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Title: Time-dependent aggrecan gene expression of articular chondrocytes in response to hyperosmotic loading. Author: Palmer GD, Chao Ph PH, Raia F, Mauck RL, Valhmu WB, Hung CT. Journal: Osteoarthritis Cartilage; 2001 Nov; 9(8):761-70. PubMed ID: 11795996. Abstract: OBJECTIVE: To investigate the effects of increasing extracellular osmolality on aggrecan gene expression and cell size in cultured chondrocytes. DESIGN: Aggrecan promoter activity and mRNA levels were measured in bovine monolayer chondrocytes subjected to hyperosmotic loading for different time periods, using transient transfection assays or RT-PCR. Cell size changes were also determined using an epifluorescence microscopy system. RESULTS: Hyperosmotic loading for 24 h suppressed aggrecan promoter activity and mRNA levels approximately two-fold. However no suppression of promoter activity was observed when exon 1 was deleted from the human aggrecan promoter construct. Osmotic regulation of aggrecan gene expression was time-dependent and found to correlate with cell shrinking and swelling. No suppression in promoter activity was observed when the hyperosmotic stimulus was applied in a cyclic manner, or when serum was present in the culture medium. CONCLUSION: Hyperosmotic loading regulates aggrecan gene expression and cell size in isolated chondrocytes. Osmotic regulation of gene expression is also affected by the time-varying nature of loading and the presence of serum.[Abstract] [Full Text] [Related] [New Search]