Protection of the differentiated Chondrocyte Phenotype during Monolayer expansion Cultures Using heat inactivated Fetal Calf Serum

Abstract

Introduction: autologous chondrocyte implantation (aci) is one successful treatment for osteoarthritic defects (1-4). However, chondrocytes undergo a conversion to a fibroblastic phenotype during their expansion in vitro. This process can lead to degradation and failure of the repaired tissue, and is termed “dedifferentiation” (5-9). we hypothesized that culturing chondrocytes in Heat inactivated Fetal calf serum (HiFcs) would lead to a slowing of the process of dedifferentiation. This study specifically examines how HiFcs affects gene expression and proliferation of bovine chondrocytes in short-term monolayer culture. Methods: we cultured primary chondrocytes extracted from bovine joints in Fcs or HiFcs for four passages (p0-p4). we then analysed the relative gene expression of aggrecan (agg), type ii-alpha1 collagen (col2a1), cartilage oligomeric matrix protein (comp), sry (sex determining region y)-box 9 (sox9), type i-alpha2 collagen (col1a2) and bcl-2-associated X protein (bax) using quantitative real-time polymerase chain reaction (qpcr). results: our results show significant down-regulation of col1a2 and up-regulations of agg, col2a1, comp and sox9 in HiFcs cultures when compared to those in Fcs cultures. discussion: Agg, col2a1 and comp are associated with the synthesis of cartilage matrix molecules while sox9 is associated with chondrogenesis (5-11). Col1a2 is associated with the presence of fibrous tissue which lacks the desired mechanical properties (5-9). Therefore, our results suggest that HiFcs can partially protect the chondrocytic phenotype from dedifferentiating to fibroblastic after one passage. To improve upon our results, more experiments are required to reveal the mechanism underlying the protection of chondrocytes offered by the heat inactivation of Fcs.