High-Frequency Pacing of Atrial Trabeculae from Sinus Rhythm Patients Induces Atrial Fibrillation-Like Alterations in Gene Expression

Background: Atrial fibrillation (AF) is a common chronic disease and can occur as perioperative complication in cardiac surgery. Mechanisms of pathophysiology are still poorly understood. After establishing long-term organotypic culture of human right-atrial trabeculae, our goal is to establish an in vitro model allowing to investigate human atrial fibrillation. Therefore, we asked if conditions of atrial fibrillation can be mimicked via high-frequency pacing (HF-pacing, mean frequency: 5–6 Hz) in trabeculae of sinus rhythm patient samples in our long-term culture approach.

Method: Right-atrial trabeculae (pectinate muscles) obtained from sinus rhythm (SR) patients undergoing open-heart surgery were brought into organotypic long-term culture with an adaptation period of 2 days of 1 Hz pacing. After 2 days, stimulation frequency was either kept at 1 Hz to simulate SR (control group) or set to 5 to 6 Hz to simulate AF (HF pacing group) for the following 10 days of culture. Afterward, tissues were snap-frozen and stored at −80°C for RT-qPCR gene expression analysis of genes described to be altered in atrial fibrillation.

Results: In our experiments (n = 7), all cultured trabeculae responded to electrical stimulation and were constantly beating over the experimental time period of 12 days. Gene expression analysis revealed CACNA1c (L-type Ca²⁺ channel pore-forming subunit, −23%, p = 0.014), ATP2A2 (SERCA, −37%, p = 0.015) and KCNJ2 (Kir2.1 inwardly rectifying K+ channel, −27%, p = 0.025) were significantly downregulated after 10 days of HF pacing (n = 7/7) as also described for postoperative atrial fibrillation. In contrast, KCNJ2 was significantly upregulated in regular pacing (1 Hz for 12 days) compared with fresh tissue in one of our previously published studies. GJA1 (connexin 43, +3%, p = 0.8) did not change significantly.

Conclusion: High-frequency pacing induced changes in expression of the investigated genes that are also described in atrial fibrillation. Therefore, we plan to adapt arrhythmic high-frequency pacing to come closer to the situation in vivo, use RNA sequencing to more comprehensively analyze gene expression, and investigate effects on ion currents and action potentials via patch-clamp and sharp-electrodes measurements.

Publication History

Article published online:
28 January 2023