TABLE 1.
Overview of bioreactors used in tendon tissue engineering which all apply mechanical stimulation.
| Study | Biomaterial + Cells | Bioreactor | Stimulation | Results | |
| Ex vivo | Angelidis et al., 2010 | Decellularized rabbit hind paw Flexor tendon + AT-MSCs, fibroblasts | Ligagen L30–4C (DynaGen systems), clamped | Uniaxial strain, 1.25 N over 5 days. 1 cycle/minute in alternating 1h periods of mechanical loading and rest. | UTS and E comparable with fresh tendons. Cells reoriented parallel to the direction of the strain. |
| Saber et al., 2010 | Decellularized rabbit hind paw Flexor tendon + tenocytes | Ligagen L30–4C (DynaGen systems), clamped | Uniaxial strain, 1.25 N over 5 days. 1 cycle/minute in alternating 1 h periods of mechanical loading and rest. | UTS and E of loaded construct superior to non-loaded controls. | |
| Wang et al., 2013 | Rabbit AT | Clamp grips, in medium | 8 h/day, 0–9%, 0.25 Hz. 6 days | Loss of structure integrity and increased collagen III expression in unloaded tendons. 6% cyclic strain optimal for structure integrity and cellular function. | |
| Lee et al., 2013 | Decellularized porcine anterior tibialis tendon | Vertically, in culture medium | 10% tension, 1 Hz, 90° torsion. 7 days | 20% lower UTS in decellularized grafts vs. normal tissue but doubled UTS after 7 days incubation | |
| Youngstrom et al., 2015 | Decellularized equine SDFT + BM-MSCs | Horizontally clamp gripped, in medium | 0%, 3%, 5% strain, 0.33 Hz, up to 1 h/day, 11 days. | Gene expression, elastic modulus and UTS favorable with 3%. | |
| Burk et al., 2016 | Decellularized equine SDFT + AT-MSCs | Clamp grips, in medium | 2% strain, 1 Hz, short (2 stretches/cycle) and long (3 stretches/cycle) protocol. | Short mechanical stimulation best cell alignment, successful tenogenic differentiation. | |
| 2D loading | Riboh et al., 2008 | Rabbit tenocytes, sheath fibroblasts, BM-MSCs, AT-MSCs | UniFlex culture plate + Flexcell Tension System (Flexcell International) | Continuous strain (8%, 1 Hz). Intermittent strain (1 h on/5 h off, 4% 0.1 Hz). | Cell proliferation, collagen I production and tenocyte morphology increased with intermittent strain. |
| Zhang and Wang, 2013 | Mice tenocytes or TSPCs of AT or patellar tendon | Silicone dishes connected to stretching apparatus | 12 h, 4% or 8% | Tenogenic gene expression increased in TSPCs with 4% mechanical stretching. Tenocyte and non-tenocyte related gene expression increased in TSPCs with 8% mechanical stretching. Tenocytes no strain-dependent response in non-tenocyte related gene expression. | |
| Gaspar et al., 2016 | Human dermal fibroblasts, tenocytes, BM-MSCs + macromolecular crowding | MechanoCulture FX (CellScale Biomaterials Testing), clamp grips | 12 h/day, 10%, 1 Hz | Cell/ECM alignment superior, increased ECM deposition and similar metabolic activity with mechanical loading. | |
| Gaspar et al., 2019 | Human tenocytes, BM-MSCs, neonatal/adult dermal fibroblasts + macromolecular crowding | MechanoCulture FX (CellScale Biomaterials Testing), clamp grips | 12 h/day, 10%, 1 Hz | Tenogenic phenotype maintained by tenocytes. No (trans)differentiation of BM-MSCs or fibroblasts. | |
| 3D loading | Altman et al., 2002 | Collagen type I gel + bovine ligament fibroblasts, human BM-MSCs | Vertically oriented ligament growth between 2 anchors | Translational (10%, 2 mm) and rotational strain (25%, 90°). 0.0167 Hz (1 cycle of stress/relaxation per minute), 21 days. | Ligament markers upregulated, cell alignment/density increased and oriented collagen fibers. |
| Garvin et al., 2003 | Collagen type I gel + avian tenocytes | Tissue Train 3D Culture System (Flexcell International), culture plate with 2 anchors | 1 h/day, 1% elongation, 1 Hz, 11 days | Tenogenic gene expression and linear morphology. Stronger loaded constructs vs. non-exercised controls. | |
| Scott et al., 2011 | Collagen type I gel + mouse multi-potent mesenchymal cell line (C3H10T1/2) | Tissue Train 3D Culture System (Flexcell International), culture plate with 2 anchors | Static vs. cyclic load, 2 h/day, 5%, 0.1 Hz for 1, 2 or 3 weeks. 2 h/day, 0, 2.5, 5, 7.5, or 10%, 0.1 Hz for 2 weeks. 2 h/day, 10%, 0.1 Hz, 10,100, or 1,000 cycles/day, 10s rest | Tenogenic gene expression increased with cyclic loading. Gene expression increased with increasing magnitude, with 10s rest and increased repetitions. | |
| Jones et al., 2013 | Collagen type I gel + human AT tenocytes | Tissue Train 3D Culture System (Flexcell International), culture plate with 2 anchors | 5% cyclic uniaxial strain, 1 Hz, 48 h | Matrix metalloproteinases and tenogenic genes anabolically influenced. | |
| Bosworth et al., 2014 | PCL + human BM-MSCs | BOSE BioDynamic chamber 5110 (TA Instruments), clamp grips | 1 h/day, 5%, 1 Hz (3,600 cycles/day), 225 N, 7 and 21 days | Cell orientation more uniaxial, tendon gene upregulation due to dynamic loading. | |
| Wu et al., 2017 | PCL/PLA scaffold + human tenocytes, AT-MSCs and HUVECs | MechanoCulture T6 Mechanical Stimulation System (CellScale Biomaterials Testing), clamp grips | 2 h/day, 4%, 0.5 Hz, 12 days | Total collagen secretion upregulated, enhanced tenogenic differentiation with dynamic stretching. | |
| Atkinson et al., 2020 | Collagen type I + equine tenocytes | Custom-designed bioreactor with clamps | 20 min/day, 10%, 0.67 Hz, 14 days | Mechanical properties improved, more gel contraction by the tenocytes with loading. | |
| Stretch and perfusion | Barber et al., 2013 | Decellularized equine SDFT + rabbit BM-MSCs | Oscillating stretch-perfusion bioreactor, 6 separate chambers | 3× 15–30–60 min of activity alternated with 15–30–60 min off, 2×/day. 3%, 0.33 Hz, 7 days. Perfusion: 100 μm/s | Collagen production and alignment superior in cyclic load vs. static culture. |
| Hohlrieder et al., 2013 | PLA nanofibers in yarns + human BM-MSCs | BOSE BioDynamic 5200 multi-chamber (TA Instruments), clamp grips | 2 h/day, 10%, 1 Hz, 10 days Perfusion: 20 ml/min | Cytoskeleton realignment in fiber/applied strain direction, BM-MSCs adherence to fibers, tenogenic differentiation when differentiation medium + cyclic tensile strain. | |
| Xu et al., 2015 | Braided silk fibroin + human ACL fibroblasts | Custom-made bioreactor, 10 independent reactor vessels, vertical movement | 45° rotational and 3.5 mm translational deformations, 0.0667 Hz | Exact control of environmental conditions possible, load and stiffness of silk scaffolds matches native ACLs. | |
| Talò et al., 2020 | PLA-PCL/Collagen scaffold + rat TSPCs | Custom-designed, in culture medium, loading plates | Cyclic tensile strain, 3 h/day, 2, 4, and 8 and 0.3, 0.5, and 1.0 Hz, 7 days | No difference in cell viability. Tenogenic gene expression highest with 4%, 0.5 Hz. |
ACL, anterior cruciate ligaments; AT, achilles tendon; AT-MSCs, adipose tissue-derived mesenchymal stem cells; BM-MSCs, bone marrow-derived mesenchymal stem cells; E, elastic modulus; HUVECs, human umbilical vein endothelial cells; PCL, poly-ε-caprolactone; PLA, polylactic acid; SDFT, superficial digital flexor tendon; TSPCs, tendon stem/progenitor cells; UTS, ultimate tensile strength.