Abstract
Osteoarthritis (OA) is the most common form of joint disease leading to disability and dependence. In severe cases of knee OA, the joint is deemed irrecoverable and total knee replacements are indicated. Tissue engineering is a possible solution for this pathology and previous work from our laboratory has demonstrated that it is possible to isolate and expand chondroprogenitor cells in vitro from healthy knee-joint articular cartilage. Work presented here describes the detection and isolation of chondroprogenitor cells derived from osteoarthritic cartilage following total knee replacement in patients with severe OA, suggesting a pool of viable cells from this degenerate region which has been previously deemed non-recoverable.
Human articular cartilage was excised from tibial plateaux (TP's) obtained from total knee replacements following the diagnoses of severe OA. Cells were isolated by a sequential pronase and collagenase digestion and subject to a fibronectin adhesion assay. Cells were expanded in monolayer in supplemented growth medium. Clonal 3D pellet cultures were established in chondrogenic and osteogenic differentiation media. Adipogenic cultures were also established in monolayer cultures. Histological procedures, immunohistochemistry and molecular biology were undertaken in order to determine the extent of differentiation. In addition, osteochondral plugs were excised from the TP's and wax embedded for further histological and immunohistochemical analysis.
Clonal cell lines obtained from osteoarthritic knee-joint cartilage using the fibronectin adhesion assay were isolated and successfully cultured to a maximum of 60 population doublings whilst still demonstrating a chondrogenic capacity. Three-D pellet cultures after 21 days of chondrogenic induction produced smooth and iridescent pellets which stained positively for toluidine blue and safranin O. Positive labelling for collagen type II and aggrecan were also observed. Following osteogenic induction; evidence of mineralisation was indicated by the von Kossa stain. Adipogenic induction revealed a positive result. Osteochondral plugs demonstrated sporadic positive labelling in the surface region for putative stem cell marker Stro-1.
Chondroprogenitor cells isolated from osteoarthritic display a strong chondrogenic phenotype, and have the ability to be induced into different lineages. These findings suggest the presence of a pool of viable chondroprogenitors from osteoarthritic tissue which was otherwise deemed irrecoverable.
