Serum hyaluronidase aberrations in metabolic and morphogenetic disorders

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.

Screening Mucopolysaccharidosis Type IX in Patients with Juvenile Idiopathic Arthritis

Mucopolysaccharidosis is a group of lysosomal disorders of a deficiency of specific enzyme required for glycosaminoglycan degradation. Mucopolysaccharidosis type IX is the rarest form of mucopolysaccharidosis. To date, only four patients have been reported. The first reported patient had mild short stature and periarticular soft tissue masses; the other reported patients are clinically indistinguishable from juvenile idiopathic arthritis. In the present study, we screened mucopolysaccharidosis type IX among patients with juvenile idiopathic arthritis with hyaluronidase enzyme assay. One hundred and eight patients with JIA and 50 healthy age-matched control subjects were enrolled in the study. Among all patients, none had deficient hyaluronidase activity. Though serum Hyal-1 activity was significantly increased in JIA patients, compared with control subjects (p < 0.000), no correlation was found between CRP, ESR, and Hyal-1 activity (p = 0.187). In conclusion, the data reported in our study indicates that systemic metabolic investigation for hyaluronidase activity is not recommended in all patients with JIA.

Fabrication of an rhBMP-2 loaded porous β-TCP microsphere-hyaluronic acid-based powder gel composite and evaluation of implant osseointegration

Methods to improve osseointegration that include implantation of rhBMP-2 with various kinds of carriers are currently of considerable interest. The present study was conducted to evaluate if the rhBMP-2 loaded β-TCP microsphere-hyaluronic acid-based powder-like hydrogel composite (powder gel) can act as an effective rhBMP-2 carrier for implantation in host bone with a bone defect or poor bone quality. The release pattern for rhBMP-2 was then evaluated against an rhBMP-2-loaded collagen sponge as a control group. Dental implants were also inserted into the tibias of three groups of rabbits: an rhBMP-2 (200 µg) loaded powder gel composite implanted group, an implant only group, and a powder gel implanted group. Micro-CT and histology of the implanted areas were carried out four weeks later. The rhBMP-2 powder gel released less rhBMP-2 than the collagen sponge, but it continued a slow release for more than 7 days. The rhBMP-2 powder gel composite improved osseointegration of the dental implant by increasing the amount of new bone formation in the implant pitch and it improved the bone quality and bone quantity of new bone. The histology results indicated that the rhBMP-2 powder gel composite improved the osseointegration in the cortical bone as well as the marrow space along the fixture. The bone-to-implant contact ratio of the rhBMP-2 (200 µg) loaded powder gel composite implanted group was significantly higher than those of the implant only group and the powder gel implanted group. The powder gel appeared to be a good carrier and could release rhBMP-2 slowly to promote the formation of new bone following implantation in a bone defect, thereby improving implant osseointegration.

Subcellular trafficking and activity of Hyal-1 and its processed forms in murine macrophages

The hyaluronidase Hyal-1 is an acid hydrolase that degrades hyaluronic acid (HA), a component of the extracellular matrix. It is often designated as a lysosomal protein. Yet few data are available on its intracellular localization and trafficking. We demonstrate here that in RAW264.7 murine macrophages, Hyal-1 is synthesized as a glycosylated precursor that is only weakly mannose 6-phosphorylated. Nevertheless, this precursor traffics to endosomes, via a mannose 6-phosphate-independent secretion/recapture mechanism that involves the mannose receptor. Once in endosomes, it is processed into a lower molecular mass form that is transported to lysosomes, where its activity could be detected using native gel zymography. Indeed, this activity co-distributed with lysosomal hydrolases in the densest fraction of a self-forming Percoll(TM) density gradient. Moreover, it shifted toward the lower density region, in parallel with those hydrolases, when a decrease of lysosomal density was induced by the endocytosis of sucrose. Interestingly, the activity of the processed form of Hyal-1 was largely underestimated when assayed by zymography after SDS-PAGE and subsequent renaturation of the proteins, by contrast to the full-length protein that could efficiently degrade HA in those conditions. These results suggest that noncovalent associations support the lysosomal activity of Hyal-1.

Hyaluronan as an immune regulator in human diseases

Accumulation and turnover of extracellular matrix components are the hallmarks of tissue injury. Fragmented hyaluronan stimulates the expression of inflammatory genes by a variety of immune cells at the injury site. Hyaluronan binds to a number of cell surface proteins on various cell types. Hyaluronan fragments signal through both Toll-like receptor (TLR) 4 and TLR2 as well as CD44 to stimulate inflammatory genes in inflammatory cells. Hyaluronan is also present on the cell surface of epithelial cells and provides protection against tissue damage from the environment by interacting with TLR2 and TLR4. Hyaluronan and hyaluronan-binding proteins regulate inflammation, tissue injury, and repair through regulating inflammatory cell recruitment, release of inflammatory cytokines, and cell migration. This review focuses on the role of hyaluronan as an immune regulator in human diseases.

Hyaluronan in tissue injury and repair

A hallmark of tissue injury and repair is the turnover of extracellular matrix components. This review focuses on the role of the glycosaminoglycan hyaluronan in tissue injury and repair. Both the synthesis and degradation of extracellular matrix are critical contributors to tissue repair and remodeling. Fragmented hyaluronan accumulates during tissue injury and functions in ways distinct from the native polymer. There is accumulating evidence that hyaluronan degradation products can stimulate the expression of inflammatory genes by a variety of immune cells at the injury site. CD44 is the major cell-surface hyaluronan receptor and is required to clear hyaluronan degradation products produced during lung injury; impaired clearance of hyaluronan results in persistent inflammation. However, hyaluronan fragment stimulation of inflammatory gene expression is not dependent on CD44 in inflammatory macrophages. Instead, hyaluronan fragments utilize both Toll-like receptor (TLR) 4 and TLR2 to stimulate inflammatory genes in macrophages. Hyaluronan also is present on the cell surface of lung alveolar epithelial cells and provides protection against tissue damage by interacting with TLR2 and TLR4 on these parenchymal cells. The simple repeating structure of hyaluronan appears to be involved in a number of important aspects of noninfectious tissue injury and repair that are dependent on the size and location of the polymer as well as the interacting cells. Thus, the interactions between the endogenous matrix component hyaluronan and its signaling receptors initiate inflammatory responses, maintain structural cell integrity, and promote recovery from tissue injury.

Recombinant human hyaluronidase Hyal-1: insect cells versus Escherichia coli as expression system and identification of low molecular weight inhibitors

The human hyaluronidase Hyal-1, one of six human hyaluronidase subtypes, preferentially degrades hyaluronic acid present in the extracellular matrix of somatic tissues. Modulations of Hyal-1 expression have been observed in a number of malignant tumors. However, its role in disease progression is discussed controversially due to limited information on enzyme properties as well as the lack of specific inhibitors. Therefore, we expressed human Hyal-1 in a prokaryotic and in an insect cell system to produce larger amounts of the purified enzyme. In Escherichia coli, Hyal-1 formed inclusion bodies and was refolded in vitro after purification by metal ion affinity chromatography. However, the enzyme was produced with extremely low folding yields (0.5%) and exhibited a low specific activity (0.1 U/mg). Alternatively, Hyal-1 was secreted into the medium of stably transfected Drosophila Schneider-2 (DS-2) cells. After several purification steps, highly pure enzyme with a specific activity of 8.6 U/mg (consistent with the reported activity of human Hyal-1 from plasma) was obtained. Both Hyal-1 enzymes showed pH profiles similar to the hyaluronidase of human plasma with an activity maximum at pH 3.5-4.0. Deglycosylation of Hyal-1, expressed in DS-2 cells, resulted in a decrease in the enzymatic activity determined by a colorimetric hyaluronidase activity assay. Purified Hyal-1 from DS-2 cells was used for the investigation of the inhibitory activity of new ascorbic acid derivatives. Within this series, l-ascorbic acid tridecanoate was identified as the most potent inhibitor with an IC(50) of 50 +/- 4 microM comparable with glycyrrhizic acid.