TABLE 1.
Core extracellular matrix components in human skin.
| ECM component | Localization within skin | Function |
| Collagen | ||
| Collagen type I | Interstitial matrix, dermis | Most common collagen type in dermis, support, tensile strength, fibrillary |
| Collagen type III | Interstitial matrix, dermis | 1/3 of fibrillary collagen in dermis, support, tensile strength, fibrillary; connected to Ehlers-Danlos syndrome |
| Collagen type IV | Basement membrane | Network-forming structure, highly flexible, provides strength, non-fibrillary |
| Collagen type V | Interstitial matrix, dermis | Minor collagen type in dermis, fibrillary; connected to Ehlers-Danlos syndrome |
| Collagen type VI | Papillary dermis and interstitial matrix | Links collagen IV to fibrillary collagen I and III in papillary dermis, binds decorin, biglycan, fibronectin, builds beaded microfibrils |
| Collagen type VII | Basement membrane, papillary dermis | Assembles into anchoring fibrils that anchor BM to papillary dermis; connected to EB |
| Collagen type XII | Interface between BM and papillary dermis | Fibril-associated, interacts with TSP-1, FACIT |
| Collagen type XIII | Keratinocyte surface | Transmembrane, ectodomain released by cleavage |
| Collagen type XIV | Interface between basement membrane and papillary matrix | Fibril-associated, interacts with TSP-1, FACIT |
| Collagen type XVII | Keratinocyte surface | Transmembrane, released by cleavage, attaches keratinocytes to basement membrane, regulates keratinocyte proliferation, maintains stem cells in hair follicles, MACIT |
| Collagen type XXIII | Keratinocyte surface | Transmembrane, released by cleavage, MACIT |
| Elastic fibers | ||
| Elastin | Interstitial matrix, dermis, vessels | Elasticity and resilience; connected to Marfan syndrome and Cutis laxa |
| Fibrillin-1 | Interstitial matrix, dermis | Predominant form, provides skin elasticity and flexibility, assists in BM anchorage to interstitial matrix, regulates TGF-β bioavailability, mechanosensor |
| Fibrillin-2 | Interstitial matrix, dermis | Present during development and wound healing, similar functions as fibrillin-1 |
| Glycoproteins and matricellular proteins | ||
| Laminin (332, 311, 511) | Epidermal basement membrane | Stabilize epidermal adhesion and mediate epidermal-dermal communication, can interact with anchoring fibrils and collagen XVII, can polymerize into network |
| Fibronectin | Interstitial matrix, dermis | Interacts with collagen, provides adhesion cues for cells |
| Nidogen/entactin | Basement membrane | Colocalizes with laminin, important in embryonic development, bridging molecule, helps maintain epidermal integrity |
| TSP-1 | Basement membrane, papillary dermis | Wound healing, stimulates cell proliferation, tissue homeostasis, stimulates ECM synthesis |
| Periostin | Papillary dermis | Wound healing, stimulates cell proliferation, involved in collagen deposition and scar formation |
| Tenascin C | Interstitial matrix, dermis, wound edges | Low expression, upregulated in wound healing, stimulates cell proliferation |
| Proteoglycans | ||
| Biglycan | Interstitial matrix, dermis | Collagen-interacting protein, highly abundant in papillary dermis, regulates collagen fibril formation |
| Decorin | Interstitial matrix, dermis | Collagen-interacting protein, highly abundant in papillary dermis, regulates collagen fibril formation, stabilizes tissue |
| Perlecan | Basement membrane | Aids laminin-collagen IV linkage, signals via integrin binding and supports keratinocyte proliferation |
| Versican | Reticular dermis | Large chondroitin sulfate PG, promotes stability via interaction with elastic fibers and matricellular proteins, stimulates fibroblast proliferation |
| Fibromodulin | Interstitial matrix, dermis | Function uncertain |
| Lumican | Interstitial matrix, dermis | Function uncertain, involved in collagen fibrillogenesis |
| Agrin | Basement membrane | Not fully understood |
| GAG | ||
| Heparan sulfate | Basement membrane | Involved in Wnt signaling, development, angiogenesis, metastasis, attachment site for viruses |
| Hyaluronan/hyaluronic acid | Interstitial matrix, dermis | Tissue repair, regulates tissue hydrodynamics by water binding, interacts with CD44 |
| Dermatan sulfate | Interstitial matrix, dermis | Involved in wound repair, infection, fibrosis, carcinogenesis |
The list shown is not comprehensive. Further details on ECM proteins and associated diseases have been summarized in Uitto et al. (1989), Bosman and Stamenkovic (2003), Mouw et al. (2014), Fidler et al. (2018), Bhattacharjee et al. (2019), Nystrom and Bruckner-Tuderman (2019). PG, proteoglycan; GAG, galactosaminoglycan/glycosaminoglycan; HS, heparan sulfate; BM, basement membrane; TSP-1, thrombospondin 1; FACIT, fibril-associated collagens with interrupted triple helices; MACIT, membrane-associated collagens with interrupted triple helices; EB, epidermolysis bullosa, a severe skin disease that manifests in skin fragility and blistering (Bhattacharjee et al., 2019).