Purpose

The sequestration of multiple hematopoietic cell lineages and inappropriate coagulation cascade activation is associated with poor outcomes in multiple liver xenotransplant models. Here we evaluate a cassette of additional genetic modifications primarily targeting coagulation and complement pathway regulation on these phenomena.

Methods

Livers from GalTKO.hCD46 (2GE: n=6) and GalTKO.hCD46.hEPCR.hCD55.hTFPI.hCD47 (6GE: n=7) pigs were perfused ex vivo with heparinized whole human blood. Complete blood counts were measured at timed intervals by hemocytometer. Perfusions were terminated at “failure”, characterized by lack of vascular flow (high resistance) or uncorrectable metabolic derangements.

Results

Mean survival in the 2GE group was 319 minutes (SEM 89 min, range 115-600 min), and 483 min (SEM 73 min, range 283-795 min; p=0.1779) in the 6GE group. White blood cell counts were better preserved in the 6GE group (p=0.0395 at 30 min), as was hematocrit (p=0.0034 at 5 min, and p=0.0262 at 30 min) (Figure 1A,B). Marked thrombocytopenia (to 54% of initial) in the first fifteen minutes of perfusion tended to be improved (70%) in the 6GE group (p nadir=0.1363) (Figure 1C). AST and ALT elaboration were not different between the two groups. Coagulation activation, as prothrombin fragment F1+2, increased in both groups, with the steeper rise in the 2GE group reaching significance at 2 hours (p=0.0234) (Figure 1D).

Conclusions

The hEPCR.hCD55.hTFPI.hCD47 cassette favorably modulates hematopoietic cell sequestration and coagulation cascade activation by GalTKO.hCD46 transgenic pigs without prolonging survival or attenuating hepatocellular injury (AST, ALT elaboration). We conclude that further genetic modifications and/or pharmacologic interventions will be necessary to better address the anemia, thrombocytopenia, inappropriate coagulation, and hepatocellular injury that currently prevents clinical liver xenotransplantation.

CITATION INFORMATION: Cimeno A, Burdorf L, Parsell D, Phelps C, Ayares D, Azimzadeh A, Pierson III R, Barth R, LaMattina J. Addition of hEPCR.hCD55.hTFPI.hCD47 Modulates Multi-Lineage Cell Sequestration and Coagulation Activation by GalTKO.hCD46 Transgenic Pig Livers Perfused Ex Vivo with Human Blood. Am J Transplant. 2017;17 (suppl 3).

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