Acteristics were used. In almost all cases (n = 29) sinusoidal waveforms were applied on the cells. Four studies did not specify the waveform. Other loading characteristics, like the loading rate or differentshaped loading curves (e. g. triangle wave, square wave) haven been investigated yet. Unless otherwise indicated, differences in cell response were always represented as differences between loaded and unloaded control cells. Control cells were cultured either on rigid-bottomed (n = 11) or on flexible-bottomed (n = 21) culture plates. In total, control cells and loaded cells were cultured for the same period of time, however, control cells remained unloaded (n = 32; not specified: n = 1).Data CollectionWith the following exceptions, all authors collected the data immediately after the last loading cycle. Madhavan et al. (2006) investigated different intervals of loading and resting (CTS/restPLOS ONE | DOI:10.1371/journal.pone.0119816 March 30,7 /Cyclic Tensile Strain and Chondrocyte MetabolismTable 2. Effects of CTS on cell proliferation. Frequency 0.003 Hz 0.03 Hz 0.17 Hz 0.25 Hz 0.5 Hz Loading duration 24 h 12 h 24 h 90 min, 2 days 12 h 24 h 24 h 2.5 Hz 12 h Strain magnitude 5 3 17 6 3 7 12 3 DNA Synthesis ” “a ” ” ” ” Reference [31] [23] [31] [32] [23] [25] [25] [23]Effects of CTS on cell proliferation (DNA synthesis) relative to unloaded controls, sorted by loading frequency Levels of loaded cells were unchanged relative to unloaded cells ” Levels of loaded cells were increased relative to unloaded cellsaIn this study cell proliferation was examined by a MTT assay, whereas the others measured the short term change in metabolism (DNA synthesis) withthe incorporation of [3H-thymidine] into the cells. doi:10.1371/journal.pone.0119816.tfor 4/20, 8/16, 12/12, 16/8, 29/4, 24/0 h), while Thomas et al. (2011) analyzed the parameters immediately after the last loading cycle and after a 4 h recovery period.Cell viability and ProliferationViability. Viability was assessed in six studies; in five of these studies, loading did not affect cell viability. In details, more than 90 of cells remained alive after 48 h of continuous CTS with 16 strain at 0.5 Hz [26]. Accordingly, Fukuda et al. (1997) reported that the cell number after two very differing loading protocols (24 h, 5 , 0.003 Hz, and 35 h, 17 , 0.17 Hz) did not vary from unloaded samples. Furthermore, no significant cell death was observed after 24 h of 5 CTS at 0.05 Hz [27] and after 24 and 48 h of 7 CTS at 0.5 Hz [28]. During 24 h of experimentation with 3 CTS at 0.25 Hz, no differences in cell viability to unloaded cells occurred [29]. However, Akagi et al. (2006) were the only group showing changes in cell viability due to loading. Here, 24 h of 5 strain at 0.17 Hz decreased cell viability Pinometostat custom synthesis significantly to 84 [30]. Proliferation/DNA Synthesis. Cell proliferation was assessed in five studies by measuring the short-term change in metabolism (DNA synthesis) with the incorporation of [3H-thymidine] into the cells [25,31], by a MTT cell proliferation assay [32], and by a Pico-Green dsDNA quantitation kit [23] (Table 2). In one case, the authors described that the proliferation rate did not differ after loading, but the method, used to assess the proliferating rate, was not specified [29]. Chondrocytes under CTS with a frequency of 0.003 or 0.03 Hz did not alter their DNA synthesis STI-571 cancer compared to unloaded samples [23,31]. However, higher frequencies (0.17?.5 Hz) increased.Acteristics were used. In almost all cases (n = 29) sinusoidal waveforms were applied on the cells. Four studies did not specify the waveform. Other loading characteristics, like the loading rate or differentshaped loading curves (e. g. triangle wave, square wave) haven been investigated yet. Unless otherwise indicated, differences in cell response were always represented as differences between loaded and unloaded control cells. Control cells were cultured either on rigid-bottomed (n = 11) or on flexible-bottomed (n = 21) culture plates. In total, control cells and loaded cells were cultured for the same period of time, however, control cells remained unloaded (n = 32; not specified: n = 1).Data CollectionWith the following exceptions, all authors collected the data immediately after the last loading cycle. Madhavan et al. (2006) investigated different intervals of loading and resting (CTS/restPLOS ONE | DOI:10.1371/journal.pone.0119816 March 30,7 /Cyclic Tensile Strain and Chondrocyte MetabolismTable 2. Effects of CTS on cell proliferation. Frequency 0.003 Hz 0.03 Hz 0.17 Hz 0.25 Hz 0.5 Hz Loading duration 24 h 12 h 24 h 90 min, 2 days 12 h 24 h 24 h 2.5 Hz 12 h Strain magnitude 5 3 17 6 3 7 12 3 DNA Synthesis ” “a ” ” ” ” Reference [31] [23] [31] [32] [23] [25] [25] [23]Effects of CTS on cell proliferation (DNA synthesis) relative to unloaded controls, sorted by loading frequency Levels of loaded cells were unchanged relative to unloaded cells ” Levels of loaded cells were increased relative to unloaded cellsaIn this study cell proliferation was examined by a MTT assay, whereas the others measured the short term change in metabolism (DNA synthesis) withthe incorporation of [3H-thymidine] into the cells. doi:10.1371/journal.pone.0119816.tfor 4/20, 8/16, 12/12, 16/8, 29/4, 24/0 h), while Thomas et al. (2011) analyzed the parameters immediately after the last loading cycle and after a 4 h recovery period.Cell viability and ProliferationViability. Viability was assessed in six studies; in five of these studies, loading did not affect cell viability. In details, more than 90 of cells remained alive after 48 h of continuous CTS with 16 strain at 0.5 Hz [26]. Accordingly, Fukuda et al. (1997) reported that the cell number after two very differing loading protocols (24 h, 5 , 0.003 Hz, and 35 h, 17 , 0.17 Hz) did not vary from unloaded samples. Furthermore, no significant cell death was observed after 24 h of 5 CTS at 0.05 Hz [27] and after 24 and 48 h of 7 CTS at 0.5 Hz [28]. During 24 h of experimentation with 3 CTS at 0.25 Hz, no differences in cell viability to unloaded cells occurred [29]. However, Akagi et al. (2006) were the only group showing changes in cell viability due to loading. Here, 24 h of 5 strain at 0.17 Hz decreased cell viability significantly to 84 [30]. Proliferation/DNA Synthesis. Cell proliferation was assessed in five studies by measuring the short-term change in metabolism (DNA synthesis) with the incorporation of [3H-thymidine] into the cells [25,31], by a MTT cell proliferation assay [32], and by a Pico-Green dsDNA quantitation kit [23] (Table 2). In one case, the authors described that the proliferation rate did not differ after loading, but the method, used to assess the proliferating rate, was not specified [29]. Chondrocytes under CTS with a frequency of 0.003 or 0.03 Hz did not alter their DNA synthesis compared to unloaded samples [23,31]. However, higher frequencies (0.17?.5 Hz) increased.
