Oxygen-derived free radical (ODFR) action on hyaluronan (HA), on two HA ester derivatives, and on the metabolism of articular chondrocytes

Role of an acidic environment in the treatment of diabetic foot infections: A review

Management of diabetic foot ulcers is the biggest challenge to the clinician, as conventional antibiotic therapies and local wound care have their own limitations. They are not effective for control of infections and promotion of healing because of cytotoxic effects. In view of cytotoxicity of routinely used topical antiseptic agents, this article focuses on the search of an ideal topical antiseptic agent that is safe and effective in controlling infectious agents and also in promoting the healing process. This review focuses on the use of various acids such as citric, acetic, hyaluronic, and hypochlorous acids as topical agents in diabetic foot infections. This article also focuses on the different roles of acids in the treatment of diabetic foot infections.

Versatile use of dermal substitutes: A retrospective survey of 127 consecutive cases

Background:

Dermal substitutes are currently largely used for the treatment of huge skin loss in patients in critical general health conditions, for the treatment of severe burns and to promote the healing process in chronic wounds.

Aims:

The authors performed a retrospective assessment of their experience with bioengineered skin to possibly identify the most appropriate clinical indication and management for each substitute.

Materials and Methods:

The study involved 109 patients with 127 skin defects repaired with dermal substitutes over a 9 years period, from 2007 to 2016. Hyalomatrix^® was used in 63 defects, whereas Integra^® and Nevelia^® were used in 56 and 8 defects, respectively.

Results:

The statistical analysis failed to reveal a correlation between the choice of a specific dermal substitute and any possible clinical variable except in the soft-tissue defects of the scalp where Hyalomatrix^® was electively used.

Conclusions:

In the authors' experience, the scalp defects followed a radical excision of skin tumours that included the periosteum. Here, the preliminary cover with a hyaluronan three-dimensional scaffold constantly allowed for the regeneration of a derma-like layer with a rich vascular network fit for supporting a split-thickness skin graft. Nevertheless, the authors still prefer Integra^® when the goal is a better cosmetic outcome and Hyalomatrix^® when a faster wound healing is required, especially in the management of deep wounds where the priority is a fast obliteration with a newly formed tissue with a rich blood supply. However, these clinical indications still are anecdotally based.

Cross-linked hyaluronic acid in pressure ulcer prevention

OBJECTIVE

Long-term bedridden patients are at high risk of acquring pressure ulcers (PUs). In this group of patients, prevention is necessary to cut the health costs, improve quality of life and reduce the mortality. Here, we evaluated the effectiveness of a cross-linked hyaluronic acid (HA) as plastic bulking-agent filling and remodelling the deep dermis and subcutaneous space of the skin areas exposed to the risk of necrosis. Our work hypothesis has been to inflate a sub-dermal elastic cushion, filled with a natural ECM component, with the aim to induce a stronger tissue background resistant to the ulcerative process.

METHOD

All the patients had an increased risk of PUs, at the sacral, ileum or heel skin. Patients were being nursed accordingly to the standard orthopaedic ward management with a pressure relieveing air mattress. The standard protocol consisted in body mobilisation every 3 hours, 24 hours a day and accurate cleaning of the skin with liquid soap and water without any towel friction and without adding any cream or lotion for the skin protection. Our filling protocol enclosed: accurate disinfection of the skin to be injected with povidone-iodine solution, followed by a local anaesthesia with 28G 13 mm needle, injecting 1.5 ml of 1% xylocaine. Then slow, deep, subcutaneous injection of cross-linked HA was performed with a 18G long needle, in order to deliver a homogeneous, soft gel layer underneath and around the whitish erythematous skin edges at risk of ulceration. Patients' tolerability of the compound and adverse events were also recorded.

RESULTS

There were 15 patients (78-94 years old) who participated in the study. All tolerated the procedure very well and no serious side effects were declared. No skin pressure ulceration was detected in the four weeks follow-up Conclusion: We have demonstrated the safety and tolerability of a cross-linked HA subdermal injection in PUs prevention. The compound stratifies in a soft, elastic, interstitial bulk into the deep dermis, thus reducing the exogenous pressure stress: thus, the induction of a thick hydrophilic substrate supports adequate mesenchymal and blood cells traffic to immediately restore any early or impending damage to the skin.

DECLARATION OF INTEREST

The authors certify that there is no conflict of interest with any financial organisation regarding the material discussed in the manuscript.

Hyaluronic acid dressing (Healoderm) in the treatment of diabetic foot ulcer: A prospective, randomized, placebo-controlled, single-center study

Fast and complete healing of a diabetic foot ulcer (DFU) is challenging due to the hostile wound healing environment of the diabetic patients. As a part of a multimodal treatment approach, advanced dressing material using hyaluronic acid (HA) has been found to be effective. However, previous studies have used HA with additional biologics, which interferes in determining the true clinical effect of HA in DFU. To examine the sole effectiveness of HA in DFU treatment, a prospective, randomized, placebo-controlled, single-center study was conducted using an HA dressing without additional substances. Thus, 34 patients who met the inclusion criteria were randomized into two groups (the study group: HA dressing material; the control group: conventional dressing material). During the 12-week study period, complete ulcer healing rate was evaluated as a primary endpoint. Additionally, healing velocity and the mean duration for achieving a 50% ulcer size reduction was compared between the two groups as a secondary endpoint. At the end of the study, the study group presented a significantly higher complete healing rate as compared to that in the control group [84.6% (11/13), 41.6% (5/12), respectively, P = 0.041]. Additionally, faster ulcer healing velocity and shorter mean duration for achieving a 50% ulcer size reduction were observed in the study group (P = 0.022 and 0.004, respectively). The Kaplan-Meier survival analysis for the median time for 50% ulcer healing rate also showed a significantly shorter duration in the study group (21 days vs. 39 days, P = 0.0127). Finally, there were no adverse events related to the dressing materials used in the study. As a major component of the extracellular matrix, this study supports the safety and efficacy of a pure HA dressing without additional substances in treating DFU.

Connective tissue response to fractionated thermo-ablative Erbium: YAG skin laser treatment

Indications for and prevalence of laser therapies with a fractionated laser beam have risen significantly. However, as of yet, little is known about the underlying molecular changes, especially with respect to dermal extracellular-matrix remodelling, wound healing and inflammation. This study aimed at the investigation of the connective tissue response of sun-damaged skin following fractionated laser treatment. Seven patients received a laser therapy on the lateral side of the neck of wrinkles grade III-IV (Glogau scale) using a fractionated thermo-ablative erbium yttrium aluminium garnet (Er:YAG) laser (2940 nm, BURANE XL; Quantel Derma, Erlangen, Germany). Skin biopsies were taken at baseline from untreated skin, 1 and 6 weeks after laser intervention to investigate hyaluronan (HA), collagen-I (Coll-I) and collagen-III (Coll-III) remodelling as well as alteration of matrix metalloproteinase 1 expression (MMP-1). To address this issue, HA synthesizing (HA synthetases, HAS) and degrading (hyaluronidases, HYAL) enzymes were measured at mRNA-level using a real-time PCR. Furthermore, immunohistochemical staining for HA was performed by using the HA binding protein (HAbP) and for Coll-I, Coll-III and MMP-1 by using monoclonal antibodies. The degree of inflammation was correlated descriptively. Our findings were that at the two examined read out points, HAS and HYAL showed a slight response alluding to HA synthesis under minimal signs of inflammatory reaction. Concordantly, although to a varying degree, an increase in the HA content of the skin after laser treatment could be detected by immunhistochemistry. During remodelling, Coll-I, Coll-III and MMP-1 showed a cyclic course with a peak after 1 week. Conclusively, our results indicate a light alteration of the HA metabolism towards synthesis and a transient collagen neogenesis caused by a single fractionated thermo-ablative laser skin intervention. Clinical improvement might be attributed to synergistic effects between collagen neogenesis and the water binding capacities of HA and its influence on skin contraction and remodelling.

The use of hyaluronic acid based dressings to treat burns: A review

Deep cutaneous lesions such as burns, traumas or ulcers are all conditions characterized by a massive loss of dermis, bringing several important consequences. For the treatment of these conditions, the evolution of material science has made available new dressings based on natural and synthetic polymers. Hyaluronic acid (HA) is involved in many steps of the wound healing process, such as inflammation, granulation and re-epithelialization. In order to overcome the poor physical properties of the native polymer, such as solubility and rapid degradation, insoluble molecules starting from the natural compound were produced via esterification. Thanks to their improved structural properties, the dressings based on these hyaluronic acid derivatives represent a valuable option for the treatment of deep burns. This narrative monograph describes the development and the outcome of the use of these products in burns. The currently available clinical experience suggests that these HA medical devices represent a safe therapeutic method useful for the treatment of acute wounds.

Glycosaminoglycan degradation by selected reactive oxygen species

SIGNIFICANCE

Inflammatory diseases (such as arthritis) of the extracellular matrix (ECM) are of considerable socioeconomic significance. There is clear evidence that reactive oxygen species (ROS) and nitrogen species released by, for instance, neutrophils contribute to the degradation of the ECM. Here we will focus on the ROS-induced degradation of the glycosaminoglycans, one important component of the ECM.

RECENT ADVANCES

The recently developed "anti-TNF-α" therapy is primarily directed against neutrophilic granulocytes that are powerful sources of ROS. Therefore, a more detailed look into the mechanisms of the reactions of these ROS is reasonable.

CRITICAL ISSUES

Since both enzymes and ROS contribute to the pathogenesis of inflammatory diseases, it is very difficult to estimate the contributions of the individual species in a complex biological environment. This particularly applies as many products are not stable but only transient products that decompose in a time-dependent manner. Thus, the development of suitable analytical methods as well as the establishment of useful biomarkers is a challenging aspect.

FUTURE DIRECTIONS

If the mechanisms of ECM destruction are understood in more detail, then the development of suitable drugs to treat inflammatory diseases will be hopefully much more successful.

Semi-interpenetrating networks of hyaluronic acid in degradable PEG hydrogels for cartilage tissue engineering

Hydrolytically biodegradable poly(ethylene glycol) (PEG) hydrogels offer a promising platform for chondrocyte encapsulation and tuning degradation for cartilage tissue engineering, but offer no bioactive cues to encapsulated cells. This study tests the hypothesis that a semi-interpenetrating network of entrapped hyaluronic acid (HA), a bioactive molecule that binds cell surface receptors on chondrocytes, and crosslinked degradable PEG improves matrix synthesis by encapsulated chondrocytes. Degradation was achieved by incorporating oligo (lactic acid) segments into the crosslinks. The effects of HA molecular weight (MW) (2.9×10(4) and 2×10(6)Da) and concentration (0.5 and 5mgg(-1)) were investigated. Bovine chondrocytes were encapsulated in semi-interpenetrating networks and cultured for 4weeks. A steady release of HA was observed over the course of the study with 90% released by 4weeks. Incorporation of HA led to significantly higher cell numbers throughout the culture period. After 8days, HA increased collagen content per cell, increased aggrecan-positive cells, while decreasing the deposition of hypertrophic collagen X, but these effects were not sustained long term. Measuring total sulfated glycosaminoglycan (sGAG) and collagen content within the constructs and released to the culture medium after 4weeks revealed that total matrix synthesis was elevated by high concentrations of HA, indicating that HA stimulated matrix production although this matrix was not retained within the hydrogels. Matrix-degrading enzymes were elevated in the low-, but not the high-MW HA. Overall, incorporating high-MW HA into degrading hydrogels increased chondrocyte number and sGAG and collagen production, warranting further investigations to improve retention of newly synthesized matrix molecules.

Long-term in vivo assessment of bioengineered skin substitutes: a clinical study

The aim of the study was an objective in vivo assessment of skin properties after reconstruction with two artificial dermal substitutes, Integra® and Hyalomatrix®. Twenty-seven patients underwent reconstruction of 36 skin-loss sites with full-thickness skin graft, split-thickness skin graft, Hyalomatrix® bioengineered skin substitute and sequential split-thickness skin graft and Integra® bioengineered skin substitute and sequential split-thickness skin graft. Objective assessments were carried out using three instrumental devices: Multi Probe Adapter System MPA; 22 MHz ultrasound skin scan; and Primos Pico for a three-dimensional (3D) skin scan. The skin parameters under study in our sample were: corneometry, transepidermal water loss, elastometry, colorimetry, skin thickness and 3D skin surface pattern. A skin reconstruction with Hyalomatrix seemed to most closely approach the hydration, transepidermal water loss and skin surface 3D pattern of normal skin. A skin reconstruction with Integra seemed to demonstrate the best skin colour feature and elastic properties. Although no statistically significant differences were observed, the descriptive analysis of the outcomes might suggest a better cell regulation, regenerated extracellular matrix and neoangiogenesis with the use of Hyalomatrix, and the formation of a more elastic regenerated dermis, with overall better physical, mechanical and optical properties, with the use of Integra.

On-line separation and characterization of hyaluronan oligosaccharides derived from radical depolymerization

Hydroxyl radicals are widely implicated in the oxidation of carbohydrates in biological and industrial processes and are often responsible for their structural modification resulting in functional damage. In this study, the radical depolymerization of the polysaccharide hyaluronan was studied in a reaction with hydroxyl radicals generated by Fenton Chemistry. A simple method for isolation and identification of the resulting non-sulfated oligosaccharide products of oxidative depolymerization was established. Hyaluronan oligosaccharides were analyzed using ion-pairing reversed phase high performance liquid chromatography coupled with tandem electrospray mass spectrometry. The sequence of saturated hyaluronan oligosaccharides having even- and odd-numbers of saccharide units, afforded through oxidative depolymerization, were identified. This study represents a simple, effective 'fingerprinting' protocol for detecting the damage done to hyaluronan by oxidative radicals. This study should help reveal the potential biological outcome of reactive-oxygen radical-mediated depolymerization of hyaluronan.

Hyaluronic acid derivatives and their healing effect on burns, epithelial surgical wounds, and chronic wounds: a systematic review and meta-analysis of randomized controlled trials

Hyaluronic acid (HA) is a polysaccharide common to most species and is found in many sites in the human body, including the skin and soft tissue. A systematic review of the literature and meta-analysis was performed to identify randomized controlled trials, evaluating the use of HA derivatives in healing burns, epithelial surgical, and chronic wounds. Nine studies were identified, which met the search criteria and clinical endpoints of complete healing and percent wound size reduction when using HA vs. either an active or passive comparator. It was found in the vast majority of randomized controlled trials (eight of nine) that HA derivatives significantly improved the healing of wounds vs. traditional therapies or placebo (either via complete healing or a significant reduction in wound size) occurring from burns, venous insufficiency, diabetes, neuropathic insufficiency, and surgical removal of the epithelial layer (for tattoo removal). In the other remaining trial, one formulation of HA was compared with another, with the higher concentration showing improved application characteristics. Further, it was found in a meta-analysis in subsets of patients with diabetic foot ulcers (neuropathic) that HA derivatives healed these types of wounds significantly faster than standard of care. These studies in aggregate show that HA derivatives accelerate the healing process in burns, epithelial surgical wounds, and chronic wounds.

Effect of elongation of alternating sequences on swelling behavior and large deformation properties of natural alginate gels

The physical properties of alginate gels correlate with alginate composition. Blocks of guluronic acid (G) strongly contribute to gel formation. Recently, the role of alternating sequences in calcium-alginate gels has been elucidated. The present contribution aimed at extending the analysis already reported (Donati, I.; Holtan, S.; Mørch, Y. A.; Borgogna, M.; Dentini, M.; Skjåk-Braek, G. Biomacromolecules 2005, 6, 1031) and at explaining some apparent mismatch of experimental data. In the present work, calcium hydrogels from different alginate samples have been analyzed by means of uniaxial compression and puncture tests to evaluate their Young's modulus and work at break. The role of long MG blocks in mechanical deformations (small and large domains) as well as in swelling experiments was investigated with natural and MG-enriched (AlgE4 epimerized) alginate samples. Alginates with elongated alternating sequences displayed, upon treatment with saline solution, a notable increase in swelling behavior, which was not paralleled by increased mechanical properties (Young's modulus). This behavior was traced back to the disentanglement of MG/MG junctions, which increased the local charge density, reducing the osmotic contribution to hydrogel swelling. The analyses of the large deformation curves for natural and epimerized alginates revealed an increase in the energy to breakage in the latter case caused by the dissipation effect of "sliding" MG/MG junctions.

Biophysical properties of phenyl succinic acid derivatised hyaluronic acid

Modification of hyaluronic acid (HA) with aryl succinic anhydrides results in new biomedical properties of HA as compared to non-modified HA, such as more efficient skin penetration, stronger binding to the skin, and the ability to blend with hydrophobic materials. In the present study, hyaluronic acid has been derivatised with the anhydride form of phenyl succinic acid (PheSA). The fluorescence of PheSA was efficiently quenched by the HA matrix. HA also acted as a singlet oxygen scavenger. Fluorescence lifetime(s) of PheSA in solution and when attached to the HA matrix has been monitored with ps resolved streak camera technology. Structural and fluorescence properties changes induced on HA-PheSA due to the presence of singlet oxygen were monitored using static light scattering (SLS), steady state fluorescence and ps time resolved fluorescence studies. SLS studies provided insight into the depolymerisation kinetics of PheSA derivatised HA matrix in the presence of singlet oxygen. Time resolved fluorescence studies grave insight into the dynamics of the reaction mechanisms induced on HA-PheSA by singlet oxygen. These studies provided insight into the medical relevance of PheSA derivatised HA: its capacity of scavenging singlet oxygen and of quenching PheSA fluorescence. These studies revealed that HA-PheSA is a strong quencher of electronic excited state PheSA and acts as a scavenger of singlet oxygen, thus medical applications of this derivatised form of HA may protect tissues and organs, such as skin, against reactive oxygen species damage.

The antioxidant effect exerted by TGF-1beta-stimulated hyaluronan production reduced NF-kB activation and apoptosis in human fibroblasts exposed to FeSo4 plus ascorbate

Previous studies suggest that Transforming growth factor-1beta (TGF-1beta) administration in human fibroblasts exposed to oxidative stress is able to modulate hyaluronan synthases (HASs). HAS modulation in turn increases high molecular weight (Hyaluronan) HA concentration. Nuclear factor kB (NF-kB) is a response transcription factor involved in inflammation and acts by enabling the expression of certain detrimental molecules. Caspases are specific proteases responsible for regulating and programming cell death. HA at medium molecular weight together with chondroitin-4-sulphate proved to be effective on NF-kB and caspases. We investigated whether the protective effect afforded by the high molecular weight HA produced by TGF-1beta treatment has any effect on NF-kB and apoptosis activation in fibroblast cultures exposed to oxidative stress. Generation of free radicals gives rise to cell death, increases lipid peroxidation, activates NF-kB, reduces its cytoplasmic inhibitor IkBalpha, augments caspase-3 and caspase-7 gene expression and their relative protein activity, and depletes catalase (CAT) and glutathione peroxidase (GPx). Treatment of fibroblasts with TGF-1beta 12 h before inducing oxidative stress greatly increased HA levels, ameliorated cell survival, inhibited lipid peroxidation, blunted NF-kB translocation, normalized IkBalpha protein, reduced caspase gene expression and protein levels, and restored the endogenous antioxidants CAT and GPx. Since it was previously reported that antioxidants can work as inhibitors of NF-kB and apoptosis induction we can hypothesize that endogenous HA, by inhibiting lipid peroxidation, may block a step whereby free radical activity converges in the signal transduction pathway leading to NF-kB and caspase activation.

Differential effect of growth factors on hyaluronan synthase gene expression in fibroblasts exposed to oxidative stress

The aim of this study was to evaluate how growth factors (PDGF-BB, EGF, and TGF-1beta) modulate hyaluronan synthase (HAS) activities in normal or stressed cultured human skin fibroblasts. The effects of concomitant treatment with cytokines and FeSO4 plus ascorbate on HAS mRNA expression, protein synthesis, and hyaluronic acid (HA) concentrations were also studied. Treatment of fibroblasts with growth factors up-regulated HAS gene expression and increased HAS enzymes and HA production. PDGF-BB induced HAS mRNA expression, protein synthesis, and HA production more efficiently than EGF and TGF-1beta. EGF was less effective than TGF-1beta. In addition, TGF-1beta reduced the expression and synthesis of HAS3, while PDGF-BB and EGF had the opposite effect. Concomitant treatment with growth factors and the oxidant was able to further increase HAS mRNA expression, once again with the exception of HAS3 with TGF-1beta. HAS protein synthesis was reduced, while HA levels were unaffected in comparison to those obtained from exposure to FeSO4 plus ascorbate alone. In conclusion, although growth factors plus the oxidant synergistically induced HAS mRNA expression in part, enzyme production was not correlated with this increase. Moreover, the increase in HAS mRNA levels was not translated into a consequent rise in HA concentration.

Effects of hyaluronan on nitric oxide levels and superoxide dismutase activities in synovial fluid in knee osteoarthritis

The aim of the present study was to evaluate the effects of hyaluronan (HA) on nitric oxide (NO) levels and superoxide dismutase (SOD) enzyme activities in synovial fluid (SF) in the treatment of patients with knee osteoarthritis (OA). SF samples were aspirated from OA patients before the commencement of the treatment (n=23) and 6 weeks after they were treated with HA products. NO levels and SOD activities were compared between the pre- and post-treatment of OA patients and of the control group (n=10). SF NO levels were significantly higher in patients with OA before the commencement of the treatment compared with the post-treatment (p<0.001) and the control groups. The SF SOD activity of patients before the commencement of the treatment was lower than the values in the controls and post-treatment (p<0.001). There is no significant correlation between SF NO and SOD levels and the radiographic changes of the OA knee according to Kellgren-Lawrence grading (p>0.05). Also, the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC) pain scores and physical function scores were gradually improved. These findings made us think that SF NO was a potent mediator in cartilage damage in OA, whereas SOD was an antioxidant mediator in the same process. Exogenous HA injections might reduce the NO levels and increase SOD activities in synovial fluid. These effects also do not seem to be dependent on the radiographic grading of the OA knee. More comprehensive studies are needed to clarify a possible clinical significance of this topic, and we suggest that this is an important area for further research into new treatment options.

Hyaluronan in human acute and chronic dermal wounds

There is growing interest in the relationship of hyaluronan and inflammation in a number of physiologic processes including wound healing. The objective of this study was to make a quantitative comparison of inflammation and hyaluronan expression in human normal healing open wounds and in pressure ulcers. Using an open dermal wound model, myeloperoxidase activity was found to peak at day 3. Hyaluronan levels showed a bimodal distribution with transient peaks occurring on days 1 and 7. Mean levels of myeloperoxidase activity in pressure ulcers were significantly higher than at any time in the acute wounds, whereas hyaluronan levels were significantly lower than at any time in the acute wounds. Levels of hyaluronidase activity increased slightly in the postwound period. Hyaluronidase activity in pressure ulcers was significantly elevated compared with the acute wounds. These results suggest a role for increased enzymatic degradation of hyaluronan as a function of inflammation during wound repair. This is the first reported quantitative examination of hyaluronan expression in human acute dermal wounds and in chronic pressure ulcers.

TNF-alpha, IFN-gamma, and IL-1beta modulate hyaluronan synthase expression in human skin fibroblasts: synergistic effect by concomital treatment with FeSO4 plus ascorbate

Several reports have shown that a number of cytokines such as tumor necrosis-alpha (TNF-alpha), interferon-gamma (IFN-gamma), and interleukin-beta (IL-1beta) are capable to induce hyaluronan sinthases (HASs) mRNA expression in different cell culture types. The obvious consequence of this stimulation is a marked increment in hyaluronan (HA) production. It has been also reported that oxidative stress, by itself, may increase HA levels. The aim of this study was to evaluate how TNF-alpha, IFN-gamma,IL-1beta, and exposition to oxidative stress may modulate HAS activities in normal human skin fibroblasts. Moreover, the effects on HAS mRNA expression of the concomitant treatment with cytokines and oxidants, and the HA concentrations after treatments, were studied. TNF-alpha, IFN-gamma, and IL-1beta were added to normal or/and exposed to FeSO(4) plus ascorbate fibroblast cultures and HAS1, HAS2 and HAS3 mRNA content, by PCR-real time, was assayed 3,h later. HA levels were also evaluated after 24,h incubation. The treatment of fibroblasts with cytokines up-regulated HASs gene expression and increased HA production. IL-1beta induced HAS mRNA expression and HA production more efficiently than TNF-alpha and IFN-gamma. The exposition of the fibroblasts with the oxidant system markedly increased HAS activities while slightly HA production. The concomitant treatment of cells with the cytokines and the oxidant was able to further enhance, in a dose dependent way, with synergistic effect on HAS mRNA expression. On the contrary HA levels resulted unaffected by the concomitant treatment, and resemble those obtained with the exposure to FeSO(4) plus ascorbate only. This lack in HA production could be due to the deleterious action of free radicals on the HA synthesis.

The efficacy of topical hyaluronic acid in the management of recurrent aphthous ulceration

BACKGROUND

The aim of this study was to evaluate the efficacy of a topical hyaluronic acid (HA) preparation (0.2%) in the management of recurrent aphthous ulceration (RAU).

METHODS

One hundred and twenty patients with RAU participated in a randomized, placebo controlled, double-blind trial to evaluate the efficacy of the topical HA and preparation. Outcome measures include soreness relief on immediate application (recorded over 60 min). Thereafter, patients completed a log diary recording soreness from the ulcers, occurrence of new ulcers and ulcer duration.

RESULTS

Both topical HA and placebo resulted in a significant reduction in ulcer soreness following immediate application (P = 0.0004). Throughout the rest of the investigation period, there was no significant differences (P > 0.05) between the treatments for reducing soreness. Patients treated with topical HA recorded few ulcers on day 5 of the investigation than those treated with placebo (P < 0.001). Likewise, the occurrence of new ulcers was lower in the HA treated group on day 4 when compared with placebo (P = 0.047).

CONCLUSION

Topical HA (0.2%) may be of benefit in the management of RAU. Immediate reduction of symptoms appears to be a barrier effect.

Degradative action of reactive oxygen species on hyaluronan

Many human diseases are associated with harmful action of reactive oxygen species (ROS). These species are involved in the degradation of essential tissue or related components. One of such components is synovial fluid that contains a high-molecular-weight polymer--hyaluronan (HA). Uninhibited and/or inhibited hyaluronan degradation by the action of various ROS has been studied in many in vitro models. In these studies, the change of the molecular weight of HA or a related parameter, such as HA solution viscosity, has been used as a marker of inflicted damage. The aim of the presented review is to briefly summarize the available data. Their correct interpretation could contribute to the implementation of modern methods of evaluation of the antioxidative capacity of natural and synthetic substances and prospective drugs--potential inflammatory disease modifying agents. Another focus of this review is to evaluate briefly the impact of different available analytical techniques currently used to investigate the structure of native high-molecular-weight hyaluronan and/or of its fragments.

The aggregation of pig articular chondrocyte and synthesis of extracellular matrix by a lactose-modified chitosan

A reductive amination reaction (N-alkylation) obtained exploiting the aldheyde group of lactose and the amino group of the glucosamine residues of chitosan (d.a. 89%) afforded a highly soluble engineered polysaccharide (chitlac) for a potential application in the repair of the articular cartilage. Chitosan derivatives with 9% and 64% of side chain groups introduced have been prepared and characterized by means of potentiometric titration, (1)H-NMR and intrinsic viscosity. Both polymers, with respect to the unmodified chitosan, induce cell aggregation when in contact with a primary culture of pig chondrocytes, leading to the formation of nodules of considerable dimensions (up to 0.5-1 mm in diameter). The nodules obtained from chondrocytes treated with chitlac with the higher degree of substitution have been studied by means of optical and electron microscopy (SEM, TEM) and the production of glycosaminoglycans (GAGs) and collagen has been measured by means of colorimetric assays. The chondro-specificity of GAG and collagen was determined by RT-PCR. The results show that the lactose-modified chitosan is non-toxic and stimulates the production of aggrecan and type II collagen.

Reduction of DNA fragmentation and hydroxyl radical production by hyaluronic acid and chondroitin-4-sulphate in iron plus ascorbate-induced oxidative stress in fibroblast cultures

Glycosaminoglycans (GAGs), components of extracellular matrix, are thought to play important roles in cell proliferation and differentiation in the repair process of injured tissue. Oxidative stress is one of the most frequent causes of tissue and cell injury and the consequent lipid peroxidation is the main manifestation of free radical damage. It has been found to play an important role in the evolution of cell death. Since several reports have shown that hyaluronic acid (HYA) and chondroitin-4-sulphate (C4S) are able to inhibit lipid peroxidation during oxidative stress, We investigated the antioxidant capacity of these GAGs in reducing oxidative damage in fibroblast cultures. Free radicals production was induced by the oxidizing system employing iron (Fe2+) plus ascorbate. We evaluated cell death, membrane lipid peroxidation, DNA damage, protein oxidation, hydroxyl radical (OH*) generation and endogenous antioxidant depletion in human skin fibroblast cultures. The exposition of fibroblasts to FeSO4 and ascorbate caused inhibition of cell growth and cell death, increased OH* production determined by the aromatic trap method; furthermore it caused DNA strand breaks and protein oxidation as shown by the DNA fragments analysis and protein carbonyl content, respectively. Moreover, it enhanced lipid peroxidation evaluated by the analysis of conjugated dienes (CD) and decreased antioxidant defenses assayed by means of measurement of superoxide dismutase (SOD) and catalase (CAT) activities. When fibroblasts were treated with two different doses of HYA or C4S a protective effect, following oxidative stress induction, was shown. In fact these GAGs were able to limit cell death, reduced DNA fragmentation and protein oxidation, decreased OH* generation, inhibited lipid peroxidation and improved antioxidant defenses. Our results confirm the antioxidant activity of HYA and C4S and this could represent a useful step in the understanding of the exact role played by GAGs in living organisms.

Effects of Hyaluronic Acid on the Polymorphonuclear Leukocyte (PMN) Release of Active Oxygen and Protection of Bovine Corneal Endothelial Cells from Activated PMNs

The goal of this study was to evaluate the function of hyaluronic acid (HA) on the active oxygen release from polymorphonuclear leukocytes (PMNs) and the protective effect of bovine corneal endothelial cells (BCEC) from activated PMNs. We used HA with three different molecular weights (MW 700,000, 2,000,000, and 4,000,000) and five different concentrations (0, 0.1, 1, 2, and 3 mg/ml). We evaluated the amount of released superoxide from activated PMNs by using dismutase-inhibitable ferricytochrome C reduction. To compare the property and protective effect of HA with those of other viscoelastic substances, we used the same concentration of methylcellulose. HA suppressed superoxide release from PMNs and protected BCEC from activated PMNs in a dose-dependent, rather than a molecular weight-dependent, manner. The effect of HA reached almost a plateau at concentration above 2 mg/ml. However, methylcellulose, another viscoelastic substance, showed a similar effect. Therefore, it seems that the suppression of superoxide released from PMNs is not a property that is unique to HA, but is a general property of viscoelastic substances. Our results indicate that the action mechanism of HA proceeds not only through cell surface HA-receptor. We think that HA also acts as a physical barrier and/or a scavenger of superoxide.

Pathophysiology of intra-abdominal adhesion and abscess formation, and the effect of hyaluronan

BACKGROUND

Intra-abdominal adhesions and abscesses cause significant morbidity and mortality. The formation of fibrin in the abdominal cavity is a common pathophysiological pathway for both. The aim of this review was to investigate the pathophysiology of intra-abdominal adhesions and abscesses, and to explore the possible sites of action of hyaluronan.

METHODS

Data were reviewed from the literature using the Medline database.

RESULTS

Both surgery and peritonitis disturb the equilibrium between coagulation and fibrinolysis in the abdominal cavity in favour of the coagulation system. Hyaluronan-based agents reduce adhesion formation after surgery. Moreover, hyaluronan solution reduces abscess formation in experimental peritonitis. Possible mechanisms of action include mechanical separation of wound surfaces, improvement of peritoneal healing, modulation of the inflammatory response and enhanced fibrinolysis.

CONCLUSION

Diminished fibrin degradation is a common pathway for the formation of adhesions and abscesses. The potential of hyaluronan-based agents to reduce intra-abdominal adhesions and abscesses in abdominal surgery and sepsis is a promising new concept. Elucidating the mechanisms involved and the clinical application of hyaluronan in peritonitis are challenges for future research.

Comparison of the antioxidant properties of wound dressing materials--carboxymethylcellulose, hyaluronan benzyl ester and hyaluronan, towards polymorphonuclear leukocyte-derived reactive oxygen species

In chronic wounds, factors are released which perpetuate inflammatory processes, including polymorphonuclear leukocyte (PMN)-derived reactive oxygen species (ROS), such as superoxide radical (O(2)*-) and hydroxyl radical (*OH) species. The glycosaminoglycan, hyaluronan, has established antioxidant properties towards ROS, although the antioxidant potential of wound dressing biomaterials, such as 75% benzyl esterified hyaluronan (BEHA) and carboxymethylcellulose (CMCH), are less characterised. This study compared the antioxidant properties of high and low molecular weight hyaluronan (HMWT HA and LMWT HA), BEHA and CMCH towards ROS, generated by stimulated PMN in vitro. The antioxidant capacities of each biomaterial were assessed by their inhibition of O(2)*- -induced cytochrome C reduction, generated via PMN stimulation by phorbol myristyl acetate (PMA); and their inhibition of *OH-induced 2-deoxy-D-ribose degradation, generated by PMA stimulated PMN in the presence of a ferric chloride-EDTA chelate. All biomaterials, except LMWT HA, possessed dose-dependent antioxidant properties against O(2)*-, BEHA having greatest antioxidant potential, followed by HMWT HA and CMCH. HMWT HA exhibited the highest dose-dependent antioxidant properties towards *OH, followed by BEHA and CMCH. LMWT HA demonstrated no antioxidant properties towards *OH. These antioxidant activities, particularly towards O(2)*-, may be beneficial in removing the initial source of ROS necessary for the secondary formation of *OH, implicated as a causal factor for the extensive metabolic alterations observed in chronic wounds.

Comparative effect of intra-articular administration of hyaluronan and/or cortisone with evaluation of malondialdehyde on degenerative osteoarthritis of the rabbit's knee

Hyaluronan and cortisone have controversial and an important role in the healing of degenerative osteoarthritis. The purpose of the research was to compare individual and combined effects of hyaluronan and cortisone on the healing of degenerative osteoarthritis and to determine the serum malondialdehyde level as a lipid peroxidation marker. A rabbit model was used in which a degenerative osteoarthritis was created in the articular cartilage by resection of anterior cruciate ligament. The rabbits divided into three groups namely were injected with hyaluronan (group A) and cortisone (group B) at days 31, 38 and 45. Cortisone at day 31 and hyaluronan at days 38 and 45 were injected to the third group (group C). We obtained blood samples from each rabbit to determine the malondialdehyde levels at days 1, 30, and 52. At day 52, 21 rabbits were sacrificed. In biopsies obtained from treated and untreated knees articular cartilage degeneration was examined by light microscopy. Histopathologically the healing rate was significantly higher in group C than the other groups. Degeneration decreased 72% in group A, 52% in group B and 88% in group C at day 22. Malondialdehyde levels were 2.056 +/- 0.37 in the control group, 1.94 +/- 0.54 in group A, 1.98 +/- 0.37 in group B and 1.55 +/- 0.41 in goup C. The malondialdehyde levels of group A and B were less than the control group (statistically insignificant, p > 0.05). But, there were statistically significant values between control group and group C (p < 0.05). The results showed that the combination of cortisone and hyaluronan is the most effective in the treatment of cartilage degeneration in the course of the ostearthritis and the malondialdehyde levels are correlated with the severity of degeneration.

Outcomes of hyaluronan therapy in diabetic foot wounds

The purpose of this study was to evaluate outcomes of persons with neuropathic diabetic foot wounds treated with a hyaluronan-containing dressing. Data were abstracted for 36 patients with diabetes, 72.2% male, aged 60.0+/-10.7 years and a mean glycated hemoglobin (HbA(1c)) of 9.5+/-2.5% presenting for care at two large, multidisciplinary wound care centers. All patients received surgical debridement for their diabetic foot wounds and were placed on therapy consisting of hyaluronan dressing (Hyalofill, Convatec, USA) with dressing changes taking place every other day. Outcomes evaluated included time to complete wound closure and proportion of patients achieving wound closure in 20 weeks. Hyalofill therapy was used until the wound bed achieved 100% granulation tissue. Therapy was then followed by a moisture-retentive dressing until complete epithelialization. In total, 75.0% of wounds measuring a mean 2.2+/-2.2 cm(2) healed in the 20-week evaluation period. Of those that healed in this period, healing took place in a mean 10.0+/-4.8 weeks. The average duration of Hyalofill therapy in all patients was 8.6+/-4.2 weeks. Deeper (UT Grade 2A) wounds were over 15 times less likely to heal than superficial (1A) wounds (94.7 vs. 52.9%, Odds Ratio=15.9, 95% Confidence Interval=1.7-142.8, P=0.006). We conclude that a regimen consisting of moist wound healing using hyaluronan-containing dressings may be a useful adjunct to appropriate diabetic foot ulcer care. We await the completion of a multicenter randomized controlled trial in this area to either support or refute this initial assessment.

Intra-articular hyaluronan (hyaluronic acid) and hylans for the treatment of osteoarthritis: mechanisms of action

Although the predominant mechanism of intra-articular hyaluronan (hyaluronic acid) (HA) and hylans for the treatment of pain associated with knee osteoarthritis (OA) is unknown, in vivo, in vitro, and clinical studies demonstrate various physiological effects of exogenous HA. HA can reduce nerve impulses and nerve sensitivity associated with the pain of OA. In experimental OA, this glycosaminoglycan has protective effects on cartilage, which may be mediated by its molecular and cellular effects observed in vitro. Exogenous HA enhances chondrocyte HA and proteoglycan synthesis, reduces the production and activity of proinflammatory mediators and matrix metalloproteinases, and alters the behavior of immune cells. Many of the physiological effects of exogenous HA may be a function of its molecular weight. Several physiological effects probably contribute to the mechanisms by which HA and hylans exert their clinical effects in knee OA.

Comparison of the antioxidant properties of HYAFF-11p75, AQUACEL and hyaluronan towards reactive oxygen species in vitro

In chronic wounds, a number of host factors are released which perpetuate the inflammatory process, including polymorphonuclear leukocyte (PMN)-derived reactive oxygen species (ROS), such as superoxide radical (O2*-) and hydroxyl radical (*OH) species. The glycosaminoglycan. hyaluronan, has been shown to act as an antioxidant towards ROS, although the potential for biomaterials, such as HYAFF -11p75 (the 75% benzyl ester of hyaluronan) and AQUACEL (carboxymethylcellulose), to act in this manner has yet to be elucidated. This study compared the antioxidant properties of high and low molecular weight hyaluronan (HMWT HA and LMWT HA), HYAFF -11p75, AQUACEL and an AQUACEL /hyaluronan composite (AQUACEL /HA) against O2*- and *OH. The antioxidant capacities of each material were assessed by their ability to inhibit cytochrome C reduction by O2*- fluxes, generated via the oxidation of hypoxanthine by xanthine oxidase, and their inhibition of 2-deoxy-D-ribose degradation by *OH fluxes, generated by the reaction of hydrogen peroxide (H2O2) and iron (Fe2+). All materials studied possessed dose dependent antioxidant properties towards O2*-, with HYAFF 11p75 having the greatest antioxidant potential towards these species, followed by AQUACEL, HMWT HA, AQUACEL /HA and LMWT HA. Only HMWT HA exhibited dose dependent antioxidant properties towards *OH at the fluxes examined. Gas chromatography/mass spectrometry analysis implied that ester bonds between the hyaluronan backbone and benzyl groups of HYAFF -11p75 are highly susceptible to O2*- hydrolysis, with the de-esterified benzyl alcohol being rapidly degraded in the presence of *OH. This data supports the hypothesis that HYAFF -11p75 has greater antioxidant capacity towards O2*-, due to the esterified benzyl groups providing alternative sites for O2*- attack other than the hyaluronan backbone of HYAFF -11p75 itself and explains the inability of HYAFF -11p75 to scavenge *OH, due to benzyl alcohol degradation by *OH. The antioxidant activities of these biomaterials, particularly HYAFF -11p75 and AQUACEL, towards O2*- could be beneficial, as the scavenging of PMN-derived O2*- may remove initial sources of O2*- and further prevent the secondary formation of *OH. These ROS are thought to be a primary causal factor for the extensive degradation and metabolic alterations observed in chronic wounds.

Expression of TGF-betas and their receptors is differentially modulated by reactive oxygen species and nitric oxide in human articular chondrocytes

OBJECTIVES

To study the effects exerted by two antioxidants, N-monomethyl-L-arginine (L-NMMA), as an inhibitor of nitric oxide (NO) synthesis, and N-acetylcysteine (NAC), a reactive oxygen species (ROS) scavenger, on the expression of the major growth factor involved in cartilage repair, TGF-beta, under the three isoforms beta1, beta2 and beta3, and the receptors I and II of this factor, using lipopolysaccharide (LPS)-treated human chondrocytes in culture.

METHODS

Suspension cultures of human chondrocytes derived from the knee of osteoarthritic patients were treated for 48 h with lipopolysaccharide (LPS) (10 microg/ml), L-NMMA (0.5 mM) or NAC (1 mM). Nitrite levels were assayed on the culture media using the Griess spectrophotometric method. After total RNA extraction, the expression of inducible NO synthase (iNOS), TGF-beta1, TGF-beta2, TGF-beta3, TGF-beta receptors I and II, was determined by semi-quantitative polymerase chain-reaction (RT-PCR).

RESULTS

LPS induced a dramatic increase of both NO production and iNOS mRNA level. The addition of L-NMMA (0.5 mM) abolished NO production without affecting iNOS mRNA levels. In contrast NAC (1 mM) strongly synergized with LPS to stimulate NO synthesis. LPS treatment did not significantly alter TGF-beta1 expression whereas L-NMMA inhibited its production. TGF-beta2 mRNA level was decreased by LPS and was not changed in the presence of L-NMMA. On the other hand, NAC was capable of counteracting the LPS-induced inhibition of TGF-beta2 expression. TGFbeta3 mRNA level was markedly reduced by LPS alone, or with both L-NMMA and NAC. Finally, the expression of TGF-betaRI was slightly increased in the presence of combined LPS and L-NMMA or NAC whereas that of TGFbeta-RII was reduced in the same conditions.

CONCLUSIONS

The modulation of TGF-beta system was found to be differentially controlled by NO and ROS productions. Indeed, the control exerted on TGF-beta expression varied according to the isoform: TGF-beta1 mRNA level depends on NO whereas that of TGF-beta2 is regulated by ROS and TGF-beta3 seems to be unaffected by both of them. The expression of TGF-beta receptors appeared to be modulated by NO and ROS levels. The relevance of the present findings to osteoarthritis (OA) physiopathology and the potential use of antioxidant therapy to treat this disease are discussed.

Glucosamine modulates IL-1-induced activation of rat chondrocytes at a receptor level, and by inhibiting the NF-kappa B pathway

We recently reported that glucosamine reversed the decrease in proteoglycan synthesis and in UDP-glucuronosyltransferase I mRNA expression induced by interleukin-1 beta (IL-1 beta) [Arthritis Rheum. 44 (2001) 351-360]. In the present work, we show that glucosamine does not exert the same effects when chondrocytes were stimulated with reactive oxygen species (ROS). In order to better understand its mechanism of action, we determined if glucosamine could prevent the binding of IL-1 beta to its cellular receptors or could interfere with its signaling pathway at a post-receptor level. Addition of glucosamine to rat chondrocytes treated with IL-1 beta or with ROS decreased the activation of the nuclear factor kappa B, but not the activator protein-1. After treatment with IL-1 beta, glucosamine increased the expression of mRNA encoding the type II IL-1 beta receptor. These results emphasize the potential role of two regulating proteins of the IL-1 beta signaling pathway that could account for the beneficial effect of glucosamine in osteoarthritis.

Polyanionic polysaccharides reduce intra-abdominal adhesion and abscess formation in a rat peritonitis model

BACKGROUND

Intra-abdominal infection is complicated by adhesion and abscess formation. We have assessed the adhesion- and abscess-reducing capacity of various solution volumes and concentrations of two polyanionic polysaccharides, hyaluronan (HA) and carboxymethylcellulose (CMC), in a rat peritonitis model.

STUDY DESIGN

In 192 male Wistar rats a bacterial peritonitis was induced using cecal ligation and puncture. After 24 h the abdomen was reopened and the ligated cecum resected. Animals were randomized into three control groups, nine groups treated with various solution volumes (1 to 8 ml) containing different HA concentrations, and four groups treated with 1.7% CMC solution. Rats were killed at day 7, postoperatively, and adhesions were scored at five abdominal sites on a scale from 0 to 4. The presence and size of intra-abdominal abscesses were noted.

RESULTS

Fifty-four rats (28%) prematurely died. There was no significant difference in mortality between treatment groups and controls. Treatment with CMC (P < 0.001) and low (0.2 and 0.4%) concentrations of HA (P < 0.005) significantly reduced intra-abdominal adhesion formation. High volumes of 0.2 and 0.4% HA were most effective (P = 0.01). The effect of CMC was volume independent. The incidence of abdominal abscesses was also significantly reduced by treatment with either CMC (P < 0.001) or low concentrations of HA (P < 0.001). With regard to abscess formation the effect was independent of the volume administered for HA, while low volumes of CMC were most effective (P < 0.005).

CONCLUSION

Intraperitoneal treatment with either CMC or low-viscosity HA solution reduced intra-abdominal adhesion and abscess formation in a rat peritonitis model. The volume-induced reduction in adhesion formation suggests a hydroflotation effect of HA solution.

Evidence supporting an increased presence of reactive oxygen species in the diseased equine joint

Reactive oxygen species (ROS) are capable of degrading many components of the joint in the presence of insufficient antioxidant defences, and as a result have been implicated in the pathogenesis of joint disease in horses. However, to our knowledge, evidence of ROS occurring in diseased joints of horses has not been reported. The objective of this experiment was to compare differences in synovial fluid protein carbonyl content (as a marker of oxidative modification of synovial fluid proteins by ROS) and the antioxidant status of synovial fluid between clinically normal and diseased equine joints. Synovial fluid was collected from the metacarpophalangeal, metatarsophalangeal, carpal and tarsal joints of 4 horses, age 2-5 years, as controls, and from diseased joints (metacarpophalangeal, metatarsophalangeal, carpal, tarsal and/or femoropatellar) of 61 horses, age 2-5 years. Synovial fluid protein carbonyl content was higher (P<0.01) in diseased joints as compared to controls. Antioxidant status of synovial fluid from diseased joints was higher, but not significantly, than that of controls (P = 0.0595). These findings require further study to determine their contribution to the overall disease process.

Purine requirements for the expression of Cape buffalo serum trypanocidal activity

Cape buffalo serum contains xanthine oxidase which generates trypanocidal H(2)O(2) during the catabolism of hypoxanthine and xanthine. The present studies show that xanthine oxidase-dependent trypanocidal activity in Cape buffalo serum was also elicited by purine nucleotides, nucleosides, and bases even though xanthine oxidase did not catabolize those purines. The paradox was explained in part, by the presence in serum of purine nucleoside phosphorylase and adenosine deaminase, that, together with xanthine oxidase, catabolized adenosine, inosine, hypoxanthine, and xanthine to uric acid yielding trypanocidal H(2)O(2). In addition, purine catabolism by trypanosomes provided substrates for serum xanthine oxidase and was implicated in the triggering of xanthine oxidase-dependent trypanocidal activity by purines that were not directly catabolized to uric acid in Cape buffalo serum, namely guanosine, guanine, adenine monophosphate, guanosine diphosphate, adenosine 3':5-cyclic monophosphate, and 1-methylinosine. The concentrations of guanosine and guanine that elicited xanthine oxidase-dependent trypanocidal activity were 30-270-fold lower than those of other purines requiring trypanosome-processing which suggests differential processing by the parasites.

Towards a molecular understanding of arthritis

Several different agents including free radicals, oxidizing compounds and proteases are believed to play a role in the onset of arthritis. The evidence and underlying chemistry presently available for each destructive agent are presented.

Functions of hyaluronan in wound repair

Hyaluronan is a major carbohydrate component of the extracellular matrix and can be found in skin, joints, eyes and most other organs and tissues. It has a simple, repeated disaccharide linear copolymer structure that is completely conserved throughout a large span of the evolutionary tree, indicating a fundamental biological importance. Amongst extracellular matrix molecules, it has unique hygroscopic, rheological and viscoelastic properties. Hyaluronan binds to many other extracellular matrix molecules, binds specifically to cell bodies through cell surface receptors, and has a unique mode of synthesis in which the molecule is extruded immediately into the extracellular space upon formation. Through its complex interactions with matrix components and cells, hyaluronan has multifaceted roles in biology utilizing both its physicochemical and biological properties. These biological roles range from a purely structural function in the extracellular matrix to developmental regulation through effects of cellular behavior via control of the tissue macro- and microenvironments, as well as through direct receptor mediated effects on gene expression. Hyaluronan is also thought to have important biological roles in skin wound healing, by virtue of its presence in high amounts in skin. Hyaluronan content in skin is further elevated transiently in granulation tissue during the wound healing process. In this review, the general physicochemical and biological properties of hyaluronan, and how these properties may be utilized in the various processes of wound healing: inflammation, granulation and reepithelization, are presented.

Sensitivity of chondrocytes of growing cartilage to reactive oxygen species

Vascular invasion of calcified cartilage, during endochondral ossification, is initiated and sustained by invasive cells (endothelial cells and macrophages) which degrade the tissue by releasing lytic enzymes. Concurrently, reactive oxygen species (ROS) are also released by these cells and we hypothesize that ROS also contribute to the degradation of the tissue. As a preliminary approach to this problem, the antioxidant activities and the effect of ROS on hypertrophic cartilage and chondrocytes (HCs) were investigated. Compared to resting or articular chondrocytes, HCs exhibited higher catalase but lower SOD specific activities and lower PHGPx concentration, thus revealing a defence activity specific against H2O2. Moreover, dose-dependent depletion of ATP occurred after few minutes of exposure to ROS, and a long-term treatment (16 h incubation with ROS) promoted the release of LDH activity and a significant variation of the poly- to mono-unsaturated fatty acid ratio. Finally, the incubation of HCs with low ROS doses induced the release of sedimentable alkaline phosphatase activity (matrix vesicles). How the obtained results fit the in vivo occurring events is discussed.

Factors related to degradation of articular cartilage in osteoarthritis: a review

OBJECTIVES

Osteoarthritis (OA) is a common joint deterioration initiated by multiple factors. To better understand related factors in the development of this disease, we focused on the mechanical stress loaded on articular cartilage.

MATERIALS AND METHODS

The anterior cruciate ligaments of rabbit knee joints were transected, and expression of protein kinase C (PKC) examined immunohistochemically. The PKC activator 12-o-tetradecanoyl-phorbol-13-acetate (TPA) was then administered intraarticularly. To determine the involvement of gas mediators, a cartilage defect was made on the medical femoral condyle of rabbit knee joints. Hydrostatic pressure was loaded on the cartilage taken from the surrounding defects, and levels of superoxide anion and nitric oxide (NO) were measured. Bovine chondrocytes were subjected to cyclic mechanical stretch using a Flexercell Strain Instrument. Proteoglycan synthesis and PKC activity were measured. Expression of matrix metalloproteinase (MMP)-3 and tissue inhibitor of metalloproteinase (TIMP)-1 in articular cartilages obtained from OA patients were examined using Northern blots.

RESULTS

Chondrocytes from experimentally induced OA were stained positively with anti-alpha-PKC antibody. Intraarticular administration of TPA prevented the development of OA changes. Cyclic tensile stretch loaded on chondrocytes decreased proteoglycan synthesis and PKC activity. Thus, PKC is involved in the stress-mediated degradation of articular cartilage. Cartilage defects led to degradation of surrounding cartilage and to enhanced superoxide anion and NO synthesis. We also noted increased and decreased expressions of MMP-3 and TIMP-1 mRNA in human OA cartilage, respectively.

CONCLUSION

PKC, gas mediators (superoxide anion, NO), and proteinases are all involved in OA.

The trypanocidal Cape buffalo serum protein is xanthine oxidase

Plasma and serum from Cape buffalo (Syncerus caffer) kill bloodstream stages of all species of African trypanosomes in vitro. The trypanocidal serum component was isolated by sequential chromatography on hydroxylapatite, protein A-G, Mono Q, and Superose 12. The purified trypanocidal protein had a molecular mass of 150 kDa, and activity correlated with the presence of a 146-kDa polypeptide detected upon reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Amino acid sequences of three peptide fragments of the 146-kDa reduced polypeptide, ligand affinity and immunoaffinity chromatography of the native protein, and sensitivity to pharmacological inhibitors, identified the trypanocidal material as xanthine oxidase (EC 1.1.3.22). Trypanocidal activity resulted in the inhibition of trypanosome glycolysis and was due to H2O2 produced during catabolism of extracellular xanthine and hypoxanthine by the purine catabolic enzyme.

Antioxidant effects of hyaluronan and its alpha-methyl-prednisolone derivative in chondrocyte and cartilage cultures

OBJECTIVE

To compare hyaluronan and its alpha-methyl prednisolone derivative (HYC-141) with respect to their potential to directly cause tissue damage and to protect tissues from attack by reactive oxygen species.

METHODS

Cartilage samples and chondrocytes were isolated from 15-day chick embryos and were exposed to enzyme-based and activated inflammatory cell-free radical generating systems in the presence of varying concentrations of alpha-methyl prednisolone, hyaluronan, and HYC-141. Tissue and cell vitality was measured by determining the incorporation of radioactive sulphate into newly synthesized glycosaminoglycans.

RESULTS

Only alpha-methyl prednisolone caused a significant decrease in biosynthetic activity. All the tested substances were capable, to some extent, of protecting tissues and cells from damage by reactive oxygen species; HYC-141 demonstrated the greatest protective effect.

CONCLUSION

These data suggest that HYC-141 may possess certain advantages over the individual component molecules in the local treatment of arthropathies.