Molecular injury and repair assessment of ex vivo perfused heart transplants

• Author / Creator

  Rotich, Silas

• Cardiac transplantation is a life-saving treatment for patients with end-stage heart disease, but it is limited by a shortage of suitable donor hearts. Strategies to expand the donor organ pool include the use of extended donor criteria and hearts donated after circulatory determination of death. The current clinical standard for organ preservation, cold static preservation (CSP), is limited to only 4-6 h, and prolonged periods of preservation have been associated with poor post-transplant outcomes. Additionally, the inability to measure cardiac function in CSP has contributed to excessive organ discard and the overall shortage of hearts for transplantation. Ex vivo heart perfusion (EVHP) represents a promising alternative for organ preservation, repair, and functional assessment. However, previous studies have reported progressive functional decline during EVHP, the underlying mechanisms of which remain poorly understood.
  The overall objective of this thesis was to assess the feasibility of using gene expression to measure cardiac tissue injury and repair during EVHP. A novel literature-based cardiac specific injury and repair gene set was developed. Biopsies were obtained from porcine hearts either in vivo (IV, n=7) or after 12 h of EVHP (n=32) or combined heart and liver perfusion (H+L, n=7). Functional parameters were recorded during perfusion. Histology was assessed for features of cardiac injury. A gene expression profiling platform (NanoString nCounter) was used to measure the changes in cardiac injury and repair gene transcripts. The differential expression of these mRNA transcripts was correlated with cardiac function and histology.
  Exploratory analysis demonstrated distinct clustering of the biopsy sample groups based on gene expression patterns. A total of 44 genes were significantly upregulated and 12 genes were significantly downregulated in EVHP versus IV group. Aggregate upregulated and downregulated gene sets showed higher and lower expression, respectively, in EVHP versus IV, EVHP versus H+L, and H+L versus IV. Except for mild interstitial edema in EVHP biopsies, no significant histologic alterations were identified. Gene set expression correlated with various functional parameters and histologic interstitial edema. Most of the upregulated genes included inflammatory and tissue remodeling genes, whereas downregulated genes predominantly represented structural genes, suggesting that pro-inflammatory and pro-fibrotic genes are the main drivers of cardiac injury during EVHP.
  The work presented in this thesis demonstrates that EVHP induces a molecular injury response that correlates with functional and histologic features of cardiac injury in a porcine model. Molecular assessment appears more sensitive and specific for measuring tissue injury compared with function and histology. This thesis thus presents a novel approach for assessing organ viability and the mechanisms of tissue injury and repair during EVHP. Additionally, this thesis highlights molecular pathways that may be further exploited to develop therapeutics which could improve cardiac function during EVHP, ultimately optimizing this promising technology and expanding the donor organ pool.

• Subjects / Keywords

  • Molecular injury and repair
  • Cardiac transplantation
  • Assessment
  • ex vivo heart perfusion
  • Molecular Pathology
  • Gene expression

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-jctn-2710

• License

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