Long‐term intermittent shear deformation improves the quality of cartilaginous tissue formed in vitro

Abstract

The formation of cartilaginous tissue in vitro is a promising alternative to repair damaged articular cartilage. However, recent attempts to tissue-engineer articular cartilage that has similar properties to the native tissue have proven to be difficult. The in vitroformed cartilaginous tissue typically has a similar proteoglycan content to native cartilage, but has a reduced collagen content and only a fraction of the mechanical properties. In this study, we investigated whether the intermittent application of cyclic shearing forces during tissue formation would improve the tissue quality. Chondrocyte cultures were stimulated a t a 2'%1 shear strain amplitude at a frequency of 1 Hz for 400 cycles every 2nd day. At one week, both collagen and proteoglycan synthesis increased (23 f 6% and 20 f 6'%1, respectively) over the unstimulated, static controls. At four weeks, an increased amount of tissue formed . Tissues that formed in the presence of shearing forces also displayed a 3-fold increase in compressive load-bearing capacity (stirnulatrri: 16 f 5, unstitnuluted: 5 f I kPa max. equilibrium stress) and a 6-fold increase in stiffness (stirnuluted 112 f 36, unstirnulutc'cl: 20 f 6 kPa max. equilibrium modulus) compared to the static controls. These results demonstrate that intermittent application of dynamic shearing forces over a four-week period improves the quality of cartilaginous tissue formed in vitro. Interestingly, low amplitudes of shear stimulation for short periods of time (6 min of stimulation applied every 2nd day) produced these changes.

Multi-axial mechanical stimulation of tissue engineered cartilage: Review

“…Based on the premise that mechanical factors play an important role in the development and maintenance of healthy cartilage in vivo (Kiviranta et al, 1988;Beaupre et al, 2000;Grodzinsky et al, 2000), numerous investigators have shown that both dynamic compressive (Buschmann et al, 1995;Lee and Bader, 1997;Lee et al, 1998;Lee et al, 2000;Waldman et al, 2004) and shear (Waldman et al, 2003a) loading of chondrocytes in 3D culture stimulate the synthesis of cartilaginous ECM macromolecules. When the stimulus is applied intermittently over a long duration (i.e.…”

“…When the stimulus is applied intermittently over a long duration (i.e. several weeks) the cells accumulate greater amounts of ECM which also results in the improved mechanical performance of the in vitro-formed tissue (Mauck et al, 2000;Mauck et al, 2003;Chowdhury et al, 2003;Waldman et al, 2003a;Waldman et al, 2003b;Waldman et al, 2004). Although the application of these relatively simple loading conditions has resulted in beneficial effects, articular cartilage in vivo is subjected to complex loading consisting of a combination of both compressive and shearing forces under normal physiological conditions (Mankin et al, 1994).…”

Aged bovine chondrocytes display a diminished capacity to produce a collagen-rich, mechanically functional cartilage extracellular matrix

“…Among the techniques under development for cartilage regeneration, certain tissue engineering strategies combine primary chondrocytes with various scaffolds to grow tissue equivalents. The effects of specific physical parameters [19,24,28,39] and growth factors [5,12,40] have been widely studied using these systems in order to produce a tissue construct which, once implanted at the site of the cartilage lesion, should lead to a well-integrated and functional hyaline-like replacement tissue. Characterization of human [2,13], equine [21], bovine [1,7,11,35], rabbit [34] and mouse [25] cultured articular cartilage explants revealed that intrinsic metabolism of chondrocytes and their response to external factors vary with animal age.…”

A Comparison of Self-Assembly and Hydrogel Encapsulation as a Means to Engineer Functional Cartilaginous Grafts Using Culture Expanded Chondrocytes

“…It has been well documented that achieving native levels of collagen accumulation is more challenging than reaching native levels of proteoglycan accumulation in tissue-engineered cartilage. [44][45][46][47] Indeed, rapid GAG synthesis has been hypothesized to be an impediment to collagen synthesis in chondrocyte seeded agarose hydrogels, with recent studies demonstrating that inducing enzymatic GAG loss during the early phase of culture can increase the ultimate collagen concentration and tensile properties of the engineered tissue. 48 The local environment within SA constructs would appear to suppress sGAG synthesis while maintaining collagen synthesis at levels approaching that found in the agarose hydrogels.…”