Engineering of cartilage tissue constructs in a 3-dimensional perfusion bioreactor culture system under controlled oxygen tension

The most relevant results generated in this thesis can be summarized as follow:
· Adult human articular chondrocytes (AHAC) from elderly individuals expanded in culture
medium supplemented with the growth factors TGFβ-1, FGF-2 and PDGF and subsequently
cultured in 3-d pellets had an enhanced chondrogenic capacity when exposed to more
physiological (i.e. 5%) oxygen levels.
· In correlation with the enhanced tissue forming capacity of AHAC from elderly donors under
low oxygen tension, the mRNA expression levels of selective matrix degrading enzymes
were reduced as compared to conventional in vitro oxygen culture condition.
· We developed an integrated bioreactor system, which streamlines within a single device the
phases of perfusion cell seeding and prolonged perfusion culture of cell seeded scaffolds in
vitro.
· The culturing of uniformly seeded adult human articular chondrocytes under direct perfusion,
where cells are continuously exposed to a normoxic range of oxygen levels, can maintain a
uniform distribution of viable cells throughout thick porous scaffolds as compared to
statically cultured constructs.
· The culturing of constructs uniformly seeded with adult human articular chondrocytes under
a more physiological range of oxygen resulted in a higher chondrogenic differentiation as
compared to culture under normoxic levels. Anyhow, this effect was less pronounced as
compared to statically cultured cell constructs or micromass cell pellets, possibly due to the
flow induced shear forces.
· Reduced perfusion flow rates applied to chondrocytes on porous scaffolds significantly
induced more cartilaginous tissue in the presents of low vs. high oxygen levels. However the
effects of low oxygen were not as marked as in pellet culture.