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Prolonged Preservation Of Partial Heart Transplant Grafts Using Vitrification
Morgan A. Hill, MD1, Kristi L. Helke1, Alicia M. Braxton1, David Fitzgerald1, Deani McVadon1, Carolyn Taylor1, Kristin Whitworth2, Randall S. Prather2, Kelvin G. M. Brockbank3, Joseph Turek4, Taufiek Konrad Rajab1.
1Medical University of South Carolina, Charleston, SC, USA, 2National Swine Resource and Research Center, Columbia, MO, USA, 3Tissue Testing Technologies LLC, Charleston, SC, USA, 4Duke University, Durham, NC, USA.

Objective(s): Partial heart transplants (PHTs) deliver growing heart valve implants for congenital cardiac surgery. However, PHT preservation using hypothermic solutions mandates a close temporal relationship between donation and implantation. In contrast, vitrified embryos can be preserved for decades before implantation. We hypothesized that PHTs could be similarly preserved using vitrification.
Methods: PHT pulmonary valve grafts from GFP-transgenic donor piglets were infiltrated with cryoprotectants to final concentrations of 3.10M DMSO, 3.10M formamide, and 2.21M 1-propanediol ≤ 0.6M disaccharides in Euro-Collins solution at 4C. Magnetic nanoparticles were added in the final infiltration step. The cryoprotected PHTs were vitrified and preserved at -135C for greater than 1 month. Fresh PHT controls were preserved at 4C for less than 4 hours. Following preservation, nanowarmed vitrified (N=2) and fresh (N=2) PHTs were orthotopically transplanted into wild type piglets (Fig. 1a). Recipient piglets were survived on full immunosuppression for approximately two months until their weight doubled.
Results: Echocardiography showed stable valve gradients in the fresh PHTs and one vitrified PHT (Fig. 1b). The second vitrified PHT developed severe stenosis due to mycoplasma endocarditis. There was no significant difference in cellular viability by alamarBlue and the vitrified PHTs remained GFP-positive on autopsy, indicating survival of donor cells despite preservation for over one month and in-vivo growth for two months.
Conclusions: Vitrification allows long-term preservation of growing PHT grafts.


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