Increased plasma hyaluronan in severe pre-eclampsia and eclampsia.

Pre-eclampsia is a serious multi-system disorder with general endothelial disease, often with a component of hepatic dysfunction. The pathogenesis of preeclampsia is not fully understood, and no specific diagnostic tests are available for early and reliable diagnosis, or for monitoring of the disease process. Hyaluronan is an extracellular matrix polysaccharide present at low concentrations in plasma. Normally, it is rapidly eliminated from the blood by the liver. Increased concentrations of circulating hyaluronan are seen in conditions with impaired hepatic function such as liver cirrhosis, and hyaluronan concentrations have previously been used to evaluate hepatic function in other diseases. In the present study, 11 pregnant women admitted to the intensive care unit with severe pre-eclampsia or eclampsia were studied. As control 31 healthy pregnant women, 18 undergoing vaginal delivery and 13 caesarean section, were included. Plasma hyaluronan was measured before and after delivery. Increased concentrations of plasma hyaluronan were found in the pre-eclampsia group both before (171 (75-586) microg/L (p<0.01)) and after delivery (215 (124-768) microg/L (p<0.001)) (median and inter-quartile range), as compared to both caesarean section (13 (7-28) microg/L before and 28 (18-48) microg/L after delivery) and vaginal delivery healthy controls (12 (8-24) microg/L before and 30 (13 63) microg/L after delivery). In the control groups, a small increase in plasma hyaluronan was seen after delivery, after both caesarean section (p<0.05) and vaginal delivery (p<0.01). In conclusion, plasma hyaluronan is increased in severe pre-eclampsia and eclampsia. The cause of the increase is unknown.

Lung hyaluronan and water content in preterm and term rabbit pups exposed to oxygen or air.

Rabbit pups were delivered by cesarean section 1 or 2 d before term, or vaginally around term, and then reared in room air or exposed to intermittent or continuous hyperoxia (> 85%) for up to 9 d. Pups were killed at different ages, and lung hyaluronan (HA; microgram/g of dry lung weight) and lung water content, measured as wet/dry lung weight, were determined. Compared with the day of birth, the lung HA concentration did not change significantly on succeeding days in pups kept in air delivered 2 d (-2 d) or 1 d (-1 d) before term, whereas the water content decreased significantly. Continuous exposure to hyperoxia resulted in a significantly raised lung HA concentration 6 d postterm in both -2 d and -1 d pups, and intermittent exposure to hyperoxia resulted in a significantly raised HA concentration 6 d postterm in -1 d pups, compared with the groups exposed to room air. These increases were accompanied by significantly elevated wet/dry lung weight ratios. Microscopic examination revealed significantly increased HA staining scores in alveoli, arterioles, and bronchioli in both hyperoxia-exposed groups of -2 d pups 6 d postterm, and nonsignificantly higher scores in -1 d and vaginally delivered pups of comparable age, compared with the scores at birth. The results indicate that oxygen exposure neonatally may result in an increase in lung HA accompanied by an increase in lung water content. The increase in lung HA concentration in our study may be an effect of oxygen free radicals or of oxygen-induced stimulation of inflammatory mediators.

Hyaluronan: its nature, distribution, functions and turnover.

Hyaluronan is a polysaccharide found in all tissues and body fluids of vertebrates as well as in some bacteria. It is a linear polymer of exceptional molecular weight, especially abundant in loose connective tissue. Hyaluronan is synthesized in the cellular plasma membrane. It exists as a pool associated with the cell surface, another bound to other matrix components, and a largely mobile pool. A number of proteins, the hyaladherins, specifically recognize the hyaluronan structure. Interactions of this kind bind hyaluronan with proteoglycans to stabilize the structure of the matrix, and with cell surfaces to modify cell behaviour. Because of the striking physicochemical properties of hyaluronan solutions, various physiological functions have been assigned to it, including lubrication, water homeostasis, filtering effects and regulation of plasma protein distribution. In animals and man, the half-life of hyaluronan in tissues ranges from less than 1 to several days. It is catabolized by receptor-mediated endocytosis and lysosomal degradation either locally or after transport by lymph to lymph nodes which degrade much of it. The remainder enters the general circulation and is removed from blood, with a half-life of 2-5 min, mainly by the endothelial cells of the liver sinuoids.

Hyaluronan production in vitro by fetal lung fibroblasts and epithelial cells exposed to surfactants of N-acetylcysteine.

Fetal human lung fibroblasts and feline lung epithelial cells were exposed to either a surfactant or N-acetylcysteine in various concentrations for 24-48 hours, after which the hyaluronan concentration in the culture medium was determined. Most of the experiments showed no stimulatory effect of either artificial or natural surfactant on hyaluronan synthesis. N-acetylcysteine 5-100 mg/mL induced progressive stimulation of hyaluronan synthesis by human fetal lung fibroblasts, resulting in a maximum hyaluronan concentration six times that released by unexposed cells. A slight increase in hyaluronan synthesis was also observed after exposure of feline fetal lung epithelial cells to N-acetylcysteine 50-100 micrograms/mL.

Hyaluronan in human cerebrospinal fluid.

We studied the concentration of hyaluronan in cerebrospinal fluid (CSF) in various diseases and attempted to define its reference interval. A radioassay utilizing cartilage proteins with affinity for hyaluronan was used in determining the concentration of 200 lumbar and 27 ventricular CSF specimens and 11 brain cyst fluids. Molecular weight distributions were determined by gel chromatography and localization in brain tissue by histochemistry. The hyaluronan level of lumbar CSF showed an increase with age; comparatively healthy children had (mean +/- SD) 50 +/- 41 micrograms/L (n = 40) and adults 166 +/- 77 micrograms/L (n = 9); i.e. significantly different values. The highest level was recorded in a patient with meningitis (> 8000 micrograms/L). More than 4000 micrograms/ L was noted in a patient with tumour metastasis in the cerebellum. Significantly elevated levels were especially found with spinal stenosis, head injury and cerebral infarction, but also in inflammatory medical disorders, hydrocephalus and encephalitis. We found no significant increase in multiple sclerosis and some other neurological diseases. Ventricular CSF of adults contained significantly less hyaluronan (53 +/- 73 micrograms/L; n = 16) than lumbar CSF. Hyaluronan in cyst fluids varied from 31 to 25,000 micrograms/L. Weight average molecular weight of hyaluronan in CSF was 2.9-3.0 x 10(5) and in brain tumour cyst fluid 2.4 x 10(6). In search for the origin of hyaluronan in CSF it was found that its concentration in the choroid plexus and leptomeninges was low, but that hyaluronan was accumulated in the superficial layer of the cerebral cortex. Continued screening for hyaluronan in CSF may be valuable in cases of inflammatory diseases, tumours and obstruction to CSF flow.

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.

The structure and function of hyaluronan: An overview.

Hyaluronan is a major component of synovial tissue and fluid as well as other soft connective tissues. It is a high-Mr polysaccharide which forms entangled networks already at dilute concentrations (< 1 mg/mL) and endows its solutions with unique rheological properties. Physiological functions of hyaluronan (lubrication, water homeostasis, macromolecular filtering, exclusion, etc.) have been ascribed to the properties of these networks. Recently a number of specific interactions between hyaluronan and a group of proteins named hyaladherins have also pointed towards a role of hyaluronan in recognition and the regulation of cellular activities. Many more or less well documented hypotheses have been proposed for the function of hyaluronan in joints, for example, that it should lubricate, protect cartilage surfaces, scavenge free radicals and debris, keep the joint cavities open, form flow barriers in the synovium and prevent capillary growth.

Effect of increased interstitial fluid flux on fractional catabolic rate of high molecular weight [3H]hyaluronan injected in rabbit skin.

The removal rate of high molecular weight (M(r) 3 x 10(6) [3H]hyaluronan has been measured in rabbit paw skin in control and during increased local venous pressure induced by ligation of the femoral vein. The increased venous pressure resulted in a 20% increase of interstitial volume at 4 h after ligation, a value which relates to at least a doubling of lymph flow, i.e. also to doubling of fluid flux through the tissues. The fractional catabolic rate of hyaluronan was 0.0918 +/- 0.0170 h-1 (n = 10) and 0.0775 +/- 0.0206 h-1 (n = 11) in control and following increased venous pressure respectively (P > 0.05). Since the fractional catabolic rate of hyaluronan is not affected by increased venous pressure, the removal of hyaluronan via lymphatic drainage in rabbit paw skin must be small compared to the local turnover of the polysaccharide.

An early look at macromolecular crowding.

Interest in the interaction between proteins and polysaccharides in semidilute systems developed in the late 1950's and early 1960's both in the field of matrix biology and in the construction of new separation techniques. The author gives an account of how his work in the 50's on the characterization of a connective tissue polysaccharide, hyaluronan, led him into studies on polysaccharide networks, sieve effects, molecular exclusion, a theory of gel filtration, solubility of proteins and chemical equilibria in polymer solutions, water and protein homeostatis in vivo, and ordered convectional flow in concentrated polymer systems.

Hepatic extraction of hyaluronic acid in porcine peritonitis.

The hepatic extraction of hyaluronic acid (HA) was studied in porcine fecal peritonitis in two groups of animals given various amounts of volume substitution. There was a progressive decrease in hepatic blood flow (QH) and a corresponding increase in the plasma concentration of HA in arterial blood over a 5-hour observation period, less pronounced in animals given more volume substitution. While hepatic clearance of HA decreased, the extraction ratio over the liver was not altered. The extracted amount of HA, which at steady state reflects the turnover of HA, was also unchanged. There was a significant correlation between QH and arterial HA concentration (r = 0.57; p < 0.05). The data suggest that the arterial HA concentration in sepsis reflects QH rather than an altered ability of the liver to eliminate HA.

Hyaluronan efflux from canine lung with increased hydrostatic pressure and saline loading.

Although lymphatic washout of hyaluronan during lung hydration has been postulated to deplete lung interstitial hyaluronan content and thereby contribute to the decreased interstitial exclusion of albumin observed under these conditions, this hypothesis has not been directly tested. In anesthetized, ventilated mongrel dogs, a prenodal lung lymphatic was cannulated for measurement of lymph flow and hyaluronan concentration. Following baseline measurements, Pla was increased in four steps of 5 cm H2O in Group 1 or set to one pressure ranging between 6 and 32 cm H2O in Group 2. In Group 3, saline (15% body weight) was infused over 30 min and then Pla increased as in Group 2. Invariably, as lymph flow increased in Groups 1 through 3, lymph hyaluronan concentration and hyaluronan flux increased significantly (p < 0.05). In a separate control group, there were no changes in lymph flow, hyaluronan concentration, or hyaluronan flux. In Group 3, lung hyaluronan content at 5 h (0.76 +/- 0.08 mg/g dry weight) was not significantly less than that during baseline (0.88 +/- 0.05 mg/g dry weight), although total uronic acid content actually increased by 38% over the same time course. In contrast, in the control group, both lung hyaluronan and uronic acid content remained stable over the experimental period. From these data, approximately 2 to 3% of lung hyaluronan is predicted to leave the interstitium via lymphatic flux per day under baseline conditions. The daily turnover of interstitial hyaluronan by this route increased to 15 to 18% of total content when Pla was elevated and to 54% following saline infusion. Thus, lung hyaluronan can be rapidly mobilized with increased lymph flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Crystalloid infusion increases plasma hyaluronan.

OBJECTIVE: To investigate the changes in plasma hyaluronan concentrations after intravenous infusion of crystalloid solution in healthy subjects. DESIGN: Crossover, controlled study. SETTING: General intensive care unit in a university hospital. SUBJECTS: Twelve healthy medical students. INTERVENTIONS: Infusion of 1000 mL i.v. Ringer's acetate solution during a 40-min period. MEASUREMENTS AND MAIN RESULTS: Plasma hyaluronan concentrations were measured before, during, and after infusion, and under the same conditions without the infusion in a separate session. Hemoglobin, hematocrit, and serum albumin concentrations were measured before and after infusion. Plasma volume at baseline and the volume of Ringer's acetate retained in the intravascular space after infusion were calculated. Plasma hyaluronan values increased from baseline mean of 12 +/- 5.8 (SD) to 20 +/- 13.1 micrograms/L (p < .01) at 30 mins and 25 +/- 13.0 micrograms/L (p < .001) at 40 mins after start of the infusion. Plasma hyaluronan concentrations peaked at 10 mins after the end of the infusion: 27 +/- 13.9 micrograms/L (p < .001). No changes in plasma hyaluronan concentrations were seen during the control period. A volume of 230 to 250 mL of Ringer's acetate solution was calculated to be retained within the intravascular space. CONCLUSIONS: Infusion of crystalloid solution increases plasma hyaluronan, probably through a washout of interstitial hyaluronan by way of increased lymph flow. The consequences of the interstitial loss of hyaluronan on tissue function are unknown.

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.

Influence of surgery on serum concentrations of hyaluronan.

OBJECTIVE: To investigate the changes in serum hyaluronan concentrations in response to surgery. DESIGN: A prospective case series evaluating serum hyaluronan concentrations before, during, and after surgery. SETTING: Operating room and recovery room of a university hospital. PATIENTS: Twelve consecutive patients undergoing vascular surgery because of arterial insufficiency of the lower extremities. MEASUREMENTS AND MAIN RESULTS: Serum hyaluronan concentrations were measured before and after induction of anesthesia and before, during, and after surgery. Routine chemical analyses of blood samples were made before and after surgery. Blood loss and fluid volumes infused were registered. Mean serum hyaluronan concentrations increased from baseline 25 +/- 10 (SD) to 36 +/- 15 micrograms/L (p < .05) during surgery, and increased further at 1 hr after the end of surgery to 52 +/- 38 micrograms/L (p < .001 compared with baseline), but had decreased nearly to baseline levels at 2 hrs postoperatively. A positive correlation was seen between peak hyaluronan concentrations and baseline serum hyaluronan levels (r2 = .73; p < .001), but no strong relationship was seen between serum hyaluronan concentrations and other parameters studied. CONCLUSIONS: Surgery is accompanied by a small increase in serum hyaluronan concentrations in humans. The major increase is seen in the postoperative period, and is probably due to increased influx of interstitial hyaluronan when the returning muscular tone activates lymph flow.

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.

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.

Lymphatic hyaluronan flux from skin increases during increased lymph flow induced by intravenous saline loading.

Hyaluronan is a structural component of the interstitial matrix in skin and is catabolized locally in skin as well as by lymphatic removal and subsequent degradation in lymph nodes and liver. The present experiments were designed to evaluate the role of interstitial fluid flux in turnover of hyaluronan in skin by measuring the maximal lymphatic flux of hyaluronan. Lymph flow, total protein concentration, hyaluronan concentration, and flux were measured every 15 min in prenodal lymph from the hind paw in 12 pentobarbital-anesthetized mongrel dogs at normal and increased interstitial fluid flux. An intravenous saline load (15% of body weight during the course of 30 min) was followed by a one-step increase in local venous pressure 30 min later (to a maximum of 50 mm Hg) and maintained at this level for the next 240 min. Lymph flow and hyaluronan concentration during the control period averaged 25.6 +/- (SD) 23.2 (range 4.7-61.9) microliters/min and 8.6 +/- 2.8 (range 2.0-11.6) micrograms/ml, respectively. The hyaluronan concentration fell by 30% during the experimental period, while the lymph flow increased up to ten times above control. Total tissue water increased from 1.73 +/- 0.11 ml/g dry weight during the control period to 1.91 +/- 0.12 ml/g dry weight at the end of the experiment (p < 0.01). The corresponding tissue contents of hyaluronan averaged 3.5 +/- 0.9 and 3.6 +/- 0.6 mg/g dry weight, respectively (p > 0.05). The average lymphatic hyaluronan flux was 8.4 +/- 5.4 micrograms/h during the control period, peaked at about 60 micrograms/h, and averaged 33.6 +/- 13.9 micrograms/h during the last hour of the experimental period.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneity of type III procollagen N-terminal peptides in BAL fluid from normal and fibrotic lungs.

Levels of the N-terminal propeptide of type III collagen (PIIINP) in bronchoalveolar lavage fluid (BALF) are thought to reflect type III collagen production by the lungs, and increased levels have been reported in patients with pulmonary fibrosis. We wanted to know more about the relative proportions of these peptides in normal BALF, whether they altered in pulmonary fibrosis, and whether lymphoid tissue is capable of clearing PIIINPs. In this study, we used a radioimmunoassay which detects the different forms of PIIINP-related antigens with equal specificity, to measure PIIINPs in serum and BALF of patients with cryptogenic fibrosing alveolitis (CFA). To investigate why PIIINP profiles in BALF differed from serum, the absolute concentration and relative proportion of PIIINPs in lymph afferent and efferent to the popliteal lymph node of a sheep were also determined. PIIINP concentrations were significantly greater in serum and BALF of patients with CFA, compared with controls. Gel chromatography indicated that serum antigen distribution, both of patients and controls, contained approximately 20% Col 1-3; the remainder being Col 1. In contrast, BALF contained Col 1-3 and Col 1, together with an antigen of high molecular weight (> 150 kD). The relative proportion of each antigen varied quite widely, but there were no apparent differences between patients and controls. The concentration of PIIINPs in afferent lymph was 295 ng.ml-1 and in efferent lymph was 104 ng.ml-1. Gel chromatography demonstrated that a significant amount of Col 1-3, together with a high molecular weight peptide, had been cleared during passage through the node.(ABSTRACT TRUNCATED AT 250 WORDS)