MMP-9. In conclusion, YKL-40 is an important factor involved in the remodeling of spleen tissue of portal hypertension patients and can be used as a therapeutic target for splenomegaly.

YKL-40 is differentially expressed in human embryonic stem cells and in cell progeny of the three germ layers

The secreted glycoprotein YKL-40 participates in cell differentiation, inflammation, and cancer progression. High YKL-40 expression is reported during early human development, but its functions are unknown. Six human embryonic stem cell (hESC) lines were cultured in an atmosphere of low or high oxygen tension, in culture medium with or without basic fibroblast growth factor, and on feeder layers comprising mouse embryonic fibroblasts or human foreskin fibroblasts to evaluate whether hESCs and their progeny produced YKL-40 and to characterize YKL-40 expression during differentiation. Secreted YKL-40 protein and YKL-40 mRNA expression were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative RT-PCR. Serial-sectioned colonies were stained for YKL-40 protein and for pluripotent hESC (OCT4, NANOG) and germ layer (HNF-3β, PDX1, CD34, p63, nestin, PAX6) markers. Double-labeling showed YKL-40 expression in OCT4-positive hESCs, PAX6-positive neuroectodermal cells, and HNF-3β-positive endodermal cells. The differentiating progeny showed strong YKL-40 expression. Abrupt transition between YKL-40 and OCT4-positive hESCs and YKL-40-positive ecto- and neuroectodermal lineages was observed within the same epithelial-like layer. YKL-40-positive cells within deeper layers lacked contact with OCT4-positive cells. YKL-40 may be important in initial cell differentiation from hESCs toward ectoderm and neuroectoderm, with retained epithelial morphology, whereas later differentiation into endoderm and mesoderm involves a transition into the deeper layers of the colony.

A complex of nuclear factor I-X3 and STAT3 regulates astrocyte and glioma migration through the secreted glycoprotein YKL-40

Nuclear factor I-X3 (NFI-X3) is a newly identified splice variant of NFI-X that regulates expression of several astrocyte-specific markers, such as glial fibrillary acidic protein. Here, we identified a set of genes regulated by NFI-X3 that includes a gene encoding a secreted glycoprotein YKL-40. Although YKL-40 expression is up-regulated in glioblastoma multiforme, its regulation and functions in nontransformed cells of the central nervous system are widely unexplored. We find that expression of YKL-40 is activated during brain development and also differentiation of neural progenitors into astrocytes in vitro. Furthermore, YKL-40 is a migration factor for primary astrocytes, and its expression is controlled by both NFI-X3 and STAT3, which are known regulators of gliogenesis. Knockdown of NFI-X3 and STAT3 significantly reduced YKL-40 expression in astrocytes, whereas overexpression of NFI-X3 dramatically enhanced YKL-40 expression in glioma cells. Activation of STAT3 by oncostatin M induced YKL-40 expression in astrocytes, whereas expression of a dominant-negative STAT3 had a suppressive effect. Mechanistically, NFI-X3 and STAT3 form a complex that binds to weak regulatory elements in the YKL-40 promoter and activates transcription. We propose that NFI-X3 and STAT3 control the migration of differentiating astrocytes as well as migration and invasion of glioma cells via regulating YKL-40 expression.

Sputum YKL-40 levels and pathophysiology of asthma and chronic obstructive pulmonary disease

BACKGROUND

Recent evidence suggests that YKL-40, also called chitinase-3-like-1 protein, is involved in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD). Details of sputum YKL-40 in asthma and COPD, however, remain unknown.

OBJECTIVES

To clarify associations of sputum YKL-40 levels with clinical indices in asthma and COPD.

METHODS

Thirty-nine patients with asthma, 14 age-matched never-smokers as controls, 45 patients with COPD, and 7 age-matched smokers as controls were recuited for this study. Sputum YKL-40 levels were measured and YKL-40 expression in sputum cells was evaluated by immunocytochemistry.

RESULTS

Sputum YKL-40 levels were higher in patients with COPD (346 ± 325 ng/ml) than in their smoker controls (125 ± 122 ng/ml; p < 0.05), but were not significantly different between patients with asthma (117 ± 170 ng/ml) and their controls (94 ± 44 ng/ml; p = 0.15). In patients with asthma only, sputum YKL-40 levels were positively correlated with disease severity (r = 0.34, p = 0.034) and negatively correlated with pre- and postbronchodilator %FEV(1) (r = -0.47 and -0.42, respectively; p < 0.01) and forced mid-expiratory flow (r = -0.48 and -0.46, respectively, p < 0.01). Sputum YKL-40 levels were positively correlated with sputum neutrophil counts in asthma (r = 0.55, p < 0.001) and with neutrophil and macrophage counts in COPD (r = 0.45 and 0.65, respectively, p < 0.01). YKL-40 was expressed in the cytoplasm of sputum neutrophils and macrophages in all groups.

CONCLUSIONS

Elevated sputum YKL-40 reflects airflow obstruction in asthma whereas the roles of YKL-40 in the proximal airways in COPD remain to be elucidated.

Carbohydrate-binding motif in chitinase 3-like 1 (CHI3L1/YKL-40) specifically activates Akt signaling pathway in colonic epithelial cells

Host-microbial interactions play a key role during the development of colitis. We have previously shown that chinase 3-like 1 (CHI3L1) is an inducible molecule overexpressed in colonic epithelial cells (CECs) under inflammatory conditions. In this study, we found that chitin-binding motif (CBM) of CHI3L1 is specifically associated with the CHI3L1-mediated activation of the Akt-signaling in CEC by transfecting the CBM-mutant CHI3L1 vectors in SW480 CECs. Downstream, CHI3L1 enhanced the secretion of IL-8 and TNFα in a dose-dependent manner. We previously show that 325 through 339 amino-acids in CBM are crucial for the biological function of CHI3L1. Here we demonstrated that 325th-339th residues of CBM in CHI3L1 is a critical region for the activation of Akt, IL-8 production, and for a specific cellular localization of CHI3L1. In conclusion, CBM region of CHI3L1 is critical in activating Akt signaling in CECs, and the activation may be associated with the development of chronic colitis.

Chitinase 3-like-1 expression in colonic epithelial cells as a potentially novel marker for colitis-associated neoplasia

Chitinase 3-like-1 (CHI3L1/YKL-40) is a protein secreted from restricted cell types including colonic epithelial cells (CECs) and macrophages. CHI3L1 is an inflammation-associated molecule, and its expression is enhanced in persons with colitis and colon cancer. The biological function of CHI3L1 on CECs is unclear. In this study, we investigated the role of CHI3L1 on CECs during the development of colitis-associated neoplasia. We analyzed colonic samples obtained from healthy persons and from persons with ulcerative colitis with or without premalignant or malignant changes. DNA microarray and RT-PCR analyses significantly increased CHI3L1 expression in non-dysplastic mucosa from patients with inflammatory bowel disease (IBD) who had dysplasia/adenocarcinoma compared with that in healthy persons and in patients with IBD who did not have dysplasia. As determined by IHC, CHI3L1 was expressed in specific cell types in the crypts of colonic biopsies obtained from patients with ulcerative colitis who have remote dysplasia. Purified CHI3L1 efficiently activated the NF-κB signaling pathway and enhanced the secretion of IL-8 and TNF-α in SW480 human colon cancer cells. In addition, colon cancer cell proliferation and migration were significantly promoted in response to CHI3L1 in these cells. In summary, CHI3L1 may contribute to the proliferation, migration, and neoplastic progression of CECs under inflammatory conditions and could be a useful biomarker for neoplastic changes in patients with IBD.

YKL-40 and MMP-9 as serum markers for patients with primary central nervous system lymphoma

OBJECTIVE

To evaluate YKL-40 and MMP-9 proteins as tumor biomarkers in serum samples from patients with primary central nervous system lymphoma (PCNSL).

METHODS

In this prospective longitudinal study, serum samples from consecutive patients with histologically confirmed PCNSL were collected concurrently with magnetic resonance imaging (MRI) scans at multiple time points and were analyzed for levels of YKL-40 and MMP-9 by enzyme-linked immunosorbent assay. Marker levels were correlated to disease status and survival.

RESULTS

Forty-five patients with PCNSL were accrued. Median follow-up for survivors was 25 months, and 21 (47%) died during the study. A total of 230 serum samples were collected, and 93% had corresponding MRI scans. PCNSL patients without evidence of radiographic disease (29 patients, 131 samples) had significantly lower levels of serum YKL-40 and MMP-9 than patients with active tumor (n = 34 patients, 84 samples; p = 0.03 and 0.01, respectively). There was a significant inverse correlation between survival and doubling of the YKL-40 level (hazard ratio, 1.7; p = 0.01).

INTERPRETATION

In patients with PCNSL, serum levels of YKL-40 and MMP-9 are associated with radiographic disease status. Longitudinal increase in serum levels of YKL-40, but not MMP-9, predicts survival in patients with PCNSL.

Overexpression of Pax6 in mouse cornea directly alters corneal epithelial cells: changes in immune function, vascularization, and differentiation

PURPOSE

To assess whether Pax6 functions directly in the cornea, a corneal-preferred promoter was used to overexpress Pax6 specifically in the cornea.

METHODS

Transgenic mice harboring a construct containing mouse Pax6 coding sequences fused downstream of the aldehyde dehydrogenase 3a1 (Aldh3a1) promoter were generated (Pax6 Tg). Pax6 expression was analyzed by Western blot and immunohistochemistry. Eye sections were stained with hematoxylin and eosin, Schiff reagent, and fluorescein, to assess morphologic changes, the presence of goblet cells, and barrier integrity, respectively. Gene expression changes in mildly affected Pax6 Tg corneas were compared to age-matched, wild-type (WT) corneas by microarray analysis and quantitative PCR. Promoter regulation of several differentially expressed genes was examined by monitoring luciferase activity of reporter constructs after cotransfection with Pax6 in COS7 cells.

RESULTS

Corneal overexpression of Pax6 produces an abnormal cornea with altered epithelial cell morphology, neovascularization, immune cell invasion, and a compromised barrier; the lens appeared normal. Major changes in expression of genes involved in immune function, vascularization, and epithelial differentiation occurred in corneas from Pax6 Tg versus WT mice. The keratin (K) profile was dramatically altered in the Pax6 Tg corneas, as were several components of the Wnt signaling pathway. In severely affected Pax6 Tg corneas, K12 was reduced, and Pax6 was redistributed into the cytoplasm. Promoters from the chitinase 3-like 3, Wnt inhibitory factor 1, and fms-related tyrosine kinase 1/soluble VEGF receptor genes were upregulated five-, seven-, and threefold, respectively, by Pax6 in transfected COS7 cells.

CONCLUSIONS

Pax6 functions directly to maintain normal, corneal epithelial cells.