Quantitative Proteomic Analysis of Rat Condylar Chondrocytes during Postnatal Development

Objective: To investigate differentially expressed proteins in rat mandibular condylar cartilage (MCC) chondrocytes caused by initial mastication for short postnatal periods. Methods: Four groups of protein samples were extracted from primary cultured rat MCC chondrocytes, harvested from eigthy postnatal SD rats aged 1,7,14 and 28 days, with twenty in each group. Total proteins were labelled with isobaric tags for relative and absolute quantification (iTRAQ) reagents. Two-dimensional nano-high-performance liquid chromatography (HPLC) and matrix-assisted laser desorption ionization-time-of-flight/ time-of-flight (MALDI-TOF/TOF) mass spectrometry analysis with iTRAQ technique were performed. All data were analysed by MASCOT software with the SWISSPROT protein database. Furthermore, bioinformatics and statistical analysis were performed to classify their cellular components, biological processes, molecular functions and metabolic pathway by the PANTHER database. Results: In total, 137 differentially expressed proteins were identified during MCC growth and were assigned to one or more cellular components. According to the PANTHER analysis, a significant proportion of proteins are involved in the metabolic process, cellular process, biological regulation, developmental process and response to stimulus. The most extensive molecular function was 43% in catalytic activity. In addition, it was found that proteins in MCC chondrocytes change markedly on the growth stage of eruption of the teeth. Conclusion: This study provides an integrated perspective of molecular mechanisms regulating early normal postnatal growth and development of rat MCC at the protein level. Keywords: Bioinformatics analysis, Chondrocyte, iTRAQ, Mandibular condylar cartilage, Proteomic analysis