Factor Xa and thrombin, but not factor VIIa, elicit specific cellular responses in dermal fibroblasts

Summary.  Coagulation factors (F)VIIa, FXa and thrombin are implicated in cellular responses in vascular, mesenchymal and inflammatory cells. Fibroblasts are the most abundant cells in connective tissue, and damage to blood vessels places coagulation factors in contact with these and other cell types. Objectives: To investigate cellular responses of primary dermal fibroblasts to FVIIa, FXa and thrombin by following changes in expression of candidate proteins: monocyte chemotactic protein-1 (MCP-1), interleukin-8 (IL-8), interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF), and to determine the expression of receptors implicated in signaling by these coagulation factors. Methods: Steady-state mRNA levels were quantified by RNase protection assay, and protein secretion by ELISA. PAR gene expression was assessed by ribonuclease protection assay and conventional and quantitative reverse-transcription–polymerase chain reaction. Results: FVIIa did not induce the candidate genes. In contrast, FXa and thrombin induced MCP-1 mRNA and protein secretion strongly, IL-8 moderately, and IL-6 weakly. Neither FXa nor thrombin induced VEGF mRNA or protein secretion, although FXa induced VEGF protein secretion in lung fibroblasts. Comparison of the presence of candidate receptors in the two fibroblast subtypes demonstrated higher levels of PAR-1 and PAR-3 in lung fibroblasts relative to their dermal counterparts and the additional expression of PAR-2. Conclusions: FXa and thrombin induce expression of MCP-1, IL-8 and IL-6, and distribution and expression of PARs on dermal fibroblasts is reduced relative to their lung counterparts. Tissue origin may influence the cellular response of fibroblasts to coagulation proteases.