Table 1.

Compilation of studies that investigated the response of non-human, large mammal-derived chondrocytes seeded into hydrogels and subjected to uniaxial dynamic compressive loading.

Reference	Study design/investigation	Cell source (n), hydrogel, and preculture duration	Loading parameters	Results [PG = proteoglycans, Eeq = equilibrium, Edyn = dynamic, Ey = Young’s, and H(A) = aggregate]
Buschmann et al. (1995)	Cellular metabolic response to single dynamic loading period	Neonatal primary bovine chondrocytes in 2 or 3% agarose precultured 3, 13, or 24 days	Frequency: 0.001, 0.01, 0.1, and 1 Hz Amplitude: 1% Duration: 10 h continuous Max duration: 10 h	RNA: not assessed PG: ↑ all frequencies at days 5 and 23 Collagen: ↑ all frequencies at days 5 and 23 Biomechanics: not assessed
Lee and Bader (1997)	Effect of loading frequency	18-month-old primary bovine chondrocytes in 3% agarose precultured for 16 h	Frequency: 0.1, 1, and 3 Hz Amplitude: 15% Duration: 48 h continuous Max duration: 48 h	RNA: not assessed PG: ↑ 1 Hz, ↓ 0.3 Hz, and ↔ 3 Hz Collagen: ↓ all conditions Biomechanics: not assessed
Mauck et al. (2000)	Agarose versus alginate hydrogels and subsequent dynamic loading of agarose hydrogels	3- to 5-month-old primary bovine chondrocytes in 1–5% alginate without preculture	Frequency: 1 Hz Amplitude: 10% Duration: 3× 1 h on/1 h off, 5 days/week for 28 days Max duration: 60 h	RNA: not assessed PG: ↑ on day 21 Collagen: ↑ on day 21 Biomechanics: ↑ Eeq and peak stress on days 21–28
Mauck et al. (2003a)	Effect of TGF-β, IGF 1, and load	2- to 12-day-old primary bovine chondrocytes (n = 3) in 2% agarose precultured for 0 or 22 days	Frequency: 1 Hz Amplitude: 10% Duration: 3× 1 h on/1 h off, 5 days/week for 35 days Max duration: 75 h	RNA: not assessed PG: ↑ on day 28–35 Collagen: ↑ on day 35 Biomechanics: ↑ H(A) on day 35, increase with TGF-β
Mauck et al. (2003b)	Cell seeding density in agarose and effect of increased FBS concentration	4- to 6-month-old primary bovine (n = 5) in 2% agarose without preculture	Frequency: 1 Hz Amplitude: 10% Duration: 3× 1 h on/1 h off, 5 days/week for 56 days Max duration: 105 h	RNA: not assessed PG: ↑ low cell density on day 42 Collagen: ↑ low cell density on days 28–56 Biomechanics: ↑ Eeq and Edyn, α cell seeding density, and % FBS
Shelton et al. (2003)	Effect of dynamic loading frequency on constructs with full-depth, superficial, or deep chondrocytes	18-month-old primary bovine chondrocytes in 3% agarose without preculture	Frequency: 0.1, 1, and 3 Hz Amplitude: 15% Duration: 48 h continuous Max duration: 48 h	RNA: not assessed PG: full thickness or deep cells: ↓ 0.3 Hz, ↑ 1 Hz, and ↔ 3 Hz; superficial cells: ↓ 0.3 Hz, ↔ 1 Hz, and ↓ 3 Hz Collagen: not assessed Biomechanics: not assessed
Wiseman et al. (2003)	Effect of cell maturity (donor age) on response to dynamic loading and the production of NO as a readout for degenerative processes	Fetal through adult primary equine chondrocytes in 4% agarose without preculture	Frequency: 1 Hz Amplitude: 15% Duration: 24 h continuous Max duration: 24 h	RNA: not assessed PG: ↑ 5-month-old chondrocytes from low-load region, ↔ any other condition Collagen: not assessed Biomechanics: not assessed
Chowdhury et al. (2003)	Effect of continuous versus intermittent dynamic loading on cell metabolism	18-month-old primary bovine chondrocytes in 2% agarose precultured for 1 day	Frequency: 1 Hz Amplitude: 15% Duration: 24 h on/24 h off or 1.5, 3, 6, and 12 h continuous Max duration: 24 h	RNA: not assessed PG: ↑ all conditions Collagen: not assessed Biomechanics: not assessed
Wiseman et al. (2004)	Effect of cell passage on response to loading	Adult primary or expanded bovine chondrocytes in 4% agarose without preculture	Frequency: 1 Hz Amplitude: 15% Duration: 24 h continuous Max duration: 24 h	RNA: not assessed PG: ↓ p0 cells, ↑ p1 and p2 cells, ↔ p3 and p4 (p = passage #) Collagen: not assessed Biomechanics: not assessed
Kisiday et al. (2004)	Effect of varied intermittent loading regimes	Neonatal primary bovine chondrocytes in 0.2 or 0.4% agarose with self-assembling peptides precultured for 0 or 22 days	Frequency: 1 Hz Amplitude: 2.5% Duration: 30 min on/30 min off, 1 h on/1 h off, or 3, 5, 7 h/day for 3, 5, 11, or 39 days Max duration: 150 h	RNA: not assessed PG: ↑ intermittent loading Collagen: not assessed Biomechanics: ↑ Eeq and Edyn for intermittent loading
Hung et al. (2004)	Summary of data regarding loading regimes, growth factors, and cell seeding density	4- to 6-month-old primary bovine chondrocytes (n = 3–5) in 2% agarose without preculture	Frequency: 1 Hz Amplitude: 10% Duration: 3× 1 h on/1 h off, 5 days/week for 3, 28, or 56 days Max duration: 105 h	RNA: ↑ ACAN at 3 days only PG: not assessed Collagen: not assessed Biomechanics: ↑ H(A) on days 21–28, ↑ Ey on days 28–56, ↑ Edyn on day 56
Hunter et al. (2004)	Static versus dynamic compression in fibrin-based gel biomaterial	2- to 3-week-old previously frozen primary bovine chondrocytes in fibrin gel precultured for 3 days	Frequency: 0.1, 1 Hz Amplitude: 4% Duration: 10 or 20 days continuous Max duration: 480 h	RNA: not assessed PG: ↓ for 0.1 and 1 Hz at days 10 and 20 Collagen: ↓ for 0.1 and 1 Hz at days 10 and 20 Biomechanics: ↓ Edyn for 0.1 and 1 Hz at days 10 and 20
Mouw et al. (2007)	Role of voltage-gated K+ and Ca2+ channels, stretch-dependent ion channels, and ATP-dependent Ca2+ channels in response to loading	2- to 3-week-old primary bovine chondrocytes in 2% agarose precultured for 1 day	Frequency: 1 Hz Amplitude: 3% Duration: 20 h continuous Max duration: 20 h	RNA: not assessed PG: ↑ dynamic load, decreased with blockage voltage-gated Ca++ channels Collagen: not assessed Biomechanics: not assessed
Mauck et al. (2007)	Effect of loading frequency and duration with gene transcription reporter promoter constructs	3- to 6-month-old primary bovine chondrocytes in 2% agarose precultured for 3 days	Frequency: 0.33, 1, and 3 Hz Amplitude: 10% Duration: 1 or 3 h continuous Max duration: 3 h	RNA: ↑ ACAN and ↓ COL2A1 promotor activity PG: not assessed Collagen: not assessed Biomechanics: not assessed
Lima et al. (2007)	Temporal effect of TGF-β and dynamic loading	4- to 6-month-old primary bovine chondrocytes (n = 3–5) in 2% agarose precultured for 0 or 14 days	Frequency: 1 Hz Amplitude: 10% Duration: 3 h/day, 5 days/week for 42 or 56 days Max duration: 105 h	RNA: not assessed PG: ↔ preculture, ↓ loaded from day 0 Collagen: ↔ preculture, ↓ loaded from day 0 Biomechanics: ↑ Ey and Edyn with preculture, ↓ Ey and Edyn when loaded from day 0
Kelly et al. (2008)	Effect of FBS and ITS in mechanical environment	3- to 4-month-old primary bovine chondrocytes (n = 4–8 pooled) in 2% agarose without preculture	Frequency: 1 Hz Amplitude: 10% Duration: 3 h/day for 28 or 42 days Max duration: 126 h	RNA: not assessed PG: ↔ 0% FBS/ITS, ↑ 0.2% FBS/ITS, and 20% FBS groups, Collagen: ↔ any group Biomechanics: ↔ Ey for 0% FBS/ITS or 20% FBS, ↑ Ey for 0.2% FBS/ITS and 2% FBS/ITS groups
Ng et al. (2009)	Effect of removal of TGF-β from system	3- to 4-month-old primary bovine chondrocytes (n = 5) in 2% agarose without preculture	Frequency: 1 Hz Amplitude: 10% Duration: 3× 1 h on/1 h off or 3 or 6 h continuous for 28 days Max duration: 168 h	RNA: not assessed PG: ↔ any group Collagen:↑ type II and type IX collagen on quant IHC Biomechanics: ↑ Eeq for all loading regimes, ↑ Edyn only 3 or 6 h continuous
Villanueva et al. (2009)	Effect of increasing concentrations of RGD in PEG hydrogel	1- to 2-year-old primary bovine chondrocytes (n = 6) in 10% PEG ± RGD precultured for 1 day	Frequency: 0.3 Hz Amplitude: 15% Duration: 48 h continuous Max duration: 48 h	RNA: not assessed relative to control PG: not assessed relative to control Collagen: not assessed relative to control Biomechanics: ↔ with 48 h loading
Nicodemus and Bryant (2010)	Continuous versus intermittent and immediate versus delayed loading regimes	1- to 3–week-old primary bovine chondrocytes (n = 2) in PEG precultured for 1 or 7 days	Frequency: 0.3 Hz Amplitude: 15% Duration: 1 h on/1 h off or continuous for 7 or 15 days Max duration: 180 h	RNA: ↑ ACAN continuous load at day 7, ↔ ACAN and ↑ COL2, MMP1, MMP3, and MMP13 intermittent load at day 7, ↔ COL2, ACAN and ↑ MMP1, MMP3 preculture + intermittent load PG: ↑ continuous load over 7 days, ↔ for intermittent load or preculture followed by continuous or intermittent load Collagen: not assessed Biomechanics: not assessed
Stojkovska et al. (2010)	Validate bioreactor and alginate system, not necessarily tissue engineering	6-month-old expanded bovine chondrocytes in 1.5% alginate microbeads without preculture	Frequency: 0.42 Hz Amplitude: 10% Duration: 1 h on/1 h off for 14 days Max duration: 168 h	RNA: not assessed PG: not assessed Collagen: not assessed Biomechanics: ↔ any group
Bian et al. (2010)	Immediate versus delayed loading and addition of shear	2- to 4-year-old expanded canine chondrocytes in 2% agarose precultured for 0, 14, or 28 days	Frequency: 1 Hz Amplitude: 5% Duration: 3 h/day, 5 days/week for 28 days Max duration: 60 h	RNA: not assessed PG: ↔ any group Collagen: ↔ any group Biomechanics: ↑ Ey continuous load at days 28–56, delayed load at day 56 only. ↑ Edyn for all loading regimes at day 56
Kaupp et al. (2012)	Effect of duration of dynamic loading	Adult primary bovine chondrocytes (n = 10–15) in 2% agarose without preculture	Frequency: 1 Hz Amplitude: 10% Duration: 20, 30, or 60 min continuous Max duration: 1 h	RNA: not assessed PG: ↑ 20 or 30 min load Collagen: ↔ any group Biomechanics: not assessed
Omata et al. (2012)	Cumulative effects of vitamin C and mechanical load	Adult primary bovine chondrocytes in 1% agarose precultured for 1 day	Frequency: 1 Hz Amplitude: 15% Duration: 6 h/day for 22 days Max duration: 132 h	RNA: not assessed PG: not assessed Collagen: ↔ any group Biomechanics: ↑ Etan with increasing AA2P
Kelly et al. (2013)	Role of osmotic loading in conditioning tissues for response to dynamic load	Adult primary canine chondrocytes (n = 3–5 pooled) in 2% agarose precultured for 14 days	Frequency: 1 Hz Amplitude: 10% Duration: 3 h/day, 5 days/week for 42 or 56 days Max duration: 105 h	RNA: not assessed PG: ↔ any group Collagen: ↑ collagen/DNA Biomechanics: ↑ Ey(steady state) and Ey(max incremental) with dynamic compression only with osmotic load
Farnsworth et al. (2013)	Effect of cell maturity (donor age) on the response to dynamic loading	2- to 3-year-old primary bovine or 1–3 week old primary bovine chondrocytes (n = 2–3) in PEG without preculture	Frequency: 0.3 and 1 Hz Amplitude: 5 or 10% Duration: 30 min on/90 min off for 16 h/day for 14 days Max duration: 56 h	RNA: not assessed PG: ↑ adult chondrocytes at 1 Hz/5% at day 14; ↑ juvenile chondrocytes at 0.3 Hz/5% at days 7 and 14 Collagen: adult chondrocytes ↑ type II collagen and pericellular type VI with quant IHC; juvenile chondrocytes ↓ type II and VI Biomechanics: not assessed
Mesallati et al. (2013)	Nutrient flow through microchannels versus solid hydrogels	4-month-old expanded porcine chondrocytes (n = 1) in 2% agarose without preculture	Frequency: Hz Amplitude: 10% Duration: 2 h/day, 5 days/week for 21 days Max duration: 30 h	RNA: not assessed PG: ↑ for solid gels but not channeled gels Collagen: ↑ for solid and channeled gels Biomechanics: not assessed