Ultrasound-Targeted Microbubble Destruction Accelerates Angiogenesis and Ameliorates Left Ventricular Dysfunction after Myocardial Infarction in Mice

Optimal Treatment Parameters for Ultrasound-Stimulated Microbubbles in Upregulating Proliferation and Stemness of Bone Marrow Mesenchymal Stem Cells

OBJECTIVES

Ultrasound-targeted microbubble disruption (UTMD) is a widely used technique to improve the differentiation and proliferation capacity of mesenchymal stem cells (MSCs), but the optimal therapeutic parameters for UTMD are unclear. In this study, we aimed to find the appropriate peak negative pressure (PNP), which is a key parameter for enhancing the stemness properties and proliferation of MSCs.

METHODS

Experiments were performed in UTMD group, ultrasound (US) group under different PNP exposure conditions (0.5, 1.0, and 1.5 MPa), and control group. Apoptosis safety was analyzed by flow cytometry and MSC proliferation was measured at 12, 24, and 36 hours after irradiation by cell counting kit 8. The expression of the stemness genes NANOG, OCT-4, and SOX-2 were determined by enzyme-linked immunosorbent assay (ELISA) or reverse transcription polymerase chain reaction.

RESULTS

The results showed that the 1.5 MPa UTMD-treated group had the highest proliferation capacity of MSCs at 24 hours. ELISA or quantitative reverse transcription polymerase chain reaction results showed that UTMD treatment of the 1.5 MPa group significantly upregulated the expression of the stemness genes NANOG, SOX-2, and OCT-4.

CONCLUSIONS

In conclusion, the appropriate peak PNP value of UTMD was 1.5 MPa, and 1.5 MPa-mediated UTMD group obviously promoted MSCs proliferation and maintained stemness by upregulating the expression of stemness genes.

Enhancement of Tumor Perfusion and Antiangiogenic Therapy in Murine Models of Clear Cell Renal Cell Carcinoma Using Ultrasound-Stimulated Microbubbles

OBJECTIVE

To explore the effect of ultrasound-stimulated microbubble cavitation (USMC) on enhancing antiangiogenic therapy in clear cell renal cell carcinoma.

MATERIALS AND METHODS

We explored the effects of USMC with different mechanical indices (MIs) on tumor perfusion, 36 786-O tumor-bearing nude mice were randomly assigned into four groups: (i) control group, (ii) USMC0.25 group (MI = 0.25), (iii) USMC1.4 group (MI = 1.4) (iv) US1.4 group (MI = 1.4). Tumor perfusion was assessed by contrast-enhanced ultrasound (CEUS) before the USMC treatment and 30 min, 4h and 6h after the USMC treatment, respectively. Then we evaluated vascular normalization(VN) induced by low-MI (0.25) USMC treatment, 12 tumor-bearing nude mice were randomly divided into two groups: (i) control group (ii) USMC0.25 group. USMC treatment was performed, and tumor microvascular imaging and blood perfusion were analyzed by MicroFlow imaging (MFI) and CEUS 30 min after each treatment. In combination therapy, a total of 144 tumor-bearing nude mice were randomly assigned to six groups (n = 24): (i) control group, (ii) USMC1.4 group, (iii) USMC0.25 group, (iv) bevacizumab(BEV) group, (v) USMC1.4 +BEV group, (vi) USMC0.25 +BEV group. BEV was injected on the 6th, 10th, 14th, and 18th d after the tumors were inoculated, while USMC treatment was performed 24 h before and after every BEV administration. We examined the effects of the combination therapy through a series of experiments.

RESULTS

Tumor blood perfusion enhanced by USMC with low MI (0.25)could last for more than 6h, inducing tumor VN and promoting drug delivery. Compared with other groups, USMC0.25+BEV combination therapy had the strongest inhibition on tumor growth, led to the longest survival time of the mice.

CONCLUSION

The optimized USMC is a promising therapeutic approach that can be combined with antiangiogenic therapy to combat tumor progression.

Nanomaterials as Ultrasound Theragnostic Tools for Heart Disease Treatment/Diagnosis

A variety of different nanomaterials (NMs) such as microbubbles (MBs), nanobubbles (NBs), nanodroplets (NDs), and silica hollow meso-structures have been tested as ultrasound contrast agents for the detection of heart diseases. The inner part of these NMs is made gaseous to yield an ultrasound contrast, which arises from the difference in acoustic impedance between the interior and exterior of such a structure. Furthermore, to specifically achieve a contrast in the diseased heart region (DHR), NMs can be designed to target this region in essentially three different ways (i.e., passively when NMs are small enough to diffuse through the holes of the vessels supplying the DHR, actively by being associated with a ligand that recognizes a receptor of the DHR, or magnetically by applying a magnetic field orientated in the direction of the DHR on a NM responding to such stimulus). The localization and resolution of ultrasound imaging can be further improved by applying ultrasounds in the DHR, by increasing the ultrasound frequency, or by using harmonic, sub-harmonic, or super-resolution imaging. Local imaging can be achieved with other non-gaseous NMs of metallic composition (i.e., essentially made of Au) by using photoacoustic imaging, thus widening the range of NMs usable for cardiac applications. These contrast agents may also have a therapeutic efficacy by carrying/activating/releasing a heart disease drug, by triggering ultrasound targeted microbubble destruction or enhanced cavitation in the DHR, for example, resulting in thrombolysis or helping to prevent heart transplant rejection.