Circulating Endothelial Cells as a Prognostic Marker in Thrombotic Microangiopathy

Background: Circulating endothelial cells (CECs) are a reliable marker of disease activity in a variety of vascular disorders. Damage to microvascular endothelial cells is a hallmark of thrombotic microangiopathy (TMA). The aim of this study is to identify and count CECs during the course of TMA and evaluate whether cell numbers may serve as a prognostic marker in patients undergoing plasma exchange. Methods: Fifteen patients (8 women, 7 men) aged 31 to 66 years with TMA of different causes were studied before and after 4 sessions of plasma exchange. CECs were isolated by using anti-CD146-driven immunomagnetic isolation and counted after staining with Ulex Europaeus lectin-1. Results: Numbers of CECs were markedly elevated in all patients before treatment (64 to 672 CEC/mL; mean, 320 ± 205 CEC/mL) compared with healthy controls (0 to 16 CEC/mL; mean, 6.4 ± 4.2 CEC/mL; P < 0.001). Patients with a favorable outcome had significantly greater initial CEC levels (mean, 426 ± 175 CEC/mL; P < 0.001), and cell numbers decreased significantly after 4 treatments of plasma exchange (mean, 101 ± 53 CEC/mL; P = 0.001). Patients with disease unresponsive to plasma exchange presented with lower initial CEC levels (mean, 108 ± 36 CEC/mL), and numbers failed to decrease after plasma exchange (mean, 114 ± 57 CEC/mL; P = 0.827). Conclusion: Markedly elevated numbers of CECs reflect severe and widespread endothelial damage in patients with TMA. Cell numbers at presentation and their degree of decrease after 4 sessions of plasma exchange could provide important prognostic clues.