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 functional, warm in-situ 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 102 animals were included in this study. Male, female, and ovariectomized (OVX) Wistar rats underwent simulated DCD with no or 22 min of functional, warm in-situ ischemia, followed by oxygenated reperfusion with left-ventricular loading. Functional recovery was assessed and left-ventricular tissue was used for RNA-sequencing.Results Recovery of left ventricular function was decreased by functional, warm in-situ ischemia, but significantly better in females than in males, with OVX resembling the males. Reperfusion induced inflammatory, stress-response and metabolic-related pathways in all groups. Expression of 110 genes correlated with cardiac recovery, many of which were more abundant in females compared to males, consistent with a role in improved post-ischemic ventricular function. Among these genes, Igfbp3, Fam78b, and Galnt10 were differentially expressed in females compared to males and OVX, suggesting an influence of 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 quality control programs that positively correlate with 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 suggests potential new therapeutic targets for optimizing cardiac DCD graft quality, and highlights the importance of underlying sex and sex-hormone differences, e.g. in inflammatory pathways and metabolic adaptations, that should be taken into consideration for the implementation of sex-specific precision therapies.Heart transplantation is currently the only treatment for patients with advanced heart failure to improve quality of life and survival. Nonetheless, the number of newly listed patients needing a transplant continues to increase and outpaces the supply of suitable donors.One promising approach to increase donor availability is using hearts from donors after circulatory death (DCD). In conventional heart donation, the donor is declared brain-dead, but machines keep the heart beating and oxygenated until removal. In DCD, the heart stops beating in the donor and it briefly receives less oxygen and nutrients, which can cause donor organ injury. Although outcomes with DCD hearts are excellent and transplant rates increase, further optimization of the protocol could allow more hearts to be used.In other situations where hearts temporarily lack oxygen, such as myocardial infarction, studies suggest that adult female hearts recover better than male hearts. In the DCD setting, little is known, but it has recently been shown in preclinical studies that female hearts are more tolerant to these conditions.In this study, we simulated the DCD protocol in a rat model. Afterwards, we identified 673 genes that were differentially expressed between male and female hearts. Many of these genes correlated with cardiac recovery; those more abundant in females were linked to better recovery, whereas those more abundant in males were linked to worse recovery. Taken together, our findings may help to identify treatments for the optimization of cardiac graft quality and improve heart transplantation options for both women and men.