title: Collagen VI-NG2 axis in human tendon fibroblasts under conditions mimicking injury response.
abstract: In response to injury, tendon fibroblasts are activated, migrate to the wound, and contribute to tissue repair by producing and organizing the extracellular matrix. Collagen VI is a microfibrillar collagen enriched in the pericellular matrix of tendon fibroblasts with a potential regulatory role in tendon repair mechanism. We investigated the molecular basis of the interaction between collagen VI and the cell membrane both in tissue sections and fibroblast cultures of human tendon, and analyzed the deposition of collagen VI during migration and myofibroblast trans-differentiation, two crucial events for tendon repair. Tendon fibroblast displayed a collagen VI microfibrillar network closely associated with the cell surface. Binding of collagen VI with the cell membrane was mediated by NG2 proteoglycan, as demonstrated by in vitro perturbation of collagen VI-NG2 interaction with a NG2-blocking antibody. Cultures subjected to wound healing scratch assay displayed collagen VI-NG2 complexes at the trailing edge of migrating cells, suggesting a potential role in cell migration. In fact, the addition of a NG2-blocking antibody led to an impairment of cell polarization and delay of wound closure. Similar results were obtained after in vitro perturbation of collagen VI extracellular assembly with the 3C4 anti-collagen VI antibody and in collagen VI-deficient tendon cultures of a Ullrich congenital muscular dystrophy patient carrying mutations in COL6A2 gene. Moreover, in vitro treatment with transforming growth factor β1 (TGFβ1) induced a dramatic reduction of NG2 expression, both at protein and mRNA transcript level, and the impairment of collagen VI association with the cell membrane. Instead, collagen VI was still detectable in the extracellular matrix in association with ED-A fibronectin and collagen I, which were strongly induced by TGFβ1 treatment. Our findings reveal a critical role of the NG2 proteoglycan for the binding of collagen VI to the surface of tendon fibroblasts. By interacting with NG2 proteoglycan and other extracellular matrix proteins, collagen VI regulates fibroblasts behavior and the assembly of tendon matrix, thereby playing a crucial role in tendon repair.
authors.affiliation: Department of Biomedical Sciences, University of Padova, Padova, Italy; SC Laboratory of Musculoskeletal Cell Biology, IOR-IRCCS, Bologna, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Sardone
authors.affiliation: SC Laboratory of Musculoskeletal Cell Biology, IOR-IRCCS, Bologna, Italy; Institute of Molecular Genetics, National Research Council of Italy, Bologna, Italy.
authors.forename: Spartaco
authors.initials: S
authors.lastname: Santi
authors.affiliation: SC Laboratory of Musculoskeletal Cell Biology, IOR-IRCCS, Bologna, Italy; Institute of Molecular Genetics, National Research Council of Italy, Bologna, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Tagliavini
authors.affiliation: University of Bologna, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Traina
authors.affiliation: SC Laboratory of Musculoskeletal Cell Biology, IOR-IRCCS, Bologna, Italy.
authors.forename: Luciano
authors.initials: L
authors.lastname: Merlini
authors.affiliation: SC Laboratory of Musculoskeletal Cell Biology, IOR-IRCCS, Bologna, Italy; Institute of Molecular Genetics, National Research Council of Italy, Bologna, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Squarzoni
authors.affiliation: Department of Molecular Medicine, University of Padova, Padova, Italy.
authors.forename: Matilde
authors.initials: M
authors.lastname: Cescon
authors.affiliation: Center for Biochemistry, University of Cologne, Cologne, Germany; Center for Molecular Medicine, University of Cologne, Cologne, Germany; Cologne Center for Musculoskeletal Biomechanics (CCMB), University of Cologne, Cologne, Germany.
authors.forename: Raimund
authors.initials: R
authors.lastname: Wagener
authors.affiliation: SC Laboratory of Musculoskeletal Cell Biology, IOR-IRCCS, Bologna, Italy.
authors.forename: Nadir Mario
authors.initials: NM
authors.lastname: Maraldi
authors.affiliation: Department of Molecular Medicine, University of Padova, Padova, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Bonaldo
authors.affiliation: University of Bologna, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Cesare
authors.initials: C
authors.lastname: Faldini
authors.affiliation: SC Laboratory of Musculoskeletal Cell Biology, IOR-IRCCS, Bologna, Italy; Institute of Molecular Genetics, National Research Council of Italy, Bologna, Italy. Electronic address: sabatelli@area.bo.cnr.it.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Sabatelli
mesh_terms: D000293:Adolescent; D000941:Antigens / Q000378:metabolism*; D002465:Cell Movement; D054338:Cell Transdifferentiation; D002478:Cells, Cultured; D024142:Collagen Type VI / Q000502:physiology*; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D008875:Middle Aged; D011485:Protein Binding; D021381:Protein Transport; D011509:Proteoglycans / Q000378:metabolism*; D013710:Tendons / Q000166:cytology; D053773:Transforming Growth Factor beta1 / Q000502:physiology; D055815:Young Adult; D000099216:Chondroitin Sulfate Proteoglycan 4
chemical_list: D000941:Antigens; D024142:Collagen Type VI; D011509:Proteoglycans; D053773:Transforming Growth Factor beta1; D000099216:Chondroitin Sulfate Proteoglycan 4; C504344:COL6A2 protein, human; C508960:TGFB1 protein, human
keywords: Cell migration; Collagen VI; NG2 proteoglycan; Tendon repair; Transforming growth factor β1