PLATELET-DERIVED GROWTH-FACTOR PRODUCTION BY CELLS FROM DACRON GRAFTSIMPLANTED IN A CANINE MODEL

Purpose: Previous studies of grafts implanted in dogs documented a tim e-dependent increase in platelet-derived growth factor (PDGF) producti on that correlated with inner-capsule thickness. The purpose of this s tudy was to identify the cells in vascular grafts that produce PDGF. M ethods: Dacron thoracoabdominal grafts were seeded with autologous end othelial cells (ECs), implanted in 11 beagles, and removed after 4 or 20 weeks. ECs and smooth muscle cells (SMCs) were cultured from grafts and adjacent aorta, and PDGF in the conditioned media was measured by radioreceptor assay. The PDGP A-chain mRNA level in freshly harvested cells was assessed using reverse transcriptase, followed by polymeras e chain reaction, and expressed as a ratio of glyceraldehyde-3-phospha te dehydrogenase signal. Localization of PDGF A-chain and B-chain prot ein was also examined with immunohistochemical analysis. Results: Graf t and aortic ECs hi primary culture did not produce significantly diff erent amounts of PDGF in 72 hours, averaging 368 +/- 160 and 340 +/- 8 1 pg/mu g DNA, respectively. Graft SMCs in primary culture produced si gnificantly more PDGF than aortic SMCs (584 +/- 43 and 113 +/- 94 pg/m u g DNA, respectively; P < 0.01). Graft SMC PDGF secretion remained gr eater than aortic SMC PDGF secretion through at least six cell passage s. PDGF A-chain mRNA levels were not significantly different for aorti c or graft ECs. The PDGF A-chain mRNA level was significantly higher f or graft SMCs than aortic SMCs (2.44 +/- 0.67 and 1.45 +/- 0.57 pg/mu g, respectively; P < 0.03). Immunocytochemical analysis detected PDGF A-chain and B-chain protein in the ECs from both native aorta and graf t as well as the subendothelial SMCs in the graft, but not in the SMCs of the native aorta. Conclusions: These results suggest that graft SM Cs are functionally altered, producing more PDGF than aortic SMCs. PDG F produced by graft SMCs may contribute to the development of intimal hyperplasia.