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Abstract: FR-OR48

Cyclosporine-Induced Endothelial Injury and Complement Activation Is Caused by Impaired Complement Factor H Binding to the Glycocalyx

Session Information

Category: Transplantation

  • 1901 Transplantation: Basic


  • Teoh, Chia Wei, The Hospital for Sick CHildren, Toronto, Ontario, Canada
  • Ortiz, Carolina, The Hospital for Sick CHildren, Toronto, Ontario, Canada
  • Riedl Khursigara, Magdalena, The Hospital for Sick CHildren, Toronto, Ontario, Canada
  • Bruno, Valentina, The Hospital for Sick CHildren, Toronto, Ontario, Canada
  • Robinson, Lisa, The Hospital for Sick CHildren, Toronto, Ontario, Canada
  • Licht, Christoph, The Hospital for Sick CHildren, Toronto, Ontario, Canada

Calcineurin inhibitors are associated with nephrotoxicity, endothelial cell (EC) dysfunction and thrombotic microangiopathy. Evolving evidence suggests a central role for complement dysregulation in the pathogenesis of CNI-induced thrombotic microangiopathy. However, the exact mechanism of calcineurin-induced complement-mediated injury remains unknown.


In an in-vitro model utilising Blood Outgrowth EC (BOEC) from healthy donors, we evaluated the effects of cyclosporine (CsA) on EC injury, complement activation (C3c, C9) and regulation (CD46, CD55, CD59 and complement factor H [CFH]) on EC surfaces, and on the EC glycocalyx, utilising flow cytometry, Western blot, and immunofluorescence imaging. Functional activity of CFH was assessed via CFH co-factor assay. Co-immunoprecipitation of Angiopoietin-2 (Angpt-2), Angiopoietin-1 (Angpt-1) and Tie2 was assessed by Western blot.


CsA resulted in a dose and time dependent enhancement of EC complement deposition and EC death. CsA (10 µg/ml for 24 h) led to upregulation of CD46, CD55 and CD59 on EC surface. CsA led to Angpt-2 mediated breakdown of the EC glycocalyx, which was mitigated by Angpt-1. This EC glycocalyx breakdown led to decrease in CFH surface binding and surface cofactor activity.


Our findings confirm a role for complement in CsA-induced EC injury, and suggest Angpt-2 mediated glycocalyx abolishment, induced by CsA, as a mechanism leading to complement alternative pathway dysregulation via decreased CFH surface binding. Insights into this mechanism may provide a potential therapeutic target that might lead to improved patient outcomes which is subject to further studies. It might also apply to other thrombotic microangiopathies, in which a role for complement has so far not been recognized.