title: Exosomes from hypoxic endothelial cells have increased collagen crosslinking activity through up-regulation of lysyl oxidase-like 2.
abstract: Exosomes are important mediators of intercellular communication. Additionally, they contain a variety of components capable of interacting with the extracellular matrix (ECM), including integrins, matrix metalloproteinases and members of the immunoglobin superfamily. Despite these observations, research on exosome-ECM interactions is limited. Here, we investigate whether the exosome-associated lysyl oxidase family member lysyl oxidase-like 2 (LOXL2) is involved in ECM remodelling. We found that LOXL2 is present on the exterior of endothelial cell (EC)-derived exosomes, placing it in direct vicinity of the ECM. It is up-regulated twofold in EC-derived exosomes cultured under hypoxic conditions. Intact exosomes from hypoxic EC and LOXL2 overexpressing EC show increased activity in a fluorometric lysyl oxidase enzymatic activity assay as well as in a collagen gel contraction assay. Concordantly, knockdown of LOXL2 in exosome-producing EC in both normal and hypoxic conditions reduces activity of exosomes in both assays. Our findings show for the first time that ECM crosslinking by EC-derived exosomes is mediated by LOXL2 under the regulation of hypoxia, and implicate a role for exosomes in hypoxia-regulated focal ECM remodelling, a key process in both fibrosis and wound healing.
authors.affiliation: Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Olivier G
authors.initials: OG
authors.lastname: de Jong
authors.affiliation: Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Bas W M
authors.initials: BW
authors.lastname: van Balkom
authors.affiliation: Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Gremmels
authors.affiliation: Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Marianne C
authors.initials: MC
authors.lastname: Verhaar
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D002460:Cell Line; D003094:Collagen / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism* / Q000502:physiology; D055354:Exosomes / Q000378:metabolism* / Q000502:physiology; D005109:Extracellular Matrix / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D015854:Up-Regulation / Q000502:physiology*
chemical_list: D003094:Collagen; D000594:Amino Acid Oxidoreductases; C119091:LOXL2 protein, human
keywords: extracellular matrix remodelling; extracellular vesicles; lysyl oxidase