Expression pattern of a novel hyaluronidase during Xenopus embryogenesis

Suppression of hyaluronidase reduces invasion and establishment of Haemonchus contortus larvae in sheep

Haemonchus contortus is a hematophagous endoparasite of small ruminants, which is responsible for huge economic losses in livestock sector. Hyaluronidase produced by infective larvae of H. contortus can degrade hyaluronic acid present in the host’s abomasal tissue. Thus, it facilitates larval tissue invasion and early establishment. We herein explored this ability of hyaluronidase in H. contortus, and tested whether hyaluronidase is utilized as a virulence factor by H. contortus while establishing the infection. We first successfully blocked the hyaluronidase gene in L3 larvae by RNA interference (RNAi), which was subsequently confirmed by qPCR, enzymatic activity, and immunohistochemistry assays. Using these larvae we then conducted in vivo and in vitro assays on sheep to assess the effects of hyaluronidase suppression on larval invasion and establishment of infection. The in vivo assay showed a significant drop in worm burden in siRNA treated group in comparison to control group. During in vitro assay we applied an ovine ex vivo model where siRNA treated group of larvae showed significantly reduced invasion of the abomasal tissue explants as compared to control group. These findings indicate that hyaluronidase plays a key role in host’s tissue invasion and larval establishment, and it is used as a virulence factor by H. contortus while establishing the infection. As an invasive virulence molecule, its functional research is thus conducive to the prevention of haemonchosis.

Clinical Applications of Hyaluronidase

Hyaluronidases are enzymes that degrade hyaluronic acid, which constitutes an essential part of the extracellular matrix. Initially discovered in bacteria, hyaluronidases are known to be widely distributed in nature and have been found in many classes including insects, snakes, fish and mammals. In the human, six different hyaluronidases, HYAL1-4, HYAL-P1 and PH-20, have been identified. PH-20 exerts the strongest biologic activity, is found in high concentrations in the testicles and can be localized on the head and the acrosome of human spermatozoa. Today, animal-derived bovine or ovine testicular hyaluronidases as well as synthetic hyaluronidases are clinically applied as adjuncts to increase the bioavailability of drugs, for the therapy of extravasations, or for the management of complications associated with the aesthetic injection of hyaluronic acid-based fillers. Further applications in the fields of surgery, aesthetic medicine, immunology, oncology, and many others can be expected for years to come. Here, we give an overview over the molecular and cellular mode of action of hyaluronidase and the hyaluronic acid metabolism, as well as over current and potential future clinical applications of hyaluronidase.

Hyaluronidase isoforms from developing embryos of the camel tick Hyalomma dromedarii

Changes in hyaluronidase activity in the camel tick Hyalomma dromedarii were followed throughout embryogenesis. Peak activity of the enzyme on days 21 and 24 during development was accompanied with a complete organization of larvae before hatching on day 27. During purification of hyaluronidase to homogeneity, ion exchange chromatography lead to four forms (HAase1, 2, 3 and 4). HAase2 and HAase4 with highest purity and specific activities after chromatography on Sephacryl S-200. The apparent molecular masses of HAase2 and HAase4 were 25 and 40 kDa, respectively. HAase2 and HAase4 had the same pH optimum of 3.6 and Km values of 0.3 and 0.34 mg/mL hyaluronic acid, respectively. Cleaving activities of HAase2 and HAase4 were demonstrated in the order: hyaluronic acid>chondroitin sulphate A>chondroitin sulphate C>chondroitin sulphate mixed>chondroitin sulphate B>heparin, low M.Wt>heparin. HAase2 and HAase4 had the same temperature optimum (40 degrees C) with heat stability up to 40 degrees C. H. dromedarii HAase2 and HAase4 had broad plateau of NaCl requirement with optimum activity recorded at 0.15 and 0.3 M NaCl, respectively. HAase2 and HAase4 were inhibited by Ca2+, Fe3+, Co2+ and Hg2+ and enhanced by Mg2+ and Mn2+.

Molecular cloning, genomic organization and developmental expression of the Xenopus laevis hyaluronan synthase 3

The content of hyaluronan (HA), a polymer of the extracellular matrix involved in a variety of physiological and pathological processes, depends on the activity of synthetic (HAS) and degrading enzymes. Since HA is also involved in embryogenesis, we have used Xenopus as a model organism because information is available for HAS1 and HAS2, but not for HAS3. We report the sequence of xlHAS3 mRNA, its genomic organization and its expression in adult tissues as well as during embryonic development. Interestingly, evidence from in situ hybridization indicates that xlHAS3 expression is restricted to the developing inner ear and cement gland. In addition, we have correlated the expression pattern of the enzymes involved in HA metabolism with the HA content during development.

Hyaluronan is an abundant constituent of the extracellular matrix of Xenopus embryos

The spatiotemporal distribution of hyaluronan (HA), a major constituent of the vertebrate extracellular matrix, was analyzed during early embryonic development of Xenopus laevis. This polysaccharide is abundantly present in ventricular structures such as the blastocoel, the archenteron as well as later on in the hepatic cavity, the brain ventricles and the developing heart. At the blastula stage, HA was detected in the extracellular matrix of the ecto- and mesodermal primordia. Shortly before gastrulation, it becomes enriched at the basal site of the superficial cell layer of the ectoderm. During gastrulation, enhanced synthesis of HA takes place in the involuting marginal zone, shortly before invagination starts, hence, resulting in a torus-like deposition in the deep layer of the equatorial mesodermal primordium. After gastrulation, HA appears to accumulate within the extracellular matrix demarcating the primary germ layers. During tailbud stages, it is found highly enriched in many mesodermal derivatives, e.g., in mesenchyme, the heart, precordal cartilage and the lung primordia. Furthermore, extracellular matrix of the ventral mesodermal cell layer in the trunk region and the immediate proximity of blood vessels contain high amounts of HA.

Hyaluronidase gene profiling and role of hyal-1 overexpression in an orthotopic model of prostate cancer

The mRNA levels of hyal-1, hyal-2, LUCA3 and PH20, the 4 hyaluronidases with demonstrated endoglucosaminidase activity, were extensively profiled in normal and tumor tissues and cell lines, using dot blot analysis and quantitative PCR. In normal tissues, hyal-1, hyal-2 and LUCA3 all showed unique patterns of mRNA expression, but were generally of widespread distribution, whereas PH20 mRNA was restricted to testes. In a small set of breast tumor samples, no elevations in hyal-1, hyal-2 or LUCA3 mRNA were seen. Hyaluronidase activity measured by a novel assay or zymography was also not elevated in sera from a number of breast cancer patients, compared to sera from normal volunteers. In ex vivo xenograft tumor cell lines, however, hyal-1 or hyal-2 mRNA levels were frequently elevated, whereas LUCA3 was only infrequently elevated and PH20 not at all. Two cell lines were engineered to overexpress hyal-1: a breast cancer line (CAL51) and a prostate cancer line (PC3M). Although the in vitro properties of the hyal-1 overexpressing cell lines were indistinguishable from the parental cells, the orthotopic growth of hyal-1 expressing PC3M cells in nu/nu mice resulted in significantly increased numbers of metastases, supportive of a role for hyal-1 in extravasation and metastatic tumor formation in this model of prostate cancer.

Hyal2--less active, but more versatile?

Hyal2 is one of several hyaluronidases present in vertebrates. The human gene encoding this enzyme is present on chromosome 3p.21.3, close to two additional hyaluronidase genes. cDNAs encoding Hyal2 homologues have been characterized from mouse and Xenopus laevis. These enzymes hydrolyze high molecular mass hyaluronan to intermediates of approximately 20 kDa, a finding which implies that structural domains of this size exist in this polysaccharide which was mostly thought to be a random coil. Hyal2 enzymes have an acidic pH-optimum with an activity that is considerably lower than observed for other types of hyaluronidases. Originally considered to be a typical lysosomal enzyme, more recent evidence has shown that Hyal2 proteins can also be exposed on the cell surface bound to the plasma membrane via a GPI anchor. Hyal2 is present in many tissues, one exception being the adult brain. In this tissue, the gene is silenced after birth by methylation. Current evidence about the role of Hyal2 in tumor growth, inflammation and frog embryogenesis is discussed.

Xenopus kidney hyaluronidase-1 (XKH1), a novel type of membrane-bound hyaluronidase solely degrades hyaluronan at neutral pH

In search for Xenopus laevis hyaluronidase genes, a cDNA encoding a putative PH-20-like enzyme was isolated. In the adult frog, this mRNA was only found to be expressed in the kidney and therefore named XKH1. When expressed by means of cRNA injection into frog oocytes, XKH1 solely exhibited at physiologic ionic strength hyaluronidase activity at neutral pH and in weakly acidic solutions. The enzyme was inactive below pH 5.4. In addition to hyaluronic acid hydrolysis, chondroitin sulfate also was degraded at low yield as assessed by fluorophore-assisted carbohydrate electrophoresis analysis of the degradation products. The enzyme is sorted to the outer surface of the cell membrane of XKH1 expressing oocytes. From there, it could not be removed by phospholipase C nor was secreted hyaluronidase activity detectable. We conclude that XKH1 represents a membrane-bound hyaluronan-degrading enzyme exclusively expressed in cells of the adult frog kidney where it either may be involved in the reorganization of the extracellular architecture or in supporting physiological demands for proper renal functions.

A developmentally regulated hyaluronidase of Haemonchus contortus

The trichostrongylid nematode Haemonchus contortus released a hyaluronic acid-degrading enzyme during in vitro development from the third (L3) to fourth (L4) larval stage. The enzyme did not degrade chondroitin sulfate A. Enzyme activity was optimal between pH 4.0 and 6.0, and the enzyme was inhibited by high concentrations of NaCl; the divalent cations Cu2+, Zn2+, Ca2+, and Mn2+ were not inhibitory. The hyaluronidase had a molecular mass estimated at 57 kDa by sucrose density gradient centrifugation and at 111 kDa by substrate sodium dodecyl sulfate polyacrylamide gel electrophoresis (reducing and nonreducing conditions), suggesting the formation of a dimer during the electrophoretic separation conditions. The level of hyaluronidase released during in vitro development peaked between 24 and 48 hr in culture and then gradually decreased, with little or no activity present in the 168-hr culture fluid. The enzyme was not detected in culture fluid from 24-hr incubations of either the mid-L4 stage (obtained from sheep 7 days postinfection) or the adult stage (obtained from sheep 30-35 days postinfection). The temporal expression of the hyaluronidase suggested a role for this enzyme in the early stages of the L3-L4 developmental process.