Culturing human fibroblasts in a three-dimensional collagen matrix leads to a reduction of collagen I by more than 90%, both on the level of mRNA steady-state as well as protein. In order to differentiate changes in de novo transcription and posttranscriptional control, nuclear run on assays and pulse/chase experiments determining mRNA stability were used. Our results indicate that de novo transcription of the COL1A1 gene and proα1(I)collagen mRNA half-life are both decreased by 50% in fibroblasts grown in three-dimensional collagen lattices as compared to monolayer cultures. The extracellular matrix therefore elicits signals which are transduced from the cell surface to the inside of fibroblasts resulting in a specific reprogramming of transcriptional as well as posttranscriptional processes.
