Age-related expression patterns of Bag-1 and Bcl-2 in growth plate and articular chondrocytes.

Age-related expression patterns of Bag-1 and Bcl-2 in growth plate and articular chondrocytes.

Kinkel Mary D; Yagi Rieko; McBurney Denise; Nugent Ashleigh; Horton Walter E Jr

The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology

2004

2004-08

Aging cartilage displays increased chondrocyte apoptosis and decreased responsiveness of chondrocytes to growth factors. The molecular mechanisms responsible for these changes have not been identified. Bag-1 is a Bcl-2-binding protein that promotes cell survival, interacts with a diverse group of cellular proteins, and may integrate multiple pathways involved in controlling cell survival, growth, and phenotype. Bcl-2 is important for maintaining chondrocyte phenotype and delaying terminal differentiation and apoptosis of chondrocytes. Comparatively little is known about the role of Bag-1 in cartilage. Here we show that both growth plate and articular chondrocytes in the mouse express the Bag-1 protein. In the growth plate, Bag-1 expression is prominent in the late proliferative and prehypertrophic chondrocytes, displaying a pattern similar to what has been reported for Bcl-2. Further, the expression of both Bcl-2 and Bag-1 declines with age in the articular cartilage. Growth assays demonstrate that knocking down Bag-1 expression causes a decrease in growth rate. These results suggest that Bag-1 is involved in the regulation of chondrocyte phenotype and cartilage aging.

Aging/*metabolism; Animals; Articular/cytology/*metabolism; Carrier Proteins/genetics/*metabolism; Cartilage; Cell Division/physiology; Cells; Chondrocytes/cytology/*metabolism; Cultured; DNA-Binding Proteins; Gene Expression Regulation; Growth Plate/*metabolism; Inbred C57BL; Mice; Proto-Oncogene Proteins c-bcl-2/*metabolism; Tissue Distribution; Transcription Factors

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