Expression of proteoglycans and hyaluronan during wound healing

A role for decorin in the structural organization of periodontal ligament

Decorin is a small leucine-rich proteoglycan that interacts with several matrix molecules, including various types of collagen and growth factors, and suppresses the growth of neoplastic cells by an epidermal growth factor (EGF) receptor-mediated pathway. Decorin is abundantly expressed in the periodontal connective tissues during development and tissue maintenance. In periodontal disease, which is one of the most common diseases in the human kind, the level of decorin is decreased in the periodontal connective tissue. Abnormal expression of decorin may also associate with certain inherited disorders that involve increased susceptibility to severe periodontal disease in the early childhood. Therefore, we investigated the periodontal tissues of mice with targeted disruption of the decorin gene. Gross and microscopic analyses showed that decorin-deficient mice appeared to have normal tooth development and eruption, and there were no signs of periodontal disease. However, electron microscopic analysis revealed abnormal morphology and organization of the collagen fibrils in the periodontal ligament. The number of periodontal ligament fibroblasts in the decorin-deficient mice was also increased about two-fold as compared with the wild-type mice. In cell culture, ectopic overexpression of decorin in NIH 3T3 fibroblasts or decorin added exogenously to periodontal fibroblasts suppressed cell growth. However, blocking the EGF receptor tyrosine kinase activity did not prevent the decorin-elicited growth suppression in periodontal fibroblasts. Additionally, decorin did not induce a marked increase in the relative expression of p21 mRNA in periodontal fibroblasts. Therefore, decorin appeared to regulate growth of normal periodontal fibroblasts by a mechanism distinct from that reported for neoplastic cells. The findings demonstrate that decorin plays a role in the organization of collagen fibrils and regulates cell proliferation in the periodontal ligament.

Expression of glycosaminoglycans and small proteoglycans in wounds: modulation by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu(2+)

Glycyl-histidyl-lysine-Cu(2+) is a tripeptide-copper complex previously shown to be an activator of wound healing. We have investigated the effects of glycyl-histidyl-lysine-Cu(2+) on the synthesis of glycosaminoglycans and small proteoglycans in a model of rat experimental wounds and in rat dermal fibroblast cultures. Repeated injections of glycyl-histidyl-lysine-Cu(2+) (2 mg per injection) stimulated the wound tissue production, as appreciated by dry weight and total protein measurements. This stimulation was accompanied by an increased production of type I collagen and glycosaminoglycans (assessed, respectively, by hydroxyproline and uronic acid contents of the chamber). Electrophoretic analysis of wound tissue glycosaminoglycans showed an accumulation of chondroitin sulfate and dermatan sulfate in control wound chambers, whereas the proportion of hyaluronic acid decreased with time. The accumulation of chondroitin sulfate and dermatan sulfate was enhanced by glycyl-histidyl-lysine-Cu(2+) treatment. The expression of two small proteoglycans of the dermis, decorin and biglycan, was analyzed by northern blot. The biglycan mRNA steady-state level in the chamber was maximal at day 12, whereas the decorin mRNA increased progressively until the end of the experiment (day 22). Glycyl-histidyl-lysine-Cu(2+) treatment increased the mRNA level of decorin and decreased those of biglycan. In dermal fibroblast cultures, the stimulation of decorin expression by glycyl-histidyl-lysine-Cu(2+) was also found. In contrast, biglycan expression was not modified. These results show that the expression of different proteoglycans in wound tissue are regulated in a different manner during wound healing. The glycyl-histidyl-lysine-Cu(2+) complex is able to modulate the expression of the extracellular matrix macromolecules differently during the wound repair process.

The wound healing properties of Channa striatus-cetrimide cream-wound contraction and glycosaminoglycan measurement

Haruan has been proved to influence the different phases of wound healing process. The current research focuses on the effects of haruan on the different constituents of extracellular matrix of healing wounds in normal and diabetic rats. Anaesthetized normal and streptozotocin induced diabetic rats were provided with excision wounds at the back and then animals were divided into four groups as: group 1, wounds treated with cetrimide+haruan cream; group 2, wounds treated with haruan cream; group 3, wounds treated with cetrimide (commercial) cream; and group 4, wounds untreated and served as control. Animals were sacrificed after 3, 6, 9 and 12 days. These wounds were used to determine the hexosamine, protein, uronic acid and glycosaminoglycan contents and the wound contraction. The results suggested a marked increase (P<0.05) in the uronic acid, hexosamine and dermatan sulfate contents on day 3 of group 1 when compared with groups 2-4. Wound contraction of group 1 was also markedly enhanced of group 1 (P<0.01) when compared with groups 2- 4. On the basis of these results, we conclude that haruan enhances the synthesis of different glycosaminoglycans in healing wounds, which are the first component of extracellular matrix to be synthesized during the wound healing process. The enhanced levels of glycosaminoglycans may help in the formation of a resistant scar and enhanced wound contraction represents the positive influence of haruan on the fibroplastic phase of wound healing.

CD44 as a receptor for colonization of the pharynx by group A Streptococcus

The pharynx is the primary reservoir for strains of group A STREPTOCOCCUS: (GAS) associated both with pharyngitis (streptococcal sore throat) and with invasive or "flesh-eating" soft tissue infections. We now report that CD44, a hyaluronic acid-binding protein that mediates human cell-cell- and cell-extracellular matrix-binding interactions, functions as a receptor for GAS colonization of the pharynx in vivo. We found that attachment of GAS to murine epithelial keratinocytes was mediated by binding of the GAS hyaluronic acid capsular polysaccharide to CD44. In studies of transgenic mice with a selective defect in epithelial expression of CD44, GAS adherence to CD44-deficient keratinocytes in vitro was reduced compared with adherence to keratinocytes expressing normal levels of CD44. After intranasal inoculation, GAS colonized the oropharynx of wild-type mice but failed to colonize transgenic mice deficient in CD44 expression. GAS colonization of wild-type mice could be blocked by coadministration of mAb to CD44 or by pretreatment of the animals with exogenous hyaluronic acid. These results provide evidence that CD44 serves as a receptor for GAS colonization of the pharynx and support the potential efficacy of disrupting the interaction between the GAS hyaluronic acid capsule and CD44 as a novel approach to preventing pharyngeal infection.

Deposition of laminin 5 in epidermal wounds regulates integrin signaling and adhesion

Adhesion of keratinocytes in a wound outgrowth to laminin 5 in the basement membrane via integrins alpha6beta4 and alpha3beta1 is distinct from adhesion to dermal collagen via alpha2beta1 or to fibronectin via alpha5beta1. Leading cells in the outgrowth are distinguished from following keratinocytes by deposition of laminin 5, failure to communicate via gap junctions and sensitivity to toxin B, an inhibitor of RhoGTPase. Laminin 5 deposited by leading keratinocytes onto dermal collagen dominates over dermal ligands and changes the cell signals required for adhesion from collagen-dependent to laminin-5-dependent. Thus, deposition of laminin 5 can instruct keratinocytes to switch from an activated phenotype to a quiescent and integrated epithelial phenotype.

Influence of phonation on basement membrane zone recovery after phonomicrosurgery: a canine model

The process of wound healing at the basement membrane zone of the vocal folds after phonomicrosurgery was investigated. The influence of phonation and the implied optimal period of voice rest were considered. Phonomicrosurgery was performed on both vocal folds of 20 adult dogs. In 10 dogs, the left recurrent laryngeal nerve was simultaneously resected to simulate iatrogenic voice rest; the remaining 10 dogs were allowed to phonate normally. The healing process of the vocal folds of each group was observed at 1, 2, 4, 8, and 12 weeks after surgery with immunohistochemical staining and transmission electron microscopy. In the voice rest group, the basement membrane was completely re-formed in 2 weeks, and the "cover" appeared completely rearranged by 8 weeks. The results of the phonation group were characterized by a delayed healing process and basement membrane changes. These results suggest that voice rest of at least 2 weeks after surgery may be beneficial and that vocal hygiene should be maintained for as long as 8 weeks.

Role of hyaluronan in acute pancreatitis

BACKGROUND

The connective tissue component hyaluronan is accumulated locally in the damaged tissue during various inflammatory conditions. Owing to the strong water-binding capacity of this glycosaminoglycan, increased tissue content of hyaluronan is paralleled by the development of interstitial edema. The aim with the current experiment was to investigate whether hyaluronan is accumulated in acute pancreatitis and if increased levels of hyaluronan can be correlated to the inflammation of the pancreatic tissue.

METHODS

Acute pancreatitis was induced in Sprague-Dawley rats by the administration of supramaximal doses of the cholecystokinin analogue caerulein. The animals were followed for 5 hours (n = 4), 24 hours (n = 6), or 48 hours (n = 5), and the pancreata were then investigated for hyaluronan and water content, hyaluronan distribution, general morphology and the presence of CD44-positive cells, macrophages, and T lymphocytes.

RESULTS

Hyaluronan accumulated in the edematous interstitium during acute pancreatitis. Twenty-four hours after the induction of pancreatitis, the hyaluronan content of the pancreata had increased by more than 100%. Simultaneously, CD44-positive cells infiltrated the tissue. However, no correlation between hyaluronan and water was seen at any time point.

CONCLUSIONS

This study shows that acute pancreatitis is associated with a strong but transient increase in interstitial hyaluronan and an infiltration of CD44-positive cells located mainly in the same region as the accumulated hyaluronan.

Hyaluronan anchoring and regulation on the surface of vascular endothelial cells is mediated through the functionally active form of CD44

CD44 on lymphocytes binding to its carbohydrate ligand hyaluronan can mediate primary adhesion (rolling interactions) of lymphocytes on vascular endothelial cells. This adhesion pathway is utilized in the extravasation of activated T cells from the blood into sites of inflammation and therefore influences patterns of lymphocyte homing and inflammation. Hyaluronan is a glycosaminoglycan found in the extracellular matrix and is involved in a number of biological processes. We have shown that the expression of hyaluronan on the surface of endothelial cells is inducible by proinflammatory cytokines. However, the manner through which hyaluronan is anchored to the endothelial cell surface so that it can resist shear forces and the mechanism of the regulation of the level of hyaluronan on the cell surface has not been investigated. In order to characterize potential hyaluronan receptors on endothelial cells, we performed analyses of cell surface staining by flow cytometry on intact endothelial cells and ligand blotting assays using membrane fractions. Hyaluronan binding activity was detected as a major species corresponding to the size of CD44, and this was confirmed to be the same by Western blotting and immunoprecipitation. Moreover, alterations in the surface level of hyaluronan after tumor necrosis factor-alpha stimulation is regulated primarily by changes in the cell surface levels of the hyaluronan-binding form of CD44. In laminar flow assays, lymphoid cells specifically roll on hyaluronan anchored by purified CD44 coated on glass tubes, indicating that the avidity of the endothelial CD44/hyaluronan interaction is sufficient to support rolling adhesions under conditions mimicking physiologic shear forces. Together these studies show that CD44 serves to anchor hyaluronan on endothelial cell surfaces, that activation of CD44 is a major regulator of endothelial surface hyaluronan expression, and that the non-covalent interaction between CD44 and hyaluronan is sufficient to provide resistance to shear under physiologic conditions and thereby support the initial steps of lymphocyte extravasation.

Immunolocalization of CD44 adhesion molecules in human periradicular lesions

OBJECTIVE

The hyaluronate receptor CD44 is a cell surface protein that is involved in several functions. To elucidate whether CD44 plays a role in periapical lesions, an immunohistochemical technique was used to study its distribution.

STUDY DESIGN

Twenty periapical lesions-16 periapical granulomas and 4 radicular cysts-constituted the sample. Formalin-fixed/paraffin-embedded tissue sections were studied by means of immunohistochemistry for the presence of the standard CD44H form and its V3 splicing variant.

RESULTS

Immunohistochemical staining for CD44H and CD44V3 was observed on epithelial, endothelial, and connective tissue cells. The cells of the fibrous lining around each granuloma were positive, showing an immune reactive pattern directly correlated with the dimension of the lesion. Epithelial rests of Malassez were strongly positive; the reaction product was also evident in the epithelial lining of the cysts. Blood vessels, mainly observed around the lesion, were immunoreactive for CD44.

CONCLUSIONS

Our findings demonstrate that CD44H and its V3 variant are expressed in at least 3 different tissue types of periapical lesions. These glycoproteins may be involved in different steps of periapical lesion pathogenesis and evolution.

Time-dependent changes of decorin in the infarct zone after experimentally induced myocardial infarction in rats: comparison with biglycan

Decorin, a small dermatan sulphate proteoglycan, has been postulated to interact with other components of the extracellular matrix. We examined time-dependent changes of decorin in the infarct zone after experimentally induced myocardial infarction in rats by Northern blotting, in situ hybridization, and immunohistochemistry. The expression of decorin mRNA was compared to that of biglycan mRNA. Northern blotting demonstrated that the decorin mRNA expression was not increased in the infarct zone on day 2, while increased biglycan mRNA was observed at that time (average 3.1-fold increase). Decorin mRNA expression was increased on day 7, and reached a peak (average 2.2-fold increase) around day 14. Biglycan mRNA expression also reached a peak level around day 14 (average 13.3-fold increase). In situ hybridization revealed that mRNA signals for decorin did not appear in the infarct zone on day 2, while biglycan mRNA signals were observed. Decorin mRNA signals were observed in spindle-shaped mesenchymal cells in the infarct peripheral zone on day 7. The decorin mRNA signals appeared later than those of biglycan. Immunopositive staining for decorin was observed in the infarct zone on day 7. The present results demonstrated a time-dependent increase in decorin mRNA expression in mesenchymal cells in the infarct zone in rats. Decorin mRNA appeared later and was increased to a lower extent in the infarct zone than biglycan mRNA.

Induction of CD44 expression in stab wounds of the brain: long term persistence of CD44 expression

We studied the expression of the hyaluronan receptor protein CD44 in the mouse brain in response to stab injuries. CD44 expression was strongly activated in the area surrounding the injury within 2 days and then persisted for over 2 months. The expression extended in a direct line the depth of the actual wound inflicted. It appears that CD44 may be involved in the wound healing processes following injury to the brain.

Inhibition of hyaluronan synthesis by vesnarinone in cultured human myofibroblasts

Hyaluronan (HA), which is a major component of the extracellular matrix (ECM), is regulated during myofibroproliferative responses to numerous forms of inflammatory stimuli. It is a key factor involved in cellular migration and adherence. The development of a potent and non-toxic inhibitor of HA synthesis would open up a new avenue for the treatment of fibrocontractive diseases such as pulmonary fibrosis and liver cirrhosis. In this study, the effects of vesnarinone (OPC-8212: 3,4-dihydro-6-[4-(3, 4-dimethoxybenzoyl)-1-piperazinyl]-2(1H)-quinolinone) on the secretion of HA in human myofibroblast cell lines (MRC-5 and LI90 cells, referred to as pulmonary and hepatic myofibroblasts, respectively) were examined. Vesnarinone specifically and dose-dependently inhibited HA secretion by myofibroblasts up-regulated by fetal calf serum (FCS). The treatment of vesnarinone did not modify the phenotype of myofibroblast cells in culture. Vesnarinone also potently inhibited the HA secretion by the two myofibroblast cell lines up-regulated by transforming growth factor-beta1 (TGF-beta1) or tumor necrosis factor-alpha (TNF-alpha). The addition of vesnarinone to myofibroblasts resulted in a significant decrease of HA synthase (HAS) activity, with or without the addition of FCS or either cytokine. These findings suggest that vesnarinone inhibits the secretion of HA in myofibroblasts by specifically suppressing HAS activity, and may therefore prove useful for the treatment of chronic inflammation and tissue fibrosis.

Proteoglycan metabolism during repair of the ruptured medial collateral ligament in skeletally mature rabbits

The metabolism of the chondroitin/dermatan sulfate (CS/DS) proteoglycans (PGs) decorin and biglycan is markedly altered during short-term (3-6 weeks) and long-term (40 weeks-2 years) repair of surgically ruptured medial collateral ligaments from mature rabbits. A PG-rich extracellular matrix accumulates in injury gaps by 3 weeks postsurgery and extends into tissue regions containing the original ligaments, and elevated PG levels remain apparent up to 2 years postinjury. CS/DS PGs were prepared from such ligaments and identified after SDS-polyacrylamide gel electrophoresis by Alcian blue staining or immunoblotting. In normal ligaments, decorin is the most abundant proteoglycan (accounting for approximately 80% of the total); the remainder is biglycan and a large PG, possibly versican. In repairing ligaments, decorin is barely detected, but instead a large proteoglycan and abundant amounts of biglycan accumulate. Biglycan is present in two forms in repairing ligaments, and they can be separated on SDS-PAGE into 200- and 140-kDa forms. The slower migrating species is absent in normal ligaments and may represent a different glycoform (containing either a single or two short chondroitin/dermatan sulfate chains) of biglycan. Alteration in PG expression and posttranslational processing during medial collateral ligament repair are similar to those reported for repair and scar formation of other connective tissues. The accumulation of biglycan observed here may interfere with proper collagen network remodeling and may lead to persistent inflammatory and matrix turnover processes, thus preventing restoration of a long-term functional ligament tissue.

Different integrins mediate cell spreading, haptotaxis and lateral migration of HaCaT keratinocytes on fibronectin

Collaborative role of various fibronectin-binding integrins (alpha5beta1, alphavbeta1 and alphavbeta6) as mediators of cell adhesion and migration on fibronectin was studied using cultured HaCaT keratinocytes. This cell line spontaneously expressed all three fibronectin-binding integrins. In addition, the expression of alphavbeta6 integrin was strongly and specifically upregulated by transforming growth factor-beta1 (TGFbeta1) whereas the amount of other integrins remained practically unchanged on the cell surface. Adhesion, spreading and motility of HaCaT keratinocytes on fibronectin were promoted by TGFbeta1. Based on antibody blocking experiments, both untreated and TGFbeta1-treated HaCaT cells used alphavbeta6 integrin as their main fibronectin receptor for cell spreading. In contrast to TGFbeta1-treated cells, the untreated cells also needed alpha5beta1 integrin for maximal cell spreading on fibronectin. Combinations of antibodies blocking both of these receptors totally prevented spreading of both untreated and TGFbeta1-treated cells. Haptotactic motility of individual HaCaT cells through fibronectin-coated membranes was again mainly dependent on alphavbeta6 integrin, while alphavbeta1 and alpha5beta1 integrins played a lesser role both in untreated and TGFbeta1-treated HaCaT cells. However, unlike haptotaxis, lateral migration of HaCaT cell sheet was mainly mediated by beta1 integrins, and alphavbeta6 integrin showed a minor role. The migration process appeared to involve a number of beta1 integrins that could adaptively replace each other when blocking antibodies were present. Thus, keratinocytes appear to use different fibronectin receptors for different functions, such as cell spreading, haptotaxis and lateral migration. The cells can also adapt to a situation where one receptor is unfunctional by switching to another receptor of the same ligand.

Expression of CD44 in kidney after acute ischemic injury in rats

De novo CD44 and ligand expression at wound margins accompanies cellular proliferation and migration that effect repair of injured mucosal and vascular endothelial tissues. To determine whether CD44 could play a role in recovery from acute ischemic renal injury, we characterized its renal expression and those of two of its ligands, hyaluronic acid and osteopontin. Although no expression is detectable in nonischemic kidneys, several mRNAs for CD44 are present within 1 day after injury. CD44 mRNA is expressed in proximal tubules undergoing repair. CD44 peptide is present in basal and lateral cell membranes. Hyaluronic acid is normally expressed in the interstitium of the renal papilla only. By 1 day postischemia, hyaluronic acid can be detected, in addition, in the interstitium surrounding regenerating tubules. Osteopontin, not normally expressed in the renal proximal tubule, is expressed in regenerating tubules by 3 days after induction of acute ischemic injury. Immunoreactive osteopontin peptide continues to be localized in those tubules still undergoing repair for as long as 7 days after the injury. Our data are consistent with a role for CD44-ligand interactions in the regenerating proximal tubule participating in the process of recovery after ischemic injury.

CD44 expression marks the onset of keratinocyte stratification and mesenchymal maturation into fibrous dermis in fetal human skin

The cell surface glycoprotein CD44 is involved in active cell movement, cancer metastasis, and morphogenesis. We studied its expression in fetal human skin using an antibody specific for CD44v3 and another that recognizes all CD44 forms. In embryonic and early fetal skin, only cells with dendritic morphology expressed CD44. The first keratinocyte expression of CD44 occurred in the basal cells on the eleventh week. Later, the suprabasal cells also turned positive, whereas periderm and the terminally differentiated cells remained negative at all stages. Maturation of the early mesenchyme towards dermis at the eleventh week was associated with an increase in the number of CD44-positive cells, and later the fibrous extracellular matrix also became CD44-positive. During hair induction, the epithelium showed a transient downregulation of CD44. Later, the follicular cells regained CD44. Cells in the primordial dermal papilla displayed a continuously strong signal. The sweat gland anlagen showed faint CD44 positivity. Exon 3 was present in the CD44 of keratinocytes and their derivatives but was absent in dermis. CD44 expression in human fetal skin is a relatively late event, associated with maturation and adult-type differentiation both in epidermal keratinocytes and in dermal fibroblastic cells.(J Histochem Cytochem 47:1617-1624, 1999)

Immunomodulatory functions of hyaluronate in the LEW-to-F344 model of chronic cardiac allograft rejection

BACKGROUND

CD44 is an important leukocyte cell surface glycoprotein with diverse functions including cell adhesion, homing, migration, and activation.

METHODS

Because administration of the principal ligand of CD44, hyaluronate (HA), in soluble form, can inhibit CD44-HA interaction, we tested the effects of HA in vivo in an established model of chronic allograft rejection. Control F344 recipients of LEW hearts received either no treatment or low-dose cyclosporine (CsA) for 30 days from the day of transplantation. Experimental animals received 30 days of CsA in combination with 30 or 90 days of low molecular weight HA (LMW-HA).

RESULTS

CsA therapy alone resulted in approximately 40% long-term (>100 days) graft survival, whereas CsA + LMW-HA (30-day and 90-day protocols) significantly increased long-term graft survival to 60% and 92%, respectively. Light microscopy and immunohistology of CsA-treated and CsA + LMW-HA-treated grafts harvested at day 30 after transplantation demonstrated that LMW-HA + CsA therapy decreased mononuclear cell infiltration and afforded better preservation of myocardial architecture. In addition, LMW-HA + CsA-treated grafts exhibited decreased expression of interferon-gamma and the growth factors transforming growth factor-beta, platelet-derived growth factor, and fibrogenic growth factor-beta. Long-term surviving grafts were assessed for arteriosclerosis, the sine qua non of chronic rejection in this model. Using a standardized scoring system, significantly less arteriosclerosis was seen in grafts from LMW-HA + CsA-treated animals at 120 days after transplantation compared with CsA alone-treated grafts. This difference was not significant, however, in grafts harvested at >150 days.

CONCLUSION

This is the first report indicating that CD44-HA interactions play an important role in chronic allograft rejection.

Functions of hyaluronan in wound repair

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

Expression of heat shock proteins in mouse skin during wound healing

Wound healing conditions generate a stressful environment for the cells involved in the regeneration process and are therefore postulated to influence the expression of heat shock proteins (Hsps). We have examined the expression of four Hsps (Hsp27, Hsp60, Hsp70 and Hsp90) and a keratin (keratin 6) by immunohistochemistry during cutaneous wound repair from Day 1 to Day 21 after wounding in the mouse. Hsps were constitutively expressed in normal mouse epidermis and their patterns of expression were modified during the healing process. The changes were not directly linked to the time course of the healing process but rather were dependent on the location of cells in the regenerating epidermis. In the thickened epidermis, Hsp60 was induced in basal and low suprabasal cells, Hsp70 showed a reduced expression, and Hsp90 and Hsp27 preserved a suprabasal pattern with an induction in basal and low suprabasal cells. All Hsps had a uniform pattern of expression in the migrating epithelial tongue. These observations suggest that the expression of Hsps in the neoepidermis is related to the proliferation, the migration, and the differentiation states of keratinocytes within the wound.

TGF-beta1 influences early gingival wound healing in rats: an immunohistochemical evaluation of stromal remodelling by extracellular matrix molecules and PCNA

The effect of topically applied transforming growth factor beta1 (TGF-beta1) on the rat gingival wound healing process after flap surgery was evaluated by immunohistochemistry for extracellular matrix molecules (ECM), such as tenascin, heparan sulfate proteoglycan (HSPG) and type IV collagen, and for proliferating cell nuclear antigen (PCNA) in fibroblasts. TGF-beta1 solution was applied to the surgical wound experimental sites. Two microg/microl were applied at the time of the operation, and 1 microg/microl at days 1 and 2 after surgery, with contralateral control sites receiving the vehicle alone. Periodontal tissues were histologically examined at 3 and 7 days post-surgery. Tenascin was found to be more strongly stained in the granulation tissue from experimental sites at 3 days post-surgery. At 7 days postsurgery, HSPG-positive areas in granulation tissue had become smaller and there was a prominent proliferation of PCNA-positive fibroblast-like cells and type IV collagen-positive blood vessels. These results suggest that TGF-beta1 applied to surgical wounds influences early proliferation of gingival fibroblast-like cells, the formation of blood vessels, and ECM remodelling. In conclusion, TGF-beta1 application appears to promote granulation tissue formation in periodontal wound healing.

Effect of rebamipide on the glycosaminoglycan content of the ulcerated rat stomach

To elucidate the mechanism of the anti-ulcer effect of rebamipide (2-(4-chlorobenzoylamino)-3-[2-(1H)-quinolinon-4-yl] propionic acid), changes in glycosaminoglycan (GAG), uronic acid and hexosamine contents of stomach tissue were examined in rats treated with the ulcer-inducing agents and/or rebamipide. Uronic acid and hexosamine contents in acid hydrolysates of stomach tissue were increased after diethyldithiocarbamate (DDC, 800 mg/kg, s.c.) or histamine (300 mg/kg, i.p.) treatment, and similar changes in the GAG, uronic acid, and hexosamine levels were observed in stomach tissue extracts. Pretreatment with rebamipide (60 mg/kg, i.p.) resulted in an additional increase in the contents of the above components after DDC or histamine treatment. However, rebamipide treatment alone did not increase the gastric contents of GAG and GAG components in normal rats. Gel filtration chromatography of extracted GAGs suggested that DDC, histamine and rebamipide treatments do not cause a change in the aggregated forms of gastric GAGs. These results suggest that rebamipide stimulates the GAG synthesis in the ulcerated stomach and that this effect may contribute to the healing process of gastric ulcer.

Hyaluronan production in human rheumatoid fibroblastic synovial lining cells is increased by interleukin 1 beta but inhibited by transforming growth factor beta 1

OBJECTIVES

To investigate the regulatory roles of interleukin 1 beta (IL1 beta), tumour necrosis factor alpha (TNF alpha), interferon gamma (IFN gamma) or transforming growth factor beta 1 (TGF beta 1) on hyaluronan (HA) synthesis by human fibroblastic synovial lining cells.

METHODS

Concentrations of HA in culture supernatants of fibroblastic synovial lining cell line (RAMAK-1 cell line) with or without stimulation by IL1 beta, TNF alpha, IFN gamma or TGF beta 1 were measured by sandwich binding protein assay. Levels of HA synthase mRNA of the cells with or without stimulation were detected by reverse transcribed polymerase chain reaction. Molecular weights of HA in the culture supernatants of the cells with or without stimulation were measured using high performance gel permeation liquid chromatography.

RESULTS

HA synthesis by the cells was not significantly augmented by TNF alpha or by IFN gamma. It was significantly stimulated by IL1 beta but inhibited by TGF beta 1. Molecular weights of HA in the culture supernatants of the cells were unchanged by stimulation with TNF alpha. They were remarkably increased by stimulation with IL1 beta and IFN gamma, but reduced with TGF beta 1.

CONCLUSION

IL 1 beta is an up regulator of HA synthesis, while TGF beta 1 is a down regulator. HA production in the synovial lining cells of inflamed joints (for example, rheumatoid arthritis) might be regulated by the balance of these cytokines.

Use of hyaluronic acid binding protein for detection of hyaluronan in ligature-induced periodontitis tissue

This study was designed to demonstrate, by use of biotin-labeled hyaluronic acid binding protein (HABP) and an avidin-enzyme system, the localization of hyaluronan (HA) in periodontal tissue of beagle dogs during experimentally induced periodontitis. Experimental periodontitis was induced in the dogs by ligation of the gingival sulcus. Experimental tissue was collected at 0, 3, 7 and 21 days after ligation. HA was revealed by strong staining in the intercellular space around epithelial cells and periodontal ligament, and by light staining in the gingival connective tissue. According to the progression of periodontal tissue breakdown, HA was detected in a small number of leukocytes and monocytes, on the surface of osteoclasts, the surface of alveolar bone, thickened endothelium and in epithelial cells related to rete peg formation. Streptomyces hyaluronidase-treated specimens gave negative staining. This study suggests that HA may be associated with the inflammatory reaction in experimental periodontitis tissue.

Hyaluronic acid capsule modulates M protein-mediated adherence and acts as a ligand for attachment of group A Streptococcus to CD44 on human keratinocytes

We used wild-type and isogenic mutant strains of group A Streptococcus (GAS) that expressed M protein, capsule, or both to study the function of M protein and the hyaluronic acid capsular polysaccharide in attachment of GAS to human keratinocytes. Types 6 and 24, but not type 18, M protein were found to mediate attachment of GAS to soft palate or skin keratinocytes, but this interaction was prevented by the hyaluronic acid capsule on highly encapsulated, or mucoid, strains. Monoclonal antibody to CD44, the principal hyaluronic acid-binding receptor on keratinocytes, inhibited attachment of both highly encapsulated and poorly encapsulated wild type strains of GAS, but not the attachment of acapsular mutants. Transfection of K562 cells with cDNA encoding human CD44 conferred the capacity to bind each of six wild-type strains of GAS, but not to bind acapsular mutants. Because, in contrast to other potential adhesins, the group A streptococcal capsule is both highly conserved and surface-exposed, it may serve as a universal adhesin for attachment of diverse strains of GAS to keratinocytes of the pharyngeal mucosa and the skin.

Hyaluronan induces scarless repair in mouse limb organ culture

BACKGROUND/PURPOSE

Wounded fetal mouse limbs harvested from two distinct time points in gestation heal differently in organ culture. The healing of a gestational day 14 limb is by scarless repair, whereas gestational day 18 (gd 18) limbs heal by scarring. The persistence of elevated levels of hyaluronic acid (HA) is a major difference in the extracellular matrix of scarless repair. The purpose of this study was to demonstrate that chronic additions of HA to incisional wounds of gd 18 limbs induces scarless repair.

METHODS

Time-dated pregnant CD-1 mice (term, 20 days) were killed on gestational day 18 and fetuses were harvested via laparotomy. A through and through stab wound was made in each forelimb with a 1-mm microscapel, and the wound was closed with a single 10-0 nylon suture. The forelimbs were amputated at the level of the shoulder and placed in organ culture. Daily medium changes with 1 mL of BGJb (devoid of serum) were made. Half the cultures received 10 microL of HA (4 mg/mL) directly to the wound site with each medium change. The other half of the cultures received 10 microL of phosphate-buffered saline (PBS-control). At day 7, the limbs were harvested, fixed in methyl Carnoys solution, paraffin embedded, and 5-microm serial sections cut. The sections were stained with H&E or Sirius red/fast green. The sections were viewed in a blinded fashion by two observers. Suture defined the wound site, and the sections were graded for healing by scarring.

RESULTS

Minimal limb growth occurred in both control and HA-treated limbs. Grossly, both control and treated limbs healed incisional wounds by 7 days in culture. Limbs from both treatment and control groups showed viability by microscopic analysis. The limbs treated with HA had no appreciable scar morphologically in sections in which epithelial dimpling and suture were evident. The orientation of the collagen fiber bundles in the control wounds were in parallel arrays perpendicular to the incision. The orientation of the collagen fiber bundles in the HA-treated limbs had a basket weave pattern that was indistinguishable from unwounded dermis. The direct repeated additions of HA to healing organ cultured limb explants of gestational day 18 fetal mice promoted scarless repair.

CONCLUSIONS

This result demonstrates that chronic elevation of HA in the microenvironment of a wound affects healing by promoting the deposition of a more dermal-like connective tissue matrix in the wound site. The maintenance of elevated levels of HA could have utility in the clinical setting to improve the organization of connective tissue, leading to the reduction of scar complications.

Wound healing: a paradigm for lumen narrowing after arterial reconstruction

PURPOSE

The intimal hyperplasia hypothesis that equates lumen narrowing after arterial injury with intimal mass has recently been challenged. Evidence has emerged to suggest that lumen narrowing is caused in large part by changes in artery wall geometry rather than intimal mass per se. We have begun to explore this hypothesis in a unique nonhuman primate model of atherosclerosis.

METHODS

Monkeys who were fed an atherogenic diet for 3 to 5 years underwent experimental angioplasty of the left iliac artery. The contralateral iliac artery served as an intraanimal control. Arteries were removed 2, 4, 7, 14, 28, or 112 days later for analysis (6 or 13 per time point). Angioplasty dilated arteries by fracturing atheroma and stretching or tearing the media. Cross-sections of injured arteries were analyzed for expression of extracellular matrix components and cell surface integrins that are important in wound healing. Antibodies, riboprobes, or histochemical stains specific for fibrin, hyaluronan, versican (chondroitin sulfate-containing proteoglycan), procollagen-I, elastin, and the alpha 2 beta 1 and alpha V beta 3 integrins were used.

RESULTS

A thin mural thrombus was seen at sites of denudation and plaque fracture (days 2 to 7). This provisional matrix was invaded by leukocytes (days 2 to 4) and alpha-actin-positive smooth muscle cells (SMCs; days 4 to 7). Thrombus was replaced by SMCs expressing hyaluronan and the associated versican proteoglycans (day 14). Versican was expressed throughout the neointima as it enlarged (day 28), but expression later subsided (day 112). Procollagen-I expression initially increased in the adventitia (day 4) and then in the forming neointima (day 14). Procollagen-I expression was found to persist within the adventitia and in the neointima in SMCs nearest the lumen (days 28 to 112). Elastin staining was prominent within the mature neointima (day 112) but not at earlier time points. Integrin expression also increased within the injured artery wall. alpha v beta 3 staining (fibrin[ogen] receptor) increased in the injured media (days 2 to 7) and was then seen throughout the early neointima (day 7). Low level expression of alpha V beta 3 subsequently persisted within the forming neointima (day 28). alpha 2 beta 1 (collagen receptor) expression increased in the neointima in SMCs nearest the lumen (day 28).

CONCLUSIONS

Lumen narrowing after angioplasty in this model of atherosclerosis is caused largely by decreased artery wall diameter. The pattern of matrix and integrin expression within the injured artery wall is in many ways analogous to that of healing wounds. These observations suggest that tissue contraction may play a role in lumen narrowing at sites of arterial reconstruction. Strategies to inhibit wound contraction may prove effective in preventing restenosis.

Influence of Aloe vera on the glycosaminoglycans in the matrix of healing dermal wounds in rats

The influence of Aloe vera (L.) Burman f. on the glycosaminoglycan (GAG) components of the matrix in a healing wound was studied. Wound healing is a dynamic and complex sequence of events of which the major one is the synthesis of extracellular matrix components. The early stage of wound healing is characterized by the laying down of a provisional matrix, which is then followed by the formation of granulation tissue and synthesis of collagen and elastin. The provisional matrix or the ground substance consists of GAGs and proteoglycans (PGs), which are protein GAG conjugates. In the present work, we have studied the influence of Aloe vera on the content of GAG and its types in the granulation tissue of healing wounds. We have also reported the levels of a few enzymes involved in matrix metabolism. The amount of ground substance synthesized was found to be higher in the treated wounds, and in particular, hyaluronic acid and dermatan sulphate levels were increased. The levels of the reported glycohydrolases were elevated on treatment with Aloe vera, indicating increased turnover of the matrix. Both topical and oral treatments with Aloe vera were found to have a positive influence on the synthesis of GAGs and thereby beneficially modulate wound healing.

Proinflammatory stimuli regulate endothelial hyaluronan expression and CD44/HA-dependent primary adhesion

The localization of circulating leukocytes within inflamed tissues occurs as the result of interactions with and migration across vascular endothelium, and is governed, in part, by the expression of adhesion molecules on both cell types. Recently, we have described a novel primary adhesion interaction between the structurally activated form of the adhesion molecule CD44 on lymphocytes and its major ligand hyaluronan on endothelial cells under physiologic laminar flow conditions, and have proposed that this interaction functions in an extravasation pathway for lymphocytes in vascular beds at sites of inflammation. While the regulation of activated CD44 on leukocytes has been characterized in depth, regulation of hyaluronate (HA) on endothelial cells has not been extensively studied. Here we demonstrate that the expression of HA on cultured endothelial cell lines and primary endothelial cultures is inducible by the proinflammatory cytokines TNFalpha and IL-1beta, as well as bacterial lipopolysaccharide. In addition, this inducibility appears strikingly restricted to endothelial cells derived from microvascular, but not large vessel, sources. The elevated HA levels thus induced result in increased CD44-dependent adhesive interactions in both nonstatic shear and laminar flow adhesion assays. Changes in mRNA levels for the described HA synthetic and degradative enzymes were not found, suggesting other more complex mechanisms of regulation. Together, these data add to the selectin and immunoglobulin gene families a new inducible endothelial adhesive molecule, hyaluronan, and help to further our understanding of the potential physiologic roles of the CD44/HA interaction; i.e., local cytokine production within inflamed vascular beds may enhance surface hyaluronan expression on endothelial cells, thereby creating local sites receptive to the CD44/HA interaction and thus extravasation of inflammatory cells.

Basal membrane heparan sulphate proteoglycan expression during wound healing in human skin

Heparan sulphate proteoglycans (HSPGs) are integral components of the basement membrane (BM) in various tissues. HSPGs are important in the assembly and structure of the BM, and their putative functions include regulation of basement membrane permeability, binding of growth factors, and a role in cellular adhesion. In this study the expression of HSPG was examined during wound healing in human skin, using monoclonal antibodies (MAbs) that recognize the HSPG core protein and two different heparan sulphate (HS) epitopes, and the dynamics of HSPG expression were investigated in relation to epidermal cellular proliferation and permeability of the BM. Healing of excisional wounds in healthy volunteers was studied from day 0 up to 1 year. Intact human skin showed strong continuous staining of the dermo-epidermal BM and the vascular BM with all MAbs. Up to day 4 after wounding, staining for HSPG was absent under the ingrowing epidermis, with any of the MAbs, indicating that no complete BM was present. From day 7 onwards, the BM of the neo-epidermis showed positive staining for the HSPG core protein and a low sulphated HS epitope, and after day 14, the staining intensity was similar to normal skin. The staining patterns of these HSPG epitopes were similar to that of laminin. The staining pattern with a MAb against an epitope in the highly sulphated part of HS was found to be distinct from the other BM markers studied. This epitope was absent under the neo-epidermis up to 2 months after wounding. One year after wounding, the epitope was found to be present again. We observed that only in the time period between 2 months and 1 year had the epidermis normalized with respect to the number of cycling cells and the absence of high molecular weight plasma proteins. These findings suggest a correlation between normalization of epidermal proliferation, BM permeability, and regeneration of BM HS. It is proposed that complete BM maturation following skin wounding is a slow process and may account for the epidermal abnormalities that persist for a considerable period of time after wound healing.

Differences in decorin and biglycan expression in patients with gastric ulcer healing

BACKGROUND

The small interstitial proteoglycans decorin and biglycan have been shown to interact with various extracellular matrix molecules and with transforming growth factor-beta. These interactions are proposed to be important for tissue repair, as the former interactions may affect the diameter and spacing of collagen fibrils, and the latter interaction the proliferation and differentiation of cells embedded in the matrix. The aim of this study is to localize these proteoglycans in the stomach and to investigate their suitability as potential markers of extracellular matrix activity in gastric lesions.

METHODS

Immunohistochemical techniques and in situ hybridization were used to study the phenotypic expression of these two proteoglycans in routinely processed specimens of human stomach tissue from 8 patients with gastric ulcer and 10 healthy control persons.

RESULTS

In normal gastric tissue, immunostaining for both proteoglycans was found in the interstitium, with a more pronounced staining in the pylorus region than in the corpus area. In addition, biglycan showed a strong staining of parietal cells. In specimens of healing gastric ulcers a larger deposition of decorin throughout scar tissue could be shown, and a higher expression of decorin was also found by in situ hybridization. Biglycan was only found at the edges of the lesions.

CONCLUSION

This study shows for the first time the presence of decorin and biglycan in human gastric mucosa. We also showed that these proteoglycans may be involved in the gastric ulcer healing processes.

Expression of heparan sulphate and small dermatan/chondroitin sulphate proteoglycans in chronically inflamed human periodontium

Proteoglycans (PGs) function in regulating aspects of cell behavior, such as proliferation, adhesion, and migration. In this report, we investigated the localization of three heparan sulphate PGs (basement membrane [BM] heparan sulphate PG, CD44, and syndecan-1) and two small dermatan/chondroitin sulphate PGs (decorin and biglycan) in chronically inflamed human periodontium. Frozen sections were analyzed by immunofluorescence microscopy. In inflamed tissue, BM heparan sulphate PG showed reduced immunostaining in subepithelial and subendothelial basement membrane. Loss of CD44 and syndecan-1 was common in epithelial cells of inflamed periodontal tissue. Suprabasal keratinocytes of epithelium expressed involucrin, a cornified envelope protein and marker for epithelial differentiation, while the expression of syndecan-1 was weak or absent. In contrast, expression of the mesenchymal variant of CD44 and syndecan-1 was strong in infiltrating lymphocytes. Small dermatan/chondroitin sulphate PGs, decorin and biglycan, were also present in markedly reduced amounts in the periodontal connective tissue in chronic inflammation. In addition, decorin localized in the connective tissue along short rod-like structures. The results suggest that proteoglycan-dependent intercellular adhesion of keratinocytes is decreased and that adhesion of lymphocytes to matrix molecules via cell surface PGs increased in chronic inflammation. Disappearance of adhesion-modulating small dermatan/chondroitin sulphate PGs may further regulate cell migration in inflamed periodontium.

Human epidermal keratinocytes are a source of tenascin-C during wound healing

Tenascin-C is a large hexameric extracellular matrix glycoprotein that is expressed in a temporally and spatially restricted pattern associated with stromal-epithelial interactions. In adult human skin, the expression level of tenascin-C is low, but tenascin-C is abundantly present in the dermal compartment during embryogenesis and wound healing and in skin tumors. Herein we have investigated the cellular source of tenascin-C production in human skin, both in vivo and in vitro, by using immunohistochemistry, mRNA in situ hybridization, western blotting, and an enzyme-linked immunosorbent assay. In addition we studied the cell-matrix interaction between epidermal keratinocytes and purified tenascin-C. By using in vitro culture models, we found that keratinocytes not only synthesize and secrete tenascin-C but can also deposit tenascin-C in de-epidermized dermis in a pattern that is very similar to that in vivo. In vivo, during wound healing of normal human skin, we found tenascin-C extracellularly in the wound bed and also in a granular pattern within the neo-epidermis. By mRNA in situ hybridization, we could identify the basal migrated keratinocytes as the main source of tenascin-C in the early phase of wound healing. In the granulation phase, tenascin-C expression by the keratinocytes is downregulated. Cultured keratinocytes were found to adhere poorly to tenascin-C, and those that did adhere retained a rounded morphology. We conclude that human keratinocytes are a major source of tenascin-C during the early phase of wound healing, and we hypothesize that tenascin-C is unlikely to be an adhesive substrate for migrating keratinocytes.

Selective suppression of CD44 in keratinocytes of mice bearing an antisense CD44 transgene driven by a tissue-specific promoter disrupts hyaluronate metabolism in the skin and impairs keratinocyte proliferation

CD44 is a broadly distributed polymorphic glycoprotein that serves as the principal cell-surface receptor for hyaluronate. Although CD44-mediated cell interaction with hyaluronate has been implicated in a variety of physiologic events, including cell-cell and cell-substrate adhesion, cell migration, proliferation, and activation, as well as hyaluronate uptake and degradation, the biologic role of CD44 in vivo in various tissues remains to be determined. In the present work we have developed transgenic mice that express an antisense CD44 cDNA driven by the keratin-5 promoter. These mice lack detectable CD44 expression in skin keratinocytes and corneal epithelium and display abnormal hyaluronate accumulation in the superficial dermis and corneal stroma, distinct morphologic alterations of basal keratinocytes and cornea, and defective keratinocyte proliferation in response to mitogen and growth factors. These alterations are reflected by a decrease in skin elasticity, impaired local inflammatory response and tissue repair, delayed hair regrowth, and failure of the epidermis to undergo hyperplasia in response to carcinogen. Our observations indicate that two major functions of CD44 in skin are the regulation of keratinocyte proliferation in response to extracellular stimuli and the maintenance of local hyaluronate homeostasis.

Extracellular matrix components reflect the dynamics of a healing tympanic membrane perforation--a histochemical study

Extracellular matrix components have hitherto been sparsely studied in tissue repair processes. In this study, the distribution of hyaluronan (HYA), fibronectin, and five chondroitin sulfate glycosaminoglycans (GAGs) was analysed in healing tympanic membrane (TM) perforations of rats, at different time points, using a HYA-binding protein probe and six monoclonal antibodies (MAbs). Hyaluronan appeared, the first day, around migrating squamous epithelial and inflammatory cells in the perforation borders and close to dilated vessels at the malleus handle. Accumulated HYA persisted in the thickened perforation rim until closure of the perforation, then it slowly disappeared from the healed TM area. Fibronectin immunoreactivity occurred around proliferating cells in the perforation edge and around collagen bundles in the connective tissue. The MAbs for chondroitin sulfate GAGs rendered specific, constant immunostaining patterns throughout the healing process. Unsulfated chondroitin, chondroitin-4-sulfate and chondroitin-6-sulfate were present in small amounts in the connective tissue surrounding collagen fibres and fibroblasts. The staining for native chondroitin and dermatan sulfate was most pronounced in the epithelial layers, in particular the squamous epithelium and its keratin layer, whereas the loose connective tissue was left unstained. After closure of the TM perforations, the immunoreactivity for unsulfated chondroitin, native chondroitin and dermatan sulfate increased in the scar tissue. It is concluded that HYA is abundant in early stages of healing of TM perforations, whereas fibronectin, unsulfated chondroitin, chondroitin-4 and 6-sulfate are constantly present in small amounts during the healing process. Unsulfated chondroitin, native chondroitin and dermatan sulfate increase in the healed TM area.

CD44: structure, function, and association with the malignant process

CD44 is a ubiquitous multistructural and multifunctional cells surface adhesion molecule involved in cell-cell and cell-matrix interactions. Twenty exons are involved in the genomic organization of this molecule. The first five and the last 5 exons are constant, whereas the 10 exons located between these regions are subjected to alternative splicing, resulting in the generation of a variable region. Differential utilization of the 10 variable region exons, as well as variations in N-glycosylation, O-glycosylation, and glycosaminoglycanation (by heparan sulfate or chondroitin sulfate), generate multiple isoforms (at least 20 are known) of different molecular sizes (85-230 kDa). The smallest CD44 molecule (85-95 kDa), which lacks the entire variable region, is standard CD44 (CD44s). As it is expressed mainly on cells of lymphohematopoietic origin, CD44s is also known as hematopoietic CD44 (CD44H). CD44s is a single-chain molecule composed of a distal extracellular domain (containing, the ligand-binding sites), a membrane-proximal region, a transmembrane-spanning domain, and a cytoplasmic tail. The molecular sequence (with the exception of the membrane-proximal region) displays high interspecies homology. After immunological activation, T lymphocytes and other leukocytes transiently upregulate CD44 isoforms expressing variant exons (designated CD44v). A CD44 isform containing the last 3 exon products of the variable region (CD44V8-10, also known as epithelial CD44 or CD44E), is preferentially expressed on epithelial cells. The longest CD44 isoform expressing in tandem eight exons of the variable region (CD44V3-10) was detected in keratinocytes. Hyaluronic acid (HA), an important component of the extracellular matrix (ECM), is the principal, but by no means the only, ligand of CD44. Other CD44 ligands include the ECM components collagen, fibronectin, laminin, and chondroitin sulfate. Mucosal addressin, serglycin, osteopontin, and the class II invariant chain (Ii) are additional, ECM-unrelated, ligands of the molecule. In many, but not in all cases, CD44 does not bind HA unless it is stimulated by phorbol esters, activated by agonistic anti-CD44 antibody, or deglycosylated (e.g., by tunicamycin). CD44 is a multifunctional receptor involved in cell-cell and cell-ECM interactions, cell traffic, lymph node homing, presentation of chemokines and growth factors to traveling cells, and transmission of growth signals. CD44 also participates in the uptake and intracellular degradation of HA, as well as in transmission of signals mediating hematopoiesis and apoptosis. Many cancer cell types as well as their metastases express high levels of CD44. Whereas some tumors, such as gliomas, exclusively express standard CD44, other neoplasms, including gastrointestinal cancer, bladder cancer, uterine cervical cancer, breast cancer and non-Hodgkin's lymphomas, also express CD44 variants. Hence CD44, particularly its variants, may be used as diagnostic or prognostic markers of at least some human malignant diseases. Furthermore, it has been shown in animal models that injection of reagents interfering with CD44-ligand interaction (e.g., CD44s- or CD44v-specific antibodies) inhibit local tumor growth and metastatic spread. These findings suggest that CD44 may confer a growth advantage on some neoplastic cells and, therefore, could be used as a target for cancer therapy. It is hoped that identification of CD44 variants expressed on cancer but not on normal cells will lead to the development of anti-CD44 reagents restricted to the neoplastic growth.

Hyaluronan (HA) fragments induce chemokine gene expression in alveolar macrophages. The role of HA size and CD44

Hyaluronan (HA) is a glycosaminoglycan constituent of extracellular matrix. In its native form HA exists as a high molecular weight polymer, but during inflammation lower molecular weight fragments accumulate. We have identified a collection of inflammatory genes induced in macrophages by HA fragments but not by high molecular weight HA. These include several members of the chemokine gene family: macrophage inflammatory protein-1alpha, macrophage inflammatory protein-1beta, cytokine responsive gene-2, monocyte chemoattractant protein-1, and regulated on activation, normal T cell expressed and secreted. HA fragments as small as hexamers are capable of inducing expression of these genes in a mouse alveolar macrophage cell line, and monoclonal antibody to the HA receptor CD44 completely blocks binding of fluorescein-labeled HA to these cells and significantly inhibits HA-induced gene expression. We also investigated the ability of HA fragments to induce chemokine gene expression in human alveolar macrophages from patients with idiopathic pulmonary fibrosis and found that interleukin-8 mRNA is markedly induced. These data support the hypothesis that HA fragments generated during inflammation induce the expression of macrophage genes which are important in the development and maintenance of the inflammatory response.

Characteristic expression of cell adhesion molecules in adhalin deficiency

We have reported the reduction of the B1 subunit of laminin and that of heparan sulfate proteoglycan (HSPG) in two Japanese patients with adhalin deficiency. We here investigated immunohistochemically the expression of cell adhesion molecules, including intercellular adhesion molecule-1 (ICAM-1), neural cell adhesion molecule (NCAM), and CD44 (HCAM), in four Japanese patients with adhalin deficiency, compared to other types of muscular dystrophy. We found that NCAM was upregulated in a fair number of muscle fibers, regardless of the type of muscular dystrophy. ICAM-1 was detected on the rare muscle cell membrane in all patients. CD44 was barely detected on the muscle cell membrane in adhalin deficiency, in contrast to the strong expression of CD44 which was observed in other types of muscular dystrophy. These findings suggest that a different degenerative or regenerative process is involved in adhalin deficiency compared to other types of muscular dystrophy.

Stimulation of collagenase (matrix metalloproteinase-1) synthesis in histiotypic epithelial cell culture by heparin is enhanced by keratinocyte growth factor

The role of heparin and heparan sulfate in the control of epithelial collagenase production was investigated utilizing a histiotypic cell culture model. The effect of keratinocyte growth factor (KGF), a heparin-binding growth factor, on collagenase secretion was also examined. Heparin, and, to a lesser extent, heparan sulfate induced release of a 58-kDa, gelatin-degrading enzyme which was subsequently identified as the collagenase, matrix metalloproteinase-1. The increase in collagenase secretion by heparin was further enhanced by the addition of KGF. KGF alone did not have any effect. Analysis of secreted radiolabelled proteins showed that the increase in collagenase activity was not due to a general increase in protein synthesis. Synthesis of collagenase protein was specifically increased by heparin and further increased by KGF plus heparin. Heparin and heparan sulfate in combination with KGF may thus have important roles in the regulation of epithelial cell collagenase under conditions such as inflammation and wound healing.

Distribution of hyaluronan during extracellular matrix remodeling in human restenotic arteries and balloon-injured rat carotid arteries

BACKGROUND

The glycosaminoglycan hyaluronan (HA) is present in developing tissues and healing wounds and forms a loose, hydrated extracellular matrix (ECM) that promotes processes such as cell migration. To investigate the potential contribution of HA to the pathogenesis of restenosis, we studied (1) human lesions obtained by directional atherectomy and (2) experimentally induced neointima formation in balloon-injured rat carotid arteries.

METHODS AND RESULTS

A biotinylated proteoglycan fragment that binds specifically to HA was used to stain atherectomy specimens from 29 human restenotic lesions (mean restenosis interval, 6.0+/-4.4 months) and 8 human primary lesions. The loose myxoid ECM typical of human restenotic arteries demonstrated intense, diffuse staining for HA. The intensity was inversely related to the density of immunostaining for collagen types I and III and was lowest in hypocellular primary atherosclerotic plaque. Among 24 rat carotid arteries retrieved 3, 7, 14, 28, 42, or 56 days after balloon injury and immunostained as well for proliferating cell nuclear antigen, staining for HA in the neointima reached a maximum 7 days after balloon injury and was associated with the presence of proliferating, PCNA-positive smooth muscle cells.

CONCLUSIONS

Hyaluronan is a characteristic constituent of the loose myxoid ECM in human restenotic arteries and of the neointima in experimentally injured arteries. The presence of hyaluronan may be a marker for an initial phase of the extracellular matrix remodeling that occurs during the development of a fibroproliferative lesion and could facilitate biological processes such as cell migration.

Modulation of collagen gel contraction by decorin

The small dermatan sulphate protein decorin interacts via its core protein with fibrillar collagens, and its glycosaminoglycan chains were proposed to be capable of self-association. It was therefore of interest to study the role of decorin in the contraction of cell-populated collagen lattices. Stable transfection of dihydrofolate reductase-deficient CHO cells with decorin cDNA resulted in impaired collagen lattice contraction. Using normal human skin fibroblasts in serum-free cultures, inclusion of 0.3 microM decorin in the culture medium also led to a delayed collagen gel contraction. Protein-free dermatan sulphate and the dermatan sulphate-degrading enzyme chondroitin ABC lyase were ineffective. Potential interactions between dermatan sulphate chains were studied by gel filtration. A shift in the elution position of [35S]sulphate-labelled decorin-derived glycosaminoglycans by unlabelled decorin could be observed only when the chains were prepared by trypsin. Chains liberated by beta-elimination or by cathepsin C were eluted at identical positions in the presence or absence of decorin. It is therefore unlikely, that the effect of decorin on collagen-gel retraction is brought about solely by glycosaminoglycan-glycosaminoglycan interactions.