The resident cells of the meniscus synthesize a fibrocartilaginous extracellular matrix in vivo composed predominantly of type I collagen fibers. To increase our understanding of matrix biosynthesis by meniscus cells in vitro, we examined matrix protein mRNA levels in cultured meniscus cells isolated from skeletally mature @entity235 . The mRNA levels of five matrix protein genes ( @entity55124 , @entity22609 , aggrecan, @entity69393 , and fibronectin) were measured in meniscus cells by Northern blotting and compared with those of patellar tendon fibroblasts and femoral articular cartilage chondrocytes. In freshly isolated cells (Day 0 cells), @entity55124 , @entity22609 , and aggrecan mRNA levels were low or undetectable in both meniscus cells and tendon fibroblasts. In intact meniscus tissue, @entity55124 mRNA levels were also low or undetectable. @entity22609 and aggrecan mRNA transcripts were readily observed, however, in Day 0 articular chondrocytes. The levels of expression of @entity69393 and fibronectin mRNA transcripts in Day 0 meniscus cells were intermediate between higher articular chondrocyte levels and lower tendon fibroblast levels. After 1 week in monolayer culture (Day 7 cells), meniscus cells expressed readily detectable levels of @entity55124 mRNA transcripts, similar to that observed for cultured tendon fibroblasts. @entity55124 mRNA transcripts were either not detected or detected at very low levels in monolayer cultures of articular chondrocytes. @entity22609 and aggrecan mRNA transcripts were readily detected in cultured articular chondrocytes but not in meniscus cells or in tendon fibroblasts. All three types of cells continued to express @entity69393 and fibronectin mRNA transcripts after 1 week in culture. These results demonstrate that the patterns of expression of @entity55124 and @entity22609 mRNA transcripts by meniscus cells are similar to those of tendon fibroblasts and dissimilar to those of articular chondrocytes both in freshly isolated cells and in monolayer cultured cells. This mRNA expression pattern supports the idea that monolayer culture of meniscus cells results in the expression of a predominantly fibroblastic phenotype.

Matrix protein mRNA levels in XXXX meniscus cells in vitro.

@entity235 :: ('9615', 'Species') :: ['dogs'] @entity22609 :: ('403826(Tax:9615)', 'Gene') :: ['COL2A1'] @entity69393 :: ('403668(Tax:9615)', 'Gene') :: ['COL6A1'] @entity55124 :: ('403651(Tax:9615)', 'Gene') :: ['COL1A1']
@entity235 :: (9615,Species) :: ['canine']
