Decreased number of nucleolar organizing regions in collagen lattice cultured fibroblasts

Dermal fibroblasts cultivated in tridimensional matrices (lattices) of coll agen exhibit a very low metabolic activity, and a low protein synthesis in particular. We have previously shown that ribosomal RNA content and half-li fe were decreased in collagen lattice cultured fibroblasts when compared to monolayer cultured fibroblasts. In this study, we seeded fibroblasts in co llagen lattices and investigated the influence of matrix on the number of n ucleolar organizing regions. We found that fibroblasts in fully retracted l attices exhibited a significant decrease of 45 % (P < 0.001) in the number of nucleolar organizing regions when compared to monolayer cultured fibrobl asts. This decrease was correlated to the decrease in ribosomal RNA content . These data suggest that extracellular matrix induces early alterations of synthesis and/or processing of ribosomal RNAs, explaining, at least partly , the resulting low metabolic activity. ((C) Academie des sciences / Elsevi er, Paris.).