Early shifts in gene expression during chondroinduction of human dermal fibroblasts

Treatment options for damaged articular cartilage are limited because of that tissue's poor capacity for repair. Possible approaches to this problem are to stimulate cartilage matrix production in situ or to engineer replacement tissue. Both of these approaches would benefit from a detailed understanding of the molecular mechanisms of chondroblast differentiation. In previous studies, we described a novel in vitro model of postnatal chondroblast differentiation. That model of induced chondrogenesis was used to test the hypothesis that cellular interactions with demineralized bone powder (DBP) would induce specific, early shifts in gene expression, prior to the expression of cartilage matrix genes. Differentially expressed genes were identified by representational difference analysis of human dermal fibroblasts cultured for 3 days with DBP in three-dimensional collagen sponges. Genes that were upregulated by DBP comprised several functional classes, including cytoskeletal elements, protein synthesis and trafficking, and transcriptional regulation. Kinetic analysis of gene expression over 21 days showed that vigilin was transiently upregulated on day 3. In contrast, expression of cartilage signature genes continued to increase. These results are an important step toward complete characterization of the mechanisms by which DBP induces chondroblastic differentiation in postnatal cells.