Influence of Retinoic Acid and TGF-β on Dermal Fibroblast Proliferation and Collagen Production in Monolayer Cultures and Dermal Equivalents

The effects of transforming growth factor-β1 (TGF-β1) and all-trans retinoic acid (RA) on human dermal fibroblast proliferation and collagen production were investigated in ‘attached’ and ‘detached’ dermal equivalent (DEs) systems compared with fibroblasts grown in monolayers. The combined effects of TGF-β1 with epidermal growth factor (EGF) on fibroblast proliferation and collagen production were also studied. Fibroblast proliferation was stimulated 0.7-fold by TGF-β1 in attached DEs and 0.3-fold in detached DEs compared with untreated control DEs. RA stimulated fibroblast proliferation 1.1-fold in attached DEs and 0.6-fold in detached DEs. Neither TGF-β1 nor RA had a significant effect on fibroblast proliferation in monolayer cultures. In the presence of EGF, the action of TGF-β1 on fibroblast proliferation was slightly suppressed in attached DEs. At 5 ng/ml TGF-β1, collagen production was stimulated 6.1-fold in attached DEs, by 3.5-fold in monolayer at 4 ng/ml and 2.9-fold in detached DEs at 1 ng/ml. RA at 5 × 10−10 M to 5 × 10−6 M stimulated collagen production in all three systems. The stimulation of collagen production by 5 ng/ml TGF-β1 was suppressed by EGF in both attached DEs and monolayer culture. Fibroblasts in attached DEs had elongated, bipolar morphology with a tendency to line up in the same direction. Fibroblasts in detached DEs were randomly distributed and exhibited stellate morphology. These data indicate that the extracellular matrix strongly influences the actions of growth factors and of RA on dermal fibroblasts. When stimulated with TGF-β1 collagen production in attached DEs was higher than that by fibroblasts in monolayer culture and detached DEs. The attached and detached DEs offer a model which resembles the in vivo situation more closely than monolayer culture with respect to collagen production and fibroblast proliferation and morphology.