Investigation on mechanism of myocardial cell injury induced by exosomes from hypothermic anoxia-reoxygenated cardiac fibroblasts

Background Exosomes derived from hypothermic anoxia-reoxygenated rat cardiac fibroblasts (RCF) cause damage to H9c2 myocardial cells, but the regulatory mechanism remains unclear.

Objective To examine the impact of exosomes secreted by hypothermic anoxia-reoxygenated RCF on the injury of H9c2 myocardial cells and its effect on the gap junction protein Connexin 43 (Cx43).

Methods Exosomes were isolated and identified from RCF culture medium under normoxic conditions (cultured in 95% air + 5% CO₂ at 37℃ for 5 hours) and hypothermic anoxia-reoxygenation conditions (cultured in 95% N₂ + 5% CO₂ at 4℃ for 1 hour followed by 95% air + 5% CO₂ at 37℃ for 4 hours). The exosomes from the respective conditions were labeled as N-exo and I/R-exo. Using a random number table, in vitro cultured rat H9c2 myocardial cells were divided into three groups: C group (cultured under standard conditions for 12 hours), N group (co-incubated with N-exo for 12 hours), and I/R group (co-incubated with I/R-exo for 12 hours). After co-incubation, myocardial cells were harvested, and flow cytometry was used to determine the apoptosis rate of H9c2 myocardial cells. Western blotting was utilized to detect the expression of Cx43 and phosphorylated Cx43 (p-Cx43), and scratch assay was conducted to assess the migration capability of myocardial cells.

Results No significant difference in apoptosis rates was observed between the C and N groups (P>0.05), but both were lower than the I/R group (P<0.05). Compared to the C group, the I/R group exhibited decreased expression of Cx43 and p-Cx43 and reduced cell migration ability (P<0.05), whereas the N group showed increased expression of Cx43 and p-Cx43 and enhanced cell migration ability (P<0.05).

Conclusion Exosomes released by hypothermic anoxia-reoxygenated cardiac fibroblasts can elevate the apoptosis rate of myocardial cells, diminish myocardial cell migration capability, and downregulate the expression of Cx43 and p-Cx43 in myocardial cells.