Articular cartilage is prone to degradation as a result of aging, disease and injury, which can lead to the onset of osteoarthritis (OA). The avascular nature of the tissue renders its endogenous repair capacity notoriously poor and its aneural nature means that disease progression is often quite advanced before symptoms present. OA places a huge burden on the NHS and UK economy and there is an urgent need for alternative therapies, which offer patients a one-off durable treatment and mitigate or significantly delay the need for joint replacement. Tissue engineering offers a possible solution, wherein replacement cartilage is developed in vitro from undifferentiated cells.
Human embryonic stem cells (hESC) are readily available, pluripotent and demonstrate huge expansion capacity in vitro; all of which makes them an appealing cell source for tissue engineered constructs. This work sought to enhance the maturity of hESC-derived chondroprogenitors with the application of a range of 2D and 3D culture techniques and regimes of mechanical stimulation.
hESC were subjected to a directed differentiation protocol (DDP), described previously (Oldershaw et al. 2010), with the addition of an immobilised Wnt base and an acellular fibrin hydrogel to enable migration into a 3D environment. Addition of the hydrogel to differentiating monolayer hESC, always resulted in improved chondrogenic gene expression and the application of a Wnt platform significantly increased the migration of cells into the gel.
Hydrostatic pressure was applied to fibrin-encapsulated progenitors and was found to increase chondrogenic matrix deposition and gene expression. In addition, the application of low level compressive forces to monolayer progenitors resulted in increased chondrogenic gene expression at low cell seeding densities.
Taken together, results suggest that both a 3D environment and the application of mechanical stimuli can significantly enhance the chondrogenic potential of hESC-derived chondroprogenitors. We believe that the work described here holds great potential for the development of a cell-based therapy for cartilage damage and degeneration.