title: Human osteoarthritic cartilage shows reduced in vivo expression of IL-4, a chondroprotective cytokine that differentially modulates IL-1β-stimulated production of chemokines and matrix-degrading enzymes in vitro.
abstract: BACKGROUND
  In osteoarthritis (OA), an inflammatory environment is responsible for the imbalance between the anabolic and catabolic activity of chondrocytes and, thus, for articular cartilage derangement. This study was aimed at providing further insight into the impairment of the anabolic cytokine IL-4 and its receptors in human OA cartilage, as well as the potential ability of IL-4 to antagonize the catabolic phenotype induced by IL-1β.
  
  
  RESULTS
  The in vivo expression of IL-4 and IL-4 receptor subunits (IL-4R, IL-2Rγ, IL-13Rα1) was investigated on full thickness OA or normal knee cartilage. IL-4 expression was found to be significantly lower in OA, both in terms of the percentage of positive cells and the amount of signal per cell. IL-4 receptor type I and II were mostly expressed in mid-deep cartilage layers. No significant difference for each IL-4 receptor subunit was noted. IL-4 anti-inflammatory and anti-catabolic activity was assessed in vitro in the presence of IL-1β and/or IL-4 for 24 hours using differentiated high density primary OA chondrocyte also exhibiting the three IL-4 R subunits found in vivo. Chemokines, extracellular matrix degrading enzymes and their inhibitors were evaluated at mRNA (real time PCR) and protein (ELISA or western blot) levels. IL-4 did not affect IL-1β-induced mRNA expression of GRO-α/CXCL1, IL-8/CXCL8, ADAMTS-5, TIMP-1 or TIMP-3. Conversely, IL-4 significantly inhibited RANTES/CCL5, MIP-1α/CCL3, MIP-1β/CCL4, MMP-13 and ADAMTS-4. These results were confirmed at protein level for RANTES/CCL5 and MMP-13.
  
  
  CONCLUSIONS
  Our results indicate for the first time that OA cartilage has a significantly lower expression of IL-4. Furthermore, we found differences in the spectrum of biological effects of IL-4. The findings that IL-4 has the ability to hamper the IL-1β-induced release of both MMP-13 and CCL5/RANTES, both markers of OA chondrocytes, strongly indicates IL-4 as a pivotal anabolic cytokine in cartilage whose impairment impacts on OA pathogenesis.
authors.affiliation: Laboratory of Immunorheumatology and Tissue Regeneration/RAMSES, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Assirelli
authors.affiliation: Laboratory of Immunorheumatology and Tissue Regeneration/RAMSES, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Lia
authors.initials: L
authors.lastname: Pulsatelli
authors.affiliation: Laboratory of Immunorheumatology and Tissue Regeneration/RAMSES, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Dolzani
authors.affiliation: Laboratory of Immunorheumatology and Tissue Regeneration/RAMSES, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Platano
authors.affiliation: Laboratory of Immunorheumatology and Tissue Regeneration/RAMSES, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Olivotto
authors.affiliation: Laboratory of Biomechanics and Technology Innovation, 2nd Orthopaedic and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Filardo
authors.affiliation: Reconstructive Hip and Knee Joint Surgery, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Trisolino
authors.affiliation: Laboratory of Immunorheumatology and Tissue Regeneration/RAMSES, Rizzoli Orthopaedic Institute, Bologna, Italy; University of Bologna, Bologna, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Facchini
authors.affiliation: Laboratory of Immunorheumatology and Tissue Regeneration/RAMSES, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Rosa Maria
authors.initials: RM
authors.lastname: Borzì
authors.affiliation: University of Bologna, Bologna, Italy; Medicine and Rheumatology Unit, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Meliconi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002358:Cartilage, Articular / Q000378:metabolism*; D018946:Chemokine CCL5 / Q000378:metabolism; D002648:Child; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism*; D005260:Female; D006801:Humans; D053583:Interleukin-1beta / Q000494:pharmacology*; D015847:Interleukin-4 / Q000378:metabolism*; D008297:Male; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism; D008875:Middle Aged; D010003:Osteoarthritis / Q000378:metabolism*; D055815:Young Adult
chemical_list: D018946:Chemokine CCL5; D016207:Cytokines; D053583:Interleukin-1beta; D015847:Interleukin-4; D053509:Matrix Metalloproteinase 13