Chronic transplant dysfunction and transplant arteriosclerosis: new insights into underlying mechanisms

Although effective in the short-term, clinical solid-organ transplantation has not achieved its goals as a long-term treatment for patients with end-stage organ failure. Development of so-called chronic transplant dysfunction (CTD)is now recognised as the predominant cause of allograft loss long-term (after the first post-operative year) following transplantation. CTD has the remarkable histological feature that the luminal areas of intragraft arteries become obliterated, predominantly with vascular smooth muscle cells intermingled with some inflammatory cells. The development of this transplant vasculopathy,referred to as transplant arteriosclerosis (TA), is a multifactorial process and many risk factors have been identified. However, the precise pathogenetic mechanisms leading to TA are largely unknown and, as a result, current prevention and treatment protocols are inadequate. This review discusses the risk factors for TA and current views on the pathogenetic mechanisms leading to this vasculopathy. We argue here that host-derived cells contribute to the development of these vascular lesions, and propose that TA results from a normal vascular repair process that proceeds beyond the needs of functional repair. Guided by the proposed sequence of events, we finally discuss possible directions for future intervention strategies to prevent TA after solid-organ transplantation.