Evaluation of a Developed MRI-Guided Focused Ultrasound System in 7 T Small Animal MRI and Proof-of-Concept in a Prostate Cancer Xenograft Model to Improve Radiation Therapy

Extracellular vesicles derived from mesenchymal stem cells ameliorate sulfur mustard-induced lung injury by regulating apoptosis via miR-146a-5p

Sulfur mustard (SM) is an extremely toxic chemical warfare agent. Although SM-induced toxicity has long been studied, due to its complexity, the characterization of the precise molecular pathway it targets has been remaining an ongoing area of research. Extracellular vesicles derived from human umbilical cord mesenchymal stem cells (hucMSC-EVs) are natural substances that participate in intercellular communication by delivering microRNA to target cells. Importantly, the microRNA content in EVs can be modified. MiR-146a-5p delivered by EVs were utilized and hucMSCs were further modified with miR-146a-5p mimics or inhibitors to collect EVs that over-(miR-146a-5p+-EVs) or underexpress (miR-146a-5p--EVs) miR-146a-5p. Transcriptome sequencing was used to identify potential mediators of the effects of miR-146a-5p delivered by hucMSC-EVs. Our results showed that hucMSC-EVs reduced SM-induced lung injury by mitigating apoptosis. These effects were enhanced by miR-146a-5p+-EVs and weakened by miR-146a-5p--EVs. Meanwhile, the relationship between apoptosis enhancing nuclease (AEN) and miR-146a-5p was discovered, a novel target of miR-146a-5p. Our study showed that hucMSC-EVs ameliorating sulfur mustard induced lung injury through miR-146a-5p, and AEN was one of the functional molecules in this process.

MRI compatibility testing of commercial high intensity focused ultrasound transducers

PURPOSE

The study aimed to compare the performance of eight commercially available single-element High Intensity Focused Ultrasound (HIFU) transducers in terms of Magnetic Resonance Imaging (MRI) compatibility.

METHODS

Imaging of an agar-based MRI phantom was performed in a 3 T MRI scanner utilizing T2-Weighted Fast Spin Echo (FSE) and Fast low angle shot (FLASH) sequences, which are typically employed for high resolution anatomical imaging and thermometry, respectively. Reference magnitude and phase images of the phantom were compared with images acquired in the presence of each transducer in terms of the signal to noise ratio (SNR), introduced artifacts, and overall image quality.

RESULTS

The degree of observed artifacts highly differed among the various transducers. The transducer whose backing material included magnetic impurities showed poor performance in the MRI, introducing significant susceptibility artifacts such as geometric distortions and signal void bands. Additionally, it caused the most significant SNR drop. Other transducers were shown to exhibit high level of MRI compatibility as the resulting images closely resembled the reference images with minimal to no apparent artifacts and comparable SNR values.

CONCLUSIONS

The study findings may facilitate researchers to select the most suitable transducer for their research, simultaneously avoiding unnecessary testing. The study further provides useful design considerations for MRI compatible transducers.

Focused Ultrasound and Ultrasound Stimulated Microbubbles in Radiotherapy Enhancement for Cancer Treatment

Radiation therapy (RT) has been the standard of care for treating a multitude of cancer types. However, ionizing radiation has adverse short and long-term side effects which have resulted in treatment complications for decades. Thus, advances in enhancing the effects of RT have been the primary focus of research in radiation oncology. To avoid the usage of high radiation doses, treatment modalities such as high-intensity focused ultrasound can be implemented to reduce the radiation doses required to destroy cancer cells. In the past few years, the use of focused ultrasound (FUS) has demonstrated immense success in a number of applications as it capitalizes on spatial specificity. It allows ultrasound energy to be delivered to a targeted focal area without harming the surrounding tissue. FUS combined with RT has specifically demonstrated experimental evidence in its application resulting in enhanced cell death and tumor cure. Ultrasound-stimulated microbubbles have recently proved to be a novel way of enhancing RT as a radioenhancing agent on its own, or as a delivery vector for radiosensitizing agents such as oxygen. In this mini-review article, we discuss the bio-effects of FUS and RT in various preclinical models and highlight the applicability of this combined therapy in clinical settings.