Acute myocardial infarction (AMI) is a common clinical cardiovascular emergency, which is defined as severe myocardial ischemia or necrosis induced by blockage of a coronary artery and termination of blood supply [1]. Percutaneous coronary intervention (PCI) is the primary therapy for AMI, restoring coronary perfusion and saving the patient's life effectively [2], [3]. However, reperfusion can induce worsened myocardial damage, known as myocardial reperfusion/injury (MIRI) [4], [5]. Programmed cell death is one of the primary contributors to MIRI. Traditionally, its mechanisms were thought to be confined to apoptosis and necrosis. However, recent studies have revealed the emerging roles of novel regulated cell death in MIRI, such as ferroptosis, necroptosis, and pyroptosis [6].

Ferroptosis is a novel programmed cell death, which is dependent on excessive iron accumulation and lethal reactive oxygen species (ROS) production [7]. The main morphological changes of ferroptosis are characterized by a decrease in the number of mitochondria, increased membrane density, and reduced numbers of cristae [8]. As research has progressed, the role of ferroptosis in MIRI has attached more and more attention [9], [10]. Iron accumulation during MIRI increases ROS, causing lipid peroxidation and ferroptosis. Ferroptosis-targeted therapies effectively reduce pathological damage in MIRI models [11], [12]. However, ferroptosis is a complex pathological process, and its exact mechanisms and downstream genes remain unclear.

Our study identified CD44 as the hub gene of MIRI-induced ferroptosis via bioinformatic analysis. CD44 is a multi-structured and multi-functional adhesion molecule that is widely distributed in various cell types. CD44 is the product of a single gene localized on chromosome 17p13.3 in human, and chromosome 11 in mouse, and is encoded by an approximately 1.5–1.6 kb mRNA [13]. The gene comprises at least 20 exons, and the extensive heterogeneity of its extracellular domain is generated by alternative splicing of 10 variable exons [14], [15]. In addition to cell surface expression, CD44 exists in soluble forms within lymph and serum [16], and can also associate with extracellular matrix components [17]. Production of soluble CD44 occurs through two distinct mechanisms: alternative splicing generating variant transcripts [18], and proteolytic release of the extracellular domain by matrix metalloproteinases [19]. CD44 is expressed in various tissues, such as muscle, adipose tissue, the liver, lung, and the central nervous system [20]. Due to its crucial role in pathological activities in cancer cells, CD44 has long been investigated as a cancer molecule [21]. A growing number of studies have demonstrated the role of CD44 in cardiovascular disease [22], [23]. CD44 negatively regulates autophagy and induces ageing in the vascular endothelium [24]. In addition, CD44 mRNA expression was markedly increased in myocardial ischemia tissue. Conversely, CD44 − deficient mice exhibited compromised enhanced and prolonged inflammation followed by reduced myofibroblast infiltration in the infarcted heart [25]. Despite these clues indicating an association between CD44 and MIRI, there is no definitive evidence that CD44 is directly involved. A previous study revealed that CD44 expression enhances the stability of solute carrier family 7 A member 11 subunit (SLC7A11) by promoting the interaction between SLC7A11 and Ovarian tumor domain, ubiquitin aldehyde binding 1 (OTUB1) to repress ferroptosis [26].However, CD44 can also mediate iron endocytosis and further promote ferroptosis in cancer cells [27], [28]. Thus, the roles and regulatory mechanisms of CD44 in ferroptosis and MIRI remain largely unexplored.

In this study, we found that reperfusion induced the progression of ferroptosis. CD44 expression was significantly increased during the reperfusion phase but not remains unchanged during the ischemia phase. We also demonstrated that CD44 attenuates MIRI-induced injury and ferroptosis in cardiomyocytes by regulating the stability of SLC7A11, at least to some extent. These findings uncover the role of CD44 in ferroptosis and suggest it as a potential target for the treatment of MIRI.