Proteoglycans and Cutaneous Vascular Defense and Repair

Richard L. GalloDivision of Dermatology, University of California San Diego and VA San Diego Healthcare System, San Diego, California, U.S.A.

Proteoglycans are hybrid molecules composed of acore protein and covalently attached glycosamino-glycan chain(s). The structure, location, and proces-sing of these molecules enables them to encodespeci®c information that is used in multiple physio-logic processes. Endothelial cells in the skin are in¯u-enced by proteoglycans through binding interactionsbetween glycosaminoglycans and extracellularmatrix, growth factors, cytokines, adhesion recep-tors, enzymes, and enzyme inhibitors. In woundrepair, proteoglycans such as the syndecans are

induced by antimicrobial peptides and can controlgrowth factor responsiveness. The glycosaminogly-cans further signal endothelial cells to increaseexpression of ICAM-1 and other molecules impor-tant for leukocyte adhesion. Thus, proteoglycansrepresent a powerful central regulatory element inskin that in¯uences a wide variety of events and par-ticipates in host defense and tissue repair. Key words:dermatan sulfate/hair development/heparan sulfate/synde-can/wound repair. Journal of Investigative DermatologySymposium Proceedings 5:55±60, 2000

There is a long history of observations regarding thecomposition and dynamic changes that take place inthe proteoglycans of the skin. Despite this, thetechnical dif®culties faced when working with thesemolecules has left them poorly understood. Over the

last decade work in several converging ®elds has greatly advancedinformation about proteoglycans, and their components theglycosaminoglycans (GAG). This work has identi®ed proteoglycansand GAG as critical for growth factor responsiveness, cell adhesion,tissue remodeling, and immune defense. Each of these functionsrelies on the unique properties of proteoglycans and on theextensive inter and intracellular enzymatic modi®cations that musttake place in order to process GAG into functional molecules.Current understanding suggests vascular cell biology is particularlystrongly in¯uenced by proteoglycans and GAG, and that theprocess of wound repair is an excellent model system to illustratethe importance of these molecules to skin biology.

THE INFORMATION CODE OF AGLYCOSAMINOGLYCAN AND PROTEOGLYCAN

A proteoglycan is a hybrid molecule composed of a central coreprotein to which one or more GAG are covalently attached (forreviews see Jackson et al, 1991; Gallo and Bern®eld, 1995; Lander,1998; Iozzo, 1998; Woods and Couchman, 1998). The proteogly-cans have a unique strategy to transmit information. Functionalinformation is encoded in the sequence of amino acids of the coreprotein, in the sequence of sugars in the GAG chain, and on the®nal enzymatic processing of the proteoglycan or GAG in thetissue. Thus, critical to the understanding of the function of these

molecules is familiarity with the elements within these moleculesthat are used to encode their unique functional properties.

GAG are understood based on the sequence and structures of thedisaccharides found within each. GAG are known as heparansulfate, chondroitin sulfate A, chondroitin sulfate B, chondroitinsulfate C, keratan sulfate, and hyaluronic acid. Hyaluronic acidcontains a glucuronic acid alternating with N-acetylglucosaminelinked b1±3 and b1±4, is not sulfated, and is not covalently attachedto core proteins. Keratan sulfate contains galactose alternating withN-acetylglucosamine linked b1±4 and b1±3. Chondroitin sulfatescontain glucuronic acid alternating with N-acetyl galactosaminelinked b1±3 and b1±4. In chondroitin sulfate B, the major GAGpresent in the skin (also known as dermatan sulfate), manyglucuronic acids undergo an isomerization reaction to iduronicacids. Finally, heparan sulfate contains iduronic or glucuronic acidsalternating with N-acetylglucosamine linked b1±4. Each of theGAG can vary in size from only a few disaccharides to thousands,thus the mass of these polymers may vary from as little as a fewthousand daltons to over 107 for hyaluronic acid. With theexception of hyaluronic acid, complexity in the GAG chain isfurther increased by varying sulfation patterns. Therefore, a GAGchain has the capacity for encoding a highly unique structuralpattern with variables that include disaccharide composition,structure, charge, and size.

The core proteins of the proteoglycans add further informa-tion to the complex by locating GAG to speci®c intercellularand extracellular locations in a cell type speci®c pattern. Severalgene families encode groups of core proteins that vary widelybut have in common consensus amino acid motifs that enablecovalent linkage of the GAG chain to the protein. Severalproteins, such as CD-44, have been described as ``part-time''proteoglycans and can be found with and without GAGattached (Brown et al, 1991). Other proteins are foundexclusively as proteoglycans. Figure 1 illustrates the structuresof some of the best known proteoglycans. These include thecell surface proteoglycans such as the syndecans and glypicans(Bern®eld et al, 1992), the extracellular matrix proteoglycans

Manuscript received January 28, 2000; revised March 23, 2000; acceptedfor publication April 6, 2000.

Reprint requests to: Dr. Richard L. Gallo, Associate Professor ofMedicine & Pediatrics, University of California, San Diego, Division ofDermatology, VA Medical Center (111B), 3350 La Jolla Village Drive, SanDiego, CA 92161. Email: rgallo@vapop.ucsd.edu

1087-0024/00/$15.00 ´ Copyright # 2000 by The Society for Investigative Dermatology, Inc.

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such as the small leucine-rich proteoglycans of the decorinfamily and the large aggregating proteoglycans like versican, andintracellular proteoglycans such as serglycin. Because similarGAG can be expressed on multiple different core proteins,expression of the core protein will in¯uence the location,interactions, and abundance of GAG expressed. For example,expression of syndecan-1 can direct heparan sulfate to the cellsurface, perlecan will locate heparan sulfate to the basementmembrane, and serglycin can send heparan sulfate inside a mastcell; however, core protein expression does not exclusivelycontrol GAG expression. When appropriately stimulated, a cellcan change the type of GAG attached to a proteoglycan core.For example, syndecan-1 can switch from a heparan sulfateproteoglycan to a chondroitin sulfate proteoglycan aftertreatment with TGF-b (Rapraeger, 1989). In addition, enzy-matic degradation of the proteoglycan during dynamic tissueremodelling processes will change the location and activity ofthe proteoglycan such that they can be further processed intoeither active or inactive forms. Thus, proteoglycan function iscontrolled by at least three separate systems; protein synthesis ofthe core, GAG synthesis in the golgi, and ®nal enzymaticreprocessing.

LOCATION OF PROTEOGLYCANS AND GAG IN THESKIN

Proteoglycans and GAG are present in all tissues but have aparticularly complex expression pattern in the skin. Hyaluronic acidis synthesized in the epidermis and hyaluronan is abundantlylocated here (Oksala et al, 1995). Syndecan-1 and syndecan-4 arealso abundant in the epidermis where they are expressed at the cellsurface as heparan sulfate proteoglycans (Gallo et al, 1996). In thebasement membrane, the extracellular matrix heparan sulfateproteoglycan perlecan is most abundant (Noonan et al, 1991). Inthe dermis, ®broblasts constitutively express low levels of syndecan-4 and glypican-1 at their surface and produce extracellular matrixproteoglycans containing dermatan sulfate such as decorin andversican (Iozzo and Murdoch, 1996) although versican has also beseen in the epidermis (Zimmermann et al, 1994).

Other cell types within the skin also add to the complex milieuof proteoglycan and GAG. Mast cells synthesize large amounts of

heparan sulfate by attachment to serglycin (Stevens et al, 1988).Neural cells express syndecan-3 (Carey et al, 1992). Endothelialcells, which will be the focus of the functional discussion of thisreview, likely have the capacity to produce multiple proteoglycansbut are best known for the expression of heparan sulfate syndecan-4at the surface (Kojima et al, 1993).

Recognizing that the skin has multiple proteoglycans and GAGlocated in a speci®c pattern illustrates the ®nding that each sitemaintains a unique proteoglycan and GAG environment. Cellbehavior will be affected in speci®c ways by the components ofeach of these environments. Thus, endothelial cell functions will bemodi®ed based on their expression of proteoglycans and GAG, andby the nature of these proteoglycans and GAG in the surroundingenvironment.

DEVELOPMENTAL REGULATION OF PROTEOGLYCANEXPRESSION

Clues to the importance of proteoglycans to cell function can befound by study of the expression pattern of syndecans duringembryogenesis. Prior to this work a prevailing belief was that GAGprovided a structural support to tissues and primarily acted tomaintain hydration of the tissue and supported intracellular spaces.Although this function may indeed be part of the action of GAG,observation of dynamic shifts in proteoglycan gene expressionduring critical periods of active morphogenesis suggested that thesemolecules participate in processes of cell growth, differentiation,adhesion, and movement. For example, syndecan-1 is expressed asearly as the fourth cell stage during murine embrogenesis(Sutherland et al, 1991). As cell patterning and differentiationprogress, expression of this gene segregates to epithelial cells.During organogenesis, cells of the invaginating epithelial placodetransiently loose syndecan-1 from their surface while the conden-sing mesenchyme beneath the placode transiently express syndecan-1 at high levels. Figure 2 illustrates the dynamic change insyndecan-1 expression that occurs during hair development. Thisrapid and transient switch in syndecan expression from ectodermaltissues to mesenchyme occurs during the development of mostorgans. Developmental patterning in proteoglycan expression hasbeen observed in many species and tends to be highlyevolutionarily conserved. Similar proteoglycan genes are known

Figure 1. Illustrations of skin proteoglycans.Proteoglycans (PG) are present in the skin in avariety of forms. The glycosaminoglycan sidechains are represented here as disaccharide chainssymbolized by stars, circles, and squares. Thecomposition of these glycosaminoglycans estab-lishes if the proteoglycan is of the heparan sulfateor chondroitan sulfate type. Core proteins of theproteoglycan locate the molecule at the cell sur-face (glypicans and syndecans), in the extracellularspace (decorin or versican), or in mast cells (ser-glycin). Disaccharide sequence in the glycosami-noglycan chain combined with amino acidsequence in the core protein provides a complexand highly effective molecule to encode informa-tion for control of a variety of cell functions.

56 GALLO JID SYMPOSIUM PROCEEDINGS

in animals as evolutionarily ancient as C. elegans or drosophila(Spring et al, 1994). Such observations suggest that proteoglycanshave a crucial role to play in the function of cells duringdevelopment.

GAG AS COFACTORS FOR GROWTH FACTORACTIVITY

The adhesive properties of GAG is a principal mechanism by whichthey control and modify cell function. Table I is a partial list of themany types of molecules to which GAG will bind. Heparan sulfateshave been most extensively studied, and relatively high af®nityconstants of heparan sulfate for proteins have been recorded (i.e.,Kd = 1±5 nM). Extensive study of this system has shown thatspeci®c disaccharide sequences and sulfation patterns withinheparan sulfate are optimal for the activation of several molecules.For example, binding to antithrombin 3 occurs by a speci®cpentasaccharide sequence with a unique 3-O-sulfated glucosamine(Lindahl et al, 1983). Other speci®c but distinct domains have beenidenti®ed for binding to FGF-2 (Walker et al, 1994). Thus, similarto highly speci®c protein±protein interactions, GAG±proteinbinding interactions have structural speci®city encoded in thesugar chain. It is not a regulation system that acts through simplecharge mediated adhesion of the anionic GAG to a cationic protein.

Study of the regulation of growth factor function has shown thatbinding to GAG is a necessary element in the activation of manysoluble growth factors and cytokines. Best studied among the growthfactors is the activation of FGF-2 by heparan sulfate. Cells cannotrespond to FGF-2 in the absence of heparan sulfate despite thepresence of a functional FGF receptor (Rapraeger et al, 1991; Yayonet al, 1991). When heparan sulfate is present, the complex of GAG andFGF-2 becomes active. Recent work has solved the structure for thiscomplex and de®ned conformational changes that occur when FGF-2 and GAG bind (DiGabriele et al, 1998). Further work has alsoidenti®ed dermatan sulfate from the skin as an alternative GAG thatcan activate FGF-2 (Penc et al, 1998). Binding to GAG is a processused by a number of proteins to control their function. GAGassociations can serve to either activate or deactivate the function ofthe protein factor. Regulation of the location of proteoglycans and/orthe sequence of the GAG will therefore create an environment thatmay be permissive or resistant to a complex mixture of solublesignaling molecules. Endothelial cells in a wound, or involved in

tumor angiogenesis, will therefore be strictly limited in theirresponsiveness by surrounding proteoglycan and GAG.

PROTEOGLYCANS AS CELL ADHESION MOLECULES

Many extracellular proteins bind GAG (Table I). Integral cellsurface proteoglycans such as syndecan-1 can hold a cell to theextracellular matrix by its GAG chains. This can occur to a varietyof extracellular matrix components, including type I, III, and VI®brillar collagen (Koda and Bern®eld, 1984; LeBaron et al, 1989),®bronectin (Saunders and Bern®eld, 1988), thrombospondin (Sunet al, 1989), and tenascin (Salmivirta et al, 1991). Expression of theproteoglycan is also consistent with its role as matrix receptor.Syndecan-1 polarizes to the basolateral surface of epithelial cells(Jalkanen et al, 1988), and as discussed earlier localizes in earlyembryogenesis to the site of matrix accumulation. In addition,syndecan-1 and -3 colocalize with tenascin during tooth and limbdevelopment, respectively (Solursh et al, 1990; Vainio et al, 1991).Syndecan-1 is only expressed on pre-B cells in bone marrow andon differentiated plasma cells in lymphoid tissues, but not when Bcell circulate (Sanderson et al, 1989) and mediates adhesion tocollagen (Ridley et al, 1993). Expression of syndecan-1 inhibits cellinvasion into type I collagen (Liebersbach and Sanderson, 1994)and mediates cell±cell adhesion via its HS chains.

Engagement of proteoglycans with cell surface receptors orextracellular matrix proteins is a common adhesion mechanism andcan occur through binding to the core protein or GAG. Examplesof this are seen in studies of decorin and cell surface proteoglycanssuch as the syndecans. Decorin core protein stabilizes dermalcollagen structure. Deletion of this core protein by targeteddeletion of the gene results in mice whose skin has markedlyincreased fragility and disorganized collagen (Danielson et al, 1997).Interaction between cell surface HSPG such as syndecan and®bronectin stimulates focal adhesion formation in cooperation withintegrins (Woods and Couchman, 1998). Syndecan-4 becomesinserted into the focal adhesions of a number of cell types such as®broblasts, smooth muscle cells, and endothelial cells (Woods andCouchman, 1994) when protein kinase C (PKC) is activated (Ohet al, 1997b). A unique sequence in the central part of thecytoplasmic domain of syndecan-4 directly activates PKCa andpotentates its activity when the cytoplasmic domain is oligomerized

Figure 2. Expression of syndecan-1 in developing hair. Hair devel-opment in the embryonic mouse was examined with a monoclonalantibody speci®c to the mouse syndecan-1 core protein (281±2). (A) Earlyectodermal placode indicated by a white arrow is invaginating into theunderlying mesenchyme. Mesenchyme condensation is indicated with ared arrow. Brown staining indicates syndecan-1 expression. Early epidermisstrongly expresses syndecan-1 except at the placode. Syndecan-1 is onlydetected in the dermis at the condensation site. (B±D) Progressivedevelopment of the hair bulb demonstrates continued loss of syndecan inthe developing ectoderm and expression in the condensed mesenchyme.Scale bar: 40 mM.

Figure 3. Syndecans-1 and -4 are induced during wound repair.Twenty-four hours after a wound to murine skin the expression ofsyndecan-1 or syndecan-4 was evaluated with antibodies speci®c to eachcore protein. (A) Early granulation tissue stained for syndecan-1. Syndecan-1 is not normally detectable on endothelia or ®broblasts but intense stainingis seen in granulation tissue and on vessels in the wound. Parts (B), (C), and(D) are adjacent sections within this granulation tissue stained for syndecan-4 (B), syndecan-1 (C), or control isotype matched IgG (D). Red arrowsplaced in vessel lumen indicate expression of syndecan on endothelia. Scalebar: (A) 100 mM; (B±D) 20 mM.

VOL. 5, NO. 1 DECEMBER 2000 PGs IN WOUND DEFENSE 57

(Oh et al, 1997a). These examples highlight the fact that the coreprotein of the proteoglycan can have speci®c functional propertiesin addition to serving as a foundation for the assembly of GAG.

REGULATION OF PROTEOGLYCANS AND GAGDURING WOUND REPAIR

Studies on wound repair in adult skin have shown the amount ofhyaluronan, sulfated GAG and proteoglycans increases in the skinfollowing injury (Gallo and Bern®eld, 1995). Here the potential

functional consequences of proteoglycans to vascular biology canbe most clearly seen. Several soluble factors present in the wound,such as members of the FGF or VEGF family, PF-4, INF-g, andAT-3, have potent effects on endothelial cells and are controlled bybinding to GAG. Changes in proteoglycan expression in thisenvironment will therefore in¯uence the responsiveness of bloodvessels or endothelia to these molecules. In the early phases ofwound repair endothelial cells and developing granulation tissueshow a dramatic increase in the surface expression of syndecan-1and -4 (Fig 3). Thus, the amount of GAG attached to the cellsurface by syndecan-1 or -4 will cause cells at this site to responddifferently to the GAG-binding cytokines, growth factors, andenzymes. Interestingly, the pattern of GAG expression afterwounding is much different in fetal human skin where hyaluronanlevels remain elevated and syndecan expression is never induced(Gallo et al, 1996). This difference in proteoglycan expression in thefetal wound correlates directly with a major difference in thetendency of fetal wounds to heal without a detectable scar. Alsonotable in the fetal wound is a relative lack of in¯ammatoryin®ltrate in the skin relative to newborn or adult. Thus, differencesin the expression of proteoglycans in the skin correlate withdifferences in the in¯ammatory response and repair characteristics.

To test the importance of GAG expression in skin during woundrepair, GAG and proteoglycans from wounds have been puri®ed.Wound ¯uids have abundant amounts of GAG and multipleproteoglycans are present in a soluble form in wound ¯uid (Pencet al, 1998). These proteoglycans include those that are normallyfound in the extracellular matrix, such as decorin and versican, andthose typically seen as integral cell surface proteoglycans such assyndecan-1 and -4 (Penc et al, 1999). As discussed earlier,proteolytic processing of the core protein and release from thecell surface or matrix is an additional mechanism to control locationand ability of proteoglycans. Finding these proteoglycans in the

Figure 4.Model of functional interactions forproteoglycans and GAG after skin injury.

Table I. Binding interactions of glycosaminoglycans(partial listings)

GAG Ligands

Heparan sulfate Extracellular matrix moleculesCollagen types I, III, IV, V, Fibronectin, Laminin,Pleiotropin, Tenascin, Thrombospondin, wnt-IGrowth factors and cytokinesFibroblast GF family, Hepatocyte GF/scatter factor,Heparin-binding epidermal GF, Platelet-derivedGF, VEGF, IL-8, IP-10, HARPEnzymes and enzyme inhibitorsElastase, Thrombin, Tissue plasminogen activator,Lipoprotein Lipase, Antithrombin III, Heparincofactor II, Leuserpin, Plasminogen activatorinhibitor-I, Protease nexin I

Chondroitin sulfates Laminin, Interferon-g, Platelet factor-4, HepatocyteGF, FGF-2Complement protein Clq, Apo B, LDL

Hyaluronic acid CD-44, RHAMM, ICAM-1

58 GALLO JID SYMPOSIUM PROCEEDINGS

soluble environment of the wound demonstrates that endothelialcells in this system can be affected by proteoglycans synthesized bydistant cells. One consequence of this observation is that release ofdistant proteoglycans causes endothelial cells in the wound torespond to proteoglycans in a manner that would not have beenpredicted by experiments designed exclusively in an in vitro system.For example, despite in vitro work that has shown FGF-2 activity isin¯uenced by heparan sulfate, FGF-2 responsiveness to GAGpuri®ed from wound ¯uids is most dependent on the presence ofdermatan sulfate that is derived from the extracellular matrixproduced by dermal ®broblasts (Penc et al, 1998).

Observations such as those discussed above show that theregulation of proteoglycans in the wound environment will dependon several distinct processes and that the proteoglycan or GAG canhave activity as a soluble paracrine factor. To understand theseparacrine effects, further information about the synthesis andprocessing of the GAG is necessary. Currently, rapid advances arebeing made in the identi®cation of mammalian enzymes involvedin GAG synthesis and degredation. Enzymes such as the hapluronicacid synthetases (Weigel et al, 1997), sulfotransferases (Falany,1997), and mammalian heparanases have now been cloned (Hulettet al, 1999) and provide tools for the study of select steps inbiosynthesis and degredation. Regulation of proteoglycan coreprotein expression is incompletely understood, although syndecan-1 expression can be in¯uenced by select growth factors such asPDGF or FGF-2 and TGF-b. Additionally, an intriguing linkbetween immune defense and proteoglycan regulation was revealedwith the discovery that antimicrobial peptides in wounds can alsostimulate ®broblasts and endothelia to increase synthesis ofproteoglycans (Gallo et al, 1994).

GAG AS MODULATORS OF IMMUNE DEFENSE

The extensive repitoir of molecules that bind to GAG includesseveral cytokines that play important roles during in¯ammation.Associations between proteoglycan expression and in¯ammationhave been seen in adult and fetal wound repair as well as in a largebody of literature that has described the release of GAG withvarious forms of collagen vascular disease. In these examples thepresence of GAG or proteoglycan can either enable soluble pro-in¯ammatory molecules to function, or simply re¯ect anepiphenomenon of in¯ammation. Furthermore, it is now apparentthat GAG can directly interact with endothelial cells to activatein¯ammatory events. Two GAG have been identi®ed with thepotential for this interaction. Dermatan sulfate, isolated fromwounds, activates nuclear translocation of NF-kB in dermalmicrovascular endothelial cells. Subsequent to the activation ofNF-kB, the expression of adhesion molecules such as ICAM-1,VCAM, and E-Selectin all increase (Penc et al, 1999). Hyaluronancan induce VCAM on renal tubular epithelial cells (Oertli et al,1998) as well as in¯uence the function of macrophages byincreasing the synthesis of metalloelastase, nitric oxide synthase,chemokines, and plasminogen activator inhibitor-1 (Horton et al,1999a,b). In this case, fragments of the HA appear to be mostactive. Thus, activity of a hyaluronidase on previously madehyaluronan will activate this system.

Finding that GAG have activity as a paracrine signalling moleculehas important implications toour understandingof vascular biology ina complex tissue such as the skin. The example of wound repairillustrates a model for understanding the critical and central roleproteoglycans play in regulating a variety of cell processes (Fig 4).Following tissue injury cells at the site respond by increasingproteolysis and GAG degradation to release soluble proteoglycansand GAG fragments. Simultaneously, antimicrobial peptides providean early innate defense system protecting against rapid bacterialproliferation in the wound and also stimulate proteoglycan synthesis.The increase in GAG fragments, proteoglycans, and solubleproteoglycans each can then in¯uence events involved in cell growthand division. Furthermore, these molecules also promote in¯amma-

tion, and through stimulation of adhesion molecule expression willlead to enhanced cellular innate defense of the wound.

FUTURE DIRECTIONS

A major challenge faced by investigators in the ®eld of proteoglycanbiology is to test the many hypotheses that have developed fromexperiments performed in vitro. As more parts of the system arede®ned we recognize greater redundancy and the capacity of thiscomplex system to accommodate a change in a single component.New information provides many opportunities to investigate thetherapeutic potential of manipulating steps in proteoglycanprocessing. Additional components of the GAG and proteoglycansystem must be identi®ed, and with this knowledge moleculesdesigned to in¯uence their function. Given our current level ofunderstanding it is likely that through an increased understanding ofproteoglycans we will be able to exert a positive in¯uence onvascular biology.

REFERENCES

Bern®eld M, Kokenyesi R, Kato M, Hinkes MT, Spring J, Gallo RL, Lose EJ:Biology of the syndecans: a family of transmembrane heparan sulfateproteoglycans. Ann Rev Cell Biol 8:365±398, 1992

Brown TA, Bouchard T, St. John T, Wayner E, Carter WG: Human keratinocytesexpress a new CD44 core protein (CD44E) as a heparan-sulfate intrinsicmembrane proteoglycan with additional exons. J Cell Biol 113:207±221, 1991

Carey DJ, Evans DM, Stahl RC, Asundi VK, Conner KJ, Garbes P, Cizmeci-SmithG: Molecular cloning and characterization of N-syndecan, a noveltransmembrane heparan sulfate proteoglycan. J Cell Biol 117:191±201, 1992

Danielson KG, Baribault H, Holmes DF, Grahm H, Kadler KE, Iozzo RV: Targeteddisruption of decorin leads to abnormal collagen ®bril morphology and skinfragility. J Cell Biol 136:729±743, 1997

DiGabriele AD, Lax I, Chen DI, Svahn CM, Jaye M, Schlessinger J, HandricksonWA: Structure of a heparin-linked biologically active dimer of ®broblastgrowth factor. Nature 393:812±817, 1998

Falany CN: Enzymology of human cytosolic sulfotransferases. FASEB J 11:206±216,1997

Gallo RL, Bern®eld M: Proteoglycans and their role in wound repair. In: RA Clark,ed. Molecular and Cellular Biology of Wound Repair. New York: Plenum, 1995

Gallo RL, Kim C, Kokenyesi R, Adzick NS, Bern®eld M: Syndecans-1 and ±4 areinduced during wound repair of neonatal but not fetal skin. J Invest Dermatol107:667±683, 1996

Gallo RL, Ono M, Povsic T, Page C, Eriksson E, Klagsbrun M, Bern®eld M:Syndecans, cell surface heparan sulfate proteoglycans, are induced by a proline-rich antimicrobial peptide from wounds. Proc Natl Acad Sci USA 91:11035±11039, 1994

Horton M, Shapiro S, Bao C, Lowenstein C, Noble PW: Induction and regulation ofmacrophage metalloelastase by hyaluronan fragments in mouse macrophages. JImmunol 162:4171±4176, 1999a

Horton MR, Olman MA, Noble PW: Hyaluronan fragments induce plasminogenactivator inhibitor-1 and inhibit urokinase activity in mouse alveolarmacrophages: a potential mechanism for impaired ®brinolytic activity inacute lung injury. Chest 116:17S, 1999b

Hulett MD, Freeman C, Hamdorf BJ, Baker RT, Harris MJ, Parish CR: Cloning ofmammalian heparanase, an important enzyme in tumor invasion and metastasis.Nat Med 5:803±809, 1999

Iozzo RV: Matrix proteoglycans: from molecular design to cellular function. AnnuRev Biochem 67:609±652, 1998

Iozzo RV, Murdoch AD: Proteoglycans of the extracellular environment: clues fromthe gene and protein side offer novel perspectives in molecular diversity andfunction. FASEB J 10:598±614, 1996

Jackson RL, Busch SJ, Cardin AD: Glycosaminoglycans: molecular properties,protein interactions, and role in physiological processes. Physiol Review 2:481±485, 1991

Jalkanen M, Rapraeger A, Bern®eld M: Mouse mammary epithelial cells producebasement membrane and cell surface heparan sulfate proteoglycan containingdistinct core protein. J Cell Biol 106:953±962, 1988

Koda JE, Bern®eld M: Heparan sulfate proteoglycans from mouse mammaryepithelial cells: Basal extracellular proteoglycan binds speci®cally to native typeI collagen ®brils. J Biol Chem 259:11763±11770, 1984

Kojima T, Inazawa J, Takamatsu J, Rosenberg RD, Saito H: Human ryudocan coreprotein: molecular cloning and characterization of the cDNA, andchromosomal localization of the gene. Biochem Biophys Res Comm 190:814±822, 1993

Lander AD: Proteoglycans: master regulators of molecular encounter? Matrix Biol17:465±472, 1998

LeBaron RG, Hook A, Esko JD, Gay S, Hook M: Binding of heparan sulfate to typeVI collagen ± a mechanism of cell-substrate adhesion. J Biol Chem 264:7950±7956, 1989

Liebersbach BF, Sanderson RD: Expression of syndecan-1 inhibits cell invasion intotype I collagen. J Biol Chem 269:20013±20019, 1994

VOL. 5, NO. 1 DECEMBER 2000 PGs IN WOUND DEFENSE 59

Lindahl U, Backstrom G, Thunberg L: The antithrombin-binding sequence inheparin. J Biol Chem 258:9826±9830, 1983

Noonan DM, Fulle A, Valente P, et al: The complete sequence of perlecan, abasement membrane heparan sulfate proteoglycan, reveals extensive similaritywith laminin A chain, low density lipoprotein-receptor, and the neural celladhesion molecule. J Biol Chem 266:22939±22947, 1991

Oertli B, Beck-Schimmer B, Fan X, Wuthrich RP: Mechanisms of hyaluronan-induced up-regulation of ICAM-1 and VCAM-1 expression by murine kidneytubular epithelial cells: hyaluronan triggers cell adhesion molecule expressionthrough a mechanism involving activation of nuclear factor-kB and activatingprotein-1. J Immunol 161:3431±3437, 1998

Oh ES, Woods A, Couchman JR: Multimerization of the cytoplasmic domain ofsyndecan-4 is required for its ability to activate protein kinase C. J Biol Chem272:11805±11811, 1997a

Oh ES, Woods A, Couchman JR: Syndecan-4 proteoglycan regulates thedistribution and activity of protein kinase C. J Biol Chem 272:8133±8136,1997b

Oksala O, Salo T, Tammi R, Hakkinen L, Jalkanen M, Inki P, Larjava H: Expressionof proteoglycans and hyaluronan during wound healing. J Histochem Cytochem43:125±135, 1995

Penc SF, Pomahac B, Winkler T, Dorschner RA, Eriksson E, Gallo RL: DermatanSulfate released after injury is a potent promoter of FGF-2 activity. J Biol Chem273:28116±28121, 1998

Penc SF, Pomahac B, Eriksson E, Detmar M, Gallo RL: Dermatan sulfate activatesnuclear factor-kappab and induces endothelial and circulating intercellularadhesion molecule-1. J Clin Invest 103:1329±1335, 1999

Rapraeger A: Transforming growth factor (type beta) promotes the addition ofchondroitin sulfate chains to the cell surface proteoglycan (syndecan) of mousemammary epithelia. J Cell Biol 109:2509±2518, 1989

Rapraeger AC, Krufka A, Olwin BB: Requirement of heparan sulfate for bFGF-mediated ®broblast growth and myoblast differentiation. Science 252:1705±1708, 1991

Ridley RC, Xiao H, Hata J, Woodliff J, Epstein J, Sanderson RD: Expression ofsyndecan regulates human myeloma plasma cell adhesion to type I collagen.Blood 81:767±774, 1993

Salmivirta M, Elenius K, Vainio S, Hofer U, Chiquet-Ehrismann R, Thesleff I,Jalkanen M: Syndecan from embryonic tooth mesenchyme binds tenascin. JBiol Chem 266:7733±7739, 1991

Sanderson RD, Lalor P, Bern®eld M: B lymphocytes express and lose syndecan atspeci®c stages of differentiation. Cell Reg 1:27±35, 1989

Saunders S, Bern®eld M: Cell surface proteoglycan binds mouse mammary epithelialcells to ®bronectin and behaves as a receptor on epithelial for interstitial matrix.J Cell Biol 106:423±430, 1988

Solursh M, Reiter RS, Jensen KL, Kato M, Bern®eld M: Transient expression of acell surface heparan sulfate proteoglycan (syndecan) during limb development.Develop Biol 140:83±92, 1990

Spring J, Paine-Saunders SE, Hynes RO, Bern®eld M: Drosophila syndecan:Conservation of a cell surface heparan sulfate proteoglycan. Proc Natl Acad SciUSA 91:3334±3338, 1994

Stevens RL, Fox CC, Lichtenstein LM, Austen KF: Identi®cation of chondroitinsulfate E proteoglycans and heparin proteoglycans in the secretory granules ofhuman lung mast cells. Proc Natl Acad Sci USA 85:2284±2287, 1988

Sun X, Mosher DF, Rapraeger A: Heparan sulfate-mediated binding of epithelial cellsurface proteoglycan to thrombospondin. J Biol Chem 264:2885±2889, 1989

Sutherland AE, Sanderson RD, Mayes M, Siebert M, Calarco PG, Bern®eld M,Damsky CH: Expression of syndecan, a putative low af®nity ®broblastgrowth factor receptor, in the early mouse embryo. Development 113:339±351, 1991

Vainio S, Jalkanen M, Vaahtokari A, Sahlberg C, Mali M, Bern®eld M, Thesleff I:Expression of syndecan gene is induced early, is transient and correlates withchanges in mesenchymal cell proliferation during tooth organogenesis. DevelopBiol 147:322±333, 1991

Walker A, Turnbull JE, Gallagher JT: Speci®c heparan sulfate saccharides mediate theactivity of basic ®broblast growth factor. J Biol Chem 269:931±935, 1994

Weigel PH, Hascall VC, Tammi M: Hyaluronan synthases. J Biol Chem 272:13997±14000, 1997

Woods A, Couchman JR: Syndecan 4 heparan sulfate proteoglycan is a selectivelyenriched and widespread focal adhesion component. Mol Biol Cell 5:183±192,1994

Woods A, Couchman JR: Syndecans: synergistic activators of cell adhesion. TrendsCell Biol 8:189±192, 1998

Yayon A, Klagsbrun M, Esko JD, Leder P, Ornitz DM: Cell surface, heparin-likemolecules are required for binding of basic ®broblast growth factor to its highaf®nity. Cell 64:841±848, 1991

Zimmermann DR, Dours-Zimmermann MT, Schubert M, Bruckner-Tuderman L:Versican is expressed in the proliferating zone in the epidermis and inassociation with the elastic network of the dermis. J Cell Biol 124:817±825,1994

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