Biomedical subjects

P Heldin

Publications and source records attributed to P Heldin.

At least 19 recordsLinked to original sources

PubMed2003

Importance of hyaluronan biosynthesis and degradation in cell differentiation and tumor formation.

Hyaluronan is an important connective tissue glycosaminoglycan. Elevated hyaluronan biosynthesis is a common feature during tissue remodeling under both physiological and pathological conditions. Through its interactions with hyaladherins, hyaluronan affects several cellular functions such as cell migration and differentiation. The activities of hyaluronan-synthesizing and -degrading enzymes have been shown to be regulated in response to growth factors. During tumor progression hyaluronan stimulates tumor cell growth and invasiveness. Thus, elucidation of the molecular mechanisms which regulate the activities of hyaluronan-synthesizing and -degrading enzymes during tumor progression is highly desired.

Animals↗

PubMed2003

Hyaluronan synthase in trabecular meshwork cells.

BACKGROUND/AIMS: Hyaluronan is present in the trabecular meshwork where it is involved in the pathophysiology of aqueous outflow environment. In this study, the expression and regulation of hyaluronan synthase (HAS), which is the enzyme synthesising hyaluronan, in trabecular meshwork cells were investigated. METHODS: Cultured bovine trabecular meshwork cells (BTMCs) were used. HAS expression in BTMCs was examined by RT-PCR. The effects of transforming growth factor beta (TGF-beta) and platelet derived growth factor BB (PDGF-BB) on HAS expression in BTMCs were examined by quantitative RT-PCR. The HAS2 expression by TGF-beta and PDGF-BB at the protein level was also confirmed immunohistochemically. The production of hyaluronan from BTMCs was detected by high performance liquid chromatography (HPLC). RESULTS: Three HAS isoforms were expressed in BTMCs at the mRNA level. Among HAS isoforms, only the expression of HAS2 mRNA was increased by the administration of TGF-beta or PDGF-BB. HAS2 upregulation by these growth factors was also confirmed at the protein level. Further, hyaluronan production from BTMCs was stimulated by TGF-beta or PDGF-BB. CONCLUSION: Expression of HAS in trabecular meshwork may maintain the hyaluronan content in the aqueous outflow pathway. Its production is regulated by TGF-beta and PDGF-BB. The regulation of the expression of HAS in trabecular meshwork might be useful for modulating the aqueous outflow environment.

Animals↗

PubMed2003

Immunohistochemical localization and expression of the hyaluronan receptor CD44 in the epithelium of the pig oviduct during oestrus.

Hyaluronan is related to essential reproductive processes in pigs. Hyaluronan produced by cumulus cells builds, via specific cell surface receptors, an extracellular matrix responsible for cumulus cell cloud expansion during final oocyte maturation, a preparatory event for ovulation and fertilization. In addition, hyaluronan that has been localized in the pig oviduct both in the intraluminal fluid and on the surface of the lining epithelium of the preovulatory sperm reservoir, has proven beneficial during in vitro fertilization and embryo culture, thus indicating that it has a role in vivo. This study monitored the immunolocalization, protein determination and gene expression of the major cell surface hyaluronan receptor CD44 in the epithelial lining of the pig oviduct during selected stages of standing oestrus, in relation to spontaneous ovulation. The CD44 immunostaining in the lining epithelium was localized to the surface membrane and the supranuclear domain of mainly the secretory cells, particularly in the sperm reservoir of both treatment (inseminated) and control (non-inseminated) specimens. Up to four hyaluronan-binding protein (HABP) bands (60, 90, 100 and 200 kDa) were detected in the tubal epithelium, and the 200 kDa band was determined as CD44 by immunoblotting. The expression of CD44 mRNA was higher before than after ovulation (P < 0.05), most conspicuously in the uterotubal junction (UTJ). In addition, CD44 expression in the preovulatory UTJ and the ampullary-isthmic junction (AIJ) of control animals was higher than in those that were inseminated (P < 0.05 and P < 0.01 for UTJ and AIJ, respectively). The results demonstrate for the first time that the specific hyaluronan receptor CD44 is expressed by the oviduct epithelial cells during spontaneous oestrus, and is particularly abundant in the sperm reservoir before ovulation. Presence of spermatozoa in this segment seemed to downregulate the receptor. The variation in the expression of CD44 in relation to spontaneous ovulation and the presence of spermatozoa indicate that the hyaluronan CD44-signalling pathway may play a role in oviduct function during sperm storage and fertilization in pigs.

Animals↗

PubMed2001

Hyaluronan production increases the malignant properties of mesothelioma cells.

Malignant pleural mesotheliomas is in most cases associated with elevated amounts of hyaluronan. To investigate the importance of hyaluronan for the malignant properties of mesotheliomas, we have expressed murine hyaluronan synthase 2 (HAS2) in the non-hyaluronan producing mesothelioma cell line, Mero-25. We found that upon hyaluronan overproduction the mesothelioma cells changed their epitheloid character to a fibroblastic phenotype and were surrounded by pericellular matrices, the size of which correlated to the amount of synthesized hyaluronan. HAS2-transfected cells with the ability to synthesize about 520 ng hyaluronan/5 x 10(4)cells/24 h exhibited about a 2-fold increase in the expression of the cell surface hyaluronan receptor CD44 and their locomotion increased compared to that of mock-transfected Mero-25 cells. Furthermore, the malignant properties of mesothelioma cell clones as determined by the ability to grow in a soft agar assay correlated to their hyaluronan production. These results provide evidence for an important role of hyaluronan in the aggressive spread of mesotheliomas in adjacent non-cancerous stromal tissues.

Adjuvants, Immunologic↗

PubMed2001

HGF/SF induces mesothelial cell migration and proliferation by autocrine and paracrine pathways.

Mesothelial repair differs from that of other epithelial-like surfaces as healing does not occur solely by centripetal in-growth of cells as a sheet from the wound margins. Mesothelial cells lose their cell-cell junctions, divide, and adopt a fibroblast-like morphology while scattering across and covering the wound surface. These features are consistent with a cellular response to hepatocyte growth factor/scatter factor (HGF/SF). In this study, we examined the ability of mesothelial cells to secrete HGF/SF and investigated its possible role as an autocrine regulator of mesothelial cell motility and proliferation. We found that human primary mesothelial cells expressed HGF/SF mRNA and secreted active HGF/SF into conditioned medium as determined by ELISA and in a scattering bioassay. These cells also expressed the HGF/SF receptor, Met, as shown by RT-PCR and by Western blot analysis and immunofluorescence. Incubation of mesothelial cells with neutralizing antibodies to HGF/SF decreased cell migration to 25% of controls, whereas addition of HGF/SF disrupted cell-cell junctions and induced scattering and enhanced mesothelial cell migration. Furthermore, HGF/SF showed a small but significant mitogenic effect on all mesothelial cell lines examined. In conclusion, HGF/SF is produced by mesothelial cells and induces both motility and proliferation of these cells. These data are consistent with HGF/SF playing an autocrine role in mesothelial healing.

Antineoplastic Agents↗

PubMed2000

Expression of human hyaluronan synthases in response to external stimuli.

In the present study we have investigated the expression of mRNAs for hyaluronan synthase isoforms (HAS1, HAS2 and HAS3) in different cells in response to various stimuli. Human mesothelial cells, which synthesize large amounts of hyaluronan, express mRNAs encoding all three HAS isoforms, whereas their transformed counterparts, mesothelioma cells, which produce only minute amounts of hyaluronan, express only HAS3 mRNA. Human lung fibroblasts and the glioma cell line U-118 MG express only the HAS2 and HAS3 genes. The expression of the transcripts was higher in subconfluent than in confluent cultures and was well correlated with the production of hyaluronan by the cells. Stimulation of mesothelial cells with platelet-derived growth factor-BB induced an up-regulation of mRNA for HAS2 to a maximum after 6 h of stimulation; HAS1 and HAS3 genes were only induced slightly. Transforming growth factor-beta1 reduced HAS2 mRNA slightly, and hydrocortisone reduced it strongly, within 6 h of stimulation in mesothelial cell cultures but did not significantly affect the expression of mRNAs for HAS1 and HAS3. Induction of HAS1 and HAS2 protein levels in response to the stimuli above correlated with HAS transcript levels. Thus the expression of the three HAS isoforms is more prominent in growing cells than in resting cells and is differentially regulated by various stimuli suggesting distinct functional roles of the three proteins.

Anti-Inflammatory Agents↗

PubMed2000

Irradiation-induced expression of hyaluronan (HA) synthase 2 and hyaluronidase 2 genes in rat lung tissue accompanies active turnover of HA and induction of types I and III collagen gene expression.

Hyaluronan (HA) is a linear glycosaminoglycan that accumulates in the interstitium of injured lung and inhibits gas exchange between air and blood. In the present study we investigated the molecular mechanisms behind the local turnover of HA during the early phase of irradiation-evoked lung fibrosis in rats. Irradiation with a single dose of 30 Gy to the lower part of the right lung of rats induced an accumulation of HA in bronchoalveolar lavage fluid 6 wk after irradiation, followed by return to almost normal levels at 10 wk after irradiation. This was parallelled with a transient downregulation of HA receptors on alveolar macrophages (AMs); 4 and 6 wk after irradiation the binding of [(3)H]HA to AMs was decreased to about 50% of that of AMs from nonirradiated control rats, returning to almost normal level at 10 wk after irradiation. Analysis of the expression of rat HA synthase (HAS) isoforms (rHAS1, rHAS2, and rHAS3) and rat hyaluronidases (rHYAL1 and rHYAL2) by Northern blotting revealed an upregulation of rHAS2 messenger RNA at 4, 6, and 10 wk after irradiation, but a progressive decrease in the constitutive expression of rHYAL2 at 6 and 10 wk after irradiation; rHAS1 was undetectable, whereas rHAS3 and rHYAL1 were faintly detectable. Although transforming growth factor-beta1 stimulated HA production by normal lung fibroblasts, it inhibited HYAL activity in lysosomes and HYAL activity released into the culture media. Another interesting observation was that HA fragments, which likely result from the action of HYAL, induced expression of types I and III collagen genes. Our results indicate that rHAS2 and rHYAL2 are involved in the turnover of HA during the early phase of lung injury and that rHAS2 and rHYAL2 as well as HA fragments may play important roles in the pathogenesis of lung fibrosis.

Animals↗

PubMed2000

Expression regulation of hyaluronan synthase in corneal endothelial cells.

PURPOSE: Our previous study showed that hyaluronan synthase (HAS), the enzyme protein of hyaluronan (HA) biosynthesis, is expressed in ocular tissues including the corneal endothelium. In the current study, the mechanism that regulates HAS expression in bovine corneal endothelial cells (BCECs) was investigated. METHODS: Cultured BCECs were used. HAS expression in BCECs at the mRNA level was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis. The effects of transforming growth factor (TGF)-beta and platelet-derived growth factor (PDGF)-BB on HAS expression were examined by quantitative RT-PCR. The involvement of the Smad family (intracellular signal transducer of TGF-beta) was also investigated. The expression of HAS in BCECs at the protein level was confirmed by immunocytochemistry and Western blot analysis. RESULTS: Three HAS isoforms in BCECs were expressed at the mRNA level. The transcriptional sizes of each HAS in BCECs were 4.9 kb for HAS1, 2.8 kb for HAS2, and 1.6 kb for HAS3. The expression of HAS2 at the mRNA level was stimulated by TGF-beta1 and/or PDGF-BB treatment. In contrast, HAS1 and HAS3 expression was not affected by these growth factors. The additive effects of TGF-beta1 and PDGF-BB were observed in the stimulation of the expression levels of HAS2. HAS2 upregulation by these growth factors was also detected by Western blot analysis. The stimulation of the expression of HAS2 at the mRNA level by TGF-beta was accelerated by the overexpression of Smad2, Smad3, and Smad4 and inhibited by that of Smad7, all of which were confirmed to be involved in the signal transduction from TGF-beta through HAS expression. CONCLUSIONS: Although three HAS isoforms were expressed in the corneal endothelial cells, the expression of HAS2 was upregulated by TGF-beta1 and/or PDGF-BB. HAS2 expression was regulated by TGF-beta through Smad family members.

Amino Acid Sequence↗

PubMed1999

Expression of recombinant hyaluronan synthase (HAS) isoforms in CHO cells reduces cell migration and cell surface CD44.

In the present study we investigated the functional properties of the three recombinant hyaluronan synthases (HAS proteins) HAS1, HAS2, and HAS3. HAS3-transfected CHO clones exhibited the highest hyaluronan polymerization rate followed by HAS2 transfectants which were more catalytically active than HAS1 transfectants. In living cells all three HAS proteins synthesized hyaluronan chains of high molecular weight (larger than 3.9 x 10(6)). In vitro, the HAS2 isoform produced hyaluronan chains of a molecular weight larger than 3.9 x 10(6), whereas HAS3 produced polydisperse hyaluronan (molecular weight 0.12-1 x 10(6)), and HAS1 synthesized much shorter chains of an average molecular weight of 0.12 x 10(6). Thus, each HAS protein may interact with different cytoplasmic proteins which may influence their catalytic activity. CHO transfectants with the ability to synthesize about 1 microgram hyaluronan/1 x 10 (5) cells/24 h were surrounded by hyaluronan-containing coats, whereas transfectants generating about 4-fold lower amounts of hyaluronan formed coats only in the presence of chondroitin sulfate proteoglycan. An inverse correlation between hyaluronan production on the one hand and cell migration and cell surface CD44 expression on the other was found; a 4-fold lower migration and a 2-fold decrease of cell surface CD44 receptors was seen when hyaluronan production increased 1000-fold over the level in the untransfected cells. The inverse relationships between hyaluronan production and migration and CD44 expression of cells are of importance for the regulation of cell-extracellular matrix interactions.

Animals↗

PubMed1999

Hyaluronan synthase expression in bovine eyes.

PURPOSE: Hyaluronan (HA), a high-molecular-weight linear glycosaminoglycan, is a component of the extracellular matrix (ECM). It is expressed in eyes and plays important roles in many biologic processes, including cell migration, proliferation, and differentiation. Hyaluronan is produced by HA synthase (HAS), which has three isoforms: HAS1, HAS2, and HAS3. In this study, the HAS expression in the anterior segment of bovine eyes was investigated to determine the significance of HA in eyes. METHODS: To obtain bovine HAS probes, degenerate oligonucleotide primers, based on well-conserved amino acid sequences including the catalytic region of each HAS isoform, were used for reverse transcription-polymerase chain reaction to amplify mRNA from bovine corneal endothelial cells (BCECs). Hyaluronan synthase-1 expression in the anterior segment of bovine eyes at the protein level was investigated by immunohistochemistry. RESULTS: All three HAS isoforms were expressed in BCECs at the mRNA level. Amplified cDNA fragments of HAS1, HAS2, and HAS3 from BCECs can be aligned to human counterparts, showing similarities of 100%, 97.3%, and 100%, respectively, at the amino acid level. Hyaluronan synthase 1 was expressed at the protein level in corneal epithelium, keratocyte, corneal endothelium, conjunctival epithelium, ciliary epithelium, capillary endothelium, and trabecular meshwork. CONCLUSIONS: Hyaluronan synthase isoforms were expressed in the ocular anterior segment and are speculated to be involved in HA production in situ.

Amino Acid Sequence↗

PubMed1998

Characterization of hyaluronan synthase from a human glioma cell line.

In the present study we describe a method to prepare membranes with high hyaluronan synthase activity from human glioma cells by pretreatment of the cells with both testicular hyaluronidase and 4-phorbol 12-myristate 13-acetate (PMA). A 23-fold increase in hyaluronan synthase activity was detected in comparison to untreated cells. Using isolated membranes as a source of hyaluronan synthase activity we demonstrate that chain elongation occurs at the reducing end of the hyaluronan molecule. We also present a method to solubilize hyaluronan synthase in active form with 1% digitonin. The solubilized synthase synthesized shorter hyaluronan chains than the membrane bound enzyme. Partial purification of the solubilized enzyme on a Superdex-200 column revealed a 12-fold increase in specific activity. Affinity purified polyclonal antibodies, raised against a synthetic peptide corresponding to the carboxy-terminus of the deduced protein sequence of human hyaluronan synthase recognized a 66 kDa component in the purified preparations. The elution position of the solubilized hyaluronan synthesizing activity immediately after V0 corresponding to a molecular mass of about 600 kDa, suggested that the 66 kDa enzyme forms a complex with other components which may have accessory or regulatory roles during hyaluronan synthesis.

Animals↗

PubMed1997

Hyaluronan oligosaccharides induce tube formation of a brain endothelial cell line in vitro.

In remodeling tissues the formation of new blood vessels is an essential process which is regulated by different factors. During such processes an increase in hyaluronan synthesis and turnover is often seen and recent observations have suggested that hyaluronan can both promote and inhibit neovascularization depending on its molecular mass. In this work we show that a brain capillary endothelial cell line forms tubes in a collagen gel after stimulation by hyaluronan oligosaccharides. Ultrastructural examination of the tubes by transmission electron microscopy revealed that the cord-like outgrowths consisted of 2-10 tightly packed cells containing a continuous lumen. The tube formation in response to hyaluronan oligosaccharide was not mediated by activation of receptors for fibroblast growth factor. The endothelial cell line, which does not synthesize hyaluronan, exhibited specific hyaluronan-binding sites, with about 3000 hyaluronan molecules (M(r) 3.85 x 10(6)) bound per cell at saturation and Kd was 0.05 x 10(-9) M. Furthermore, the cell line was stained with mAb IVd4 that recognizes a novel class of hyaluronan-binding proteins and mAb IM7 which recognizes CD44 molecules.

Animals↗

PubMed1997

Mechanism of impaired local hyaluronan turnover in bleomycin-induced lung injury in rat.

Hyaluronan, a linear polysaccharide, is accumulated in lung interstitium during different pathological conditions, causing interstitial edema and thereby impaired lung function. We investigated the mechanism of local hyaluronan turnover during the early phase of bleomycin-induced fibrotic lung injury in rats. The binding of [3H]hyaluronan to alveolar macrophages (AM) established from bleomycin-treated rats 1 and 5 days after induction of injury was decreased 8- and 15-fold, respectively, compared with that of AM from saline-treated control counterparts, but at day 14 returned almost to the normal level. Data was confirmed by quantitative cytochemistry, using fluorescein-labeled hyaluronan. Analysis of the expression of CD44, a receptor for hyaluronan, by Western blotting revealed a 30% increase of CD44 molecules expressed on AM from bleomycin-treated rats at day 5 compared with control rats. In particular a lower molecular mass form of CD44 appeared. No expression of the receptor for hyaluronan-mediated motility (RHAMM) could be detected. The internalization and degradation of [3H]hyaluronan by AM, obtained from bleomycin-treated rats at days 1, 5, and 14, were decreased about 65%, 35%, and 30%, respectively, compared with AM from the control rats. The AM lysosomal hyaluronidase activity did not differ significantly between bleomycin-treated and control rats. Our results indicate that a decreased hyaluronan binding capacity of AM may account for the impairment of internalization and thereby degradation of excessive hyaluronan during the early phase of fibrotic lung injury.

Animals↗

PubMed1997

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.

Acetylcysteine↗

PubMed1997

[Functions of the transforming growth factor-beta superfamily in eyes].

One human body is composed of 6 x 10(13) cells, and eyes are also composed of many cells of different functions. The cellular functions and intercellular interaction are regulated by many regulators including cytokines and growth factors to maintain the homeostasis. The transforming growth factor-beta (TGF-beta) superfamily, a large family of multifunctional factors, regulates various cellular functions, including cellular proliferation, migration, differentiation, apoptosis and extracellular matrix production. The TGF-beta superfamily contains about 30 multifunctional factors, and is divided into several families according to the sequence homology. The TGF-beta family, the activin family, and bone morphogenic proteins belong to the TGF-beta superfamily. TGF-beta superfamily members transduce signals through type I and type II serine/threonine type transmembrane receptors. The signals are transduced from receptors through nuclei by Smad family members, which are phosphorylated by the activated type I receptors and translocate from cytoplasm into nuclei. TGF-beta family members and the TGF-beta superfamily receptor family are expressed in ocular tissues including the cornea, ciliary epithelium, lens epithelium, retina, and blood vessels. This observation suggests the importance of the TGF-beta superfamily in eyes. Smad family members (Smad 1, Smad 2, Smad 3 and Smad 4) are expressed in the cultured retinal pigmant epithelial cell line (D407), in which TGF-beta and activin A stimulate the translocation of Smad 2, but not Smad 1 into nuclei, whereas bone morphogenetic protein (BMP) stimulates that of Smad 1, but not Smad 2. TGF-beta superfamily members play important roles in the pathogenesis of retinal neovascularization and in the wound healing process of corneal tissue. TGF-beta inhibits the endothelial functions, but, stimulates angiogenesis in vivo. TGF-beta is involved in the formation of abnormal connective tissue in corneal wound healing. In these processes, many cytokines and growth factors are involved, interacting with each other and forming networks. It is mandatory to clarify the networks to investigate molecular pathogenesis and new therapeutic agents.

Diabetic Retinopathy↗

PubMed1996

Functional cloning of the cDNA for a human hyaluronan synthase.

Hyaluronan is a constituent of the extracellular matrix of connective tissue and is actively synthesized during wound healing and tissue repair to provide a framework for ingrowth of blood vessels and fibroblasts. Changes in the serum concentration of hyaluronan are associated with inflammatory and degenerative arthropathies such as rheumatoid arthritis. In addition, hyaluronan has been implicated as an important substrate for migration of adhesion of leukocytes during inflammation. A human hyaluronan synthase (HuHAS1) cDNA was isolated by a functional expression cloning approach. Transfection of CHO cells conferred hyaluronidase-sensitive adhesiveness of a mucosal T cell line via the lymphocyte hyaluronan receptor, CD44, as well as increased hyaluronan levels in the cultures of transfected cells. The HuHAS1 amino acid sequence shows considerable homology to the hasA gene product of Streptococcus pyogenes, a glycosaminoglycan synthetase from Xenopus laevis (DG42), and is the human homolog of a recently described murine hyaluronan synthase.

Amino Acid Sequence↗

PubMed1996

Stimulatory effects of pleural fluids from mesothelioma patients on CD44 expression, hyaluronan production and cell proliferation in primary cultures of normal mesothelial and transformed cells.

Cell lines established from human malignant mesotheliomas, but not from normal mesothelial cells, have been shown to possess hyaluronan receptors, and to secrete factors that stimulate hyaluronan production by fibroblasts and normal mesothelial cells. In the present study we investigated the generality of this observation, namely the presence of hyaluronan receptors and factors which induce stimulation of hyaluronan synthesis in primary mesothelioma and mesothelial cell cultures. Functionally active hyaluronan-binding sites on the surface of malignant mesothelioma cells in primary cultures, established from pleural effusions of 3 different patients, were demonstrated using 3H-hyaluronan. Primary cultures of normal mesothelial cells from non-mesothelioma effusions did not exhibit any binding ability. Pleural fluids from mesothelioma patients both stimulated hyaluronan synthesis and promoted proliferation of normal mesothelial cells to a larger extent than non-mesothelioma fluids. The hyaluronan-stimulatory activity was only slightly neutralized by antibodies against PDGF-BB or TGF-beta; antibodies against bFGF had no effect. Although the concentration of hyaluronan was much higher in pleural fluids from mesothelioma than from non-mesothelioma patients, its molecular weight was almost the same. The hyaluronan-binding capacity of early-passage mesothelioma cells derived from pleural effusions can be an additional marker, in combination with other diagnostic tools, to distinguish between mesothelioma and mesothelial cells.

Biological Factors↗

PubMed1996

Biosynthesis and degradation of hyaluronan by nonparenchymal liver cells during liver regeneration.

Hepatic stellate cells (HSC) and endothelial cells of the liver sinusoids synthesize and degrade hyaluronan, respectively. The roles of these cell types in the biosynthesis and degradation of hyaluronan were studied during regeneration following partial hepatectomy. Pure cultures of HSC and liver endothelial cells (LEC) were obtained from regenerating liver at different stages using a Nycodenz gradient followed by discontinuous Percoll gradient. The HSC that established 3 or 4 days after partial hepatectomy synthesized large amounts of hyaluronan when cultured in the presence of fetal calf serum (FCS) or platelet-derived growth factor B-chain homodimer (PDGF)-BB. These cells, as well as LEC, expressed active PDGF beta-receptors. Furthermore, the ability of LEC to degrade hyaluronan was decreased at early stages of liver regeneration. The increased synthesis of hyaluronan by HSC and the failure of LEC to catabolize the polysaccharide resulted in elevated hyaluronan concentrations in the blood.

Animals↗