The diurnal variation of serum hyaluronan in health and disease

Abundance and size of hyaluronan in naked mole-rat tissues and plasma

Large amounts of ultra-high molecular weight hyaluronan (HA) have been described as the main cause of cancer resistance in naked mole-rats (Heterocephalus glaber, NMR). Our work examined HA metabolism in these rodents more closely. HA was localized and quantified using HA binding proteins. Its molecular weight was determined using size exclusion chromatography and gel electrophoresis, HA family gene expression using RNAseq analysis, and hyaluronidase activity using zymography. Guinea pigs (Cavia porcellus) and mice (Mus musculus) were used as controls for some experiments. We found that HA localization was similar in NMR, guinea pig, and mouse tissues but NMR had larger amounts and higher molecular weight (maximum, around 2.5 MDa) of HA in serum and almost all tissues tested. We could not find ultra-high molecular weight HA (≥ 4 MDa) in NMR samples, in contrast to previous descriptions. Hyaluronidase-1 had lower expression and activity in NMR than mouse lymph nodes. RNAseq results showed that, among HA family genes, Tnfaip6 and hyaluronidase-3 (Hyal3) were systematically overexpressed in NMR tissues. In conclusion, NMR samples, contrary to expectations, do not harbor ultra-high molecular weight HA, although its amount and average molecular weight are higher in NMR than in guinea pig tissues and serum. Although hyaluronidase expression and activity are lower in NMR than mouse lymph nodes, this not sufficient to explain the presence of high molecular weight HA. A different activity of the NMR HA synthases remains possible. These characteristics, together with extremely high Hyal3 and Tnfaip6 expression, may provide the NMR with a bespoke, and perhaps protective, HA metabolism.

Correlation between synovial fluid cytokine concentrations and limb function in normal dogs and in dogs with lameness from spontaneous osteoarthritis

OBJECTIVE

To determine the relationship between synovial biomarker concentrations and severity of lameness and to assess the ability to differentiate normal from osteoarthritic joints with synovial biomarker concentrations.

STUDY DESIGN

Prospective clinical study.

SAMPLE POPULATION

Twelve hounds with no evidence of osteoarthritis (OA) and 27 client-owned dogs with unilateral lameness and joint pain in a single joint from naturally occurring OA.

METHODS

Enrollment in the OA group required a history of lameness, radiographic evidence of OA on orthogonal joint radiographs, and ≥6% gait asymmetry between contralateral limbs. The concentrations of 14 synovial OA biomarkers in synovial samples obtained after gait analysis were measured with enzyme-linked immunosorbent assays and compared between normal and OA joints.

RESULTS

Concentrations of monocyte chemoattractant protein (MCP)-1, substance P, interleukin (IL)-6, IL-8, KC-like, matrix metalloproteinase (MMP)-1, and MMP-3 were greater (P ≤ .05) in OA than in normal joints. The concentrations of bradykinin and tissue inhibitors of metalloproteinase-4 were decreased in OA compared with normal joints. Monocyte chemoattractant protein 1 was identified as the most accurate marker to distinguish OA from normal joints. No correlation was detected between any OA biomarker concentration, individually or in combination, and severity of gait asymmetry at the walk.

CONCLUSION

Differences in proinflammatory and anti-inflammatory biomarkers were detected between OA and normal joints, but no relationship was identified between biomarker concentrations and gait asymmetry in dogs with OA.

CLINICAL IMPACT

This information will help guide future studies to elucidate how factors such as disease chronicity, severity, and etiology affect these relationships.

Plasma hyaluronic acid level as a prognostic and monitoring marker of metastatic breast cancer

Conventional tumor markers have limited value for prognostication and treatment monitoring in metastatic breast cancer (MBC) patients and novel circulating tumor markers therefore need to be explored. Hyaluronic acid (HA) is a major macropolysaccharide in the extracellular matrix and is reported to be associated with tumor progression. In our study, we investigated plasma HA level with respect to progression free survival (PFS) and overall survival (OS), as well as the treatment monitoring value in MBC patients. The prognostic value of plasma HA level was investigated in a discovery cohort of 212 MBC patients with 2.5-year follow-up and validated in an independent validation cohort of 334 patients with 5-year follow-up. The treatment monitoring value of plasma HA level was investigated in 61 MBC patients from discovery cohort who had been radiographically examined after first complete cycle of chemo therapy. We found a robust association between high plasma HA level and poor prognosis of MBC patients in both discovery (pPFS = 7.92 × 10(-6) and pOS = 5.27 × 10(-5)) and validation studies (pPFS = 3.66 × 10(-4) and pOS = 1.43 × 10(-4)). In the discovery cohort, the plasma HA level displayed independent prognostic value after adjusted for age and clinicopathological factors, with respect to PFS and OS. Further, the decrease of plasma HA level displayed good concordance with treatment response evaluated by radiographic examination (AUC = 0.79). Plasma HA level displays prognostic value, as well as treatment monitoring value for MBC patients.

Hyaluronan in the healthy and malignant hematopoietic microenvironment

The fate of both endogenous and transplanted stem cells is dependent on the functional status of the regulatory local microenvironment, which is compromised by disease and therapeutic intervention. The glycosaminoglycan hyaluronan (HA) is a critical component of the hematopoietic microenvironment. We summarize recent advances in our understanding of the role of HA in regulating mesenchymal stem cells, osteoblasts, fibroblasts, macrophages, and endothelium in bone marrow (BM) and their crosstalk within the hematopoietic microenvironment. HA not only determines the volume, hydration, and microfluidics of the BM interstitial space, but also, via interactions with specific receptors, regulates multiple cell functions including differentiation, migration, and production of regulatory factors. The effects of HA are dependent on the polymer size and are influenced by the formation of complexes with other molecules. In healthy BM, HA synthases and hyaluronidases form a molecular network that maintains extracellular HA levels within a discrete physiological window, but HA homeostasis is often perturbed in pathological conditions, including hematological malignancies. Recent studies have suggested that HA synthases may have functions beyond HA production and contribute to the intracellular regulatory machinery. We discuss a possible role for HA synthases, intracellular and extracellular HA in the malignant BM microenvironment, and resistance to therapy.

PIIANP and HELIXII diurnal variation

OBJECTIVE

Serum levels of procollagen type IIA N-terminal propeptide (sPIIANP) and type-II collagen helical peptide (sHELIXII) biomarkers were evaluated for variation diurnally and with physical activity and food in participants with osteoarthritis (OA) of the knee.

METHODS

Forty participants with OA of at least one knee were admitted overnight to the General Clinical Research Center for serial serum sampling. Samples were obtained on the evening (6-8 pm) of Day 1 (T3, n=40); prior to rising (8 am) from bed (T0, n=40); 1 h after rising (9 am) without food consumption (T1a, n=20); 1-2 h after rising (9-10 am) with food consumption (T1, n=40); and additionally at noon, 4 h after rising (T2, n=20). sPIIANP and sHELIXII were measured by enzyme-linked immunosorbent assay. Results were analyzed using non-parametric Freidman's test with Dunn's post-hoc multiple comparison test.

RESULTS

Normalized mean concentrations for sPIIANP and sHELIXII increased significantly from T0 to T1 (P<0.05).

CONCLUSIONS

This is the first study to demonstrate diurnal variation of these collagen-II biomarkers in individuals with knee OA. These results suggest that serum sampling for these markers should be standardized for purposes of clinical trials.

Exercise and injury increase chondroitin sulfate chain length and decrease hyaluronan chain length in synovial fluid

OBJECTIVES

(1) To investigate the effects of exercise and osteochondral (OC) injury on synovial fluid (SF) chondroitin sulfate (CS) and hyaluronan (HA) concentration and chain length, (2) to compare SF and cartilage CS data from joints with OC fragmentation, and (3) to compare SF CS and HA profiles with those seen in serum from the same horses.

METHODS

Serum and SF were obtained from (1) normal horses after 8 weeks rest, (2) the same horses after 9 months treadmill training, and (3) horses with OC injury from racing. Articular cartilage was also collected from group 3 horses. Concentrations and chain lengths of CS and HA were determined by gel chromatography and fluorophore-assisted carbohydrate electrophoresis.

RESULTS

SF CS peak chain length in the OC injury group increased significantly (18.7kDa) when compared to rested horses (11.6kDa), with exercise producing an intermediate chain length (15.6kDa). Cartilage and serum from the OC injury group had the abnormally long CS chains seen in SF from these horses. Total SF HA was significantly lower in the OC injury group compared to the rested group. Both the OC injury group and the exercised group had significant decreases in SF HA chain length compared to the rested group.

CONCLUSIONS

Chain length of SF CS was increased by exercise and OC injury. Exercise resulted in a modest increase, whereas OC injury caused a marked increase. In contrast to CS, SF HA chain length was decreased by OC injury, and to a lesser extent by exercise. Chain length analysis of SF CS and HA may provide a useful tool for evaluation of joint health.

Variation of serum hyaluronan with activity in individuals with knee osteoarthritis

PURPOSE

Serum hyaluronan (HA) was evaluated for diurnal variation in participants with osteoarthritis (OA) of the knee.

METHODS

Twenty participants with radiographic OA of at least one knee were admitted overnight to the General Clinical Research Center for serial serum sampling. Serum was obtained between 6:00 p.m. and 8:00 p.m. on Day 1 (T3) after a day of normal activity. During the night of bed rest, participants remained supine for a minimum of 5 h between the hours of 3:00 a.m. and 8:00 a.m. Blood was drawn prior to arising from bed (T0), and 1h (T1) and 4 h (T2) after arising and performing usual morning activities, including eating breakfast. During the morning, participants were encouraged to remain physically active and were not permitted to sit for more than 30 min at a time. Serum HA was measured by enzyme-linked immunosorbent assay. Results were analyzed using non-parametric Freidman's test with Dunn's post-hoc Multiple Comparison test.

RESULTS

Serum levels of HA increased significantly from T0 to T1 (P < 0.01). There were no other significant changes in serum HA levels observed between any of the other time points.

CONCLUSIONS

Although a rise in serum HA with activity and eating has been demonstrated previously in individuals with rheumatoid arthritis, this is the first study to demonstrate a similar rise in individuals with OA. These results suggest that serum sampling for HA in OA clinical trials should be performed more than 1h after arising in the morning and at least 1h after breaking an overnight fast.

Elimination of stabilised hyaluronan from the knee joint in healthy men

OBJECTIVE

To investigate the elimination of stabilised hyaluronan following intra-articular injection into the knee joint.

DESIGN

This was a single-centre, single-dose study in healthy human volunteers.

PARTICIPANTS

Six healthy men, aged 28 to 47 (mean 38) years, were enrolled in the study.

METHODS

Subjects received a single intra-articular injection (3ml; 20 mg/ml) of (131)I-labelled non-animal stabilised hyaluronic acid (NASHA). Radioactivity in the knee, blood, urine and over the liver was measured with gamma counters for 3 weeks post-injection; magnetic resonance and gamma camera imaging of the knee were also performed at 24 hours post-injection. Radioactivity uptake data were tested for conformity of fit to different mathematical models.

RESULTS

Elimination of (131)I-labelled NASHA from the knee was characterised by a fast initial phase and a slow late phase, and conformed to a three-exponential-function model with elimination half-lives of 1.5 hours, 1.5 days and 4 weeks. Radioactivity distribution within the knee joint was homogenous, and no local leakage was observed. Hepatic radioactivity uptake was low, but significantly above background levels, for the first 2 days post-injection, before declining to background levels. Visual imaging indicated an increase in intra-articular fluid volume at 24 hours post-injection.

CONCLUSIONS

The elimination kinetics of (131)I-labelled NASHA from the human knee joint were described by three distinct phases, with half-times of 1.5 hours, 1.5 days and 4 weeks. Most likely, the last value reflects the true half-life of NASHA following intra-articular injection since the labelling method used causes minimal modification of hyaluronan.

Increased serum levels of non-collagenous matrix proteins (cartilage oligomeric matrix protein and melanoma inhibitory activity) in marathon runners

OBJECTIVE

Marathon runners have an increased risk of developing joint disease. During and after a 42-km run, elevation of multiple cytokines occurs in the blood, reflecting inflammatory processes. We compared this cytokine response with serum levels of cartilage oligomeric matrix protein (COMP) and melanoma inhibitory activity (MIA), two markers for joint metabolism and/or damage.

METHODS

Serum from eight endurance-trained runners was collected shortly before the start of a marathon run, after 31 km, 42 km, 2 h after the end, on the first and on the second morning after the run. For comparison, serum was obtained from 35 healthy controls and 80 patients with knee joint injury, rheumatoid arthritis or osteoarthritis. Serum levels of C-reactive protein (CRP), interleukin-1beta (IL-1beta), interleukin-1 receptor antagonist (IL-1RA), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), soluble interleukin-6 receptor (sIL-6R, gp80), soluble tumor necrosis factor receptor II (sTNFRII, p75), COMP and MIA were measured by ELISA.

RESULTS

Compared with healthy controls, the runner's baseline serum levels of TNF-alpha, sIL-6R, COMP and MIA were significantly increased. COMP and MIA levels, higher than the upper normal limits of 5 microg/ml and 6 ng/ml respectively, were found in seven and five of eight runners. The elevated levels of COMP were similar to those found in joint injury or osteoarthritis, and the elevated levels of MIA were comparable to those reported in rheumatoid arthritis. During the run, the serum levels of IL-1RA, IL-6, TNF-alpha and COMP rose significantly, and gradually returned to baseline within 24 h. Only modest changes of CRP, sIL-6R, sTNFRII and MIA occurred during the run. Late elevations of CRP and MIA were observed after 24 and 48 h. The correlation analysis suggests associations between COMP, sIL-6R, TNF-alpha, IL-1RA on one hand and sTNFRII, and MIA and CRP on the other hand.

CONCLUSIONS

Elevated baseline levels of COMP and MIA might reflect increased joint matrix turnover and/or damage due to prior extreme physical training. During the run, COMP was increasing possibly due to the severe physical strain on joint structures, associated with the early inflammation. After the run, MIA and CRP increased within 24 h, suggesting a correlation with later inflammatory processes. Thus, our data suggest that COMP and MIA are markers for distinct aspects of joint metabolism and/or damage in both disease and sport.

Evaluation of various models of hyaluronan kinetics for assessment of liver function

The purpose of this study of various models of hyaluronan kinetics has been to find the most appropriate model for estimation of parameters which characterize liver endothelial cell function. Five theoretical models for serum hyaluronan distribution and elimination were evaluated by computer analysis of serial measurements of the mass concentration of hyaluronan in serum following an intravenous bolus dose. Three of the models were based on one-compartment distribution of intravenously injected hyaluronan. Model 1A, with assumed first-order elimination, was found to be compatible with measured data and had identifiable parameters. Model 1B, with assumed non-linear Michaelis-Menten kinetics, was also found to be compatible but the Michaelis-Menten constant (K(m)) was not well determined. In model 1C, with non-linear Michaelis-Menten elimination kinetics, K(m) was set to a fixed value of 340 micrograms l-1, and the remaining parameters were well determined and the model was found to be compatible. Two models with an assumed two-compartment distribution of intravenously injected hyaluronan, were not acceptable due to unidentified parameters not discriminating between patients and healthy persons. In conclusion, model 1C, with one-compartment distribution and non-linear Michaelis-Menten kinetics, best fulfilled the criteria of validity and was accepted for further evaluation of clinical materials.

Serum hyaluronan as a disease marker

Hyaluronan is a connective tissue polysaccharide which has also been found in blood serum in concentrations < 100 micrograms/L (average 30-40 micrograms/L in middle-aged persons). The serum level is regulated by the influx of the polysaccharide from the tissues via lymph and its receptor-mediated clearance by liver endothelial cells. Markedly high serum levels are noted in certain liver diseases, especially in patients with cirrhosis, when the clearance is impaired. In these cases serum hyaluronan can be used to follow the development of the disease. Serum hyaluronan is also a sensitive marker for impending rejection of liver transplants. Patients with rheumatoid arthritis constitute another major group with increased serum hyaluronan, but in this case the level varies markedly during the day corresponding to physical activity. There are good indications that in these subjects the excess hyaluronan comes from the joints. Under stringent sampling conditions of serum it should be possible to extract interesting information on the inflammatory joint process. Increased hyaluronan levels are also seen in other inflammatory diseases and it is of special interest that high hyaluronan levels in patients with septic conditions is a sign of poor prognosis. Certain tumours, notably Wilms' tumour and mesothelioma, produce factors which activate synthesis of hyaluronan and increase its serum level. Rare hereditary diseases with disturbances of hyaluronan metabolism and elevated blood levels have also been discovered, e.g. Werner's syndrome and cutaneous hyaluronanosis. Information accumulated during the last decade regarding the metabolism of hyaluronan has made this polysaccharide an interesting clinical marker for a number of pathological conditions.

Circulating hyaluronan levels in the rodent: effects of age and diet

Circulating hyaluronan (HA) levels were investigated as a function of age and diet in Fischer 344 male rats. A biphasic pattern of age-related changes was observed in rats fed ad libitum a diet in which the protein source was soya/fish meal. HA levels in 3- to 6- and 22- to 29-mo-old rats were not statistically different. However, HA levels in 12- to 20-mo-old rats were 10-29% of the levels in younger or aged adults. HA levels were also measured in rats fed ad libitum a semisynthetic diet in which the protein source was hydrolyzed casein. Whereas the two colonies exhibited similar biphasic age-related changes, HA levels differed 4- to 20-fold at every age examined. Caloric restriction affected HA levels in 19-mo-old casein-fed rats; HA levels were 2.3 times higher than age-matched controls and were not statistically different from young or aged animals. Serum and plasma HA levels were identical in the same individuals at all ages tested. These data suggest that HA turnover and metabolism in the rat are affected by age, dietary composition, and caloric intake.

Kinetics of circulating hyaluronan in humans. 4

The elimination of intravenously injected hyaluronan (HA) from the blood was investigated in 12 healthy volunteers. Three consecutive 30 min infusions of HA were given, separated by 90 min washout periods. Blood samples were taken before, during and after each infusion and the plasma HA concentration was determined. The deposition of HA was modelled according to a Michaelis-Menten kinetic model which included natural synthesis of HA. Km and Vmax was estimated to 0.34 +/- 0.13 microgram ml-1 and 3.48 +/- 0.97 microgram min-1 kg-1 b.w., respectively. The endogenous input was calculated to be 24 +/- 11 micrograms min-1 and was found to correlate to the age of the subjects (P < 0.05). As the baseline HA concentration was 0.031 +/- 0.21 microgram ml-1, the rate of elimination was linear in the normal concentration range. The calculated Vd was about 75% higher than a weight-estimated plasma volume. The total amount of HA excreted by the kidneys during the study period was 394 +/- 77 micrograms, which corresponded to approximately 1.7% of the total input of HA into the circulation during the experiment.

Hyaluronan and myeloperoxidase in human peritoneal fluid during genital inflammation

The changes in concentration of hyaluronan (HYA) and myeloperoxidase in peritoneal fluid (PF) were studied during genital intraperitoneal inflammation. PF were collected from 111 women undergoing laparatomy for adhesiolysis and reconstructive surgery of the fallopian tubes, or laparoscopy in search of causes of infertility or low abdominal pain. When the number of leukocytes in the PF had been counted, the fluid samples were centrifuged and the supernatants analyzed for the concentrations of HYA and of myeloperoxidase. During genital inflammation, whether post-operative or postinfectious, leukocytosis and elevated levels of HYA and myeloperoxidase were found in the PF. Concentrations of these substances in the PF may be usable as clinical markers for genital inflammation.

Hyaluronic acid. A review of its pharmacology and use as a surgical aid in ophthalmology, and its therapeutic potential in joint disease and wound healing

Hyaluronic acid is a naturally occurring polysaccharide with distinct physicochemical properties which underlie its application as a viscoelastic tool in ophthalmological surgery. In cataract surgery the role of hyaluronic acid in facilitating procedures and protecting the corneal endothelium is well established. Some benefit has also been gained with the use of hyaluronic acid in penetrating keratoplasty, trabeculectomy, retinal reattachment and trauma surgery, although its efficacy in these indications is less well-defined in the published literature. In addition to its lubricating and cushioning properties, demonstration of some in vitro anti-inflammatory activity and a possible disease-modifying effect for hyaluronic acid in animals has prompted its investigation as a treatment in osteoarthritis and, to a much lesser extent, in rheumatoid arthritis. Hyaluronic acid 20 mg, as weekly intra-articular injections for 3 to 7 weeks, improved knee pain and joint motion in patients with osteoarthritis. Although this occurred to a greater degree than with placebo in most comparisons, the effects of hyaluronic acid was similar to those of placebo in the largest trial. In the few available comparisons with other agents, hyaluronic acid appeared equivalent to methylprednisolone 40 mg (for 3 weeks) and to a single injection of triamcinolone 40 mg. Hyaluronic acid was distinguished from other therapies by providing a sustained effect after treatment discontinuation. Together with its very good tolerability profile, these properties justify further study of hyaluronic acid in patients with osteoarthritis. Some limited evidence of improvement in patients with rheumatoid arthritis, and a possible healing effect of hyaluronic acid on tympanic membrane perforations, represent additional areas of interest for future investigation. In summary, hyaluronic acid is a well-established adjunct to cataract surgery and may prove to be a promising option in the treatment of patients with osteoarthritis. Its very good tolerability provides further impetus for examination of its potential role in an extended scope of arthritic and ophthalmological indications, and in wound healing.

Hyaluronan and myeloperoxidase in human peritoneal fluid during genital inflammation

The changes in concentration of hyaluronan (HYA) and myeloperoxidase in the peritoneal fluid (PF) were studied during genital intraperitoneal inflammation. PF were collected from 111 women undergoing laparotomy for adhesiolysis and reconstructive surgery of the fallopian tubes or laparoscopy in search of causes of infertility or low abdominal pain. When the number of leukocytes in the PF had been counted, the fluid samples were centrifuged and the supernatants analyzed for the concentrations of HYA and myeloperoxidase. During genital inflammation, whether postoperative or postinfectious, leukocytosis and elevated levels of HYA and myeloperoxidase were found in the PF. Concentrations of these substances in the PF may be usable as clinical markers for genital inflammation.

Serum concentration of hyaluronan, IgM and IgA rheumatoid factors in a population based study of juvenile chronic arthritis

Increased serum levels of hyaluronan (HA) have been found in patients with liver diseases, psoriasis, malignancies as well as in rheumatoid arthritis and osteoarthritis. In the two latter groups serum HA levels may reflect the extent of synovial involvement and inflammation, rather than only unspecific information. This study was performed to elucidate the value of measuring HA in children with juvenile chronic arthritis (JCA) and to study its relation to class specific rheumatoid factors (IgM Rf and IgA Rf). HA was analysed in sera from 271 patients with JCA and 130 controls using a radiometric assay and IgM Rf and IgA Rf were analysed using an enzyme immunoassay. The results were analysed in relation to JCA subgroup, disease activity and functional outcome. In patients and controls higher levels of HA were found in young children than in older. Raised levels of HA and IgM Rf were mainly found in children with polyarticular disease. Impaired functional outcome was related to raised HA levels. No correlation was found between HA levels and IgM Rf or IgA Rf. Measurement of HA levels in JCA is of no diagnostic value because of low sensitivity. Quantification of HA may, however, have prognostic value in a subgroup of patients belonging to the polyarticular subgroup.

Prognostic relevance of serum hyaluronan levels in patients with breast cancer

The serum hyaluronan (HA) level of 238 women with breast cancer was measured by means of a specific radiometric assay. The results show no significant increase in serum HA when compared to levels in 120 control sera. A number of prognostic factors were evaluated including stage of disease, lymph-node involvement, tumour size, histology and presence of oestrogen and progesterone receptors in the tumour. No correlation was found with serum HA concentration and we conclude that serum HA level is of no prognostic significance in breast cancer.

Serum hyaluronan and aminoterminal propeptide of type III procollagen: variation with age

The serum levels of hyaluronan and the aminoterminal propeptide of Type III procollagen (PIIINP) were compared in 585 healthy individuals as a function of age. Newborn children displayed high hyaluronan (695 +/- 634 micrograms l-1, mean +/- SD) and PIIINP (295 +/- 152 micrograms l-1) values. The values were not correlated to the gestational week in which the children were born or to the birth weight but there was a significant correlation (p < 0.05) between the hyaluronan and PIIINP levels. During the first year the levels dropped and in childhood (1-16 years of age) both hyaluronan and PIIINP levels were fairly constant at 27 +/- 16 and 22 +/- 8.4 micrograms l-1, respectively. The PIIINP level showed a marked drop in adults compared to children. The drop continued to about 50 years of age (6.5 +/- 2.2 micrograms l-1) and then there was a slight increase in elderly people. The hyaluronan showed a continued increase with age from the level at 16 years of 29 +/- 17 micrograms l-1 to a mean value of 177 +/- 133 micrograms l-1 in people over 75 years. There was no increase in serum hyaluronan in women during pregnancy but the PIINP level increased in the later part of the gestational period. There was no correlation between the serum values of hyaluronan and PIIINP when compared throughout the life span which indicates that the blood levels of the two markers are regulated by independent factors.

A hyaluronan-loading test applied to patients with liver and joint diseases

The serum hyaluronan disappearance data, after an intravenous bolus injection of hyaluronan, were evaluated in terms of model-based parameters. The loading test was performed in 10 healthy persons (basal serum hyaluronan concentration, C0, 24.9 +/- 8.9 micrograms/l [mean +/- S.D.]), 6 patients with joint disease (62.3 +/- 41.1 micrograms/l) and 19 patients with liver disease (206 +/- 214 micrograms/l). The highest maximum Michaelis-Menten elimination rate (Vmax = 287 +/- 86 micrograms/min) was found in patients with joint disease, significantly higher than in healthy persons (Vmax = 179 +/- 16, P = 0.0015) and in patients with liver disease (Vmax = 149 +/- 59, P = 0.0002). C0 and Vmax were evaluated as discriminants for assessment of residual liver function. In patients with liver disease C0 correlated with liver function score (r = 0.875, P < 0.0001) and serum albumin concentration (r = -0.813, P < 0.0001). The Vmax parameter did not correlate with conventional liver function tests or with the liver score but a significantly negative correlation of Vmax with C0 was found in patients with liver disease. A combination of the C0 level and the Vmax parameter was found to discriminate between healthy persons, patients with joint disease and patients with liver disease and should be of benefit in separating patients, with or without elevated serum hyaluronan levels, into groups having increased influx or reduced elimination, respectively, of circulating hyaluronan.

Elevated plasma levels of hyaluronate in patients with osteoarthritis and rheumatoid arthritis

Plasma levels of hyaluronate (HA) in patients with rheumatoid arthritis (RA) and patients with osteoarthritis (OA), measured by enzyme-linked immunosorbent assay, were compared with levels in a healthy, age-matched non-arthritic control group, in a retrospective study. Compared with the controls, the mean level of plasma HA was sevenfold higher in the RA group and twofold higher in the OA group. There was no statistically significant correlation between HA levels and 7 other clinical and biochemical parameters in patients with RA. In the OA group, however, plasma HA levels were found to correlate with an objective functional capacity score and with an articular index based on the total amount of cartilage in involved joints. In a retrospective longitudinal study of 6 patients with RA, plasma levels of HA did not show a significant correlation with plasma levels of elastase or with the erythrocyte sedimentation rate. These data support in part the contention that plasma HA may be unique as a marker, in that it may be a reflection of synovial involvement and inflammation, rather than only of inflammation, in arthritis.

Plasma hyaluronan levels in rabbit immobilization osteoarthritis: effect of remobilization

The right knee joint of 11 rabbits was immobilized in full extension with a splint for a period of three days. The effect of the immobilization and subsequent remobilization on plasma hyaluronan (HA) level was measured, using a sensitive radiometric HA binding protein (125I-HABP) assay. No significant effect of the immobilization on plasma HA level (54 +/- 4 micrograms/l) was noted, but shortly (45 minutes) after splint removal, plasma hyaluronate was at its highest (91 +/- 20 micrograms/l). One day after removal of the splint a return to baseline (53 +/- 6 micrograms/l) was observed. It is suggested that HA may accumulate in the joint during immobilization. Shortly after removing the splint, the level of HA shows a rise in many of the rabbits, even if this is not a consistent finding, probably due to variation in the extent and kinetics of the HA mobilization. Such an accumulation of HA could be deleterious for joint tissues, since HA is an-effective stimulator of interleukin-1 (also called catabolin) synthesis and secretion, and since immobilization osteoarthritis ensues in the splinted rabbit joints.

Assay of circulating hyaluronic acid in the rat: study of diurnal variation and effect of anesthesia

Serum hyaluronic acid (HA) may provide a good marker for the severity of joint disease in the rat since a positive correlation was observed in experimental models of arthritis. However, little is known about its physiological variation in rats. In the present work, we do not find any circadian rhythm of HA in healthy Sprague-Dawley rats in contrast to that observed in humans, whose serum levels vary during daytime. Furthermore, the influence of blood sampling conditions on HA concentrations was evaluated in conscious animals and by using different anesthetics. The greater reproducibility for the assay of HA is observed with the intracardiac puncture under ether inhalation. Blood sample collection in the absence of anesthesia leads to a significant increase in serum levels of HA, which could be attributed partly to enhanced joint movements generated by psychological stress.

An ELISA plate-based assay for hyaluronan using biotinylated proteoglycan G1 domain (HA-binding region)

An enzyme-linked absorbent assay for the determination of hyaluronan (HA) has been developed. The procedure is sensitive, simple and is based on a microtitre plate format. The assay involves competition between HA absorbed to the plate and HA free in solution for binding to biotinylated cartilage proteoglycan binding region (G1 domain). The range of the assay is 10-2500 ng/ml with 50% inhibition at about 200 ng/ml. The assay can be used in guanidine HCl up to 0.6 M and in 0.5% deoxycholate or 0.5% nonidet. This new technique involves fewer experimental steps and is simpler to perform than other methods.

Clinical significance of the immunometric measurements of hyaluronic acid

Hyaluronic acid (HA), an unbranched high molecular weight polysaccharide can now be measured by several immunometric assays. The connective tissues are the main source of HA and it is destroyed mainly in the liver. Very high levels of HA occur in mesothelioma. Wilms' tumour and acute liver failure, and moderate increases in rheumatoid diseases, renal failure and cirrhosis. Local increased production of HA is a feature of several forms of lung disease. HA is an indicator of connective tissue turnover, of the function of the receptor mechanisms for its capture and destruction by the liver, and of the removal of low molecular weight fragments by the kidney.