Elastogenesis in inverted vein graft. An electron microscopic study

The process of elastogenesis was followed by electron microscopy, from 6 hours to 360 days, in autogenous inverted vein grafts of dogs. The initial processes of the new wall formation over the grafts were similar to those observed in the organization of thrombis. At 40 days, the new wall consisted of three layers comparable to the intima, media and adventitia. New elastic fibers, as demonstrated by orcein stain, were formed around fibroblasts in teh granulation tissue after 20 days and in the adventitia after 40 days. In the media, elastogenesis was associated with smooth muscle cells and began after 40 days. A basement membrane-like material accumulated around smooth muscle cells and, to a much smaller degree, fibroblasts. Elastin aggregates appeared within the basement membrane-like material. These aggregates were stainable with orcein and selectivity digestable with elastase at pH 8.8. The earliest recognizable forms of elastic fibers were the small, spherical to elongated bodies not surrounded by microfibrils. Fused and enlarging elastin aggregates were surrounded by microfibrils.