Targeted immunotherapy with sphingosine-1-phosphate improves myocardial contractility and mitochondrial function in a novel murine ex vivo perfusion and transplantation model.

Abstract

Objective: To develop a reproducible ex vivo heart perfusion (EVHP) and murine heart transplantation model and to evaluate the efficacy of hypothermic, acellular ex vivo perfusion with sphingosine-1-phosphate (S1P) as a strategy to mitigate transplantation-associated ischemia-reperfusion injury (IRI).

Methods: Donor hearts from wild-type (WT) mice were stratified by preservation technique. Group 1 (n=4) hearts served as non-transplanted controls. Group 2 (n=10) hearts underwent 90 minutes of cold static preservation (CSP) following cardioplegic arrest in donor mice. Group 3-5 hearts (n=10/group) underwent EVHP with hypothermic, acellular solution (Krebs-Henseleit buffer, KH) alone (Group 3), KH+S1P (FTY-720)(Group 4), and KH+S1P+S1P receptor subtype 2 antagonist (JTE-013)(Group 5). Group 2-5 hearts were then transplanted into recipient mice with 120 minutes of reperfusion. Hearts evaluated for function by echocardiography, histopathologic injury by neutrophil infiltration, and mitochondrial bioenergetics by Seahorse Bioanalysis.

Results: Functional assessment demonstrated comparable post-transplantation allograft function as defined by fractional shortening (FS) and fractional area change (FAC) for CSP and KH-only EVHP mice (p>0.05). EVHP with S1P improved post-transplantation function by both FS and FAC (p<0.05). Co-administration of S1P with S1PR2 antagonist abrogated the functional improvement of S1P alone (p<0.05). EVHP with S1P also reduced injury severity scoring based on neutrophil infiltration (p<0.05). Lastly, EVHP with S1P transplanted hearts demonstrated improved mitochondrial function compared to hearts transplanted after standard CSP (p<0.05).

Conclusions: Donor hearts perfused with hypothermic, acellular perfusate and S1P demonstrated improved post-transplantation heart function, decreased histologic injury, and increased mitochondrial performance compared to cold-static CSP, representing a potential strategy to mitigate IRI within heart transplantation.