Hyaluronan histochemistry-a potential new tool to assess the progress of liver disease from simple steatosis to hepatocellular carcinoma

Interplay between Cellular and Non-Cellular Components of the Tumour Microenvironment in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common and lethal cancers worldwide. Currently, treatments available for advanced HCC provide dismal chances of survival, thus there is an urgent need to develop more effective therapeutic strategies. While much of the focus of recent decades has been on targeting malignant cells, promising results have emerged from targeting the tumour microenvironment (TME). The extracellular matrix (ECM) is the main non-cellular component of the TME and it profoundly changes during tumorigenesis to promote the growth and survival of malignant cells. Despite this, many in vitro models for drug testing fail to consider the TME leading to a high failure rate in clinical trials. Here, we present an overview of the function and properties of the ECM in the liver and how these change during malignant transformation. We also discuss the relationship between immune cells and ECM in the TME in HCC. Lastly, we present advanced, 3D culture techniques of cancer modelling and argue that the incorporation of TME components into these is essential to better recapitulate the complex interactions within the TME.

Hyaluronidases in Human Diseases

With the burgeoning interest in hyaluronic acid (HA) in recent years, hyaluronidases (HYALs) have come to light for their role in regulating catabolism of HA and its molecular weight (MW) distribution in various tissues. Of the six hyaluronidase-like gene sequences in the human genome, HYALs 1 and 2 are of particular significance because they are the primary hyaluronidases active in human somatic tissue. Perhaps more importantly, for the sake of this review, they cleave anti-inflammatory and anti-fibrotic high-molecular-weight HA into pro-inflammatory and pro-fibrotic oligosaccharides. With this, HYALs regulate HA degradation and thus the development and progression of various diseases. Given the dearth of literature focusing specifically on HYALs in the past decade, this review seeks to expound their role in human diseases of the skin, heart, kidneys, and more. The review will delve into the molecular mechanisms and pathways of HYALs and discuss current and potential future therapeutic benefits of HYALs as a clinical treatment.

Immunomodulatory Role of the Extracellular Matrix Within the Liver Disease Microenvironment

Chronic liver disease when accompanied by underlying fibrosis, is characterized by an accumulation of extracellular matrix (ECM) proteins and chronic inflammation. Although traditionally considered as a passive and largely architectural structure, the ECM is now being recognized as a source of potent damage-associated molecular pattern (DAMP)s with immune-active peptides and domains. In parallel, the ECM anchors a range of cytokines, chemokines and growth factors, all of which are capable of modulating immune responses. A growing body of evidence shows that ECM proteins themselves are capable of modulating immunity either directly via ligation with immune cell receptors including integrins and TLRs, or indirectly through release of immunoactive molecules such as cytokines which are stored within the ECM structure. Notably, ECM deposition and remodeling during injury and fibrosis can result in release or formation of ECM-DAMPs within the tissue, which can promote local inflammatory immune response and chemotactic immune cell recruitment and inflammation. It is well described that the ECM and immune response are interlinked and mutually participate in driving fibrosis, although their precise interactions in the context of chronic liver disease are poorly understood. This review aims to describe the known pro-/anti-inflammatory and fibrogenic properties of ECM proteins and DAMPs, with particular reference to the immunomodulatory properties of the ECM in the context of chronic liver disease. Finally, we discuss the importance of developing novel biotechnological platforms based on decellularized ECM-scaffolds, which provide opportunities to directly explore liver ECM-immune cell interactions in greater detail.

Detection of TSG-6-like protein in human corneal epithelium. Simultaneous presence with CD44 and hyaluronic acid

INTRODUCTION

Tumor necrosis factor-inducible gene 6 protein (TSG-6) is member of the hyaluronan-binding protein family (hyaladherins) to which CD44 also belongs. Inflammatory mediators such as tumor necrosis factor α (TNF-α) and interleukin-1 (IL-1) stimulate TSG-6 production. Recently, however, externally applied TSG-6 has been shown to be effective in the treatment of inflammatory dry eye. On the other hand, it is still unknown whether TSG-6 is naturally present in human corneal epithelium.

MATERIAL AND METHODS

Corneal sections of 15 eyes enucleated for posterior segment uveal melanoma were immunohistochemically stained for hyaluronic acid (HA), CD44, and TSG-6.

RESULTS

Throughout the corneal epithelium of all sections, CD44 and hyaluronic acid were detected most intensely in the basal epithelial layer. Whereas the presence of HA was intense even in the cytoplasm of the cells, CD44 was located predominantly at the cell membranes. The intensity of the specific staining decreased towards the surface, where CD44 was barely detectable. Hyaluronic acid was, on the other hand, detectable in the extracellular matrix and cells, even at the surface. TSG-6 like immunoreactivity was detected in all sections in a pattern similar to CD44 but much more distinct and intense, with a marked localization in the cell membranes and intercellular spaces, i.e., extracellular matrix. TSG-6 like immunoreactivity was clearly detectable through all cell layers of the corneal epithelium. All control sections were negative.

DISCUSSION

Tumor necrosis factor-inducible gene 6 (TSG-6)- like protein is present in human corneal epithelium. It might be a natural component of this tissue which is constantly exposed and mechanically traumatized, and displays localization with similarities to that of CD44. The immunohistological detection of HA as major component of the ECM and epithelial tissue only confirms the results of earlier studies. However, the simultaneous presence and colocalization of CD44 and TSG-6, both HA-binding proteins, requires further investigation of the individual role, regulation and interaction of this system.

CONCLUSION

The detection of TSG-6 in human corneal epithelium in the absence of inflammation underlines the importance of normal mechanical forces on the gene expression and regulation of this protein in ocular surface tissues. Given the relationship between inflammation and the protein, TSG-6 may be a major unknown and underestimated player in the regulation of the inflammation encountered in the presence of ocular surface desiccation and dry eye disease.