Short wave ultraviolet laser energy in porcine coronary arteries: Medial cell death and neointimal formation

Background and Objective: Smooth muscle cell migration and proliferation from arterial media into the neointima are major factors in the restenosis process following coronary angioplasty. Because short wave ultraviolet (UV) radiation is cytotoxic for rat carotid artery smooth muscle cells, the aims of this study were to determine the effects of short wave UV irradiation on normal pig coronary arteries and to evaluate the efficacy of UV laser energy for reducing neointimal hyperplasia (NI). Study Design/Materials and Methods: In 13 pigs fed a normal diet, 37 coronary arteries were studied. UV laser light (275 nm) was applied in escalating doses from 0-16353 mJ/cm² via fiber-optic through a 20 mm PTCA balloon catheter. The pigs were euthanized at 21 days and histologic analysis performed. Arterial media was rendered acellular (ACM) in 20 of 33 irradiated coronary arteries (61%). The minimum UV energy density inducing ACM was 1348 mJ/cm². The fraction of acellular media to internal elastic lamina length (ACM/IEL) was 0.79 ± 0.29. Results: No statistically significant difference was found between NI thickness at normal media sites (NM) vs. ACM sites (0.17 ± 0.14 mm vs. 0.16 ± 0.17 mm). No correlation was found between UV dose and NI formation (r = 0.307, P = 0.08). Conclusion: Short wave UV irradiation induces ACM in normal porcine coronary arteries. Induction of acellular media is not associated with a reduction of NI formation in this porcine coronary model.