THE NEOINTIMA FORMED IN ENDOTHELIAL-CELL SODDED EPTFE VASCULAR GRAFTSRESULTS FROM BOTH CELLULAR-HYPERPLASIA AND EXTRACELLULAR-HYPERTROPHY

Endothelial cell transplantation onto polymeric vascular grafts result s in the formation of a neointima, The formation of this neointima is often suggested to result from a chronic cellular hyperplasia where th e terms intimal hyperplasia and intimal thickening are used interchang eably. While the formation of a midgraft neointima in sodded grafts in volves a level of cell proliferation, the synthesis and deposition of extracellular matrix proteins is also a ubiquitous observation in thes e grafts. To assess the composition of midgraft neointima in sodded gr afts, a morphometric method was developed to provide a differential qu antitation of the cellular-hyperplastic and extracellular-hypertrophic elements of intimal thickening. The formed neointima on microvessel e ndothelial cell sodded and control (noncell-treated) ePTFE vascular gr afts was quantified after 3, 12, and 52 wk of graft implantation in a canine carotid artery model. Midgraft sections of grafts were evaluate d for both intimal thickness (IT) and cell density per unit volume and quantified using a PC-based image analysis program, Sodded grafts exp lanted at 3 wk exhibited an average neointimal cell density (3 x 10(9) cells/cm(3); IT 30 mu m) equivalent to cell densities observed in nor mal arterial media, After 12 wk the mean cell density approached a hyp erplastic value (3.7 x 10(9) cells/cm(3); IT 76 mu m), while grafts ex planted after 52 wk exhibited a mean cell density (2.8 x 10(9) cells/c m(3); IT 30 mu m) similar to 3-wk values, Control grafts that received no cells exhibited no midgraft cellular coverage, These results indic ate that neointima formation in the midgraft region of sodded grafts o ccurred via mechanisms involving both a cellular hyperplasia and an ex tracellular hypertrophy, Differential responses occur presumably due t o localized differences in cellular proliferation and cellular biosynt hetic activity.