title: Hyaluronan accumulation in thyroid tissue: evidence for contributions from epithelial cells and fibroblasts.
abstract: Graves' disease (GD) and Hashimoto's thyroiditis (HT) are autoimmune processes often associated with hyperthyroidism and hypothyroidism, respectively. Despite their diverging clinical presentations, immune activation drives both diseases and results in connective tissue accumulation of the nonsulfated glycosaminoglycan, hyaluronan. The hydrophilic property of hyaluronan contributes to the pathogenesis of thyroid-associated ophthalmopathy, dermopathy and hypothyroid myxedema. Whether hyaluronan accumulates in the thyroid and plays a role in goiter formation in GD and HT remains unknown. We report here that levels of hyaluronan are increased in thyroid tissue from individuals with both diseases compared with glands uninvolved with autoimmune disorders. The transcript encoding hyaluronan synthase (HAS)-3, one of three mammalian HAS isoforms, was detected in thyroid tissue. Isolated thyrocytes in primary culture express all three HAS isoforms when treated with IL-1beta. Thyrocytes and thyroid fibroblasts produce hyaluronan under basal culture conditions and IL-1beta enhances levels of this molecule in both cell types. On a per-cell basis, fibroblasts produce more hyaluronan than do thyrocytes under basal conditions and after cytokine treatment. Synthesis in thyrocytes can also be altered by increasing serum concentration in the medium and by modifying culture density. Our findings suggest that hyaluronan accumulation in thyroid tissue might derive from thyrocytes and fibroblasts. Moreover, this glycosaminoglycan becomes more abundant as a consequence of autoimmune disease. It may therefore contribute to increased thyroid volume in GD and HT. Coupled with the newly identified influence exerted by hyaluronan on immunocompetent cells, our findings represent potentially important insights into the pathogenesis of autoimmune thyroid diseases.
authors.affiliation: Division of Molecular Medicine, Harbor-UCLA Medical Center, Torrance, California 90502, USA. tjsmith@ucla.edu.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Gianoukakis
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Jennings
authors.forename: Chris S
authors.initials: CS
authors.lastname: King
authors.forename: Christine E
authors.initials: CE
authors.lastname: Sheehan
authors.forename: Neil
authors.initials: N
authors.lastname: Hoa
authors.forename: Paraskevi
authors.initials: P
authors.lastname: Heldin
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Smith
mesh_terms: D002452:Cell Count; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D005312:Fetal Blood; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D014453:Glucuronosyltransferase / Q000235:genetics; D006111:Graves Disease / Q000378:metabolism* / Q000473:pathology; D050031:Hashimoto Disease / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D053583:Interleukin-1beta / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D013954:Thyroglobulin / Q000378:metabolism; D013961:Thyroid Gland / Q000378:metabolism* / Q000473:pathology; D014157:Transcription Factors; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D004268:DNA-Binding Proteins; D036341:Intercellular Signaling Peptides and Proteins; D053583:Interleukin-1beta; D012333:RNA, Messenger; C504003:TTF1 protein, human; D014157:Transcription Factors; D006820:Hyaluronic Acid; D013954:Thyroglobulin; D014453:Glucuronosyltransferase; C101754:HAS2 protein, human; C105458:HAS3 protein, human; D000076002:Hyaluronan Synthases