Arterial regenerative activity after prosthetic implantation.

Factors modifying arterial regenerative activity were evaluated by replacing adult rabbit aortas with either absorbable polyglycolic acid (PGA) or nonabsorbable Dacron prostheses, 3.5 mm in internal diameter by 24 mm in length, woven to identical specifications including pore size, wall thickness, and elastic modulus, and were followed up for 12 months. At death, 48 PGA and 20 Dacron specimens were studied grossly and by arteriography, light microscopy, scanning and transmission electron microscopy, and by bursting strength determinations. There were no aortic-related deaths or transaortic hemorrhages. Both materials elicited a surrounding inflammatory reaction containing macrophages which transgressed the interstices of only the PGA prostheses. Between two and four weeks, circumferentially oriented smooth-musclelike myofibroblasts proliferated in the PGA inner capsule yielding a neointima 3.2 times thicker than Dacron's. Early ultrastructurally primitive cells progressively differentiated into these smooth-musclelike myofibroblasts. The few myofibroblasts later appearing with Dacron were radially oriented. After one month proliferation stopped in both groups and neointimal thickness became constant. The luminal surface in the PGA group was endothelial-like but was fibrinous in the Dacron group. All specimens withstood saline infusion at three to five times systolic pressure. These studies demonstrate great arterial regenerative potential and suggest hemodynamic and intercellular mitogens controlling it.