Effects of IGF-IR iRNA on the growth of condylar cartilage by electric pulse delivery

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The purpose of this study was to examine the role of endogenous insulin-like growth factor I (IGF-I) in promoting survival of cells of the mandibular condyle in culture. Mandibular condyles dissected from 12-day-old rats were cultured for 1, 3 or 5 days in medium containing antisense oligodeoxynucleotide (AS-ODN) or sense-ODN (S-ODN) for IGF-I. Quantitative real-time RT-PCR analysis showed that the levels of IGF-I and IGF binding protein (IGFBP)3 mRNAs in tissues treated with AS-ODN were significantly decreased compared with control and S-ODN group. On days 3 and 5, the number of denatured cells was observed in the undifferentiated mesenchymal cell layer. These cells were TUNEL positive and confirmed to be apoptotic by electron microscopic observation. Immunoblotting revealed that expression of cleaved caspase3 was increased with AS-ODN. These results indicate that the cells in the undifferentiated mesenchymal cell layer of mandibular condyle require IGF-I for survival.