Osteogenic Responses in Fibroblasts Activated by Elastin Degradation Products and Transforming Growth Factor-@b1

Am J Pathol 171(1):8 (2007) PMID 17591959 PMCID 1941602

Our objective was to establish the role of fibroblasts in medial vascular calcification, a pathological process known to be associated with elastin degradation and remodeling. Rat dermal fibroblasts were treated in vitro with elastin degradation products and transforming growth factor (TGF)-@b1, factors usually present in deteriorated matrix environments. Cellular changes were monitored at the gene and protein level by reverse transcriptase-polymerase chain reaction, enzyme-linked immunosorbent assay, immunofluorescence, and von Kossa staining for calcium deposits. By 21 days, multicellular calcified nodules were formed in the presence of elastin degradation products and TGF-@b1 separately and to a significantly greater extent when used together. Before mineralization, cells expressed @a-smooth muscle actin and large amounts of collagen type I and matrix metalloproteinase-2, characteristic features of myofibroblasts, key elements in tissue remodeling and repair. Stimulated cells expressed increased levels of core-binding factor @a1, osteocalcin, alkaline phosphatase, and osteoprotegerin, representative bone-regulating proteins. For most proteins analyzed, TGF-@b1 synergistically amplified responses of fibroblasts to elastin degradation products. In conclusion, elastin degradation products and TGF-@b1 promote myofibroblastic and osteogenic differentiation in fibroblasts. These results support the idea that elastin-related calcification involves dynamic remodeling events and suggest the possibility of a defective tissue repair process.

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