title: First in vivo detection and characterization of hyaluronan-coated extracellular vesicles in human synovial fluid.
abstract: Extracellular vesicles (EVs) function in intercellular signaling by transporting different membrane and cytosolic molecules, including hyaluronan (HA) and its synthesis machinery. As both EVs and HA are abundant in synovial fluid, we hypothesized that HA synthesized in synovial membrane would be carried on the surface of EVs. Synovial fluid (n = 15) and membrane samples (n = 5) were obtained from knee surgery patients. HA concentrations were analyzed in synovial fluid and HA and its synthesis machinery were examined with histochemical stainings in synovial membrane. To assess the size distribution of EVs in synovial fluid and to visualize HA on EVs, nanoparticle tracking analysis (NTA), confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM) were utilized. The average HA concentration in synovial fluid was 2.0 ± 0.21 mg/ml without significant differences between the patients with trauma/diagnostic arthroscopy and primary or post-traumatic osteoarthritis. Positive stainings of HA synthases (HAS1-3), HA and its receptor CD44 in synovial cells indicated active HA secretion in synovial membrane. According to NTA, EVs were abundant in synovial fluid and their main populations were ≤300 nm in diameter after differential centrifugation. There were no significant differences in the EV counts between the patients with primary or post-traumatic osteoarthritis. TEM verified that HA-positive particles detected by CLSM were lipid membrane vesicles surrounded by a HA coat. Our results provide the first in vivo evidence that human synovial fluid contains HA-positive EVs, one source of which presumably is the long HAS-positive protrusions of synovial fibroblasts. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1960-1968, 2016.
authors.affiliation: Faculty of Health Sciences, Institute of Biomedicine/Anatomy, University of Eastern Finland, School of Medicine, P.O. Box 1627, FI-70211 Kuopio, Finland.|Faculty of Science and Forestry, Department of Biology, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: Anne-Mari
authors.initials: AM
authors.lastname: Mustonen
authors.affiliation: Faculty of Health Sciences, Institute of Biomedicine/Anatomy, University of Eastern Finland, School of Medicine, P.O. Box 1627, FI-70211 Kuopio, Finland.|Faculty of Science and Forestry, Department of Biology, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: Petteri
authors.initials: P
authors.lastname: Nieminen
authors.affiliation: Department of Orthopaedics, Traumatology and Hand Surgery, Kuopio University Hospital, P.O. Box 100, FI-70290 Kuopio, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Joukainen
authors.affiliation: Department of Orthopaedics, Traumatology and Hand Surgery, Kuopio University Hospital, P.O. Box 100, FI-70290 Kuopio, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Jaroma
authors.affiliation: Department of Orthopaedics, Traumatology and Hand Surgery, Kuopio University Hospital, P.O. Box 100, FI-70290 Kuopio, Finland.
authors.forename: Tommi
authors.initials: T
authors.lastname: Kääriäinen
authors.affiliation: Department of Orthopaedics, Traumatology and Hand Surgery, Kuopio University Hospital, P.O. Box 100, FI-70290 Kuopio, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Kröger
authors.affiliation: Faculty of Biological and Environmental Sciences, Division of Biochemistry and Biotechnology, Department of Biosciences, University of Helsinki, P.O. Box 56 (Viikinkaari 4), FI-00014 Helsinki, Finland.|Faculty of Pharmacy, Division of Pharmaceutical Biosciences, Centre for Drug Research, University of Helsinki, P.O. Box 56 (Viikinkaari 4), FI-00014 Helsinki, Finland.
authors.forename: Elisa
authors.initials: E
authors.lastname: Lázaro-Ibáñez
authors.affiliation: Faculty of Biological and Environmental Sciences, Division of Biochemistry and Biotechnology, Department of Biosciences, University of Helsinki, P.O. Box 56 (Viikinkaari 4), FI-00014 Helsinki, Finland.|Faculty of Pharmacy, Division of Pharmaceutical Biosciences, Centre for Drug Research, University of Helsinki, P.O. Box 56 (Viikinkaari 4), FI-00014 Helsinki, Finland.
authors.forename: Pia R-M
authors.initials: PR
authors.lastname: Siljander
authors.affiliation: Department of Pathology, Kuopio University Hospital, P.O. Box 1777, FI-70211 Kuopio, Finland.
authors.forename: Vesa
authors.initials: V
authors.lastname: Kärjä
authors.affiliation: Faculty of Health Sciences, Institute of Biomedicine/Anatomy, University of Eastern Finland, School of Medicine, P.O. Box 1627, FI-70211 Kuopio, Finland.
authors.forename: Kai
authors.initials: K
authors.lastname: Härkönen
authors.affiliation: University of Eastern Finland, SIB Labs, P.O. Box 1627, FI-70211 Kuopio, Finland.
authors.forename: Arto
authors.initials: A
authors.lastname: Koistinen
authors.affiliation: Faculty of Health Sciences, Institute of Biomedicine/Anatomy, University of Eastern Finland, School of Medicine, P.O. Box 1627, FI-70211 Kuopio, Finland.
authors.forename: Kirsi
authors.initials: K
authors.lastname: Rilla
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000067128:Extracellular Vesicles / Q000737:chemistry*; D005260:Female; D006801:Humans; D006820:Hyaluronic Acid / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D013582:Synovial Fluid / Q000378:metabolism*; D055815:Young Adult
chemical_list: D006820:Hyaluronic Acid
keywords: extracellular vesicles; hyaluronan; nanoparticle tracking analysis; osteoarthritis; synovial fluid