Tumor Necrosis Factor-stimulated Gene 6 (TSG-6)-mediated Interactions with the Inter-α-inhibitor Heavy Chain 5 Facilitate Tumor Growth Factor β1 (TGFβ1)-dependent Fibroblast to Myofibroblast Differentiation

An Overview on the Emerging Role of the Plasma Protease Inhibitor Protein ITIH5 as a Metastasis Suppressor

Most cancers are not detected until they have progressed to the point of becoming malignant and life-threatening. Chemotherapy and conventional medicines are often ineffective against cancer. Although we have made significant progress, new conceptual discoveries are still required to investigate new treatments. The role of metastasis suppressor genes as a therapeutic option for limiting tumor progression and metastasis has been on the anvil for some time. In this review, we discuss the role of ITIH5 as a metastasis suppressor gene and catalog its involvement in different cancers. We further shed light on the mode of action of ITIH5 based on the available data. The review will provide a new perspective on ITIH5 as an anti-metastatic protein and hopefully serve as an impetus for future studies towards the application of ITIH5 for clinical intervention in targeting metastatic cancers.

ITIH5 inhibits proliferation, adipogenic differentiation, and secretion of inflammatory cytokines of human adipose stem cells-A new key in treating obesity?

Inter-α-trypsin inhibitor heavy chain 5 (ITIH5) is widely expressed in the human body, and it is detected to be particularly abundant in adipose tissue. ITIH5 expression is increased in people with obesity compared to lean persons and is decreased by diet-induced weight loss. This suggests that ITIH5 may be involved in the development of adiposity and clinical metabolic variables, although its exact function remains unknown. We measured the protein concentration of ITIH5 in adipose samples from patients undergoing abdominoplasty and tested for correlation with the subjects' BMI as well as inflammatory mediators. We stimulated human adipose stem cells (ASCs) with recombinant (r)ITIH5 protein and tested for an effect on proliferation, differentiation, and immunosuppressive properties when the cells were exposed to an artificial inflammatory environment. We found positive correlations between ITIH5 levels and the BMI (p < .001) as well as concentrations of inflammatory cytokines (TNF-α, IL-6, and MCP-1) in adipose tissue (p < .01). Application of the rITIH5 protein inhibited both proliferation (p < .001) and differentiation of ASCs. Especially, the development of mature adipocytes was reduced by over 50%. Moreover, rITIH5 decreased the release of IL-6 and MCP-1 when the cells were exposed to TNF-α and IL-1β (p < .001). Our data suggest that ITIH5 is an adipokine that is increasingly released during human adipose tissue development, acting as a regulator that inhibits proliferation and adipogenic differentiation of ASCs. ITIH5 thus presents itself as a positive regulator of adipose tissue homeostasis, possibly protecting against both hyperplasia and hypertrophy of adipose tissue and the associated chronic inflammation.

The impact of inflammation and acute phase activation in cancer cachexia

The development of cachexia in the setting of cancer or other chronic diseases is a significant detriment for patients. Cachexia is associated with a decreased ability to tolerate therapies, reduction in ambulation, reduced quality of life, and increased mortality. Cachexia appears intricately linked to the activation of the acute phase response and is a drain on metabolic resources. Work has begun to focus on the important inflammatory factors associated with the acute phase response and their role in the immune activation of cachexia. Furthermore, data supporting the liver, lung, skeletal muscle, and tumor as all playing a role in activation of the acute phase are emerging. Although the acute phase is increasingly being recognized as being involved in cachexia, work in understanding underlying mechanisms of cachexia associated with the acute phase response remains an active area of investigation and still lack a holistic understanding and a clear causal link. Studies to date are largely correlative in nature, nonetheless suggesting the possibility for a role for various acute phase reactants. Herein, we examine the current literature regarding the acute phase response proteins, the evidence these proteins play in the promotion and exacerbation of cachexia, and current evidence of a therapeutic potential for patients.

Dysfunctional Extracellular Matrix Remodeling Supports Perianal Fistulizing Crohn's Disease by a Mechanoregulated Activation of the Epithelial-to-Mesenchymal Transition

BACKGROUND AND AIMS

Perianal fistula represents one of the most disabling manifestations of Crohn's disease (CD) due to complete destruction of the affected mucosa, which is replaced by granulation tissue and associated with changes in tissue organization. To date, the molecular mechanisms underlying perianal fistula formation are not well defined. Here, we dissected the tissue changes in the fistula area and addressed whether a dysregulation of extracellular matrix (ECM) homeostasis can support fistula formation.

METHODS

Surgical specimens from perianal fistula tissue and the surrounding region of fistulizing CD were analyzed histologically and by RNA sequencing. Genes significantly modulated were validated by real-time polymerase chain reaction, Western blot, and immunofluorescence assays. The effect of the protein product of TNF-stimulated gene-6 (TSG-6) on cell morphology, phenotype, and ECM organization was investigated with endogenous lentivirus-induced overexpression of TSG-6 in Caco-2 cells and with exogenous addition of recombinant human TSG-6 protein to primary fibroblasts from region surrounding fistula. Proliferative and migratory assays were performed.

RESULTS

A markedly different organization of ECM was found across fistula and surrounding fistula regions with an increased expression of integrins and matrix metalloproteinases and hyaluronan (HA) staining in the fistula, associated with increased newly synthesized collagen fibers and mechanosensitive proteins. Among dysregulated genes associated with ECM, TNFAI6 (gene encoding for TSG-6) was as significantly upregulated in the fistula compared with area surrounding fistula, where it promoted the pathological formation of complexes between heavy chains from inter-alpha-inhibitor and HA responsible for the formation of a crosslinked ECM. There was a positive correlation between TNFAI6 expression and expression of mechanosensitive genes in fistula tissue. The overexpression of TSG-6 in Caco-2 cells promoted migration, epithelial-mesenchymal transition, transcription factor SNAI1, and HA synthase (HAs) levels, while in fibroblasts, isolated from the area surrounding the fistula, it promoted an activated phenotype. Moreover, the enrichment of an HA scaffold with recombinant human TSG-6 protein promoted collagen release and increase of SNAI1, ITGA4, ITGA42B, and PTK2B genes, the latter being involved in the transduction of responses to mechanical stimuli.

CONCLUSIONS

By mediating changes in the ECM organization, TSG-6 triggers the epithelial-mesenchymal transition transcription factor SNAI1 through the activation of mechanosensitive proteins. These data point to regulators of ECM as new potential targets for the treatment of CD perianal fistula.

Abnormal expression of TSG-6 disturbs extracellular matrix homeostasis in chondrocytes from endemic osteoarthritis

Background and aims: Kashin-Beck disease (KBD) is a unique endemic osteochondropathy with unclear pathogenesis in China. T-2 toxin exposure has been identified as a significant risk factor of KBD. However, the mechanism of articular cartilage damage induced by T-2 toxin is a conundrum. We explored the role of the extracellular matrix-related gene TSG-6 in the articular chondrocyte damage process under the exposure of HT-2 toxin.

Methods: TSG-6 was identified as a candidate gene by mining our previous gene expression profiling of KBD and verified by qRT-PCR and immunohistochemistry. Then, TSG-6 was silenced by RNA interference technology and overexpressed induction by TNF-α. Gradient concentrations of HT-2 toxin were added to intervene with C28/I2 chondrocytes. MTT was used to observe the proliferation and cell viability of chondrocytes, and qRT-PCR was utilized to detect the expression changes of MMP1, MMP3, MMP13, COL2A1, and proteoglycan before and after treatments for verification.

Results: TSG-6 was upregulated in KBD chondrocytes at the mRNA level and upregulated in the superficial, middle, and deep zones of KBD cartilage. After TSG-6 silencing, the expression of MMP1, MMP3, MMP13, and proteoglycan was significantly decreased while COL2A1 expression was significantly increased, which was reversed after the overexpression of TSG-6 induced by TNF-α (p &lt; 0.05). The survival rate of chondrocytes was correspondingly reduced with an increase in the HT-2 toxin concentration. Compared with the blank control group, the expression of MMPs was increased in the intervention group of HT-2 toxin, while the expression of proteoglycan and COL2A1 decreased (p &lt; 0.05).

Conclusion: The upregulation of the TSG-6 gene may play a role in promoting the damage and degradation of the extracellular matrix in KBD chondrocytes under the exposure of HT-2 toxin.

Pediatric Non-Myofibroblastic Primitive Spindle Cell Tumors with ALK Gene Rearrangements and Response to Crizotinib

We describe two poorly differentiated, non-myofibroblastic (SMA-, S100+, CD34±), spindle cell neoplasms with immunohistochemical positivity for ALK and with ALK gene rearrangements leading to PLEKHH2::ALK and CLTC::ALK fusions, respectively. ALK protein overexpression and/or gene fusions should be evaluated in poorly differentiated spindle cell neoplasms, even when there is an absence of a myofibroblastic phenotype. A positive ALK evaluation has therapeutic implications as both tumors responded to single-agent treatment with the tyrosine kinase inhibitor crizotinib.

ITIH5-Derived Polypeptides Covering the VIT Domain Suppress the Growth of Human Cancer Cells In Vitro

Oncogenic drivers such as mutated EGFR are the preferred targets in modern drug development. However, restoring the lost function of tumor suppressor proteins could also be a valid approach to combatting cancer. ITIH5 has been revealed as a potent metastasis suppressor in both breast and pancreatic cancer. Here, we show that ITIH5 overexpression in MDA-MB-231 breast cancer cells can also locally suppress tumor growth by 85%, when transplanted into the mammary fat pad of nude mice. For a potential drug development approach, we further aimed to define downsized ITIH5 polypeptides that still are capable of mediating growth inhibitory effects. By cloning truncated and His-tagged ITIH5 fragments, we synthesized two recombinant N-terminal polypeptides (ITIH5681aa and ITIH5161aa), both covering the ITI heavy chain specific “vault protein inter-alpha-trypsin” (VIT) domain. Truncated ITIH5 variants caused dose-dependent cell growth inhibition by up to 50% when applied to various cancer cell lines (e.g., MDA-MB-231, SCaBER, A549) reflecting breast, bladder and lung cancer in vitro. Thus, our data suggest the substantial role of the ITIH5-specific VIT domain in ITIH5-mediated suppression of tumor cell proliferation. As extracellularly administered ITIH5 peptides mimic the growth-inhibitory effects of the full-length ITIH5 tumor suppressor protein, they may constitute the basis for developing anticancer drugs in the future.

Switched alternative splicing events as attractive features in lung squamous cell carcinoma

Background

Alternative splicing (AS) plays important roles in transcriptome and proteome diversity. Its dysregulation has a close affiliation with oncogenic processes. This study aimed to evaluate AS-based biomarkers by machine learning algorithms for lung squamous cell carcinoma (LUSC) patients.

Method

The Cancer Genome Atlas (TCGA) database and TCGA SpliceSeq database were utilized. After data composition balancing, Boruta feature selection and Spearman correlation analysis were used for differentially expressed AS events. Random forests and a nested fivefold cross-validation were applied for lymph node metastasis (LNM) classifier building. Random survival forest combined with Cox regression model was performed for a prognostic model, based on which a nomogram was developed. Functional enrichment analysis and Spearman correlation analysis were also conducted to explore underlying mechanisms. The expression of some switch-involved AS events along with parent genes was verified by qRT-PCR with 20 pairs of normal and LUSC tissues.

Results

We found 16 pairs of splicing events from same parent genes which were strongly related to the splicing switch (intrapair correlation coefficient = − 1). Next, we built a reliable LNM classifier based on 13 AS events as well as a nice prognostic model, in which switched AS events behaved prominently. The qRT-PCR presented consistent results with previous bioinformatics analysis, and some AS events like ITIH5-10715-AT and QKI-78404-AT showed remarkable detection efficiency for LUSC.

Conclusion

AS events, especially switched ones from the same parent genes, could provide new insights into the molecular diagnosis and therapeutic drug design of LUSC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02429-2.

Recombinant TSG-6 protein inhibits the growth of capsule fibroblasts in frozen shoulder via suppressing the TGF-β/Smad2 signal pathway

Background

The tumor necrosis factor-stimulated gene-6 (TSG-6) has been confirmed to inhibit inflammation. It is now generally accepted that local inflammatory stimulation around shoulder capsule causes proliferative fibrosis. This study aims to investigate the mechanism of recombinant TSG-6 protein inhibiting the growth of capsule fibroblasts in frozen shoulder via the TGF-β/Smad2 signal pathway.

Methods

Human frozen shoulder capsule tissue was taken for primary and passage culture, and the 3rd generation fibroblasts from pathological frozen shoulder capsule were treated with different concentrations of recombinant TSG-6 protein, or with TGF-β1 agonist SRI-011381. Immunoconfocal analysis was used to identify the isolated fibroblasts, and MTT assay, colony formation assay, and flow cytometry were used to detect the viability, proliferation, and apoptosis rate of fibroblast. The contents of fibrosis and inflammation indexes COL1A1, TNF-α, IL-6, and IL-1β in the cell supernatant were detected using ELISA and then further examined by qRT-PCR. The expression of Bax, Bcl-2, and proteins related to TGF-β/Smad2 pathway were detected by Western Blot.

Results

Compared with the blank control group, fibroblasts intervened with TSG-6 (2 μg and 5 μg) showed significantly decreased viability and proliferation ability and enhanced cell apoptosis, concurrent with the reductions in Bcl-2 expression; COL1A1, TNF-α, IL-6, and IL-1β levels; and the expression of TGF-β1 and phosphorylated Smad22, and an increase in Bax expression, while SRI-011381 treatment would reverse the effect of recombinant TSG-6 protein.

Conclusion

Recombinant TSG-6 protein inhibited the growth of primary fibroblasts from human frozen shoulder capsule by suppressing the TGF-β/Smad2 signaling pathway.

Anti-inflammatory protein TNFα-stimulated gene-6 (TSG-6) reduces inflammatory response after brain injury in mice

BACKGROUND

Current research suggests that the glial scar surrounding penetrating brain injuries is instrumental in preserving the surrounding uninjured tissue by limiting the inflammatory response to the injury site. We recently showed that tumor necrosis factor (TNF)-stimulated gene-6 (TSG-6), a well-established anti-inflammatory molecule, is present within the glial scar. In the present study we investigated the role of TSG-6 within the glial scar using TSG-6 null and littermate control mice subjected to penetrating brain injuries.

RESULTS

Our findings show that mice lacking TSG-6 present a more severe inflammatory response after injury, which was correlated with an enlarged area of astrogliosis beyond the injury site.

CONCLUSION

Our data provides evidence that TSG-6 has an anti-inflammatory role within the glial scar.

Myofibroblasts: Function, Formation, and Scope of Molecular Therapies for Skin Fibrosis

Myofibroblasts are contractile, α-smooth muscle actin-positive cells with multiple roles in pathophysiological processes. Myofibroblasts mediate wound contractions, but their persistent presence in tissues is central to driving fibrosis, making them attractive cell targets for the development of therapeutic treatments. However, due to shared cellular markers with several other phenotypes, the specific targeting of myofibroblasts has long presented a scientific and clinical challenge. In recent years, myofibroblasts have drawn much attention among scientific research communities from multiple disciplines and specialisations. As further research uncovers the characterisations of myofibroblast formation, function, and regulation, the realisation of novel interventional routes for myofibroblasts within pathologies has emerged. The research community is approaching the means to finally target these cells, to prevent fibrosis, accelerate scarless wound healing, and attenuate associated disease-processes in clinical settings. This comprehensive review article describes the myofibroblast cell phenotype, their origins, and their diverse physiological and pathological functionality. Special attention has been given to mechanisms and molecular pathways governing myofibroblast differentiation, and updates in molecular interventions.

Reduced hyaluronan cross-linking induces breast cancer malignancy in a CAF-dependent manner

Hyaluronan (HA) cross-linking is a conformational state of HA, a covalent complex between HA and heavy chains (HCs) from inter-α-trypsin inhibitor (I-α-I) mediated by tumor necrosis factor-induced protein 6 (TSG6). Cross-linked HA has been identified as a protective factor in physiological and inflammatory conditions. However, the state of HA cross-linking in tumor microenvironment has not been fully elucidated. As a major constituent of the extracellular matrix (ECM), HA is mainly synthesized by cancer-associated fibroblasts (CAFs). Our study aimed to clarify the role of HA cross-linking in breast cancer malignancy. Compared to normal mammary gland tissues, cross-linked HA levels were significantly decreased in breast cancer and associated with tumor malignancy. When NFbs were activated into CAFs, the levels of cross-linked HA and TSG6 were both suppressed. Through upregulating TSG6, CAFs restored the high level of cross-linked HA and significantly inhibited breast cancer malignancy, whereas NFbs promoted the malignancy when the cross-linked HA level was reduced. Furthermore, the inhibitory role of HA cross-linking in tumor malignancy was directly verified using the synthesized HA-HC complex. Collectively, our study found that the deficiency of cross-linked HA induced breast cancer malignancy in a CAF-dependent manner, suggesting that recovering HA cross-linking may be a potential therapeutic strategy.

The ECM Modulator ITIH5 Affects Cell Adhesion, Motility and Chemotherapeutic Response of Basal/Squamous-Like (BASQ) Bladder Cancer Cells

This study aims at characterizing the role of the putative tumor suppressor ITIH5 in basal-type bladder cancers (BLCA). By sub-classifying TCGA BLCA data, we revealed predominant loss of ITIH5 expression in the basal/squamous-like (BASQ) subtype. ITIH5 expression inversely correlated with basal-type makers such as KRT6A and CD44. Interestingly, Kaplan–Meier analyses showed longer recurrence-free survival in combination with strong CD44 expression, which is thought to mediate ITIH-hyaluronan (HA) binding functions. In vitro, stable ITIH5 overexpression in two basal-type BLCA cell lines showing differential CD44 expression levels, i.e., with (SCaBER) and without squamous features (HT1376), demonstrated clear inhibition of cell and colony growth of BASQ-type SCaBER cells. ITIH5 further enhanced HA-associated cell-matrix attachment, indicated by altered size and number of focal adhesion sites resulting in reduced cell migration capacities. Transcriptomic analyses revealed enrichment of pathways and processes involved in ECM organization, differentiation and cell signaling. Finally, we provide evidence that ITIH5 increase sensitivity of SCaBER cells to chemotherapeutical agents (cisplatin and gemcitabine), whereas responsiveness of HT1376 cells was not affected by ITIH5 expression. Thus, we gain further insights into the putative role of ITIH5 as tumor suppressor highlighting an impact on drug response potentially via the HA-CD44 axis in BASQ-type BLCA.

Transcriptome Analysis of Hypoxic Lymphatic Endothelial Cells Indicates Their Potential to Contribute to Extracellular Matrix Rearrangement

Lymphedema (LE) affects millions of people worldwide. It is a chronic progressive disease with massive development of fibrosclerosis when untreated. There is no pharmacological treatment of lymphedema. The disease is associated with swelling of the interstitium of the affected organ, mostly arm or leg, impressive development of adipose tissue, fibrosis and sclerosis with accumulation of huge amounts of collagen, and Papillomatosis cutis. Malnutrition and reduced oxygenation of the affected tissues is a hallmark of lymphedema. Here, we investigated if the hypoxia of lymphatic endothelial cells (LECs) might contribute to fibrosis. We applied RNASeq and qPCR to study the concordant changes of the exome of three human foreskin-derived LEC isolates after 4 days of hypoxia (1% O₂) vs. normoxia (21% O₂). Of the approximately 16,000 genes expressed in LECs, 162 (1%) were up- or down-regulated by hypoxia. Of these, 21 genes have important functions in the production or modification of the extracellular matrix (ECM). In addition to the down-regulation of elastin, we found up-regulation of druggable enzymes and regulators such as the long non-coding RNA H19, inter-alpha-trypsin inhibitor heavy chain family member 5 (ITIH5), lysyl-oxidase (LOX), prolyl 4-hydroxylase subunit alpha 1 (P4HA1), procollagen-lysine 2-oxoglutarate 5-dioxygenase 2 (PLOD2), and others that are discussed in the paper. Initial lymphatics do not produce a continuous basement membrane; however, our study shows that hypoxic LECs have an unexpectedly high ability to alter the ECM.

Hyperoxia-induced bronchopulmonary dysplasia: better models for better therapies

Bronchopulmonary dysplasia (BPD) is a chronic lung disease caused by exposure to high levels of oxygen (hyperoxia) and is the most common complication that affects preterm newborns. At present, there is no cure for BPD. Infants can recover from BPD; however, they will suffer from significant morbidity into adulthood in the form of neurodevelopmental impairment, asthma and emphysematous changes of the lung. The development of hyperoxia-induced lung injury models in small and large animals to test potential treatments for BPD has shown some success, yet a lack of standardization in approaches and methods makes clinical translation difficult. In vitro models have also been developed to investigate the molecular pathways altered during BPD and to address the pitfalls associated with animal models. Preclinical studies have investigated the efficacy of stem cell-based therapies to improve lung morphology after damage. However, variability regarding the type of animal model and duration of hyperoxia to elicit damage exists in the literature. These models should be further developed and standardized, to cover the degree and duration of hyperoxia, type of animal model, and lung injury endpoint, to improve their translational relevance. The purpose of this Review is to highlight concerns associated with current animal models of hyperoxia-induced BPD and to show the potential of in vitro models to complement in vivo studies in the significant improvement to our understanding of BPD pathogenesis and treatment. The status of current stem cell therapies for treatment of BPD is also discussed. We offer suggestions to optimize models and therapeutic modalities for treatment of hyperoxia-induced lung damage in order to advance the standardization of procedures for clinical translation.

Formalin-fixed paraffin-embedded renal biopsy tissues: an underexploited biospecimen resource for gene expression profiling in IgA nephropathy

Primary IgA nephropathy (IgAN) diagnosis is based on IgA-dominant glomerular deposits and histological scoring is done on formalin-fixed paraffin embedded tissue (FFPE) sections using the Oxford classification. Our aim was to use this underexploited resource to extract RNA and identify genes that characterize active (endocapillary–extracapillary proliferations) and chronic (tubulo-interstitial) renal lesions in total renal cortex. RNA was extracted from archival FFPE renal biopsies of 52 IgAN patients, 22 non-IgAN and normal renal tissue of 7 kidney living donors (KLD) as controls. Genome-wide gene expression profiles were obtained and biomarker identification was carried out comparing gene expression signatures a subset of IgAN patients with active (N = 8), and chronic (N = 12) renal lesions versus non-IgAN and KLD. Bioinformatic analysis identified transcripts for active (DEFA4,TNFAIP6,FAR2) and chronic (LTB,CXCL6, ITGAX) renal lesions that were validated by RT-PCR and IHC. Finally, two of them (TNFAIP6 for active and CXCL6 for chronic) were confirmed in the urine of an independent cohort of IgAN patients compared with non-IgAN patients and controls. We have integrated transcriptomics with histomorphological scores, identified specific gene expression changes using the invaluable repository of archival renal biopsies and discovered two urinary biomarkers that may be used for specific clinical decision making.

Inter-α-Trypsin Inhibitor Heavy Chain 5 (ITIH5) Is a Natural Stabilizer of Hyaluronan That Modulates Biological Processes in the Skin

INTRODUCTION

Hyaluronan (HA) is a major component of the skin that exerts a variety of biological functions. Inter-α-trypsin inhibitor heavy chain (ITIH) proteins comprise a family of hyaladherins of which ITIH5 has recently been described in skin, where it plays a functional role in skin morphology and inflammatory skin diseases including allergic contact dermatitis (ACD).

OBJECTIVE

The current study focused on the ITIH5-HA interaction and its potential clinical and functional impact in extracellular matrix (ECM) stabilization.

METHODS

Studying the molecular effects of ITIH5 in skin, we established skin models comprising murine skin cells of Itih5 knockout mice and corresponding wild-type controls. In addition, human dermal fibroblasts with an ITIH5 knockdown as well as a murine recombinant Itih5 protein were established to examine the interaction between ITIH5 and HA using in vitro adhesion and HA degradation assays. To understand more precisely the role of ITIH5 in inflammatory skin diseases such as ACD, we generated ITIH5 knockout cells of the KeratinoSens® cell line.

RESULTS

Using murine skin models, ITIH5 knockdown fibroblasts, and a reactive oxygen species (ROS)-mediated HA degradation assay, we proved that ITIH5 binds to HA, thereby acting as a stabilizer of HA. Moreover, microarray profiling revealed the impact of ITIH5 on biological processes such as skin development and ECM homeostasis. Performing the in vitro KeratinoSens skin sensitization assay, we detected that ITIH5 decreases the sensitizing potential of moderate and strong contact sensitizers.

CONCLUSION

Taken together, our experiments revealed that ITIH5 forms complexes with HA, thereby on the one hand stabilizing HA and facilitating the formation of ECM structures and on the other hand modulating inflammatory responses.

The Inter-α-Trypsin Inhibitor Family: Versatile Molecules in Biology and Pathology

Inter-α-trypsin inhibitor (IαI) family members are ancient and unique molecules that have evolved over several hundred million years of vertebrate evolution. IαI is a complex containing the proteoglycan bikunin to which heavy chain proteins are covalently attached to the chondroitin sulfate chain. Besides its matrix protective activity through protease inhibitory action, IαI family members interact with extracellular matrix molecules and most notably hyaluronan, inhibit complement, and provide cell regulatory functions. Recent evidence for the diverse roles of the IαI family in both biology and pathology is reviewed and gives insight into their pivotal roles in tissue homeostasis. In addition, the clinical uses of these molecules are explored, such as in the treatment of inflammatory conditions including sepsis and Kawasaki disease, which has recently been associated with severe acute respiratory syndrome coronavirus 2 infection in children.

Inter-α-inhibitor heavy chain-1 has an integrin-like 3D structure mediating immune regulatory activities and matrix stabilization during ovulation

Inter-α-inhibitor is a proteoglycan essential for mammalian reproduction and also plays a less well-characterized role in inflammation. It comprises two homologous "heavy chains" (HC1 and HC2) covalently attached to chondroitin sulfate on the bikunin core protein. Before ovulation, HCs are transferred onto the polysaccharide hyaluronan (HA) to form covalent HC·HA complexes, thereby stabilizing an extracellular matrix around the oocyte required for fertilization. Additionally, such complexes form during inflammatory processes and mediate leukocyte adhesion in the synovial fluids of arthritis patients and protect against sepsis. Here using X-ray crystallography, we show that human HC1 has a structure similar to integrin β-chains, with a von Willebrand factor A domain containing a functional metal ion-dependent adhesion site (MIDAS) and an associated hybrid domain. A comparison of the WT protein and a variant with an impaired MIDAS (but otherwise structurally identical) by small-angle X-ray scattering and analytical ultracentrifugation revealed that HC1 self-associates in a cation-dependent manner, providing a mechanism for HC·HA cross-linking and matrix stabilization. Surprisingly, unlike integrins, HC1 interacted with RGD-containing ligands, such as fibronectin, vitronectin, and the latency-associated peptides of transforming growth factor β, in a MIDAS/cation-independent manner. However, HC1 utilizes its MIDAS motif to bind to and inhibit the cleavage of complement C3, and small-angle X-ray scattering-based modeling indicates that this occurs through the inhibition of the alternative pathway C3 convertase. These findings provide detailed structural and functional insights into HC1 as a regulator of innate immunity and further elucidate the role of HC·HA complexes in inflammation and ovulation.

The intestinal injury caused by ischemia-reperfusion is attenuated by amniotic fluid stem cells via the release of tumor necrosis factor-stimulated gene 6 protein

Ischemia/reperfusion (I/R) is implicated in the pathogenesis of various acute intestinal injuries. Amniotic fluid stem cells (AFSC) are beneficial in experimental intestinal diseases. Tumor necrosis factor-induced protein 6 (TSG-6) has been shown to exert anti-inflammatory effects. We aimed to investigate if AFSC secreted TSG-6 reduces inflammation and rescues intestinal I/R injury. The superior mesenteric artery of 3-week-old rats was occluded for 90 minutes and green fluorescent protein-labeled AFSC or recombinant TSG-6 was injected intravenously upon reperfusion. AFSC distribution was evaluated at 24, 48, and 72 hours after I/R. AFSC and TSG-6 effects on the intestine were assessed 48 hours postsurgery. Intestinal organoids were used to study the effects of TSG-6 after hypoxia-induced epithelial damage. After I/R-induced intestinal injury, AFSC migrated preferentially to the ileum, the primary site of injury, through blood circulation. Engrafted AFSC reduced ileum injury, inflammation, and oxidative stress. These AFSC-mediated beneficial effects were dependent on secretion of TSG-6. Administration of TSG-6 protected against hypoxia-induced epithelial damage in intestinal organoids. Finally, TSG-6 attenuated intestinal damage during I/R by suppressing genes involved in wound and injury pathways. This study indicates that AFSC or TSG-6 have the potential of rescuing the intestine from the damage caused by I/R.

Extracellular Superoxide Dismutase Regulates Early Vascular Hyaluronan Remodeling in Hypoxic Pulmonary Hypertension

Chronic hypoxia leads to pathologic remodeling of the pulmonary vasculature and pulmonary hypertension (PH). The antioxidant enzyme extracellular superoxide dismutase (SOD3) protects against hypoxia-induced PH. Hyaluronan (HA), a ubiquitous glycosaminoglycan of the lung extracellular matrix, is rapidly recycled at sites of vessel injury and repair. We investigated the hypothesis that SOD3 preserves HA homeostasis by inhibiting oxidative and enzymatic hyaluronidase-mediated HA breakdown. In SOD3-deficient mice, hypoxia increased lung hyaluronidase expression and activity, hyaluronan fragmentation, and effacement of HA from the vessel wall of small pulmonary arteries. Hyaluronan fragmentation corresponded to hypoxic induction of the cell surface hyaluronidase-2 (Hyal2), which was localized in the vascular media. Human pulmonary artery smooth muscle cells (HPASMCs) demonstrated hypoxic induction of Hyal2 and SOD-suppressible hyaluronidase activity, congruent to our observations in vivo. Fragmentation of homeostatic high molecular weight HA promoted HPASMC proliferation in vitro, whereas pharmacologic inhibition of hyaluronidase activity prevented hypoxia- and oxidant-induced proliferation. Hypoxia initiates SOD3-dependent alterations in the structure and regulation of hyaluronan in the pulmonary vascular extracellular matrix. These changes occurred soon after hypoxia exposure, prior to appearance of PH, and may contribute to the early pathogenesis of this disease.

Matrix-degrading protease ADAMTS-5 cleaves inter-α-inhibitor and releases active heavy chain 2 in synovial fluids from arthritic patients

Destruction of the cartilage matrix in joints is an important feature of arthritis. Proteolytic degradation of cartilage glycoproteins can contribute to the loss of matrix integrity. Human inter-α-inhibitor (IαI), which stabilizes the extracellular matrix, is composed of the light-chain serine proteinase inhibitor bikunin and two homologous heavy chains (HC1 and HC2) covalently linked through chondroitin 4-sulfate. Inflammation promotes the transfer of HCs from chondroitin 4-sulfate to hyaluronan by tumor necrosis factor-stimulated gene-6 protein (TSG-6). This reaction generates a covalent complex between the heavy chains and hyaluronan that can promote leukocyte invasion. This study demonstrates that both IαI and the HC-hyaluronan complex are substrates for the extracellular matrix proteases ADAMTS-5 and matrix metalloprotease (MMP) -3, -7, and -13. The major cleavage sites for all four proteases are found in the C terminus of HC2. ADAMTS-5 and MMP-7 displayed the highest activity toward HC2. ADAMTS-5 degradation products were identified in mass spectrometric analysis of 29 of 33 arthropathic patients, indicating that ADAMTS-5 cleavage occurs in synovial fluid in arthritis. After cleavage, free HC2, together with TSG-6, is able to catalyze the transfer of heavy chains to hyaluronan. The release of extracellular matrix bound HC2 is likely to increase the mobility of the HC2/TSG-6 catalytic unit and consequently increase the rate of the HC transfer reaction. Ultimately, ADAMTS-5 cleavage of HC2 could alter the physiological and mechanical properties of the extracellular matrix and contribute to the progression of arthritis.

Fibrosis: Shared Lessons From the Lens and Cornea

Regenerative repair in response to wounding involves cell proliferation and migration. This is followed by the reestablishment of cell structure and organization and a dynamic process of remodeling and restoration of the injured cells' extracellular matrix microenvironment and the integration of the newly synthesized matrix into the surrounding tissue. Fibrosis in the lungs, liver, and heart can lead to loss of life and in the eye to loss of vision. Learning to control fibrosis and restore normal tissue function after injury repair remains a goal of research in this area. Here we use knowledge gained using the lens and the cornea to provide insight into how fibrosis develops and clues to how it can be controlled. The lens and cornea are less complex than other tissues that develop life‐threatening fibrosis, but they are well characterized and research using them as model systems to study fibrosis is leading toward an improved understanding of fibrosis. Here we summarize the current state of the literature and how it is leading to promising new treatments. Anat Rec, 2019. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Hyaluronan and Its Interactions With Immune Cells in the Healthy and Inflamed Lung

Hyaluronan is a hygroscopic glycosaminoglycan that contributes to both extracellular and pericellular matrices. While the production of hyaluronan is essential for mammalian development, less is known about its interaction and function with immune cells. Here we review what is known about hyaluronan in the lung and how it impacts immune cells, both at homeostasis and during lung inflammation and fibrosis. In the healthy lung, alveolar macrophages provide the first line of defense and play important roles in immunosurveillance and lipid surfactant homeostasis. Alveolar macrophages are surrounded by a coat of hyaluronan that is bound by CD44, a major hyaluronan receptor on immune cells, and this interaction contributes to their survival and the maintenance of normal alveolar macrophage numbers. Alveolar macrophages are conditioned by the alveolar environment to be immunosuppressive, and can phagocytose particulates without alerting an immune response. However, during acute lung infection or injury, an inflammatory immune response is triggered. Hyaluronan levels in the lung are rapidly increased and peak with maximum leukocyte infiltration, suggesting a role for hyaluronan in facilitating leukocyte access to the injury site. Hyaluronan can also be bound by hyaladherins (hyaluronan binding proteins), which create a provisional matrix to facilitate tissue repair. During the subsequent remodeling process hyaluronan concentrations decline and levels return to baseline as homeostasis is restored. In chronic lung diseases, the inflammatory and/or repair phases persist, leading to sustained high levels of hyaluronan, accumulation of associated immune cells and an inability to resolve the inflammatory response.

A Strategy for Discovery of Endocrine Interactions with Application to Whole-Body Metabolism

Inter-tissue communication via secreted proteins has been established as a vital mechanism for proper physiologic homeostasis. Here, we report a bioinformatics framework using a mouse reference population, the Hybrid Mouse Diversity Panel (HMDP), which integrates global multi-tissue expression data and publicly available resources to identify and functionally annotate novel circuits of tissue-tissue communication. We validate this method by showing that we can identify known as well as novel endocrine factors responsible for communication between tissues. We further show the utility of this approach by identification and mechanistic characterization of two new endocrine factors. Adipose-derived Lipocalin-5 is shown to enhance skeletal muscle mitochondrial function, and liver-secreted Notum promotes browning of white adipose tissue, also known as "beiging." We demonstrate the general applicability of the method by providing in vivo evidence for three additional novel molecules mediating tissue-tissue interactions.

Identification of potential urine proteins and microRNA biomarkers for the diagnosis of pulmonary tuberculosis patients

This study identified urinary biomarkers for tuberculosis (TB) diagnosis. The urine proteomic profiles of 45 pulmonary tuberculosis patients prior to anti-TB treatment and 45 healthy controls were analyzed and compared using two-dimensional electrophoresis with matrix-assisted laser desorption/ionization time of flight mass spectrometry. Nineteen differentially expressed proteins were identified preliminarily, and western blotting and qRT-PCR were performed to confirm these changes at the translational and transcriptional levels, respectively, using samples from 122 additional pulmonary tuberculosis patients and 73 additional healthy controls. Two proteins, mannose-binding lectin 2 and a 35-kDa fragment of inter-α-trypsin inhibitor H4, exhibited the highest differential expression. We constructed a protein-microRNA interaction network that primarily involved complement and inflammatory responses. Eleven microRNAs from microRNA-target protein interactions were screened and validated using qRT-PCR with some of the above samples, including 97 pulmonary tuberculosis patients and 48 healthy controls. Only miR-625-3p exhibited significant differential expression (p < 0.05). miR-625-3p was increased to a greater extent in samples of smear-positive than smear-negative patients. miR-625-3p was predicted to target mannose-binding lectin 2 protein. A binary logistic regression model based on miR-625-3p, mannose-binding lectin 2, and inter-α-trypsin inhibitor H4 was further established. This three-biomarker combination exhibited better performance for tuberculosis diagnosis than individual biomarkers or any two-biomarker combination and generated a diagnostic sensitivity of 85.87% and a specificity of 87.50%. These novel urine biomarkers may significantly improve tuberculosis diagnosis.

TSG-6: A multifunctional protein with anti-inflammatory and tissue-protective properties

Tumor necrosis factor- (TNF) stimulated gene-6 (TSG-6) is an inflammation-associated secreted protein that has been implicated as having important and diverse tissue protective and anti-inflammatory properties, e.g. mediating many of the immunomodulatory and beneficial activities of mesenchymal stem/stromal cells. TSG-6 is constitutively expressed in some tissues, which are either highly metabolically active or subject to challenges from the environment, perhaps providing protection in these contexts. The diversity of its functions are dependent on the binding of TSG-6 to numerous ligands, including matrix molecules such as glycosaminoglycans, as well as immune regulators and growth factors that themselves interact with these linear polysaccharides. It is becoming apparent that TSG-6 can directly affect matrix structure and modulate the way extracellular signalling molecules interact with matrix. In this review, we focus mainly on the literature for TSG-6 over the last 10 years, summarizing its expression, structure, ligand-binding properties, biological functions and highlighting TSG-6's potential as a therapeutic for a broad range of disease indications.

Glycosaminoglycans in extracellular matrix organisation: are concepts from soft matter physics key to understanding the formation of perineuronal nets?

Conventional wisdom has it that proteins fold and assemble into definite structures, and that this defines their function. Glycosaminoglycans (GAGs) are different. In most cases the structures they form have a low degree of order, even when interacting with proteins. Here, we discuss how physical features common to all GAGs-hydrophilicity, charge, linearity and semi-flexibility-underpin the overall properties of GAG-rich matrices. By integrating soft matter physics concepts (e.g. polymer brushes and phase separation) with our molecular understanding of GAG-protein interactions, we can better comprehend how GAG-rich matrices assemble, what their properties are, and how they function. Taking perineuronal nets (PNNs)-a GAG-rich matrix enveloping neurons-as a relevant example, we propose that microphase separation determines the holey PNN anatomy that is pivotal to PNN functions.

ITIH5 induces a shift in TGF-β superfamily signaling involving Endoglin and reduces risk for breast cancer metastasis and tumor death

ITIH5 has been proposed being a novel tumor suppressor in various tumor entities including breast cancer. Recently, ITIH5 was furthermore identified as metastasis suppressor gene in pancreatic carcinoma. In this study we aimed to specify the impact of ITIH5 on metastasis in breast cancer. Therefore, DNA methylation of ITIH5 promoter regions was assessed in breast cancer metastases using the TCGA portal and methylation-specific PCR (MSP). We reveal that the ITIH5 upstream promoter region is particularly responsible for ITIH5 gene inactivation predicting shorter survival of patients. Notably, methylation of this upstream ITIH5 promoter region was associated with disease progression, for example, abundantly found in distant metastases. In vitro, stably ITIH5-overexpressing MDA-MB-231 breast cancer clones were used to analyze cell invasion and to identify novel ITIH5-downstream targets. Indeed, ITIH5 re-expression suppresses invasive growth of MDA-MB-231 breast cancer cells while modulating expression of genes involved in metastasis including Endoglin (ENG), an accessory TGF-β receptor, which was furthermore co-expressed with ITIH5 in primary breast tumors. By performing in vitro stimulation of TGF-β signaling using TGF-β1 and BMP-2 we show that ITIH5 triggered a TGF-β superfamily signaling switch contributing to downregulation of targets like Id1, known to endorse metastasis. Moreover, ITIH5 predicts longer overall survival (OS) only in those breast tumors that feature high ENG expression or inversely regulated ID1 suggesting a clinical and functional impact of an ITIH5-ENG axis for breast cancer progression. Hence, we provide evidence that ITIH5 may represent a novel modulator of TGF-β superfamily signaling involved in suppressing breast cancer metastasis.

Genome-wide DNA methylation analysis in lung fibroblasts co-cultured with silica-exposed alveolar macrophages

Background

Exposure to crystalline silica is considered to increase the risk of lung fibrosis. The primary effector cell, the myofibroblast, plays an important role in the deposition of extracellular matrix (ECM). DNA methylation change is considered to have a potential effect on myofibroblast differentiation. Therefore, the present study was designed to investigate the genome-wide DNA methylation profiles of lung fibroblasts co-cultured with alveolar macrophages exposed to crystalline silica in vitro.

Methods

AM/fibroblast co-culture system was established. CCK8 was used to assess the toxicity of AMs. mRNA and protein expression of collagen I, α-SMA, MAPK9 and TGF-β1 of fibroblasts after AMs exposed to 100 μg /ml SiO₂ for 0–, 24–, or 48 h were determined by means of quantitative real-time PCR, immunoblotting and immunohistochemistry. Genomic DNA of fibroblasts was isolated using MeDIP-Seq to sequence. R software, GO, KEGG and Cytoscape were used to analyze the data.

Results

SiO₂ exposure increased the expression of collagen I and α-SMA in fibroblasts in co-culture system. Analysis of fibroblast methylome identified extensive methylation changes involved in several signaling pathways, such as the MAPK signaling pathway and metabolic pathways. Several candidates, including Tgfb1 and Mapk9, are hubs who can connect the gene clusters. MAPK9 mRNA expression was significantly higher in fibroblast exposed to SiO₂ in co-culture system for 48 h. MAPK9 protein expression was increased at both 24-h and 48-h treatment groups. TGF-β1 mRNA expression of fibroblast has a time-dependent manner, but we didn’t observe the TGF-β1 protein expression.

Conclusion

Tgfb1 and Mapk9 are helpful to explore the mechanism of myofibroblast differentiation. The genome-wide DNA methylation profiles of fibroblasts in this experimental silicosis model will be useful for future studies on epigenetic gene regulation during myofibroblast differentiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0576-z) contains supplementary material, which is available to authorized users.

Strategies in regenerative medicine for intervertebral disc repair using mesenchymal stem cells and bioscaffolds

The intervertebral disc (IVD) is a major weight bearing structure that undergoes degenerative changes with aging limiting its ability to dissipate axial spinal loading in an efficient manner resulting in the generation of low back pain. Low back pain is a number one global musculoskeletal disorder with massive socioeconomic impact. The WHO has nominated development of mesenchymal stem cells and bioscaffolds to promote IVD repair as primary research objectives. There is a clear imperative for the development of strategies to effectively treat IVD defects. Early preclinical studies with mesenchymal stem cells in canine and ovine models have yielded impressive results in IVD repair. Combinatorial therapeutic approaches encompassing biomaterial and cell-based therapies promise significant breakthroughs in IVD repair in the near future.