The fate of injected mucopolysac-charides

Hyaluronic acid and chondroitin sulfate (meth)acrylate-based hydrogels for tissue engineering: Synthesis, characteristics and pre-clinical evaluation

Hydrogels based on photocrosslinkable Hyaluronic Acid Methacrylate (HAMA) and Chondroitin Sulfate Methacrylate (CSMA) are presently under investigation for tissue engineering applications. HAMA and CSMA gels offer tunable characteristics such as tailorable mechanical properties, swelling characteristics, and enzymatic degradability. This review gives an overview of the scientific literature published regarding the pre-clinical development of covalently crosslinked hydrogels that (partially) are based on HAMA and/or CSMA. Throughout the review, recommendations for the next steps in clinical translation of hydrogels based on HAMA or CSMA are made and potential pitfalls are defined. Specifically, a myriad of different synthetic routes to obtain polymerizable hyaluronic acid and chondroitin sulfate derivatives are described. The effects of important parameters such as degree of (meth)acrylation and molecular weight of the synthesized polymers on the formed hydrogels are discussed and useful analytical techniques for their characterization are summarized. Furthermore, the characteristics of the formed hydrogels including their enzymatic degradability are discussed. Finally, a summary of several recent applications of these hydrogels in applied fields such as cartilage and cardiac regeneration and advanced tissue modelling is presented.

Biomarker responses correlate with antibody status in mucopolysaccharidosis type I patients on long-term enzyme replacement therapy

BACKGROUND

Antibody formation can interfere with effects of enzyme replacement therapy (ERT) in lysosomal storage diseases. Biomarkers are used as surrogate marker for disease burden in MPS I, but large systematic studies evaluating the response of biomarkers to ERT are lacking. We, for the first time, investigated the response of a large panel of biomarkers to long term ERT in MPS I patients and correlate these responses with antibody formation and antibody mediated cellular uptake inhibition.

METHODS

A total of 428 blood and urine samples were collected during long-term ERT in 24 MPS I patients and an extensive set of biomarkers was analyzed, including heparan sulfate (HS) and dermatan sulfate (DS) derived disaccharides; total urinary GAGs (DMBu); urinary DS:CS ratio and serum heparin co-factor II thrombin levels (HCII-T). IgG antibody titers and the effect of antibodies on cellular uptake of the enzyme were determined for 23 patients.

RESULTS

Median follow-up was 2.3 years. In blood, HS reached normal levels more frequently than DS (50% vs 12.5%, p=0.001), though normalization could take several years. DMBu normalized more rapidly than disaccharide levels in urine (p=0.02). Nineteen patients (83%) developed high antibody titers. Significant antibody-mediated inhibition of enzyme uptake was observed in 8 patients (35%), and this correlated strongly with a poorer biomarker response for HS and DS in blood and urine as well as for DMBu, DS:CS-ratio and HCII-T (all p<0.006).

CONCLUSIONS

This study shows that, despite a response of all studied biomarkers to initiation of ERT, some biomarkers were less responsive than others, suggesting residual disease activity. In addition, the correlation of cellular uptake inhibitory antibodies with a decreased biomarker response demonstrates a functional role of these antibodies which may have important clinical consequences.

Heparan sulfate derived disaccharides in plasma and total urinary excretion of glycosaminoglycans correlate with disease severity in Sanfilippo disease

BACKGROUND

Sanfilippo disease (Mucopolysaccharidosis III) is a neurodegenerative lysosomal disorder characterized by accumulation of the glycosaminoglycan heparan sulfate (HS). MPS III has a large phenotypic variability and early assessment of disease severity is difficult. We investigated the correlation between disease severity and the plasma concentration of HS (pHS, defined by the sum of the heparan sulfate derived disaccharides obtained after enzymatic digestion) and urinary total GAGs level (uGAGs, measured by the dimethylene blue test) in a cross-sectional cohort of 44 MPS III patients.

METHODS

Disease severity was established on the basis of the age of complete loss of independent walking and of full loss of speech in all patients. Hazard ratios (HR) were obtained with cox-regression analysis. In order to allow prediction of a severe phenotype based on a cut-off value for pHS, patients were divided in two groups (severely affected and less severely affected) based on predictive mutations or on the age of full loss of speech. Receiver operator characteristics (ROC) were obtained for pHS.

RESULTS

pHS and uGAGs were independently and linearly associated with an increased risk of speech loss with a HR of 1.8 (95 % CI 1.3-2.7) per 500 ng/ml increase of HS in plasma (p = 0.002), and a HR of 2.7 (95 % CI 1.6-4.4) per 10 mg/mmol creatinine increase of uGAGs (p < 0.001). pHS and uGAGS were less strongly associated with loss of walking. The area under the ROC curve for pHS was 0.85, indicating good discrimination.

CONCLUSION

pHS and uGAGs may be useful biomarkers for prediction of severity in MPS III.

Urine glycosaminoglycans in children with transient hip synovitis and Perthes disease

Urine glycosaminoglycan concentrations were measured in 24-h urine samples collected from ninety children (30 children with Perthes disease, 30 with transient synovitis and 30 control participants). Significantly decreased levels of urine glycosaminoglycans were found in Perthes disease patients compared with those with transient synovitis and the control group.

Serum N-acetyl-beta-D-gulucosaminidase activity increases in association with insulin resistance in patients with coronary artery disease

N-acetyl-beta-D-glucosaminidase (NAG) is released from lysosomes, but the clinical significance of its serum activity in the pathogenesis of coronary artery disease has not been well understood. We measured serum NAG activity by a colorimetric method in consecutive 168 patients suspected of having coronary artery disease who underwent diagnostic coronary angiography. In addition, we evaluated the relationship between the activity and severity of coronary artery disease, as well as various coronary risk factors. Serum NAG activity was higher in the multi-vessel disease group than in the no stenotic lesion group (9.2+/-2.3 vs. 7.8+/-1.8 U/l, P<0.01) and in the single-vessel disease group (vs. 8.2+/-2.2 U/l, P<0.05). In all patients, Gensini score was closely correlated with the serum NAG activity (r = 0.39, P<0.001). Multiple regression analysis showed that serum NAG activity was correlated with plasma insulin level (r = 0.49, P<0.01), but not correlated with other coronary risk factors. In 126 patients without apparent diabetes mellitus, serum NAG was also correlated with plasma insulin level (r = 0.37, P<0.01) and additionally with insulin resistanc determined by homeostasis model assessment (r = 0.47, P<0.01). Our results suggested that serum NAG activity correlates with the severity of coronary artery disease in relation to plasma insulin level and insulin resistance, and thus can be an indicator of coronary artery disease based upon abnormalities of glucose metabolism.

Measurement of glycosaminoglycans and keratan sulphate in canine arthropathies

Glycosaminoglycans (GAG) and keratan sulphate (KS) were measured in sera and synovial fluids from dogs with either osteoarthritis (OA) or rupture of the cranial cruciate ligament (CCL) and normal dogs. The dogs with OA had higher synovial fluid GAG levels (P < 0.002) and serum KS (P < 0.03) compared to the normal dogs. No significant differences in serum GAG were found in either group. In both OA and rupture of the CCL, GAG levels were increased in the synovial fluid from the affected joint compared with the clinically normal (inactive) contralateral joint. Neither GAG nor KS measurements correlated with serum and synovial fluid antibodies to collagen type II, synovial fluid white cell count or age of dog. It is unlikely that the measurement of these cartilage breakdown products is of value for diagnostic or prognostic use in canine arthropathies.

Plasma glycosaminoglycans in endocrine ophthalmopathy

With evidence on the important role of glycosaminoglycans (GAG) in the pathogenesis of endocrine ophthalmopathy (EO) having accumulated, the present study focused on the biochemical assessment of plasma GAG content in 37 EO patients as compared to 20 controls. Glycosaminoglycans were isolated from plasma samples by protein elimination, dialysis, and precipitation with ethanol and cetylpyridinium chloride. Patients (9.71, 5.09, 15.09 mg/100 ml; median, 25th, 75th percentile) exhibited significantly (p = 0.0021) higher plasma GAG levels than controls (4.6, 3.38, 6.8 mg/100 ml). Plasma GAG content was unrelated to age, sex, or antithyroid treatment. However, an even higher level of significance (p = 0.0001) was reached when discriminating between untreated patients with EO of recent onset (14.16, 10.35, 15.51 mg/100 ml) and controls. By contrast, steroid therapy of EO led to values (3.82, 1.85, 6.52 mg/100 ml) indistinguishable from those of the controls. Further statistical analysis of the results, based on a specificity of 95% for the control group, revealed a sensitivity of 91% for patients with untreated EO of recent onset, and a specificity of 100% for patients receiving steroid therapy. In comparison, plasma GAG content was determined in 8 untreated and in 6 treated EO patients by a second method already published. All untreated patients exhibited high GAG levels (median 2.23 mg/100 ml) whereas in treated EO patients normal plasma GAG values (0.17-0.34 mg/100 ml) were found. Follow-up determination of plasma GAG content in 7 patients undergoing steroid treatment unveiled a marked decrease of initially elevated values. These findings correlated well with clinical improvement of thyroid eye disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of glycosaminoglycans in human serum after oral administration of chondroitin sulfate

Chondroitin sulfate was administered orally to six healthy volunteers, six patients with rheumatoid arthritis and six patients with osteoarthritis. Blood was collected at intervals before and after treatment and the glycosaminoglycan concentration was analyzed in serum using a sensitive assay based on the metachromatic reaction with 1,9-dimethylmethylene blue. The glycosaminoglycan concentration in serum before and after ingestion of chondroitin sulfate was statistically unchanged in all of the subjects studied. We suggest that chondroprotection by orally administered chondroitin sulfate is a biologically and pharmacologically unfounded theory. Any possible benefit to osteoarthritic patients after ingestion of chondroitin sulfate should be sought at the gastrointestinal rather than at the plasmatic or articular cartilage level.

Glycosaminoglycans in thyroid-associated ophthalmopathy

Glycosaminoglycan (GAG) accumulation in the retrobulbar space of patients with thyroid-associated ophthalmopathy (TAO) has been documented in a number of immunohistochemical studies. In order to gain further insight into possible immunopathogenic mechanisms, the influence of humoral immunity on retrobulbar fibroblasts (RF) as GAG producing cells as well as on GAGs themselves was investigated. The effect of lymphocytes on hyaluronic acid (HA) synthesis of RF as well as in turn the influence of RF on lymphocytes were evaluated. In search of methods which would facilitate management of patients with TAO and allow assessment of disease activity, GAGs were determined in both urine and plasma. Immunoglobulin G (IgG) of patients with TAO were found to markedly stimulate the 3H-GAG secretion of RF. Patients with TAO exhibited significantly greater antibody values directed against HA than controls. Preliminary results concerning the influence of lymphocytes on RF indicate a tendency for patients' lymphocytes to increase the synthesis of HA. Furthermore, these lymphocytes in turn were stimulated more by irradiated autologous RF than by irradiated heterologous RF. Urine and plasma GAG determination proved to be suitable for the routine assessment of disease activity and outcome of therapy. In conclusion, GAGs seem to play an important role in the pathogenesis of the disease and their measurement may provide aid to the endocrinological evaluation of patients with TAO.

Urinary glycosaminoglycans in Graves' ophthalmopathy

An increased accumulation of glycosaminoglycans (GAG) in retrobulbar tissues has been reported in patients with thyroid eye disease. We examined the quantitative urinary GAG excretion in 101 patients with Graves' ophthalmopathy of different classes, 36 patients with Graves' hyperthyroidism without ophthalmopathy, 14 patients with toxic nodular goitre and 103 control subjects. Glycosaminoglycans were isolated from 24-h urine collections by precipitation with cetylpyridinium chloride and ethanol followed by photometrical quantification of hexuronic acids after reaction with carbazole. In comparison with the control group (15.8, 10.4, 21.6 mg/24 h; median, 25th, 75th percentile) a significant (P less than 0.005) elevation of urinary GAG excretion was found in patients with ophthalmopathy (19.2, 12.2, 28.7 mg/24 h), whereas patients with Graves' hyperthyroidism and no ophthalmopathy (16.2, 11.9, 21.7 mg/24 h) and patients with toxic nodular goitre (15.8, 11.5, 21.2 mg/24 h) exhibited no markedly increased values. Especially, patients with active, untreated ophthalmopathy showed on average a twofold increase (36.7, 28.1, 48.4 mg/24 h) in urinary GAG excretion. In contrast, high values were not found in patients with inactive ophthalmopathy and elevated values decreased under treatment, which correlated with clinical findings. Further, relapses were also accompanied by high GAG excretion. Thus, using a simple laboratory method, quantitative determination of urinary GAG excretion appears to present an effective parameter for the activity of Graves' ophthalmopathy.

Mechanism of action of intradiscal chymopapain in the treatment of sciatica: a clinical, biochemical, and radiological study

Seventeen patients with intractable sciatica due to prolapse of a lumbar disc, treated by intradiscal injection of chymopapain (chemonucleolysis) were studied. Analysis of serial 24 hour urine collections showed a significant increase in urinary glycosaminoglycan after chemonucleolysis. This was not detected in four patients undergoing routine discography. Enzymic analysis of urinary glycosaminoglycan after chemonucleolysis suggested that the increase in levels was largely due to an increase in the amounts of chondroitin sulphate present, probably resulting from proteoglycan breakdown in the intervertebral disc. Eight of the patients treated by chemonucleolysis underwent serial computed tomography (CT). One month after the injection the only change seen was a loss of definition of the disc prolapse, which could be interpreted as a loss of turgidity in the disc as a result of proteoglycan breakdown by chymopapain. By six months the CT of those patients whose symptoms had improved showed that the degree of disc prolapse was usually less marked and the disc margin more clearly defined, suggesting that by this stage anatomical remodelling had occurred.

Elimination of hyaluronic acid from the blood stream in the human

The removal of hyaluronic acid (HA) from the blood-stream was studied in four normal human subjects after injection of high molecular weight preparations labelled with 3H in the acetyl position. The plasma half-life of the injected material ranged between 2.5 and 5.5 min. The daily turnover of HA in the circulation was estimated to be at least 150 mg. Its elimination was predominantly extrarenal, the upper molecular weight limit for renal excretion being 25 000. Evidence for rapid degradation was provided by the identification of 3H2O in urine. Calculations from the specific activity of urinary 3H2O indicated that approximately 55% of the acetyl content of the injected HA was completely oxidized within 3 h, and 85% within the first day. It is concluded that hyaluronic acid in the amounts currently used for therapeutic purposes should not accumulate significantly in the circulation.

Tissue uptake of circulating hyaluronic acid. A whole body autoradiographic study

Previous work in the rabbit has shown that there is a significant flux of plasma hyaluronic acid (HA) which is taken up and degraded mainly in the liver but also concentrated in the spleen. Purified 14C-labelled HA of high average molecular wt prepared by biosynthesis from D-[U-14C] glucose was injected i.v. in mice and its tissue distribution was determined by whole-body autoradiography during the next 24 h. As blood levels declined, radioactivity was concentrated in the liver and spleen as found in the rabbit, and also in bone marrow and lymph nodes. Distribution was uniform in liver tissue, concentrated and relatively persistent in the periphery of lymph nodes, and distinctly nodular within the spleen. Analysis of an aqueous liver extract taken 4 h after injection identified 14C in HA, in a macromolecular fraction resistant to fungal hyaluronidase, and in metabolites of low molecular wt. These findings confirm and extend observations based on tissue extraction in rabbits. The pattern of distribution through the body and the restricted localization within spleen and lymph nodes further suggest that HA is absorbed from plasma and tissue fluids by elements of the reticuloendothelial system.

Structure and metabolism of proteoglycans and glycosaminoglycans

Proteoglycans and glycosaminoglycans have the common structural characteristics of linear polysaccharide chains consisting of a hexosamine alternating with another sugar. They play an important role in skin as part of the support matrix of connective tissue, and may be related to cell-cell, and cell-matrix interactions. In general the polysaccharide chains are covalently linked to protein and may contain varying amounts of sulfate resulting in a strong negative charge. Biosynthesis consists of the formation of the protein core followed by the sequential addition of sugars and sulfate to the nonreducing ends of growing chains. The synthetic process is highly organized with the final polysaccharide polymerization and sulfation taking place in the Golgi. Degradation of the proteoglycans is less well understood but probably involves endoglycosidases, exoglycosidases, and proteases which work in concert to degrade these substances.

Plasma clearance, tissue distribution and metabolism of hyaluronic acid injected intravenously in the rabbit

The plasma clearance, tissue distribution and metabolism of hyaluronic acid were studied with a high average molecular weight [3H]acetyl-labelled hyaluronic acid synthesized in synovial cell cultures. After intravenous injection in the rabbit the label disappeared from the plasma with a half-life of 2.5--4.5 min, which corresponds to a normal hyaluronic acid clearance of approx. 10 mg/day per kg body weight. Injection of unlabelled hyaluronic acid 15 min after the tracer failed to reverse its absorption. Clearance of labelled polymer was retarded by prior injection of excess unlabelled hyaluronic acid. The maximum clearance capacity was estimated in these circumstances to be about 30 mg/day per kg body wt. The injected material was concentrated in the liver and spleen. As much as 88% of the label was absorbed by the liver, where it was found almost entirely in non-parenchymal cells. Degradation was rapid and complete, since volatile material, presumably 3H2O, appeared in the plasma within 20 min. Undegraded [3H]hyaluronic acid, small labelled residues and 3H2O were detected in the liver, but there was little evidence of intermediate oligosaccharides. No metabolite except 3H2O was recognized in plasma or urine. Two-thirds of the radioactivity was retained in the body water 24 h later, and small amounts were found in liver lipids. Radioactivity did not decline in the spleen as rapidly as in the liver. The upper molecular weight limit for renal excretion was about 25 000. Renal excretion played a negligible part in clearance. It is concluded that hyaluronic acid is removed from the plasma and degraded quickly by an efficient extrarenal system with a high reserve capacity, sited mainly in the liver.

Circadian rhythms and the urinary excretion of acid glycosaminoglycans in normal human adults

Urine from normal human adults (11 males, 4 females) was collected for 24 hours in four-hour samples, commencing at 08.00 hours. The urine volume, and concentrations of chondroitin sulfate, heparan sulfate, cetylpyridinium turbidity, and creatinine were measured on every sample. Concentrations and total output of glycosaminoglycans were significantly higher in male urine than in female urine. Chondroitin sulfate total output/four hours showed a significant negative correlation with creatinine concentration in males, but not in females. A testicular hyaluronidase is implicated. No such correlation was observed for heparan sulfate. Glycosaminoglycans are filtered into the urine. Plasma clearances are very low. Heparan sulfate is excreted with a circadian rhythm, as is glycosaminoglycan assayed by cetyl pyridinium turbidity. Peak excretions are at 06.00 and 10.00 hours respectively. Chondroitin sulfate excretion is not rhythmic in the male, perhaps because hyaluronidase activity in the urine complicates the assay. A rhythm may be present in the female.

Distribution of biologically labelled radioactive hyaluronic acid injected into joints

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The excretion and degradation of chondroitin 4-sulphate administered to guinea pigs as free chondroitin sulphate and as proteoglycan

The excretion and degradation was studied of (35)S-labelled 4-chondroitin sulphate injected into guinea pigs in the form of proteoglycan isolated from cartilage and in the form of free chondroitin 4-sulphate prepared from the same proteoglycan by proteolysis. When the proteoglycan was injected there was a delay of about 15-20min before significant amounts or radioactivity were excreted, whereas after injection of chondroitin 4-sulphate a considerable amount of radioactivity was excreted within 10min and a much higher proportion of the radioactive dose was excreted in 1h or 24h compared with the proteoglycan. In both cases, however, a major part of the radioactivity was not excreted even in 24h. Sterile conditions were used to collect the radioactive material directly from the bladder. When chondroitin 4-sulphate was injected, the molecular sizes of injected and excreted materials were similar, as assessed by gel chromatography on Sephadex G-200, whereas when proteoglycan was injected the molecular size of the excreted labelled material was similar to that of the chondroitin 4-sulphate chains in the original proteoglycan. In neither case did the size of the excreted labelled material change with time over 1h, and low-molecular-weight labelled material was virtually absent. In contrast, when urine was collected for 24h without preservative the labelled material in it was extensively degraded after either the proteoglycan or chondroitin 4-sulphate had been given. Chondroitin 4-sulphate became similarly degraded when incubated with non-sterile urine, but not when the urine was passed through a bacterial filter, suggesting that degradation was caused by contaminating micro-organisms in the experiments in which urine was collected for 24 h. It is concluded that chondroitin 4-sulphate chains of about 18000 molecular weight can be excreted readily as such, whereas intact proteoglycans must be degraded to free glycosaminoglycans first, although both are taken up by the tissues more rapidly than they are excreted.

Arterial wall metabolism in experimental hypertension of coarctation of the aorta of short duration

Coarctation of the mid-thoracic aorata was surgically produced in mongrel dogs which were sacrificed from 4-12 wk after the operation. As compared to the findings in control animals, the sodium, chloride, and water content of the hypetensive portion of the coarcted thoracic aorta was significantly elevated, whereas the electrolyte and water content of the relatively normotensive portion of the coarcted aorta was normal. The sodium, potassium, and water content of the pulmonary artery, skeletal muscle, and cardiac muscle of the coarcted dog was not altered. These observations suggest that an elevated arterial pressure may influence the electrolyte and water composition of the arteries. The arterial pressure also may influence the content and synthesis of acid mucopolysaccharides (MPS) in the arteries since the content of sulfated MPS and the incorporation of injected radiosulfate into sulfated MPS were significantly increased in the hypertensive portion of the coarcted thoracic aorta but were significantly reduced in the relatively normotensive ("hypotensive") portion of the coarcted aorta. The observed increase in MPS may have been a factor directly responsible for the increase in the sodium content of the hypertensive aorta since MPS can act as polyelectrolytes and bind cations. Although the arterial pressure may influence certain metabolic functions in the arteries, it did not appear to have a direct effect on the arterial lipids since the lipid content of the hypertensive and of the relatively normotensive portions of the coarcted aorta were comparable to the values found in the normal aorta.