Expression of fibronectin matrix in cybrids of fibroblasts and epithelial cells

The pericellular fibronectin matrix of human fibroblasts is lost when they are fused with normal or malignant cells, which do not produce fibronectin matrix. In the present study we have investigated whether also the cytoplasmic fraction of fibronectin-negative HeLa or MDCK cells can cause this effect. Enucleated epithelial cells (cytoplasts) were therefore fused with norman human fibroblasts. Fibronectin expression of the resulting cytoplasmic hybrids (cybrids) was studied by the indirect immunofluorescence technique. Three hours after fusion cybrids formed between fibroblasts and enucleated epithelial cells showed fibronectin matrix expression clearly weaker than that seen on the intact fibroblasts. An accumulation of fibronectin matrix was observed in the cybrids, analogously to the intact fibroblasts, and already 12-24 h after fusion the cybrids showed a fibronectin matrix expression similar to that of the fibroblasts. No fibronectin matrix was detected in the epithelial cells or their cytoplast. Our results indicate that cytoplasmic factors from epithelial cells are able to cause an initial suppression in the formation of fibronectin matrix. However, the cytoplasts are not capable of causing a long-term effect on the fibroblasts.