We investigated how aging effects human chondrocyte yield, proliferation, post-expansion chondrogenic capacity, and response to specific growth factors supplemented during expansion.
Fifty-two samples of human articular cartilage were harvested from cadavers 20 to 91 years old and grouped into age decades. Cell yields were normalised to tissue wet weight. Cell proliferation rates were calculated during expansion in medium without (CTR) or with TGF beta 1, FGF-2 and PDGF-BB (TFP). Chondrogenic capacity of CTR- and TFP-expanded cells was assessed by cultivation as 3D pellets in a defined serum-free medium, followed by histological, immunohistochemical, biochemical and real-time RT-PCR analyses.
Cell yields were similar in donors up to 40 years of age and significantly lower (1.8-fold) in older donors. Cell proliferation rates in CTR medium significantly decreased after 30 years of age and remained similar in older donors. In the presence of TFP, proliferation rates were higher (up to 3.7-fold) in all age groups and decreased only slightly with age. The glycosaminoglycan (GAG) content of pellets obtained from CTR-expanded cells was not correlated with age. Pellets from TFP-expanded cells reproducibly contained more GAG (up to 3.2-fold) than those from CTR-expanded cells only if donors were younger than 40. Safranin O staining intensity and collagen type II expression and accumulation were consistent with GAG contents.
Medium supplementation with the growth factor combination TFP during chondrocyte expansion supports higher proliferation rates at any age and higher post-expansion chondrogenic capacity in donors up to 40 years. These findings may be relevant for chondrocyte-based cartilage repair procedures.