Articular Chondroprogenitors as tools for cartilage tissue engineering

The use of stem/progenitor cells to form good quality cartilage matrix has been targeted as a therapeutic goal for cartilage repair treatment. We have characterised a progenitor cell population that resides in the surface layer of neonatal bovine articular cartilage [1]. Here, we assess the progenitor cell's chondrogenic potential. Cloned chondroprogenitors exhibited exponential growth for the first 20 population doublings (PD), then slower linear growth with evidence of replicative senescence at later passages. Mean telomere lengths of exponentially growing chondroprogenitors were significantly longer than dedifferentiated chondrocytes that had undergone a similar number of PD (P<0.05). Chondroprogenitors also had 2.6-fold greater telomerase activity and maintained sox9 and Notch-1 mRNA expression whereas dedifferentiated chondrocytes demonstrated little or no detectable expression. Induced differentiation to cartilage in 3D pellet cultures, demonstrated sox9, Notch-1, aggrecan and PCNA expression.Maintenenace of telomerase activity, Notch-1 and sox9 gene expression distinguish clonal chondroprogenitor cells from dedifferentiated chondrocytes. When placed in chondrogenic medium chondroprogenitors appear to engage in co-ordinated growth and differentiation in stark contrast to dedifferentiated chondrocytes. UK DBERF