Identification of the chondrocyte lineage using microfibril-associated glycoprotein-2, a novel marker that distinguishes chondrocytes from synovial cells.

Methods for the lineage identification of cell or tissue-engineered therapeutics must provide a high degree of performance to confidently distinguish the intended cell type from other lineages that could be present in the finished product. For many applications, these methods also require rapid, high-throughput capability. In this work, methods for the identification of autologous cultured chondrocytes for implantation were investigated. A histological analysis confirmed that fibrous tissue occasionally present in biopsies procured for autologous chondrocyte implantation production comprised synovium. Chondrocyte and synovial cell cultures were then examined using a full transcriptome microarray analysis, which revealed cartilage link protein and microfibril-associated glycoprotein-2 (MAGP2) as the most differentially expressed transcripts between the culture types. Performance characteristics of gene expression assays formed by the analysis of cartilage link protein with normalization to either standard reference genes or to MAGP2 were evaluated. The results demonstrate that the MAGP2-based assay provided superior performance for the purpose of cell culture identification compared to assays using standard reference genes. The selectivity against synovial and heterogeneous samples provided by the novel assay suggests it as an appropriate lineage identification method for cell cultures derived from cartilage.