Objective: To explore whether vasoocclusion in giant cell (temporal) arteritis (GCA) is related to intimal hyperplasia and in situ production of platelet-derived growth factor (PDGF).
Methods: Temporal artery biopsy specimens from patients with GCA were analyzed for the presence of intimal hyperplasia. Expression of PDGF-A and PDGF-B was assessed by immunohistochemistry and digitized image analysis.
Results: PDGF-A and PDGF-B were widely expressed in inflamed arteries. CD68+ macrophages, smooth muscle cells, and multinucleated giant cells produced PDGF, whereas hyperplastic intimal tissue did not. Arteries with marked luminal narrowing and those with no or minimal luminal narrowing differed in the extent and distribution of PDGF expression. Concentric intimal hyperplasia was associated with the accumulation of PDGF-A- and PDGF-B-producing CD68+ macrophages at the media-intima junction. PDGF+,CD68+ macrophages in close proximity to the internal elastic lamina frequently coproduced matrix metalloproteinase 2. Intimal hyperplasia of the temporal artery correlated with ischemic complications of GCA, such as ocular involvement, jaw claudication, and aortic arch syndrome.
Conclusion: Production of PDGF has a role in arterial occlusion in GCA. The excessive fibroproliferative response leading to luminal narrowing can be distinguished from the stenosing process in atherosclerosis and postangioplasty restenosis, suggesting that there are different response patterns to arterial injury. In GCA, macrophages at the media-intima border are the dominant source of PDGF. Since vasoocclusion is associated with a number of serious complications in GCA, inhibition of intimal proliferation should be a major goal of treatment.