Sonoporation-Based Gene Therapy for Cardiovascular Disease and Cancer: A Novel Platform for Targeted Drug Delivery

A recent article published in the Proceedings of the National Academy of Sciences (PNAS) pointed out that combining ultrasound energy with ultrasound microbubbles to create pores in cells may become a new tool in the fight against cardiovascular diseases and cancer. Researchers from the University of Pittsburgh refer to this gene therapy approach as sonoporation therapy. VCBeat (WeChat ID: vcbeat) has compiled and translated the relevant information.

Briefly put, we refer to the biophysical mechanism by which ultrasound triggers cell membrane rupture as sonoporation. Research on sonoporation primarily focuses on the physical stimulation induced by ultrasound microbubble oscillations and the resulting changes in cell membrane permeability. Studies have demonstrated that there is a shear stress threshold caused by microbubble oscillation, approximately 1 kilopascal; when the pressure exceeds this value, the permeability of endothelial cell membranes increases. This shear stress threshold exhibits an inverse square-root relationship with both the number of oscillation cycles and the ultrasound frequency ranging from 0.5 Hz to 2 MHz. Furthermore, measurements using real-time three-dimensional confocal microscopy have shown that the sonoporation process directly leads to the immediate formation of membrane pores through the apical and basal layers of the cell membrane along their outer surfaces (with a sealing time of less than 2 minutes). Sonoporation also holds significant potential for cell fusion, enabling the fusion of two adjacent cells within 30–60 minutes.

Dr. Brandon Helfield, a researcher at UPMC’s Center for Ultrasound Molecular Imaging and Therapeutics, stated, “Researchers harness ultrasonic energy and microbubbles to selectively create small pores in cells for drug delivery. By using focused ultrasound beams, we can accurately deliver drugs to diseased sites while preserving healthy tissue. We are dedicated to studying the role of biophysics in this process, aiming to refine this diagnostic method through technological advancements.”

In current gene therapy approaches, researchers typically use viruses to deliver genes into cells for expression, a method that can cause severe side effects, such as immune system reactions. To address this issue, researchers have developed intravascular microbubbles carrying genes, which can release their genetic cargo in a targeted manner via focused ultrasound energy.

Researchers at the University of Pittsburgh have developed an ultra-high-speed imaging camera capable of capturing 25 million frames per second, the only one of its kind in North America. With the aid of this camera, researchers can better investigate the biophysical phenomena associated with sonoporation. They have determined the minimum local shear stress required for targeted therapy after bubbles traverse the cell membrane.

Xu Caichen, an Associate Professor of Medicine at the University of Pittsburgh, collaborated with the university’s Heart, Lung, and Blood Institute to develop a camera system. He stated, “Using ultra-high-speed imaging cameras, we observed that microbubbles can vibrate millions of times per second, allowing us to determine that shear stress induced by microbubbles is a key factor in sonoporation. This insight also facilitates the intelligent design of treatment protocols and the preparation of microbubbles, enabling the prediction of expected outcomes following cell permeabilization. Furthermore, it provides a starting point for investigating how cells respond to this type of therapy.”

Researchers believe that these findings will help them understand the principles of sonoporation, assist experts in setting appropriate parameters—including ultrasound amplitude levels and microbubble design—to achieve ultimate clinical applications.

“Understanding the biophysical mechanisms of sonoporation is crucial for us, as it can help translate this approach into an effective tool for gene or drug delivery. Building on the research published in PNAS, we continue to investigate how sonoporation affects cellular function post-treatment and develop strategies to maximize its therapeutic efficacy,” said Professor Flordeliza Villanueva, Director of the Center for Ultrasound Molecular Imaging and Therapeutics.