Turnover and Metabolism of Hyaluronan

Biomimetic Hyaluronan Binding Biomaterials to Capture the Complex Regulation of Hyaluronan in Tissue Development and Function

Within native ECM, Hyaluronan (HA) undergoes remarkable structural remodeling through its binding receptors and proteins called hyaladherins. Hyaladherins contain a group of tandem repeat sequences, such as LINK domains, BxB7 homologous sequences, or 20-50 amino acid long short peptide sequences that have high affinity towards side chains of HA. The HA binding sequences are critical players in HA distribution and regulation within tissues and potentially attractive therapeutic targets to regulate HA synthesis and organization. While HA is a versatile and successful biopolymer, most HA-based therapeutics have major differences from a native HA molecule, such as molecular weight discrepancies, crosslinking state, and remodeling with other HA binding proteins. Recent studies showed the promise of HA binding domains being used as therapeutic biomaterials for osteoarthritic, ocular, or cardiovascular therapeutic products. However, we propose that there is a significant potential for HA binding materials to reveal the physiological functions of HA in a more realistic setting. This review is focused on giving a comprehensive overview of the connections between HA's role in the body and the potential of HA binding material applications in therapeutics and regenerative medicine. We begin with an introduction to HA then discuss HA binding molecules and the process of HA binding. Finally, we discuss HA binding materials anf the future prospects of potential HA binding biomaterials systems in the field of biomaterials and tissue engineering.

Therapeutic effects of dexamethasone-loaded hyaluronan nanogels in the experimental cholestasis

A major function of the intrahepatic biliary epithelium is bicarbonate excretion in bile. Recent reports indicate that budesonide, a corticosteroid with high receptor affinity and hepatic first pass clearance, increases the efficacy of ursodeoxycholic acid, a choleretic agent, in primary biliary cholangitis patients. We have previously reported that bile ducts isolated from rats treated with dexamethasone or budesonide showed an enhanced activity of the Na⁺/H⁺ exchanger isoform 1 (NHE1) and Cl^-/HCO₃^- exchanger protein 2 (AE2) . Increasing the delivery of steroids to the liver may result in three beneficial effects: increase in the choleresis, treatment of the autoimmune or inflammatory liver injury and reduction of steroids' systemic harmful effects. In this study, the steroid dexamethasone was loaded into nanohydrogels (or nanogels, NHs), in order to investigate corticosteroid-induced increased activities of transport processes driving bicarbonate excretion in the biliary epithelium (NHE-1 isoform) and to evaluate the effects of dexamethasone-loaded NHs (NHs/dex) on liver injury induced by experimental cholestatis. Our results showed that NHs and NHs/dex do not reduce cell viability in vitro in human cholangiocyte cell lines. Primary and immortalized human cholangiocytes treated with NHs/dex show an increase in the functional marker expression of NHE1 cholangiocytes compared to control groups. A mouse model of cholangiopathy treated with NHs/dex shows a reduction in markers of hepatocellular injury compared to control groups (NHs, dex, or sham group). In conclusion, we believe that the NHs/dex formulation is a suitable candidate to be investigated in preclinical models of cholangiopathies.

The Labeling, Visualization, and Quantification of Hyaluronan Distribution in Tumor-Bearing Mouse Using PET and MR Imaging

PURPOSE

Hyaluronan (HA) based biomaterials are widely used as tissue scaffolds, drug formulations, as well as targeting ligands and imaging probes for diagnosis and drug delivery. However, because of the presence of abundant endogenous HA presented in various tissues in vivo, the pharmacokinetic behavior and biodistribution patterns of exogenously administered HAs have not been well characterized.

METHODS

The HA backbone was modified with Diethylenetriamine (DTPA) to enable the chelation of gadolinium (Gd) and aluminum (Al) ions. Series of PET and MR imaging were taken after the injection of HA-DTPA-Gd and HA-DTPA-Al¹⁸F while using¹⁸F-FDG and Magnevist(DTPA-Gd) as controls. The Tomographic images were analyzed and quantified to reveal the distribution and locations of HA in tumor-bearing mice.

RESULTS

The labeled HAs had good stability in plasma. They retained binding affinity towards CD44s on tumor cell surface. The injected HAs distributed widely in various organs, but were found to be cleared quickly except inside tumor tissues where the signals were higher and persisted longer.

CONCLUSION

Medical imaging tools, including MR and PET, can be highly valuable for examining biomaterial distribution non-invasively. The HA tumor accumulation properties may be explored for the development of active targeting drug carriers and molecular probes.

Respective roles of hyaluronidases 1 and 2 in endogenous hyaluronan turnover

We studied the physiologic roles of the hyaluronidase (HYAL) 1 and HYAL2 in hyaluronan (HA) turnover. HA was localized and quantified using HA binding proteins in various tissues of Hyal1(-/-) and Hyal2(-/-) mice (knockout mice) as well as control mice. HA MW was determined using gel filtration chromatography. HA endocytosis in liver nonparenchymal cells (NPCs) was quantified in vivo Both Hyal1 and Hyal2 knockout mice showed HA accumulation in peripheral tissues without changes in HA MW distribution. HYAL2 deficiency induced buildup of very high MW (>3.10(6) Da) HA in lymph and serum with severe lymph node distortion. The lack of HYAL2 also impaired high MW HA endocytosis by liver NPCs. HYAL1 deficiency led to a moderate increase in serum HA concentration without changes in HA MW distribution and to HA overload of liver NPCs. Wild-type C57BL/6 mice served as controls. In HA injection experiments, saline-injected mice served as additional controls. We conclude that: 1) HYAL1 and HYAL2 are both needed for tissue HA catabolism; 2) HYAL2 is required for high MW HA clearance in lymph nodes and plasma and for HA endocytosis by liver NPCs; and 3) the main role of HYAL1 is HA degradation within liver NPCs.-Bourguignon, V., Flamion, B. Respective roles of hyaluronidases 1 and 2 in endogenous hyaluronan turnover.

Hyaluronidase 2 (HYAL2) is expressed in endothelial cells, as well as some specialized epithelial cells, and is required for normal hyaluronan catabolism

Hyaluronidase 2 (HYAL2) is a membrane-anchored protein that is proposed to initiate the degradation of hyaluronan (HA) in the extracellular matrix. The distribution of HYAL2 in tissues, and of HA in tissues lacking HYAL2, is largely unexplored despite the importance of HA metabolism in several disease processes. Herein, we use immunoblot and histochemical analyses to detect HYAL2 and HA in mouse tissues, as well as agarose gel electrophoresis to examine the size of HA. HYAL2 was detected in all tissues that were examined, including the brain. It was localized to the surface and cytoplasm of endothelial cells, as well as specialized epithelial cells in several tissues, including the skin. Accumulated HA, often of higher molecular mass than that in control tissues, was detected in tissues from Hyal2 (-/-) mice. The accumulating HA was located near to where HYAL2 is normally found, although in some tissues, it was distant from the site of HYAL2 localization. Overall, HYAL2 was highest in tissues that remove HA from the circulation (liver, lymph node and spleen), but the levels of HA accumulation in Hyal2 (-/-) mice were highest in tissues that catabolize locally synthesized HA. Our results support HYAL2's role as an extracellular enzyme that initiates HA breakdown in somatic tissues. However, our findings also suggest that HYAL2 contributes to HA degradation through other routes, perhaps as a soluble or secreted form.

Water soluble complexes of chitosan‐g‐MPEG and hyaluronic acid

Novel water soluble, biocompatible, and highly viscoelastic polyelectrolyte complexes were prepared by mixing of positively charged chitosan grafted with poly (ethylene glycol) monomethyl ether (CS-g-MPEG) and negatively charged hyaluronic acid (HA). CS-g-MPEGs having different degrees of substitution were synthesized by reacting chitosan with MPEG-aldehyde. The molecular structure, thermal and rheological properties, as well as biocompatibility of CS-g-MPEG/HA complexes were characterized. Rheological results showed that a small amount of HA could greatly enhance the viscosity of CS-g-MPEG solution. The highest viscosity was obtained when the charge ratio of CS-g-MPEG/HA was close to 1.0. Small-angle X-ray scattering measurements provided some insights into the lamellar structure of the CS-g-MPEG/HA complex. The CS-g-MPEG/HA complex system offers promising potentials in pharmaceutical, cosmetic, and biotechnology applications (e.g., cell scaffold, artificial synovial fluid, and drug/gene delivery medium).

Renomedullary and intestinal hyaluronan content during body water excess: a study in rats and gerbils

Our previous studies in rats have suggested a role for renomedullary hyaluronan (HA) in water homeostasis. The gerbil is known for its unique ability to conserve water. In the present study renal papillary and intestinal HA were compared between groups of anaesthetized gerbils and rats before and after up to 6 h of I.V. water loading. Baseline papillary HA in gerbils was only 37 % of that in the rat. Water loading in rats increased the papillary HA content. Elevation was maximal (+27 %, P < 0.05) after 2 h of water loading and then declined to control levels after 6 h of water loading (+3 %, n.s.). In contrast, the gerbil responded with a decreased papillary HA content during water loading. The depression was maximal after 2 h (-49 %, P < 0.05) and was still 41 % below the control values after 6 h (P < 0.05). The urine flow rate increased rapidly in the rat and its maximum, 21 times above the control level (P < 0.05), occurred at the HA peak, i.e. after 2 h of water loading while in the gerbil, the urine flow rate increased slowly and slightly and was only six times above control values after 6 h of water loading (P < 0.05). The HA content along the intestine was similar in the two species: lowest in the duodenum and jejunum and highest in the distal colon. To conclude, in the rat, the elevation of papillary interstitial HA during acute water loading would counteract water reabsorption by changing the physico-chemical characteristics of the interstitial matrix favouring rapid water diuresis. This would work as a complement to the powerful regulation by ADH. The gerbil has a diametrically different regulation of papillary HA turnover during water loading. The decreased papillary HA level during water loading and the slow and small diuretic response may represent a genetic difference in adaptation to enhance the ability to conserve water in an arid environment.

Expression of PH-20 in normal and neoplastic breast tissue

BACKGROUND

Tumor metastasis involves a sequence of interrelated steps, of which penetration beyond the basement membrane is an essential component. Hyaluronic acid (HA) is a major structural component of the complex proteoglycans found in extracellular matrices and basement membranes. Hyaluronidase (PH-20) degrades HA, resulting in the disruption of basement membrane integrity and possible tumor dissemination.

MATERIALS AND METHODS

Total RNA was extracted from samples (n = 51) of normal breast tissue (n = 12), ductal carcinoma in situ (DCIS) (n = 12), infiltrating ductal breast adenocarcinoma (n = 13), and metastatic breast cancer to lymph nodes (n = 14). RT-PCR was used to determine the relative level of PH-20 in each specimen.

RESULTS

PH-20 was detected in 41/51 (80.4%) of the specimens evaluated. PH-20 was present in 12/12 (100%) normal breast tissues; 8/12 (66.7%) DCIS; 13/13 (100%) invasive breast cancers; and 8/14 (57.1%) metastases. Of those specimens in which PH-20 was detected, there were increased levels of PH-20 in metastatic breast cancer to lymph nodes compared to DCIS and invasive breast cancer. Stratification of specimen by race revealed that African American women had higher levels of PH-20 with invasive and metastatic beast cancer.

CONCLUSIONS

Increased levels of PH-20 are noted in invasive and metastatic breast cancer compared to DCIS. Tumors from African American women with invasive and metastatic breast cancer demonstrated higher levels of PH-20 than Caucasians. Varying levels of PH-20 in mammary tissue may contribute to early invasion and metastasis of breast cancer.

Effect of in vitro aging on the biosynthesis of glycosaminoglycans by human skin fibroblasts. Modulation by the elastin-laminin receptor

The incorporation of a radioactive precursor 3H-glucosamine in glycoconjugates, essentially glycosaminoglycans (GAG) was evaluated in the culture medium and cell fraction of human skin fibroblasts. Using increasing passage numbers, we could estimate the effect of in vitro aging on these biosynthetic activities. The incorporation in different free (hyaluronan) and protein bound (proteoglycans) GAGs was evaluated after specific enzymatic digestion. Most newly synthesized GAGs were excreted in the extracellular medium. Incorporation of the tracer in hyaluronan, the major biosynthetic product, increased with passage number but its titratable concentration decreased with in vitro aging, suggesting a rapid post-synthetic degradation. The proportion of chondroitin sulfates 4 (A) and 6 (C) and heparan sulfate decreased and that of dermatan sulfate increased with increasing passage number. We explored the modulation of these biosynthetic activities by the elastin laminin receptor. Using agonists (elastin peptides) and an antagonist (melibiose) of the receptor, their action on GAG biosynthesis was evaluated. Both elastin peptides and melibiose increased incorporation of the tracer in GAGs, but only melibiose inhibited post-synthetic degradation of hyaluronan, therefore increasing its concentration. The effect of passage number on the receptor mediated modulations was also investigated.

Pharmacokinetics and tissue distribution of bovine testicular hyaluronidase and vinblastine in mice: an attempt to optimize the mode of adjuvant hyaluronidase administration in cancer chemotherapy

The influence of the route of administration (i.v., i.p. and s.c.) on pharmacokinetics and tissue distribution of bovine testicular hyaluronidase and vinblastine was studied in mice (plasma, skeletal muscle, liver, kidney and human melanoma). After i.v. injection, hyaluronidase was accumulated in liver and kidney, whereas i.p. and s.c. administration led to almost equal distribution in plasma, muscle, liver and kidney. In melanoma, the highest levels of hyaluronidase were found after s.c. injection of the enzyme close to the tumor. Hyaluronidase s.c. increased the intratumoral concentration of s.c. co-administered vinblastine most efficiently, making local simultaneous application as in interstitial chemotherapy most promising.