Movement-induced orientation: a potential mechanisms of cartilage collagen network morphogenesis

Articular cartilage is a layer of tissue lining the articulating osseous ends in diarthroidal joints. Its primary function is to provide a durable, low friction, load-bearing surface. Cartilage on cartilage, lubricated with synovial fluid, has a coefficient of friction of 0.02–0.005 (Charnley 1959), and regularly provides problem-free performance for a lifetime. Although this may not seem so remarkable, comparison to synthetic bearings is quite revealing. The coefficient of friction for steel on steel lubricated with oil is 0.1 (Jones 1936) and that of dry Teflon on Teflon is 0.04 (Bowden and Tabor 1950). Furthermore, the life of mechanical bearings is often less than 20 years. Articular cartilage is an exceptional material with an optimal design for its function

Novel Electrospun Scaffolds for the Molecular Analysis of Chondrocytes Under Dynamic Compression

Mechanical training of engineered tissue constructs is believed necessary to improve regeneration of cartilaginous grafts. Nevertheless, molecular mechanisms underlying mechanical activation are not clear. This is partly due to unavailability of appropriate scaffolds allowing exposure of cells to dynamic compressive strains (DCS) in vitro while permitting subsequent molecular analyses. We demonstrate that three-dimensional macroporous electrospun poly(ɛ-caprolactone) scaffolds can be fabricated that are suitable for the functional and molecular analysis of dynamically loaded chondrocytes. These scaffolds encourage chondrocytic proliferation promoting expression of collagen type II, aggrecan, and Sox9 while retaining mechanical strength after prolonged dynamic compression. Further, they exhibit superior infiltration of exogenous agents into the cells and permit easy retrieval of cellular components postcompression to allow exploration of molecular mechanisms of DCS. Using these scaffolds, we observed that chondrocytes responded to DCS in a magnitude-dependent manner exhibiting antiinflammatory and proanabolic responses at low physiological magnitudes. Proinflammatory responses and decreased cellular viability were observed at hyperphysiological magnitudes. These scaffolds provide a means of unraveling the mechanotransduction-induced transcriptional and posttranslational activities involved in cartilage regeneration and repair