554 The potential significance of NeuGc in the structural valve deterioration of bioprosthetic heart valves
Tuesday November 17, 2015 from 15:30 to 16:30
Room 109

Whayoung Lee, United States

Postdoctoral research fellow


Thomas E. Starzl Transplantation Institute


The potential significance of NeuGc in the structural valve deterioration of bioprosthetic heart valves

Whayoung Lee1, Cassandra Long 1, Hidetaka Hara 1, David K. C. Cooper 1, Jagdeece Ramsoondar 2, David Ayares2, Rizwan A. Manji 3,4.

1Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsuburgh, PA, United States; 2Revivicor, Blacksburg, VA, United States; 3Department of Surgery, University of Manitoba, Winnipeg, MB, Canada; 4Cardiac Sciences Program, Winnipeg Regional Health Authority and St Boniface Hospital, Winnipeg, MB, Canada

Purpose: There is mounting evidence that glutaraldehyde (0.2%)-fixed bioprosthetic heart valves (GBHVs) from wild-type (WT) pigs undergo structural valve deterioration (SVD) related to an immune response to pig antigens (e.g., galactose-α1,3-galactose [Gal]). A second antigen, N-glycolylneuraminic acid (NeuGc), that is not present in humans, but is expressed on porcine tissues, may be important in xenograft rejection. The use of valves from genetically-engineered pigs that do not express specific pig antigens (e.g., Gal and/or NeuGc) may prevent or delay SVD. The aims of this present study were to determine expression of Gal and NeuGc on (i) fresh porcine valve/pericardial tissue, (ii) 3 different commercially-available GHBVs, and (iii) glutaraldehyde-fixed valves from WT, GTKO, and GTKO/NeuGcKO pigs, and to determine human antibody binding to these various valves.
Methods: Aortic valves, pulmonary valves, and pericardium from WT, GTKO, and GTKO/NeuGcKO pigs (n=3 of each) were tested (i) fresh and (ii) after fixation with 0.2% glutaraldehyde. Three different commercially-available GBHVs (2 derived from WT porcine aortic valves and 1 derived from bovine pericardium) were also studied. Frozen-sections of GBHVs, fresh, and glutaraldehyde-fixed porcine valves/pericardium were stained for Gal and NeuGc expression. These valves/pericardium were also incubated with pooled human serum and then stained for human antibody (IgM and IgG) binding.
Results: Gal and NeuGc expression was high on all WT pig tissue and GBHVs. There was no difference in the level of Gal or NeuGc expression on different tissues (aortic valve, pulmonary valve, pericardium) nor on different parts of the cusps of the valves. Gal was not detected on GTKO valves, and neither Gal nor NeuGc was detected on GTKO/NeuGcKO valves. Glutaraldehyde-fixation did not attenuate the expression level of Gal or NeuGc. Human IgM and IgG binding was present on GBHVs and WT pig valves/ pericardium after incubation with human serum. However, compared to binding to GBHVs and valves from WT pigs, valves from GTKO pigs and, particularly, GTKO/NeuGcKO pigs, showed less IgM and IgG binding with or without glutaraldehyde-fixation. 
Conclusions: There is expression of Gal and NeuGc on WT porcine valves/pericardium as well as commercially-available GBHVs, and this expression is not reduced after glutaraldehyde-fixation. There is strong human IgM and IgG antibody binding to all GBHVs and WT pig valves that potentially accelerates SVD in vivo. The implantation of valves from GTKO or, particularly, GTKO/NeuGcKO pigs may reduce this antibody response.

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