Abstract: TH-OR122

Tacrolimus Prevents Von Willebrand Factor Exocytosis from Human Glomerular Endothelial Cells Treated with Anti-HLA Antibodies

Session Information

Category: Transplantation

  • 1701 Transplantation: Basic and Experimental

Authors

  • Beland, Stephanie, University Health Center (CHU) of Quebec, Laval University, Quebec, Quebec, Canada
  • Desy, Olivier, University Health Center (CHU) of Quebec, Laval University, Quebec, Quebec, Canada
  • Vallin, Patrice, University Health Center (CHU) of Quebec, Laval University, Quebec, Quebec, Canada
  • De Serres, Sacha A., University Health Center (CHU) of Quebec, Laval University, Quebec, Quebec, Canada
Background

Mechanistic knowledge about the direct effect of DSA on the endothelium is lacking. Von Willebrand factor (vWF) is a glycoprotein involved in endothelial hemostasis. Previous studies reported that anti-HLA-I antibodies promote vWF exocytosis. It is known that higher CNI levels associates with better outcomes in patients with DSA. We hypothesized that TAC prevents endothelial damage by inhibiting vWF exocytosis from cells exposed to anti-HLA antibodies.

Methods

We measured in vitro the vWF expression of human glomerular endothelial cells treated with anti-HLA-I or II, in the presence and absence of TAC. Cell viability was confirmed in all experiments. vWF was quantified by immunofluorescence and ELISA. Platelet adhesion on the endothelial cells was assessed by immunofluorescence. We next measured the association between vWF and TAC blood levels in 71 samples from 69 kidney recipients.

Results

Anti-HLAs antibodies increased surface expression of vWF as well as vWF levels in cell supernatants (anti-HLA I 36±4, anti-HLA-II 40±5 vs. NS 22±4%, both p<0.05). vWF release in the supernatant following anti-HLA-II stimulation was higher than with anti-HLA-I (3.4±2.5 vs. 5.6±3.2 ng/mL; p=0.03). Treatment with TAC (5, 10 ng/mL) abrogated the percentage of vWF-positive cells after anti-HLA stimulation (for anti-HLA-I, TAC0 vs. TAC5 vs. TAC10 : 32±5 vs. 5±3 vs. 5±3% respectively; for anti-HLA-II, TAC0 vs. TAC5 vs. TAC10 36±7 vs. 7±3 vs. 2±1% respectively; all p<0.01) and led to a decrease in platelet adhesion (all p<0.01). In patients, TAC was a significant negative predictor of vWF blood levels (-768±239 ng/mL per 1ng/mL increase in TAC); this association was robust to adjustment for clinical and histological predictors.

Conclusion

Direct disruption of endothelial hemostasis through vWF exocytosis is a potential mechanism for the higher occurrence of transplant glomerulopathy in patients with DSA. Mechanistic studies are underway to better understand these observations, given that TAC is seldom associated with thrombotic microangiopathy.