Al. 2008 [60] Matsukawa et al. 2004 [47]Collagen I74h0.33 HzCollagen I/II, Fibronectin, Albumin Collagen II724 h0.167 Hzbuy Trichostatin A proteoglycan, iNOS, NOOhno et al. 2005 [24] Perera et el. 2010 [32]126, 12, 24 h, some days 90 min a day, 2 days0.5 HzCollagen II mRNA, collagen X mRNA, aggrecan mRNA, TGF-1 Proliferation, cMyc, SOX-9, VEGF, ERK1/2, MEK ? IL-Collagen I60.25 HzRu-Song et al. 2012 [13] Shimizu et al. 2004 [33] Tanaka et al. 2005 [25] Tanimoto et al. 2009 [75] Tanimoto et al. 2011 [45]Not specified100, 1, 6, 12, 24 h 12, 16, 24 h0.167 HzMorphology, collagen II mRNA, aggrecan mRNA Morphology, collagen II mRNA, aggrecan mRNA, fibronectin DNA Synthesis, morphology, collagen II, proteoglycan, HYAL1, HYAL2, IL1-, TNF-Collagen I70.5 HzCollagen II7, 1212 h, 24 h0.5 HzNot specified22.806, 12, 24, 48 h 0, 6, 12, 24, 48 h0.5 HzNot specified7, 210.5 HzSuperficial zone proteinThomas et al. 2011 [46]Pronectin7.530 min1 HzCollagen II mRNA, aggrecan mRNA, MMP-3, MMP-13, ADAMTS-4, ADAMTS-5, SOX-9, c-fos, c-jun, Lef-1, Wnt3A DNA Synthesis, proteoglycan, collagen II Morphology, cell ACY-241 site viability, collagen II mRNA, aggrecan mRNA, gene expression in 23 different genes (Continued)Ueki et al. 2008 [23] Wang et al. 2011 [26]Collagen II312 h0.03, 0.5, 2.5 Hz 0.5 HzFibronectin1612, 24, 48 hPLOS ONE | DOI:10.1371/journal.pone.0119816 March 30,6 /Cyclic Tensile Strain and Chondrocyte MetabolismTable 1. (Continued) Author Xu et al. 2000 [27] Cell type 6? pounds, young adult New Zealand white rabbits; chondrocytes from shoulder and knee articular cartilage 160?80 grams SpragueDawley rats; chondrocytes from lumbar spine end-plate articular cartilage 10 months old calves; chondrocytes from metacarpophalangeal joint condyle articular cartilage 7 days old Wistar rats; chondrocytes from epiphyseal femoral condyle articular cartilage Culture plate coating Pronectin Strain magnitude 6 Loading duration 4, 24, 48, 72, 96 h Loading frequency 0.05 Hz Investigated parameters Cell viability, collagen II mRNA, aggrecan mRNA, proteoglycans, versican, biglycan, MMP-1, TIMP1, TIMP-2, iNOS, COX-2, NO, PGE2 Morphology, TGF-Xu et al. 2011 a [97]Collagen I103, 6, 12, 24, 36, 48 h0.5, 1, 1.5, 2 HzYamazaki et al. 2003 [74]Not specified1724 h3 s strain–6 min relaxation, 0.5 Hz 0.5 HzHyaluronanYorimitsu et al. 2008 [28]Collagen I724, 48 hCell viability, iNOS, NOListing of included studies with description of cell source, culture plate coating, loading protocol and parameters that were investigated. doi:10.1371/journal.pone.0119816.tLoading DeviceThe commercially available Flexercell strain unit (types FX2000, FX3000, FX4000 or FX5000; n = 32) or a custom made strain instrument (n = 1) [26] were used as loading devices. All loading devices were vacuum driven. The vacuum pulled the deformable membranes of the culture plates over loading posts (Fig. 1B). Once the vacuum was released, the membranes returned to their original shape. The cells that were attached on the membranes followed the deformation of the membrane and thereby experienced tensile strain. Depending on the setup, biaxial and uniaxial forms of strain can be applied.Loading ProtocolsLoading protocols encompassed strains of the membranes of 0?3 at frequencies of 0.03?2.5 Hz and loading durations of 0?6 h. The most commonly used loading protocol was 7 strain at 0.5 Hz for 24 h, which was investigated in 6 studies. Strain characteristics were biaxial in 11 publications. In 22 cases, it remained unclear if uni- or biaxial strain char.Al. 2008 [60] Matsukawa et al. 2004 [47]Collagen I74h0.33 HzCollagen I/II, Fibronectin, Albumin Collagen II724 h0.167 HzProteoglycan, iNOS, NOOhno et al. 2005 [24] Perera et el. 2010 [32]126, 12, 24 h, some days 90 min a day, 2 days0.5 HzCollagen II mRNA, collagen X mRNA, aggrecan mRNA, TGF-1 Proliferation, cMyc, SOX-9, VEGF, ERK1/2, MEK ? IL-Collagen I60.25 HzRu-Song et al. 2012 [13] Shimizu et al. 2004 [33] Tanaka et al. 2005 [25] Tanimoto et al. 2009 [75] Tanimoto et al. 2011 [45]Not specified100, 1, 6, 12, 24 h 12, 16, 24 h0.167 HzMorphology, collagen II mRNA, aggrecan mRNA Morphology, collagen II mRNA, aggrecan mRNA, fibronectin DNA Synthesis, morphology, collagen II, proteoglycan, HYAL1, HYAL2, IL1-, TNF-Collagen I70.5 HzCollagen II7, 1212 h, 24 h0.5 HzNot specified22.806, 12, 24, 48 h 0, 6, 12, 24, 48 h0.5 HzNot specified7, 210.5 HzSuperficial zone proteinThomas et al. 2011 [46]Pronectin7.530 min1 HzCollagen II mRNA, aggrecan mRNA, MMP-3, MMP-13, ADAMTS-4, ADAMTS-5, SOX-9, c-fos, c-jun, Lef-1, Wnt3A DNA Synthesis, proteoglycan, collagen II Morphology, cell viability, collagen II mRNA, aggrecan mRNA, gene expression in 23 different genes (Continued)Ueki et al. 2008 [23] Wang et al. 2011 [26]Collagen II312 h0.03, 0.5, 2.5 Hz 0.5 HzFibronectin1612, 24, 48 hPLOS ONE | DOI:10.1371/journal.pone.0119816 March 30,6 /Cyclic Tensile Strain and Chondrocyte MetabolismTable 1. (Continued) Author Xu et al. 2000 [27] Cell type 6? pounds, young adult New Zealand white rabbits; chondrocytes from shoulder and knee articular cartilage 160?80 grams SpragueDawley rats; chondrocytes from lumbar spine end-plate articular cartilage 10 months old calves; chondrocytes from metacarpophalangeal joint condyle articular cartilage 7 days old Wistar rats; chondrocytes from epiphyseal femoral condyle articular cartilage Culture plate coating Pronectin Strain magnitude 6 Loading duration 4, 24, 48, 72, 96 h Loading frequency 0.05 Hz Investigated parameters Cell viability, collagen II mRNA, aggrecan mRNA, proteoglycans, versican, biglycan, MMP-1, TIMP1, TIMP-2, iNOS, COX-2, NO, PGE2 Morphology, TGF-Xu et al. 2011 a [97]Collagen I103, 6, 12, 24, 36, 48 h0.5, 1, 1.5, 2 HzYamazaki et al. 2003 [74]Not specified1724 h3 s strain–6 min relaxation, 0.5 Hz 0.5 HzHyaluronanYorimitsu et al. 2008 [28]Collagen I724, 48 hCell viability, iNOS, NOListing of included studies with description of cell source, culture plate coating, loading protocol and parameters that were investigated. doi:10.1371/journal.pone.0119816.tLoading DeviceThe commercially available Flexercell strain unit (types FX2000, FX3000, FX4000 or FX5000; n = 32) or a custom made strain instrument (n = 1) [26] were used as loading devices. All loading devices were vacuum driven. The vacuum pulled the deformable membranes of the culture plates over loading posts (Fig. 1B). Once the vacuum was released, the membranes returned to their original shape. The cells that were attached on the membranes followed the deformation of the membrane and thereby experienced tensile strain. Depending on the setup, biaxial and uniaxial forms of strain can be applied.Loading ProtocolsLoading protocols encompassed strains of the membranes of 0?3 at frequencies of 0.03?2.5 Hz and loading durations of 0?6 h. The most commonly used loading protocol was 7 strain at 0.5 Hz for 24 h, which was investigated in 6 studies. Strain characteristics were biaxial in 11 publications. In 22 cases, it remained unclear if uni- or biaxial strain char.
