title: Tendon degeneration is not mediated by regulation of Toll-like receptors 2 and 4 in human tenocytes.
abstract: We hypothesized that expression of Toll-like receptors (TLRs) 2 and 4 by tenocytes is involved in the catabolic processes of tendon degeneration. We investigated TLR2 and TLR4 expression by tenocytes in healthy and tendinotic Achilles tendons. We also investigated whether TLR2 and TLR4 could be upregulated in tendon explants using proinflammatory cytokines interleukin (IL)-1beta and tumor necrosis factor alphpa (TNFalpha). Peroperatively harvested healthy (n = 5) and tendinotic (n = 13) Achilles tendon samples were examined by real-time RT-PCR and immunohistochemical staining for TLR2 and TLR4. In addition, the catabolic process in tendinopathy was analyzed by real-time RT-PCR for matrix metalloproteinases MMP1, MMP3, MMP9, and MMP13. Furthermore, healthy tendon explants were cultured in the presence of 20 ng/ml IL-1beta (n = 10) or 10 ng/mL TNFalpha (n = 8) for 4, 24, 48, and 72 h before analysis of TLR and MMP expression levels. Although mRNA levels for both TLR2 and TLR4 were detected in healthy and tendinotic Achilles tendons, we could not confirm expression of these receptors by immunohistochemical staining in either healthy or tendinotic tendon samples. Both receptors did not show significant transcriptional regulation in tendinopathy, although MMP3 was downregulated and MMP9 was upregulated in tendinopathy. In tendon explant cultures TLR2 mRNA was upregulated by TNFalpha (p < 0.05) and IL-1beta (not significant). TLR4 gene expression was not altered by addition of IL-1beta or TNFalpha. Tendon tissue can be stimulated to increase TLR2 gene expression by addition of catabolic factors TNFalpha or IL-1beta. However, the catabolic processes in Achilles tendinopathy cannot be attributed to regulation of TLR2 and TLR4 by tenocytes.
authors.affiliation: Erasmus MC, Department of Orthopaedics, University Medical Centre, Room Ee1618, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
authors.forename: Marieke
authors.initials: M
authors.lastname: de Mos
authors.forename: Leo A B
authors.initials: LA
authors.lastname: Joosten
authors.forename: Birgitte
authors.initials: B
authors.lastname: Oppers-Walgreen
authors.forename: Johannes T M
authors.initials: JT
authors.lastname: van Schie
authors.forename: Holger
authors.initials: H
authors.lastname: Jahr
authors.forename: Gerjo J V M
authors.initials: GJ
authors.lastname: van Osch
authors.forename: Jan A N
authors.initials: JA
authors.lastname: Verhaar
mesh_terms: D000125:Achilles Tendon / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D053583:Interleukin-1beta / Q000494:pharmacology; D008297:Male; D020781:Matrix Metalloproteinase 1 / Q000096:biosynthesis; D053509:Matrix Metalloproteinase 13 / Q000096:biosynthesis; D019278:Matrix Metalloproteinase 3 / Q000096:biosynthesis; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis; D008875:Middle Aged; D013708:Tendon Injuries / Q000503:physiopathology*; D013710:Tendons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000235:genetics*; D051197:Toll-Like Receptor 4 / Q000235:genetics*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D053583:Interleukin-1beta; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13; C511768:MMP3 protein, human; D019278:Matrix Metalloproteinase 3; D020780:Matrix Metalloproteinase 9; C522360:MMP1 protein, human; D020781:Matrix Metalloproteinase 1