Sex differences in cardiac recovery and ventricular gene expression in a rat model of donation after circulatory death

Background Heart donation after circulatory death (DCD) is a promising strategy to increase graft supply. However, in contrast to conventional heart transplantation, in which organs are retrieved from heart-beating donors, DCD hearts are subjected to damaging conditions before and during warm ischemia in the donor, leading to ischemia-reperfusion injury (IRI). Although sex differences have been identified in other contexts of cardiac IRI, such as myocardial infarction, they remain underexplored in DCD. Therefore, we aimed to investigate whether sex differences induce changes in the expression of genes in response to cardiac DCD conditions, including IRI, which may contribute to sexual dimorphism in graft quality. Methods Male, female, and ovariectomized (OVX) Wistar rats underwent simulated DCD with no or 22 minutes of warm in situ ischemia, followed by oxygenated reperfusion under left-ventricular loading. Functional recovery was assessed and left-ventricular tissue was analyzed by bulk RNA-sequencing. Results Recovery of left ventricular function was decreased by warm ischemia, but significantly better in females than in males, with OVX resembling the males. Reperfusion induced inflammatory and hypoxia-responsive gene programs in all groups. Expression of 110 genes correlated with recovery, many of which were more abundant in females compared to males, consistent with a role in improved post-ischemic function. Among these genes, Igfbp3, Fam78b, and Galnt10 were enriched in females compared to males and OVX, supporting a role for female sex hormones. Conclusions Compared to male hearts, cardiac recovery is significantly higher in female hearts after exposure to DCD conditions and is accompanied by an increased expression of genes related to core homeostatic programs that correlate with recovery of ventricular function. Significantly higher expression of genes related to energy metabolism, including fatty acid metabolism and inflammatory pathways, was revealed in males compared to females and is associated with decreased recovery. This study identifies potential new therapeutic targets for optimizing cardiac DCD graft quality, and highlights the importance of underlying sex differences, eg. in inflammatory pathways and metabolic adaptations, that should be taken into consideration for the implementation of sex-specific precision therapies.