The mammalian chitinase-like lectin, YKL-40, binds specifically to type I collagen and modulates the rate of type I collagen fibril formation

Fully human chitinase-3 like-1 monoclonal antibody inhibits tumor growth, fibrosis, angiogenesis, and immune cell remodeling in lung, pancreatic, and colorectal cancers

Considering the limited efficacy of current therapies in lung, colorectal, and pancreatic cancers, innovative combination treatments with diverse mechanisms of action are needed to improve patients' outcomes. Chitinase-3 like-1 protein (CHI3L1) emerges as a versatile factor with significant implications in various diseases, particularly cancers, fostering an immunosuppressive tumor microenvironment for cancer progression. Therefore, pre-clinical validation is imperative to fully realize its potential in cancer treatment. We developed phage display-derived fully human monoclonal CHI3L1 neutralizing antibodies (nAbs) and verified the nAbs-antigen binding affinity and specificity in lung, pancreatic and colorectal cancer cell lines. Tumor growth signals, proliferation and migration ability were all reduced by CHI3L1 nAbs in vitro. Orthotopic or subcutaneous tumor mice model and humanized mouse model were established for characterizing the anti-tumor properties of two CHI3L1 nAb leads. Importantly, CHI3L1 nAbs not only inhibited tumor growth but also mitigated fibrosis, angiogenesis, and restored immunostimulatory functions of immune cells in pancreatic, lung, and colorectal tumor mice models. Mechanistically, CHI3L1 nAbs directly suppressed the activation of pancreatic stellate cells and the transformation of macrophages into myofibroblasts, thereby attenuating fibrosis. These findings strongly support the therapeutic potential of CHI3L1 nAbs in overcoming clinical challenges, including the failure of gemcitabine in pancreatic cancer.

Potential Role of Macrophage Polarization in the Progression of Hunner-Type Interstitial Cystitis

BACKGROUND

Hunner-type interstitial cystitis (HIC) is a chronic inflammatory condition of the bladder. However, it remains unclear whether there is a causal relationship between the presence of Hunner lesions and seemingly normal-appearing areas in the bladder (non-Hunner lesions). This study aimed to investigate the fundamental aspects of HIC by examining potential genetic differences between Hunner and non-Hunner lesions and elucidate their role as potential markers in the progression and suppression of the disease.

METHODS

This cross-sectional study enrolled patients with HIC (n = 10) who underwent supratrigonal cystectomy along with augmentation cystoplasty. Full-thickness bladder tissue was collected from Hunner and non-Hunner lesions in the same patient. Normal bladder tissue biopsies were also obtained as controls. Whole transcriptome analysis was performed to analyze the gene expression patterns and immune cell populations.

RESULTS

The mucosal layers of patients exhibited similar pathway dysregulation across Hunner and non-Hunner lesions, with immunerelated pathways being prominently affected. In the mucosal layer, genes related to anti-inflammatory and immune suppression were downregulated in Hunner lesions compared to non-Hunner lesions. Moreover, in Hunner lesions, genes related to macrophage differentiation and polarization, such as VSIG4, CD68, MAFB, and LIRB4, were downregulated. The cell fraction of M2 macrophages was found to decrease in Hunner lesions. Immunohistochemical staining revealed an elevated fraction of M1 macrophages and a reduced fraction of M2 macrophages in Hunner lesions compared to those in non-Hunner lesions. In the muscular layer, transcriptomic evidence of muscle thickness was observed in both Hunner and non-Hunner lesions; however, the difference was not significant.

CONCLUSION

Hunner lesions showed a reduced expression of anti-inflammatory and immunosuppressive factors compared to non-Hunner lesions, along with alterations in immune cell populations. This study suggests the possibility that macrophage polarization is related to the progression from non-Hunner lesions to Hunner lesions, suggesting its relevance to the characteristics of autoimmune diseases.

Chitinases and chitinase-like proteins in asthma

Despite the lack of endogenous chitin synthesis, mammalian genomes encode two enzymatically active true chitinases (chitotriosidase and acidic mammalian chitinase) and a variable number of chitinase-like proteins (CLPs) that have no enzyme activity but bind chitin. Chitinases and CLPs are prominent components of type-2 immune response-mediated respiratory diseases. However, despite extensive research into their role in allergic airway disease, there is still no agreement on whether they are mere biomarkers of disease or actual disease drivers. Functions ascribed to chitinases and CLPs include, but are not limited to host defense against chitin-containing pathogens, directly promoting inflammation, and modulating tissue remodeling and fibrosis. Here, we discuss in detail the chitin-dependent and -independent roles of chitinases and CLPs in the context of allergic airway disease, and recent advances and emerging concepts in the field that might identify opportunities for new therapies.

Do Elevated YKL-40 Levels Drive the Immunosuppressive Tumor Microenvironment in Colorectal Cancer? Assessment of the Association of the Expression of YKL-40, MMP-8, IL17A, and PD-L1 with Coexisting Type 2 Diabetes, Obesity, and Active Smoking

The influence of chitinase-3-like protein 1 (YKL-40 or CHI3L1) expression on the immunological properties of the tumor microenvironment, which may affect the effectiveness of immunotherapy, is currently not sufficiently understood in colorectal cancer (CRC). The aim of this study was to investigate the relationship between YKL-40 expression and the immunological properties of the tumor microenvironment in CRC. We performed in silico analysis, including analysis of immune cell infiltration scores and the immune landscape depending on YKL-40 expression, gene set enrichment analysis (GSEA), and analysis of three Gene Expression Omnibus (GEO) datasets. In 48 CRC tissue homogenates and the surgical margin, we analyzed the expression of YKL-40, MMP8, IL17A, and PD-L1. Moreover, we analyzed the expression of YKL-40 in tissue homogenates retrieved from patients with coexisting diabetes, obesity, and smoking. The expression of YKL-40 was significantly higher in CRC tumor tissue compared to healthy tissue and correlated with MMP-8, IL17A, and PD-L1 expression. In silico analysis revealed an association of YKL-40 with disease recurrence, and GSEA revealed a potential link between elevated YKL-40 expression and immunosuppressive properties of the tumor microenvironment in CRC.

Myeloid- and hepatocyte-specific deletion of group VIA calcium-independent phospholipase A2 leads to dichotomous opposing phenotypes during MCD diet-induced NASH

Polymorphisms of phospholipase A2VIA (iPLA2β or PLA2G6) are associated with body weights and blood C-reactive protein. The role of iPLA2β/PLA2G6 in non-alcoholic steatohepatitis (NASH) is still elusive because female iPla2β-null mice showed attenuated hepatic steatosis but exacerbated hepatic fibrosis after feeding with methionine- and choline-deficient diet (MCDD). Herein, female mice with myeloid- (MPla2g6^-/-) and hepatocyte- (LPla2g6^-/-) specific PLA2G6 deletion were generated and phenotyped after MCDD feeding. Without any effects on hepatic steatosis, MCDD-fed MPla2g6^-/- mice showed further exaggeration of liver inflammation and fibrosis as well as elevation of plasma TNFα, CCL2, and circulating monocytes. Bone-marrow-derived macrophages (BMDMs) from MPla2g6^-/- mice displayed upregulation of PPARγ and CEBPα proteins, and elevated release of IL6 and CXCL1 under LPS stimulation. LPS-stimulated BMDMs from MCDD-fed MPla2g6^-/- mice showed suppressed expression of M1 Tnfa and Il6, but marked upregulation of M2 Arg1, Chil3, IL10, and IL13 as well as chemokine receptors Ccr2 and Ccr5. This in vitro shift was associated with exaggeration of hepatic M1/M2 cytokines, chemokines/chemokine receptors, and fibrosis genes. Contrarily, MCDD-fed LPla2g6^-/- mice showed a complete protection which was associated with upregulation of Ppara/PPARα and attenuated expression of Pparg/PPARγ, fatty-acid uptake, triglyceride synthesis, and de novo lipogenesis genes. Interestingly, LPla2g6^-/- mice fed with chow or MCDD displayed an attenuation of blood monocytes and elevation of anti-inflammatory lipoxin A4 in plasma and liver. Thus, PLA2G6 inactivation specifically in myeloid cells and hepatocytes led to opposing phenotypes in female mice undergoing NASH. Hepatocyte-specific PLA2G6 inhibitors may be further developed for treatment of this disease.

Association between YKL-40 and asthma: a systematic meta-analysis

PURPOSE

Many studies have shown that chitinase-3-like protein 1 (CHI3L1), also known as YKL-40, is associated with asthma. The purpose of this meta-analysis was to evaluate the role of serum YKL-40 in the diagnosis and differential diagnosis of asthma, severity grading, and determination of disease state.

METHODS

The PubMed, Ovid, and Cochrane databases were searched. A total of 17 articles involving 5696 subjects were included in this meta-analysis.

RESULTS

The results showed that the level of YKL-40 was significantly higher in asthmatic patients than in the normal group regardless of age and residential location, and increased with severity and acute exacerbation (p < 0.05). YKL-40 levels were significantly different between chronic obstructive pulmonary disease (COPD) and asthma, and also between asthma-COPD overlap syndrome (ACO) and asthma (p < 0.05).

CONCLUSION

YKL-40 may act as a potential serological marker for the diagnosis of asthma, assessment of severity, indicator of the disease state, and differential diagnosis of COPD, ACO, and asthma.

Chitinases and Chitinase-Like Proteins as Therapeutic Targets in Inflammatory Diseases, with a Special Focus on Inflammatory Bowel Diseases

Chitinases belong to the evolutionarily conserved glycosyl hydrolase family 18 (GH18). They catalyze degradation of chitin to N-acetylglucosamine by hydrolysis of the β-(1-4)-glycosidic bonds. Although mammals do not synthesize chitin, they possess two enzymatically active chitinases, i.e., chitotriosidase (CHIT1) and acidic mammalian chitinase (AMCase), as well as several chitinase-like proteins (YKL-40, YKL-39, oviductin, and stabilin-interacting protein). The latter lack enzymatic activity but still display oligosaccharides-binding ability. The physiologic functions of chitinases are still unclear, but they have been shown to be involved in the pathogenesis of various human fibrotic and inflammatory disorders, particularly those of the lung (idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, sarcoidosis, and asthma) and the gastrointestinal tract (inflammatory bowel diseases (IBDs) and colon cancer). In this review, we summarize the current knowledge about chitinases, particularly in IBDs, and demonstrate that chitinases can serve as prognostic biomarkers of disease progression. Moreover, we suggest that the inhibition of chitinase activity may be considered as a novel therapeutic strategy for the treatment of IBDs.

The potential of biomarkers of fibrosis in chronic lung allograft dysfunction

Chronic lung allograft dysfunction (CLAD) is the major long-term cause of morbidity and mortality after lung transplantation. Both bronchiolitis obliterans syndrome and restrictive lung allograft syndrome, two main types of CLAD, lead to fibrosis in either the small airways or alveoli and pleura. Pathological pathways in CLAD and other types of fibrosis, for example idiopathic pulmonary fibrosis, are assumed to overlap and therefore fibrosis biomarkers could aid in the early detection of CLAD. These biomarkers could help to differentiate between different phenotypes of CLAD and could, in comparison to biomarkers of inflammation, possibly distinguish an infectious event from CLAD when a decline in lung function is present. This review gives an overview of known CLAD specific biomarkers, describes new promising fibrosis biomarkers currently investigated in other types of fibrosis, and discusses the possible use of these fibrosis biomarkers for CLAD.

Melanoma Associated Chitinase 3-Like 1 Promoted Endothelial Cell Activation and Immune Cell Recruitment

Chitinase 3-like 1 (CHI3L1) is an enzymatically inactive mammalian chitinase that is associated with tumor inflammation. Previous research indicated that CHI3L1 is able to interact with different extracellular matrix components, such as heparan sulfate. In the present work, we investigated whether the interaction of CHI3L1 with the extracellular matrix of melanoma cells can trigger an inflammatory activation of endothelial cells. The analysis of the melanoma cell secretome indicated that CHI3L1 increases the abundance of various cytokines, such as CC-chemokine ligand 2 (CCL2), and growth factors, such as vascular endothelial growth factor A (VEGF-A). Using a solid-phase binding assay, we found that heparan sulfate-bound VEGF-A and CCL2 were displaced by recombinant CHI3L1 in a dose-dependent manner. Microfluidic experiments indicated that the CHI3L1 altered melanoma cell secretome promoted immune cell recruitment to the vascular endothelium. In line with the elevated VEGF-A levels, CHI3L1 was also able to promote angiogenesis through the release of extracellular matrix-bound pro-angiogenic factors. In conclusion, we showed that CHI3L1 is able to affect the tumor cell secretome, which in turn can regulate immune cell recruitment and blood vessel formation. Accordingly, our data suggest that the molecular targeting of CHI3L1 in the course of cancer immunotherapies can tune patients’ response and antitumoral inflammation.

Chemosensory Neurons Modulate the Response to Oomycete Recognition in Caenorhabditis elegans

Understanding how animals detect and respond to pathogen threats is central to dissecting mechanisms of host immunity. The oomycetes represent a diverse eukaryotic group infecting various hosts from nematodes to humans. We have previously shown that Caenorhabditis elegans mounts a defense response consisting of the induction of chitinase-like (chil) genes in the epidermis to combat infection by its natural oomycete pathogen Myzocytiopsis humicola. We provide here evidence that C. elegans can sense the oomycete by detecting an innocuous extract derived from animals infected with M. humicola. The oomycete recognition response (ORR) leads to changes in the cuticle and reduction in pathogen attachment, thereby increasing animal survival. We also show that TAX-2/TAX-4 function in chemosensory neurons is required for the induction of chil-27 in the epidermis in response to extract exposure. Our findings highlight that neuron-to-epidermis communication may shape responses to oomycete recognition in animal hosts.

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C. elegans senses its natural oomycete pathogen M. humicola without infection

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Exposure to a pathogen extract triggers an oomycete recognition response

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Upon pathogen detection, C. elegans resists infection through changes in the cuticle

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The response involves signaling between sensory neurons and the epidermis

Adenovirus vector-mediated YKL-40 shRNA attenuates eosinophil airway inflammation in a murine asthmatic model

Recent studies have revealed that YKL-40 is involved in the pathogenesis of asthma. However, its specific mechanism remains unclear. The present study aims to investigate the effect of adenovirus vector-mediated YKL-40 short hairpin RNA (shRNA) on regulation of airway inflammation in a murine asthmatic model. Mice were assessed for airway hyperresponsiveness (AHR), total leukocytes and the percentage of eosinophil cells in bronchoalveolar lavage fluid (BALF). YKL-40 mRNA and protein expression levels were detected using quantitative real-time PCR and western blot assays. Enzyme-linked immunosorbent assay (ELISA) was used to detect YKL-40 and eosinophil-related chemokine expression levels in BALF and serum. Lung histology analyses were performed to evaluate the degree of inflammatory cell infiltration around the airway and airway mucus secretion.YKL-40 shRNA significantly inhibited the YKL-40 gene expression in asthmatic mice. In addition, YKL-40 shRNA alleviated eosinophilic airway inflammation, AHR, airway mucus secretion and decreased the levels of YKL-40 in BALF and serum in a murine asthmatic model. The levels and mRNA expression of IL-5, IL-13 in asthmatic mice lung tissues, eotaxin, and GM-CSF in BALF and serum significantly decreased. Bone marrow signaling molecules including IL-5, eotaxin, and GM-CSF were correlated with decreased levels of YKL-40. The study reveals that YKL-40 could be involved in asthma inflammation by altering bone marrow signaling molecules. YKL-40 gene RNA interference could provide new therapeutic strategies for asthma.

Chitinase-3 like-protein-1 function and its role in diseases

Non-enzymatic chitinase-3 like-protein-1 (CHI3L1) belongs to glycoside hydrolase family 18. It binds to chitin, heparin, and hyaluronic acid, and is regulated by extracellular matrix changes, cytokines, growth factors, drugs, and stress. CHI3L1 is synthesized and secreted by a multitude of cells including macrophages, neutrophils, synoviocytes, chondrocytes, fibroblast-like cells, smooth muscle cells, and tumor cells. It plays a major role in tissue injury, inflammation, tissue repair, and remodeling responses. CHI3L1 has been strongly associated with diseases including asthma, arthritis, sepsis, diabetes, liver fibrosis, and coronary artery disease. Moreover, following its initial identification in the culture supernatant of the MG63 osteosarcoma cell line, CHI3L1 has been shown to be overexpressed in a wealth of both human cancers and animal tumor models. To date, interleukin-13 receptor subunit alpha-2, transmembrane protein 219, galectin-3, chemo-attractant receptor-homologous 2, and CD44 have been identified as CHI3L1 receptors. CHI3L1 signaling plays a critical role in cancer cell growth, proliferation, invasion, metastasis, angiogenesis, activation of tumor-associated macrophages, and Th2 polarization of CD4⁺ T cells. Interestingly, CHI3L1-based targeted therapy has been increasingly applied to the treatment of tumors including glioma and colon cancer as well as rheumatoid arthritis. This review summarizes the potential roles and mechanisms of CHI3L1 in oncogenesis and disease pathogenesis, then posits investigational strategies for targeted therapies.

Inflammatory-sensitive CHI3L1 protects nucleus pulposus via AKT3 signaling during intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the main cause of low back pain and the mechanism of which is far from fully revealed. Although inflammation directed nucleus pulposus (NP) extracellular matrix metabolism dysregulation is known to be the main cause of the degeneration process, few is known about the protective factors. Using high-throughput label-free proteomics, we found that inflammation-related autocrine factor Chitinase-3-like protein 1 (CHI3L1, or YKL-40) is highly expressed in the NP cells during degeneration. Immunohistochemical analysis show that the expression of CHI3L1 is NP tissue specific, and increase significantly during degeneration. Overexpression of CHI3L1 significantly decrease the catabolism, and increase the anabolism of extracellular matrix. Knockdown of CHI3L1 using siRNAs show the opposite results, which imply that the protective role of CHI3L1 in IDD. Using high-throughput RNA sequencing and functional analyses, we find that AKT3 expression and its phosphorylation is mainly regulated by CHI3L1. And lastly, the mechanism of which is also validated using human and mouse degenerated NP tissues. In summary, our findings show that the inflammation-related autocrine factor CHI3L1 is NP specific, and it protects IDD by promoting the AKT3 signaling, which may serve as a potential therapeutic target in intervertebral disc degeneration.

YKL-39 as a Potential New Target for Anti-Angiogenic Therapy in Cancer

YKL-39 belongs to the evolutionarily conserved family of Glyco_18-containing proteins composed of chitinases and chitinase-like proteins. Chitinase-like proteins (CLPs) are secreted lectins that lack hydrolytic activity due to the amino acid substitutions in their catalytic domain and combine the functions of cytokines and growth factors. One of the major cellular sources that produce CLPs in various pathologies, including cancer, are macrophages. Monocytes recruited to the tumor site and programmed by tumor cells differentiate into tumor-associated macrophages (TAMs), which are the primary source of pro-angiogenic factors. Tumor angiogenesis is a crucial process for supplying rapidly growing tumors with essential nutrients and oxygen. We recently determined that YKL-39 is produced by tumor-associated macrophages in breast cancer. YKL-39 acts as a strong chemotactic factor for monocytes and stimulates angiogenesis. Chemotherapy is a common strategy to reduce tumor size and aggressiveness before surgical intervention, but chemoresistance, resulting in the relapse of tumors, is a common clinical problem that is critical for survival in cancer patients. Accumulating evidence indicates that TAMs are essential regulators of chemoresistance. We have recently found that elevated levels of YKL-39 expression are indicative of the efficiency of the metastatic process in patients who undergo neoadjuvant chemotherapy. We suggest YKL-39 as a new target for anti-angiogenic therapy that can be combined with neoadjuvant chemotherapy to reduce chemoresistance and inhibit metastasis in breast cancer patients.

Differences in the chitinolytic activity of mammalian chitinases on soluble and insoluble substrates

Chitin is an abundant polysaccharide used by many organisms for structural rigidity and water repulsion. As such, the insoluble crystalline structure of chitin poses significant challenges for enzymatic degradation. Acidic mammalian chitinase, a processive glycosyl hydrolase, is the primary enzyme involved in the degradation of environmental chitin in mammalian lungs. Mutations to acidic mammalian chitinase have been associated with asthma, and genetic deletion in mice increases morbidity and mortality with age. We initially set out to reverse this phenotype by engineering hyperactive acidic mammalian chitinase variants. Using a screening approach with commercial fluorogenic substrates, we identified mutations with consistent increases in activity. To determine whether the activity increases observed were consistent with more biologically relevant chitin substrates, we developed new assays to quantify chitinase activity with insoluble chitin, and identified a one-pot fluorogenic assay that is sufficiently sensitive to quantify changes to activity due to the addition or removal of a carbohydrate-binding domain. We show that the activity increases from our directed evolution screen were lost when insoluble substrates were used. In contrast, naturally occurring gain-of-function mutations gave similar results with oligomeric and insoluble substrates. We also show that activity differences between acidic mammalian chitinase and chitotriosidase are reduced with insoluble substrate, suggesting that previously reported activity differences with oligomeric substrates may have been driven by differential substrate specificity. These results highlight the need for assays against physiological substrates when engineering metabolic enzymes, and provide a new one-pot assay that may prove to be broadly applicable to engineering glycosyl hydrolases.

Roles of chitinase 3-like 1 in the development of cancer, neurodegenerative diseases, and inflammatory diseases

Chitinase 3-like 1 (CHI3L1) is a secreted glycoprotein that mediates inflammation, macrophage polarization, apoptosis, and carcinogenesis. The expression of CHI3L1 is strongly increased by various inflammatory and immunological conditions, including rheumatoid arthritis, multiple sclerosis, Alzheimer's disease, and several cancers. However, its physiological and pathophysiological roles in the development of cancer and neurodegenerative and inflammatory diseases remain unclear. Several studies have reported that CHI3L1 promotes cancer proliferation, inflammatory cytokine production, and microglial activation, and that multiple receptors, such as advanced glycation end product, syndecan-1/αVβ3, and IL-13Rα2, are involved. In addition, the pro-inflammatory action of CHI3L1 may be mediated via the protein kinase B and phosphoinositide-3 signaling pathways and responses to various pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, interleukin-6, and interferon-γ. Therefore, CHI3L1 could contribute to a vast array of inflammatory diseases. In this article, we review recent findings regarding the roles of CHI3L1 and suggest therapeutic approaches targeting CHI3L1 in the development of cancers, neurodegenerative diseases, and inflammatory diseases.

Concentration of Chondrogenic Soluble Factors in Freshly Harvested Lipoaspirate

BACKGROUND

Cartilage tissue has a limited capacity for healing with the consequence that patients are often treated symptomatically until they become candidates for osteotomy or total joint replacement. Alternative biological therapies, for example, application of platelet-rich plasma and implantation of chondrocytes and mesenchymal stem cells, have emerged as a new treatment modality to repair articular cartilage. In addition, autologous fat transfer is performed for treatment of cartilage defects, example given, in osteoarthrosis, but several questions regarding basic biochemical properties of the transplant remain unanswered. Bone morphogenetic protein 4 (BMP4), matrix metalloproteinase (MMP)-8, cartilage oligomeric matrix protein (COMP), and chitinase-3-like protein 1 (CHI3L1) have been shown to be involved in chondrogenic regeneration and represent potential therapeutic agents for cartilage repair. However, no study regarding naturally occurring levels of these soluble factors in transplanted adipose tissue has yet been performed.

METHODS

To investigate the influence of age, body mass index, donor site, and sex on the concentration of BMP4, MMP-8, COMP, and CHI3L1 in freshly aspirated adipose tissue, their content was measured by means of enzyme-linked immunosorbent assay readings.

RESULTS

There were significant quantities of BMP4, MMP-8, COMP, and CHI3L1 (23.6, 249.9, 298.0, and 540.6 pg/mg, respectively) in the lipoaspirate harvested for transplantation. There was no correlation between the content of soluble factors and the patients' age or body mass index. Furthermore, the sex did not affect the amount of the investigated factors. However, there were significantly lower contents of BMP4, COMP, and CHI3L1 found in lipoaspirates harvested from the abdomen compared with nonabdominal donor sites.

CONCLUSIONS

Naturally occurring differences in the concentrations of the investigated soluble factors will favor certain donor sites for autologous fat transfer in the field of cartilage repair. Thus, increasing knowledge will enable researchers and clinicians to make autologous fat transfer procedures more reliable and efficient for treatment of articular cartilage defects.

Human stem cells home to and repair laser-damaged trabecular meshwork in a mouse model

Glaucoma is the leading cause of irreversible vision loss, and reducing elevated intraocular pressure is currently the only effective clinical treatment. The trabecular meshwork is the main resistance site for aqueous outflow that maintains intraocular pressure. In this study, we transplanted human trabecular meshwork stem cells (TMSCs) intracamerally into mice that received laser photocoagulation over a 180° arc of the trabecular meshwork. TMSCs preferentially homed and integrated to the laser-damaged trabecular meshwork region and expressed differentiated cell markers at 2 and 4 weeks. Laser-induced inflammatory and fibrotic responses were prevented by TMSC transplantation with simultaneous ultrastructure and function restoration. Cell affinity and migration assays and elevated expression of CXCR4 and SDF1 in laser-treated mouse trabecular meshwork suggest that the CXCR4/SDF1 chemokine axis plays an important role in TMSC homing. Our results suggest that TMSCs may be a viable candidate for trabecular meshwork refunctionalization as a novel treatment for glaucoma.

Hongmin Yun et al. show that implanted human stem cells can accurately home to and repair damaged trabecular meshwork tissue in the mouse eye via a chemokine axis defined by CXCR4 and SDF1. The study suggests that stem cells from the trabecular meshwork could be used to refunctionalize the outflow pathway as a treatment for glaucoma.

Ym1 induces RELMα and rescues IL-4Rα deficiency in lung repair during nematode infection

Ym1 and RELMα are established effector molecules closely synonymous with Th2-type inflammation and associated pathology. Here, we show that whilst largely dependent on IL-4Rα signaling during a type 2 response, Ym1 and RELMα also have IL-4Rα-independent expression patterns in the lung. Notably, we found that Ym1 has opposing effects on type 2 immunity during nematode infection depending on whether it is expressed at the time of innate or adaptive responses. During the lung migratory stage of Nippostrongylus brasiliensis, Ym1 promoted the subsequent reparative type 2 response but once that response was established, IL-4Rα-dependent Ym1 was important for limiting the magnitude of type 2 cytokine production from both CD4+ T cells and innate lymphoid cells in the lung. Importantly, our study demonstrates that delivery of Ym1 to IL-4Rα deficient animals drives RELMα production and overcomes lung repair deficits in mice deficient in type 2 immunity. Together, Ym1 and RELMα, exhibit time and dose-dependent interactions that determines the outcome of lung repair during nematode infection.

Chitin, chitinases, and chitin lectins: Emerging roles in human pathophysiology

Chitin is a simple β-linked repeating sugar polymer prominent in the building block structures of a wide variety of organisms, from the yeast cell wall to the exoskeleton and shells of arthropods and other forms of invertebrate life. It had previously been assumed that vertebrates did not contain chitins. However, chitin and chitinases are now documented to occur in vertebrate tissues. Chitin, chitinases and particularly chitinase-like proteins are involved in important human pathologies, though the mechanisms by which these function is unknown. These chitinase-like proteins bind to chitin and function as chitin lectins in that they bind to chitin but have lost the ability to degrade it. Emphasis is placed on one of the chitinase-like proteins, CHI3L1, that has acquired wide clinical importance. The purpose of this review is to place an array of bewildering observations associated with various human disorders into a framework, particularly the pathologies of the human gastro-intestinal tract. A reasonably cohesive story may eventually emerge.

Chitinase-like proteins as regulators of innate immunity and tissue repair: helpful lessons for asthma?

Chitinases and chitinase-like proteins (CLPs) belong to the glycoside hydrolase family 18 of proteins. Chitinases are expressed in mammals and lower organisms, facilitate chitin degradation, and hence act as host-defence enzymes. Gene duplication and loss-of-function mutations of enzymatically active chitinases have resulted in the expression of a diverse range of CLPs across different species. CLPs are genes that are increasingly associated with inflammation and tissue remodelling not only in mammals but also across distant species. While the focus has remained on understanding the functions and expression patterns of CLPs during disease in humans, studies in mouse and lower organisms have revealed important and overlapping roles of the CLP family during physiology, host defence and pathology. This review will summarise recent insights into the regulatory functions of CLPs on innate immune pathways and discuss how these effects are not only important for host defence and tissue injury/repair after pathogen invasion, but also how they have extensive implications for pathological processes involved in diseases such as asthma.

Human Chitinases and Chitinase-Like Proteins as Indicators for Inflammation and Cancer

Human Glyco_18 domain-containing proteins constitute a family of chitinases and chitinase-like proteins. Chitotriosidase and AMCase are true enzymes which hydrolyse chitin and have a C-terminal chitin-binding domain. YKL-40, YKL-39, SI-CLP and murine YM1/2 proteins possess solely Glyco_18 domain and do not have the hydrolytic activity. The major sources of Glyco_18 containing proteins are macrophages, neutrophils, epithelial cells, chondrocytes, synovial cells, and cancer cells. Both macrophages and neutrophils use the regulated secretory mechanism for the release of Glyco_18 containing proteins. Glyco_18 containing proteins are established biomarkers for human diseases. Chitotriosidase is overproduced by lipid-laden macrophages and is a major marker for the inherited lysosomal storage Gaucher disease. AMCase and murine lectin YM1 are upregulated in Th2-environment, and enzymatic activity of AMCase contributes to asthma pathogenesis. YKL proteins act as soluble mediators for the cell proliferation and migration, and are also involved in rheumatoid arthritis, inflammatory bowel disease, hepatic fibrosis and cirrhosis. Chitotriosidase and YKL-40 reflect the macrophage activation in atherosclerotic plaques. Serum level of YKL-40 is a diagnostic and prognostic marker for numerous types of solid tumors. YKL-39 is a marker for the activation of chondrocytes and the progression of the osteoarthritis in human. Recently identified SI-CLP is upregulated by Th2 cytokine IL-4 as well as by glucocorticoids. This unique feature of SI-CLP makes it an attractive candidate for the examination of individual sensitivity of patients to glucocorticoid treatment and prediction of side effects of glucocorticoid therapy. Human chitinases and chitinase-like proteins are found in tissues and circulation, and can be detected by non-invasive technologies.

YKL-40 expression in abnormal invasive placenta cases

OBJECTIVE

YKL-40 is a secreted glycoprotein and has been implicated in the proliferation and differentiation of malignant cells, extracellular tissue remodelling, neovascularisation, inhibition of cancer cell apoptosis and stimulation of tumour-associated fibroblasts. The purpose of this study was to evaluate YKL-40 tissue expression in extravillous trophoblast invasion and its possible implication in placenta creta.

METHODS

A total of 35 placenta creta cases and six control cases were included in the study, of which eight cases were placenta accreta, 12 were increta and 15 were percreta. Histological YKL-40 staining was scored in tissue as weak (1), medium (2) and strong (3).

RESULTS

YKL-40 immunoreactivity intensity in the percreta group was significantly higher compared to the increta and accreta groups (2.47±0.74, 1.33±0.49 and 1.37±0.52, respectively; P=0.000). YKL-40 immunoreactivity intensity was positively correlated with creta (r=0.6; P=0.000), depth of invasion (r=0.49; P=0.003) and depth of invasion to full thickness ratio (r=0.58; P=0.000).

CONCLUSION

This study demonstrated that YKL-40 is strongly expressed in placenta percreta and is correlated with extravillous trophoblast invasion. These findings may be informative for understanding the pathophysiology of placenta creta.

New Insights Into the Relationship Between Chitinase-3-Like-1 and Asthma

PURPOSE OF REVIEW

CHI3L1 (also known as YKL-40), a member of "mammalian chitinase-like proteins," is a serum protein lacking enzymatic activity. Although the protein is highly conserved in mammals, a consensus regarding its role in human pathologies is currently lacking. In an attempt to shed light on the many physiological functions of the protein, specifically with regard to asthma, a comprehensive overview of recent studies is provided.

RECENT FINDINGS

In asthma, CHI3L1 is secreted from macrophages and airway epithelial cells through an IL-13 related mechanism. Th2-associated inflammatory responses due to allergen exposure, resulting in airway hyper-responsiveness and smooth muscle contraction, play a role in tissue remodeling. The importance of CHI3L1 in initiation and development of asthma is not limited to its involvement in highly orchestrated events of inflammatory cytokines but further research is needed for further elucidation. Levels of the protein are associated with severity for numerous pathologies, including asthma, suggesting limited specificity as a biomarker.

Glycoprotein YKL-40 Levels in Plasma Are Associated with Fibrotic Changes on HRCT in Asbestos-Exposed Subjects

YKL-40 is a chitinase-like glycoprotein produced by alternatively activated macrophages that are associated with wound healing and fibrosis. Asbestosis is a chronic asbestos-induced lung disease, in which injury of epithelial cells and activation of alveolar macrophages lead to enhanced collagen production and fibrosis. We studied if YKL-40 is related to inflammation, fibrosis, and/or lung function in subjects exposed to asbestosis. Venous blood samples were collected from 85 men with moderate or heavy occupational asbestos exposure and from 28 healthy, age-matched controls. Levels of plasma YKL-40, CRP, IL-6, adipsin, and MMP-9 were measured with enzyme-linked immunosorbent assay (ELISA). Plasma YKL-40 levels were significantly higher in subjects with asbestosis (n = 19) than in those with no fibrotic findings in HRCT following asbestos exposure (n = 66) or in unexposed healthy controls. In asbestos-exposed subjects, plasma YKL-40 correlated negatively with lung function capacity parameters FVC (Pearson's r −0.259, p = 0.018) and FEV₁ (Pearson's r −0.240, p = 0.028) and positively with CRP (Spearman's rho 0.371, p < 0.001), IL-6 (Spearman's rho 0.314, p = 0.003), adipsin (Spearman's rho 0.459, p < 0.001), and MMP-9 (Spearman's rho 0.243, p = 0.025). The present finding suggests YKL-40 as a biomarker associated with fibrosis and inflammation in asbestos-exposed subjects.

Fibroblasts drive an immunosuppressive and growth-promoting microenvironment in breast cancer via secretion of Chitinase 3-like 1

Cancer-Associated Fibroblasts (CAFs) are the most prominent stromal cell type in breast tumors. CAFs promote tumor growth and metastasis by multiple mechanisms, including by mediating tumor-promoting inflammation. Immune modulation in the tumor microenvironment plays a central role in determining disease outcome. However, the functional interactions of CAFs with immune cells are largely unknown. Here we report a novel signaling axis between fibroblasts, cancer cells and immune cells in breast tumors that drives an immunosuppressive microenvironment, mediated by CAF-derived Chi3L1. We demonstrate that Chi3L1 is highly upregulated in CAFs isolated from mammary tumors and pulmonary metastases of transgenic mice, and in the stroma of human breast carcinomas. Genetic ablation of Chi3L1 in fibroblasts in vivo attenuated tumor growth, macrophage recruitment and reprogramming to an M2-like phenotype, enhanced tumor infiltration by CD8⁺ and CD4⁺ T cells and promoted a Th1 phenotype. These results indicate that CAF-derived Chi3L1 promotes tumor growth and shifts the balance of the immune milieu towards type 2 immunity. Taken together, our findings implicate fibroblast-derived Chi3L1 as a novel key player in the complex reciprocal interactions of stromal cells that facilitate tumor progression and metastasis, and suggest that targeting Chi3L1 may be clinically beneficial in breast cancer.

A longitudinal assessment of circulating YKL-40 levels in preschool children with wheeze

BACKGROUND

The chitinase-like protein YKL-40 (CHI3L1) is elevated in the circulation of adults and schoolchildren with chronic severe asthma. It is unknown whether YKL-40 is altered in younger, preschool children with wheeze, acute or chronic. We therefore examined YKL-40 in preschool children during an acute episode of wheeze and during remission, in comparison with healthy controls.

METHODS

Blood was obtained from 128 children (aged 6-44 months) at the emergency department during an acute episode of wheeze, and at two follow-up visits (approximately 3 months and 1 year later), as well as from 100 age-matched healthy controls on one occasion. Plasma YKL-40 levels were examined in relation to CHI3L1 rs4950928 genotype and clinical characteristics including Asthma Predictive Index, medication use, time spent with respiratory symptoms, atopic status, and blood leukocytes.

RESULTS

Children with wheeze had higher median YKL-40 levels at the acute visit (14.7 (11.5-22.6) ng/ml, p < 0.001) and 3-month follow-up (15.9 (11.5-20.2), p < 0.001) compared to the 1-year follow-up (11.9 (9.5-17.3)). YKL-40 levels in healthy controls (13.6 (11.0-17.0)) tended to be lower than those during acute wheeze (p = 0.07) and 3-month follow-up (p = 0.04), but were no different at the 1-year follow-up. CHI3L1 rs4950928 affected YKL-40 in all subjects, with highest levels present in those with the CC genotype (p < 0.001). Genotype frequency was similar in the two subject groups. YKL-40 levels showed a positive correlation with blood neutrophil counts but no consistent relationships with clinical characteristics of relevance to continuous wheeze.

CONCLUSION

YKL-40 levels were elevated during acute wheeze in preschool children, a finding which may be related to current neutrophilic inflammation, but YKL-40 was not associated with characteristics of persistent wheeze in this young cohort.

Inhibition of Mammalian Glycoprotein YKL-40: IDENTIFICATION OF THE PHYSIOLOGICAL LIGAND

YKL-40 is a mammalian glycoprotein associated with progression, severity, and prognosis of chronic inflammatory diseases and a multitude of cancers. Despite this well documented association, identification of the lectin's physiological ligand and, accordingly, biological function has proven experimentally difficult. YKL-40 has been shown to bind chito-oligosaccharides; however, the production of chitin by the human body has not yet been documented. Possible alternative ligands include proteoglycans, polysaccharides, and fibers like collagen, all of which makeup the extracellular matrix. It is likely that YKL-40 is interacting with these alternative polysaccharides or proteins within the body, extending its function to cell biological roles such as mediating cellular receptors and cell adhesion and migration. Here, we consider the feasibility of polysaccharides, including cello-oligosaccharides, hyaluronan, heparan sulfate, heparin, and chondroitin sulfate, and collagen-like peptides as physiological ligands for YKL-40. We use molecular dynamics simulations to resolve the molecular level recognition mechanisms and calculate the free energy of binding the hypothesized ligands to YKL-40, addressing thermodynamic preference relative to chito-oligosaccharides. Our results suggest that chitohexaose and hyaluronan preferentially bind to YKL-40 over collagen, and hyaluronan is likely the preferred physiological ligand, because the negatively charged hyaluronan shows enhanced affinity for YKL-40 over neutral chitohexaose. Collagen binds in two locations at the YKL-40 surface, potentially related to a role in fibrillar formation. Finally, heparin non-specifically binds at the YKL-40 surface, as predicted from structural studies. Overall, YKL-40 likely binds many natural ligands in vivo, but its concurrence with physical maladies may be related to associated increases in hyaluronan.

YKL-40 expression in chronic obstructive pulmonary disease: relation to acute exacerbations and airway remodeling

BACKGROUND

Recent studies suggest that YKL-40, also called chitinase-3-like-1 protein, has been implicated in the pathogenesis of various inflammatory diseases. It is currently unknown, however, whether YKL-40 plays a role in acute exacerbations of chronic obstructive pulmonary disease (AECOPD) and airway remodeling.

METHODS

We evaluated serum YKL-40 levels in patients with AECOPD (n = 37) and stable COPD (n = 44), as well as in controls (n = 47). The association between YKL-40 expression and airway remodeling was analyzed. The effects of YKL-40 on collagen synthesis of primary human lung fibroblasts were also evaluated.

RESULTS

Serum YKL-40 levels were elevated at AECOPD onset as compared to stable disease (median [interquartile range], 78.6 [52.3-122.2] ng/ml versus 46.7 [31.2-75.5] ng/ml; p = 0.0005). The ideal cutoff point for distinguishing patients with AECOPD from those with stable COPD was 64.7 ng/ml (AUC: 0.71; 95%CI: 0.596 to 0.823). YKL-40 expression correlated with airflow obstruction, C-reactive protein, and collagen deposition. Stimulation with YKL-40 promoted collagen production in lung fibroblasts through ERK- and p38-dependent mechanisms.

CONCLUSIONS

YKL-40 expression is up-regulated in patients with COPD and correlates with exacerbation attacks and may contribute to airway remodeling by acting on lung fibroblasts. The current data may provide insight into the underlying pathogenesis of COPD, in which YKL-40 has an important pathogenic role.

TRIAL REGISTRATION

ChiCTR-OCC-13003567.

Expression of YKL-40 and MIP-1a proteins in exudates and transudates: biomarkers for differential diagnosis of pleural effusions? A pilot study

Background

YKL-40 is an extracellular matrix glycoprotein with a significant role in tissue inflammation and remodeling. MIP-1a has chemotactic and pro-inflammatory properties, and is induced by YKL-40 in several lung disorders. The aim of this study was to determine the levels of YKL-40 and MIP-1a in blood serum and pleural fluids of various pulmonary diseases, and to evaluate their potential role as differential diagnosis biomarkers.

Methods

We recruited 60 patients (age: 62.5 ± 20.6 years) with pleural effusions: 49 exudates and 11 transudates (T). Exudates were further classified based on the underlying disease: ten with tuberculosis (TB), 13 with lung cancer (LCa), 15 with metastatic cancer (MCa) of non-lung origin and 11 with parapneumonic (PN) effusions. YKL-40 and MIP-1a levels were measured by ELISA.

Results

Pleural YKL-40 levels (ng/ml) were similar among all patient groups (TB: 399 ± 36, LCa: 401 ± 112, MCa: 416 ± 34, PN: 401 ± 50, T: 399 ± 42, p = 0.92). On the contrary, YKL-40 was significantly lower in the serum of TB patients (TB: 58 ± 22, LCa: 212 ± 106, MCa: 254 ± 140, PN: 265 ± 140, T: 229 ± 123, p < 0.001). Pleural MIP-1a protein levels (ng/ml) were statistically lower only in patients with LCa (TB: 25.0 ± 20.2, LCa: 7.3 ± 6.0, MCa: 16.1 ± 14.9, PN: 25.4 ± 27.9, T: 18.5 ± 7.9, p = 0.012), a finding also observed in serum MIP-1a levels (TB: 17.1 ± 7.6, LCa: 9.4 ± 7.0, MCa: 28.7 ± 28.7, PN: 33.3 ± 24.0, T: 22.9 ± 8.7, p = 0.003).

Conclusions

Our data suggest that both YKL-40 and MIP-1a, particularly in serum, could prove useful for the differentiation of pleural effusions in clinical practice, especially of TB or LCa origin. However, large-scale studies are needed to validate these findings.

Serum YKL-40: a new independent prognostic marker for skeletal complications in patients with multiple myeloma

In a time of increasing treatment options for multiple myeloma bone disease, risk factors predicting progression need to be elucidated. This study investigated the value of serum YKL-40, previously shown to be associated with radiographic progression of bone destruction, as a predictor for time to clinical progression, i.e. skeletal-related events (SREs), in 230 newly diagnosed patients with multiple myeloma receiving intravenous bisphosphonates. Serum concentrations of YKL-40 and biochemical bone markers (CTX-MMP, CTX-I, PINP) were measured at diagnosis. Patients were evaluated every third month for SRE and at 9 and 24 months for radiographic progression. Elevated serum YKL-40 was seen in 47% of patients and associated with high-risk disease (International Staging System stage III; p < 0.001), increased bone resorption (serum CTX/MMP; p < 0.001) and early radiographic progression at 9 months (p = 0.01). Serum YKL-40 together with serum CTX-MMP/PINP ratio and World Health Organization status were independent predictors of time to first SRE.

Keeping track of the growing number of biological functions of chitin and its interaction partners in biomedical research

Chitin is a vital polysaccharide component of protective structures in many eukaryotic organisms but seems absent in vertebrates. Chitin or chitin oligomers are therefore prime candidates for non-self-molecules, which are recognized and degraded by the vertebrate immune system. Despite the absence of polymeric chitin in vertebrates, chitinases and chitinase-like proteins (CLPs) are well conserved in vertebrate species. In many studies, these proteins have been found to be involved in immune regulation and in mediating the degradation of chitinous external protective structures of invading pathogens. Several important aspects of chitin immunostimulation have recently been uncovered, advancing our understanding of the complex regulatory mechanisms that chitin mediates. Likewise, the last few years have seen large advances in our understanding of the mechanisms and molecular interactions of chitinases and CLPs in relation to immune response regulation. It is becoming increasingly clear that their function in this context is not exclusive to chitin producing pathogens, but includes bacterial infections and cancer signaling as well. Here we provide an overview of the immune signaling properties of chitin and other closely related biomolecules. We also review the latest literature on chitinases and CLPs of the GH18 family. Finally, we examine the existing literature on zebrafish chitinases, and propose the use of zebrafish as a versatile model to complement the existing murine models. This could especially be of benefit to the exploration of the function of chitinases in infectious diseases using high-throughput approaches and pharmaceutical interventions.

New treatment and markers of prognosis for idiopathic pulmonary fibrosis: lessons learned from translational research

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease with increasing prevalence, high mortality rates and poor treatment options. The diagnostic process is complex and often requires an interdisciplinary approach between different specialists. Information gained over the past 10 years of intense research resulted in improved diagnostic algorithms, a better understanding of the underlying pathogenesis and the development of new therapeutic options. Specifically, the change from the traditional concept that viewed IPF as a chronic inflammatory disorder to the current belief that is primarily resulting from aberrant wound healing enabled the identification of novel treatment targets. This increased the clinical trial activity dramatically and resulted in the approval of the first IPF-specific therapy in many countries. Still, the natural history and intrinsic behavior of IPF are very difficult to predict. There is an urgent need for new therapies and also for development and validation of prognostic markers that predict disease progression, survival and also response to antifibrotic drugs. This review provides an up to date summary of the most relevant clinical trials, novel therapeutic drug targets and outlines a spectrum of potential prognostic biomarkers for IPF.

CHI3L1 plays a role in cancer through enhanced production of pro-inflammatory/pro-tumorigenic and angiogenic factors

Elevated serum levels of a glycoprotein known as chitinase-3-like protein 1 (CHI3L1) have been correlated with poor prognosis and shorter survival of patients with cancer and inflammatory diseases. The biological and physiological functions of CHI3L1 in cancer have not yet been completely elucidated. In this review, we describe the role of CHI3L1 in inducing pro-inflammatory/pro-tumorigenic and angiogenic factors that could promote tumor growth and metastasis.

YKL-40 as a novel factor associated with inflammation and catabolic mechanisms in osteoarthritic joints

YKL-40 is associated with tissue injury and inflammation, and consequently to diseases in which these mechanisms lead to tissue degradation, for example, asthma and rheumatoid arthritis. The purpose of the present study was to investigate if YKL-40 is also a significant factor in osteoarthritis (OA) by assessing associations of YKL-40 with mediators related to the pathogenesis of OA: cartilage destructing matrix metalloproteinases (MMPs) and proinflammatory cytokines interleukin-6 (IL-6) and interleukin-17 (IL-17). Cartilage, synovial fluid (SF), and plasma samples were obtained from 100 OA patients undergoing total knee replacement surgery. SF levels of YKL-40 (1027.9 ± 78.3 ng/mL) were considerably higher than plasma levels (67.2 ± 4.5 ng/mL) and correlated with YKL-40 released from cartilage samples obtained from the same patients (r = 0.37, P = 0.010), indicating that YKL-40 is produced by OA cartilage. Interestingly, YKL-40 concentrations in OA SF correlated positively with MMP-1 (r = 0.36, P = 0.014), MMP-3 (r = 0.46, P = 0.001), IL-6 (r = 0.57, P < 0.001), and IL-17 (r = 0.52, P = 0.010) levels. Moreover, IL-6 and IL-17 enhanced YKL-40 production in human primary chondrocyte cultures. The present study introduces YKL-40 as a cartilage-derived factor associated with mediators of inflammation and cartilage destruction involved in the pathogenesis of OA.

Increased expression of YKL-40 in mild and moderate/severe persistent allergic rhinitis and its possible contribution to remodeling of nasal mucosa

BACKGROUND

Prominent expression of YKL-40 has been associated with pathological conditions characterized by tissue remodeling. We determined the expression level and distribution pattern of YKL-40 in allergic nasal mucosa and evaluated the effect of YKL-40 on the proliferation and migration of fibroblasts, the production of the mediators related to tissue remodeling, and collagen production. Additionally, the cytokine-driven regulation of YKL-40 expression was evaluated in cultured epithelial cells.

METHODS

The expression of YKL-40 in normal, mild, and moderate/severe allergic nasal mucosa was evaluated using real-time polymerase chain reaction (PCR), Western blot, and immunohistochemistry. Fibroblast migration was observed using a scratch wound method, and proliferation was determined by the MTT methods. Expression of proteoglycans, transforming growth factor (TGF) beta1, MMP2, MMP9, TIMP1, TIMP2, and collagen concentration were analyzed in fibroblasts treated with YKL-40. The expression levels of YKL-40 in cultured epithelial cells were examined after stimulation with mediators including Th2 cytokines, interferon (IFN)gamma, and TNF-alpha with real-time PCR and ELISA.

RESULTS

The expression of YKL-40 was up-regulated in allergic rhinitis and distributed in superficial epithelium, submucosal glands, and vascular endothelium, in addition to infiltrating cells. TGF-beta1, TIMP1, MMP9, and biglycan were up-regulated in fibroblasts on stimulation with YKL-40, accompanying increased proliferation and migration, and collagen production. IL-13, IFN-gamma, and TNF-alpha induced the increased production of YKL-40 in cultured epithelial cells.

CONCLUSION

YKL-40 is up-regulated in mild and moderate/severe persistent allergic rhinitis, and its expression can be regulated differentially by different cytokines, possibly contributing to the remodeling of nasal mucosa in allergic rhinitis.

The chitinase-like protein YKL-40 is not a useful biomarker for severe persistent asthma in children

BACKGROUND

The chitinase-like protein YKL-40 is thought to play a role in inflammation and tissue remodeling. In adults with severe asthma, YKL-40 is expressed in the airway and YKL-40 levels are elevated in the serum.

OBJECTIVE

To compare YKL-40 levels in children with severe persistent asthma with those in adults with severe persistent asthma and to determine whether YKL-40 levels correlate with increasing asthma severity in childhood asthma.

METHODS

In this prospective, cross-sectional study, 23 adults and 19 children with severe persistent asthma, 23 children with moderate persistent asthma, and 19 children with mild persistent asthma were enrolled. The following data were collected on each patient: spirometry, exhaled nitric oxide, percutaneous skin testing results to aeroallergens, peripheral eosinophils, serum IgE levels, and serum YKL-40 levels.

RESULTS

Compared with adults, children with severe persistent asthma had significantly lower YKL-40 levels, higher values for forced vital capacity and forced expiration volume in 1 second, higher serum IgE levels, and higher exhaled nitric oxide levels. YKL-40 levels did not correlate with increasing asthma severity in the pediatric cohort.

CONCLUSION

Severe persistent asthma in childhood is not associated with elevated YKL-40 levels, unlike in adults with severe persistent asthma. YKL-40 is not a useful biomarker for asthma severity in childhood asthma.

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.

Brain barriers and a subpopulation of astroglial progenitors of developing human forebrain are immunostained for the glycoprotein YKL-40

YKL-40, a glycoprotein involved in cell differentiation, has been associated with neurodevelopmental disorders, angiogenesis, neuroinflammation and glioblastomas. We evaluated YKL-40 protein distribution in the early human forebrain using double-labeling immunofluorescence and immunohistochemistry. Immunoreactivity was detected in neuroepithelial cells, radial glial end feet, leptomeningeal cells and choroid plexus epithelial cells. The subpial marginal zone was YKL-40-positive, particularly in the hippocampus, from an early beginning stage in its development. Blood vessels in the intermediate and subventricular zones showed specific YKL-40 reactivity confined to pericytes. Furthermore, a population of YKL-40-positive, small, rounded cells was identified in the ventricular and subventricular zones. Real-time quantitative RT-PCR analysis showed strong YKL-40 mRNA expression in the leptomeninges and the choroid plexuses, and weaker expression in the telencephalic wall. Immunohistochemistry revealed a differential distribution of YKL-40 across the zones of the developing telencephalic wall. We show that YKL-40 is associated with sites of the brain barrier systems and propose that it is involved in controlling local angiogenesis and access of peripheral cells to the forebrain via secretion from leptomeningeal cells, choroid plexus epithelium and pericytes. Furthermore, we suggest that the small, rounded, YKL-40-positive cells represent a subpopulation of astroglial progenitors, and that YKL-40 could be involved in the differentiation of a particular astrocytic lineage.

Protective role of bortezomib in steatotic liver ischemia/reperfusion injury through abrogation of MMP activation and YKL-40 expression

Steatotic liver grafts tolerate ischemia-reperfusion (I/R) injury poorly, contributing to poor survival following transplantation. However the molecular mechanisms leading to I/R injury still remain to be defined. We have previously reported that the protective effect of bortezomib towards inhibiting cold induced I/R injury in obese rat liver transplant model is through NF-κB down modulation. In this report using an orthotopic liver transplant (OLT) model in Zucker rats (from obese, leptin deficient donor, to lean recipient) we defined the mechanisms of steatotic liver injury, and characterized the role of bortezomib in inhibiting MMP activation and YKL-40, both of which are involved in extracellular matrix deposition and fibrosis, the key pathological features of liver allograft failure. Obese donor rats were treated with bortezomib (i.v., 0.1mg/kg immediately prior to liver procurement) to assess the role of MMP and YKL-40 in steatotic liver I/R injury. I/R injury in steatotic livers resulted in significant increases in expression of YKL-40 (9 fold), and activation of MMP-2 (15 fold)/MMP-9 (12 fold). Bortezomib treatment reduced the expression of YKL-40 and MMP to basal levels. Bortezomib also inhibited the pro-fibrotic (VEGF, HGF, bFGF, TGF-β) and pro-inflammatory (IL-1β, TNF-α and IFN-γ) cytokines significantly in comparison to untreated animals with I/R injury. These results demonstrate that I/R injury in steatotic livers following transplantation are associated with MMP activation and YKL-40 upregulation resulting in pro-fibrotic and pro-inflammatory cytokine release. Administration of the proteosomal inhibitor, bortezomib, effectively attenuated the I/R injury by inhibiting MMP and YKL-40 expression and therefore support the clinical utility of this drug in donor management for preventing I/R injury and its sequelae.

Potential association between TLR4 and chitinase 3-like 1 (CHI3L1/YKL-40) signaling on colonic epithelial cells in inflammatory bowel disease and colitis-associated cancer

Inflammatory bowel disease (IBD) is a group of inflammatory disorders in the small and large intestines. Several studies have proved that persistent and disregulated host/microbial interactions are required for the development of IBD. It is well known that chronic IBD is strongly associated with an increased risk of developing colorectal cancer by 0.5-1% annually, 8-10 years after the initial diagnosis. To detect the tiny dysplasia or early stage of cancer in chronic IBD patients, a tremendous amount of effort is currently directed for improving colonoscopic technology and noninvasive serological marker development. However, there is only a limited amount of data available to understand the exact mechanism of how long term chronic colitis is connected to the development of colorectal tumors. Recently, our group has identified significantly increased expression of chitinase 3-like 1 (CHI3L1) molecule in non-dysplastic mucosa from patients with IBD and remote dysplasia/cancer, compared to patients with IBD without dysplasia or healthy controls. CHI3L1 seems to contribute to the proliferation, migration, and neoplastic progression of colonic epithelial cells (CECs) under inflammatory conditions. Furthermore, the TLR4-mediated intracellular signaling cascade is likely to interact with CHI3L1 signaling in CECs. In this review article, we have concisely summarized the cellular and molecular mechanisms underlining the development of IBD and colitis-associated cancer, with particular focus on the TLR4- and CHI3L1-signaling pathways in CECs.