Synthesis and assembly of fibrillin by fibroblasts and smooth muscle cells.

The expression and assembly of the microfibrillar glycoprotein fibrillin has been investigated in cultures of nuchal ligament fibroblasts, skin fibroblasts and vascular smooth muscle cells. The level of fibrillin expression varied with the cell type and growth conditions. Higher levels of synthesis were recorded in quiescent post-confluent cells than in actively dividing subconfluent cultures. Nuchal ligament fibroblasts consistently synthesized the highest levels of fibrillin. Growth of cells in the presence of ascorbate resulted in an increased proportion of newly synthesized fibrillin retained within cell layers. Fibrillin was immunoprecipitated from medium and cell layer extracts in the form of monomers and high-M(r) disulphide-bonded aggregates. Rotary shadowing electron microscopy of cell layer extracts and collagen gels provided direct evidence for the assembly of extensive intact microfibrils by smooth muscle cells and fibroblast cultures. Gel filtration chromatography of medium and cell layer extracts, in combination with immunoprecipitation of column fractions, provided a means of analysing the size distribution and assembly of newly synthesized fibrillin. This cell culture approach provides an opportunity to evaluate normal and aberrant synthesis and assembly of fibrillin in a wide range of cell types.