Transcriptional comparisons between equine articular repair tissue, neonatal cartilage, cultured chondrocytes and mesenchymal stromal cells

Human and equine cell transplant strategies for cartilage lesions usually result in scar tissue that is similar to what is produced naturally during the repair process. In this study, culture-expanded de-differentiated chondrocytes and primary bone marrow stromal cells at a pre-transplantation time-point were compared along with neonatal cartilage to repair tissue. Transcriptional profiling using a 9413-probeset equine-specific cDNA microarray and targeted real-time quantitative polymerase chain reaction validation were used to characterize relationships between these cell types and repair tissue both broadly and for individual cartilage biomarkers. The greatest divergence in expression was detected for transcripts encoding matrix proteins that typically define the differentiation status of normal articular cartilage and fibrocartilage repair tissue. Expression patterns and gene ontology analyses indicated that while the repair cells were more chondrogenic than bone marrow stromal cells and de-differentiated cultured chondrocytes, steady-state levels of transcripts encoding cartilage biomarkers were substantially lower than the amounts found in neonatal articular cartilage. By characterizing gene expression differences amongst these tissues, we present important targets to monitor when developing improvements to cartilage engineering therapies.