Differences in gene expression between sonoporation in tumor and in muscle

A T-Cell Inspired Sonoporation System Enhances Low-Dose X-Ray-Mediated Pyroptosis and Radioimmunotherapy Efficacy by Restoring Gasdermin-E Expression

Genome editing has the potential to improve the unsatisfactory therapeutic effect of antitumor immunotherapy. However, the cell plasma membrane prevents the entry of almost all free genome-manipulation agents. Therefore, a system can be spatiotemporally controlled and can instantly open the cellular membrane to allow the entry of genome-editing agents into target cells is needed. Here, inspired by the ability of T cells to deliver cytotoxins to cancer cells by perforation, an ultrasound (US)-controlled perforation system (UPS) is established to enhance the delivery of free genome-manipulating agents. The UPS can perforate the tumor cell membrane while maintaining cell viability via a controllable lipid peroxidation reaction. In vitro, transmembrane-incapable plasmids can enter cells and perform genome editing with the assistance of UPS, achieving an efficiency of up to 90%. In vivo, the UPS is biodegradable, nonimmunogenic, and tumor-targeting, enabling the puncturing of tumor cells under US. With the application of UPS-assisted genome editing, gasdermin-E expression in 4T1 tumor-bearing mice is successfully restored, which leads to pyroptosis-mediated antitumor immunotherapy via low-dose X-ray irradiation. This study provides new insights for designing a sonoporation system for genome editing. Moreover, the results demonstrate that restoring gasdermin expression by genome editing significantly improves the efficacy of radioimmunotherapy.

Ultrasonic particles: An approach for targeted gene delivery

Gene therapy has been widely investigated for the treatment of genetic, acquired, and infectious diseases. Pioneering work utilized viral vectors; however, these are suspected of causing serious adverse events, resulting in the termination of several clinical trials. Non-viral vectors, such as lipid nanoparticles, have attracted significant interest, mainly due to their successful use in vaccines in the current COVID-19 pandemic. Although they allow safe delivery, they come with the disadvantage of off-target delivery. The application of ultrasound to ultrasound-sensitive particles allows for a direct, site-specific transfer of genetic materials into the organ/site of interest. This process, termed ultrasound-targeted gene delivery (UTGD), also increases cell membrane permeability and enhances gene uptake. This review focuses on the advances in ultrasound and the development of ultrasonic particles for UTGD across a range of diseases. Furthermore, we discuss the limitations and future perspectives of UTGD.

Sonodelivery in Skeletal Muscle: Current Approaches and Future Potential

There are currently multiple approaches to facilitate gene therapy via intramuscular gene delivery, such as electroporation, viral delivery, or direct DNA injection with or without polymeric carriers. Each of these methods has benefits, but each method also has shortcomings preventing it from being established as the ideal technique. A promising method, ultrasound-mediated gene delivery (or sonodelivery) is inexpensive, widely available, reusable, minimally invasive, and safe. Hurdles to utilizing sonodelivery include choosing from a large variety of conditions, which are often dependent on the equipment and/or research group, and moderate transfection efficiencies when compared to some other gene delivery methods. In this review, we provide a comprehensive look at the breadth of sonodelivery techniques for intramuscular gene delivery and suggest future directions for this continuously evolving field.

Low-frequency ultrasound-mediated cytokine transfection enhances T cell recruitment at local and distant tumor sites

Robust cytotoxic T cell infiltration has proven to be difficult to achieve in solid tumors. We set out to develop a flexible protocol to efficiently transfect tumor and stromal cells to produce immune-activating cytokines, and thus enhance T cell infiltration while debulking tumor mass. By combining ultrasound with tumor-targeted microbubbles, membrane pores are created and facilitate a controllable and local transfection. Here, we applied a substantially lower transmission frequency (250 kHz) than applied previously. The resulting microbubble oscillation was significantly enhanced, reaching an effective expansion ratio of 35 for a peak negative pressure of 500 kPa in vitro. Combining low-frequency ultrasound with tumor-targeted microbubbles and a DNA plasmid construct, 20% of tumor cells remained viable, and ∼20% of these remaining cells were transfected with a reporter gene both in vitro and in vivo. The majority of cells transfected in vivo were mucin 1+/CD45- tumor cells. Tumor and stromal cells were then transfected with plasmid DNA encoding IFN-β, producing 150 pg/106 cells in vitro, a 150-fold increase compared to no-ultrasound or no-plasmid controls and a 50-fold increase compared to treatment with targeted microbubbles and ultrasound (without IFN-β). This enhancement in secretion exceeds previously reported fourfold to fivefold increases with other in vitro treatments. Combined with intraperitoneal administration of checkpoint inhibition, a single application of IFN-β plasmid transfection reduced tumor growth in vivo and recruited efficacious immune cells at both the local and distant tumor sites.

The relation of Bleomycin Delivery Efficiency to Microbubble Sonodestruction and Cavitation Spectral Characteristics

The concurrent assessment of principal sonoporation factors has been accomplished in a single systemic study. Microbubble sonodestruction dynamics and cavitation spectral characteristics, ultrasound scattering and attenuation, were examined in relation to the intracellular delivery of anticancer drug, bleomycin. Experiments were conducted on Chinese hamster ovary cells coadministered with Sonovue microbubbles. Detailed analysis of the scattering and attenuation temporal functions culminated in quantification of metrics, inertial cavitation dose and attenuation rate, suitable for cavitation control. The exponents, representing microbubble sonodestruction kinetics were exploited to derive dosimetric, microbubble sonodestruction rate. High intracorrelation between empirically-attained metrics defines the relations which indicate deep physical interdependencies within inherent phenomena. Subsequently each quantified metric was validated to be well-applicable to prognosticate the efficacy of bleomycin delivery and cell viability, as indicated by strong overall correlation (R² > 0.85). Presented results draw valuable insights in sonoporation dosimetry and contribute towards the development of universal sonoporation dosimetry model. Both bleomycin delivery and cell viability reach their respective plateau levels by the time, required to attain total microbubble sonodestruction, which accord with scattering and attenuation decrease to background levels. This suggests a well-defined criterion, feasible through signal-registration, universally employable to set optimal duration of exposure for efficient sonoporation outcome.

Localized Delivery of shRNA against PHD2 Protects the Heart from Acute Myocardial Infarction through Ultrasound-Targeted Cationic Microbubble Destruction

Hypoxia-inducible factor 1α (HIF-1α) plays a critical protective role in ischemic heart disease. Under normoxic conditions, HIF-1α was degraded by oxygen-dependent prolyl hydroxylase-2 (PHD2). Gene therapy has become a promising strategy to inhibit the degradation of HIF-1α and to improve cardiac function after ischemic injury. However, conventional gene delivery systems are difficult to achieve a targeted and localized gene delivery into the ischemic myocardia. Here, we report the localized myocardial delivery of shRNA against PHD2 through ultrasound-targeted microbubble destruction (UTMD) for protection the heart from acute myocardial infarction. In this study, a novel cationic microbubble was fabricated by using of the thin-film hydration and sonication method. The resulting microbubbles had a 28.2 ± 2.21 mV surface zeta potential and could greatly improve DNA binding performance, achieving 17.81 ± 1.46 μg of DNA loading capacity per 5 × 10⁸ microbubbles. Combined with these cationic microbubbles, UTMD-mediated gene delivery was evaluated and the gene transfection efficiency was optimized in the H9C2 cardiac cells. Knockdown of PHD2 gene was successfully realized by UTMD-mediated shPHD2 transfection, resulting in HIF-1α-dependent protective effects on H9C2 cells through increasing the expression of HIF-1α, VEGF and bFGF. We further employed UTMD-mediated shPHD2 transfection into the localized ischemic myocardia in a rat ischemia model, demonstrating significantly reduced infarct size and greatly improved the heart function. The silencing of PHD2 and the up-regulation of its downstream genes in the treated myocardia were confirmed. Histological analysis further revealed numbers of HIF-1α- and VEGF-, and CD31-positive cells/mm² in the shPHD2-treated group were significantly greater than those in the sham or control vector groups (P < 0.05). In conclusion, our study provides a promising strategy to realize ultrasound-mediated localized myocardial shRNA delivery to protect the heart from acute myocardial infarction via cationic microbubbles.

Investigation of Microbubble Cavitation-Induced Calcein Release from Cells In Vitro

In the present study, microbubble (MB) cavitation signal analysis was performed together with calcein release evaluation in both pressure and exposure duration domains of the acoustic field. A passive cavitation detection system was used to simultaneously measure MB scattering and attenuation signals for subsequent extraction efficiency relative to MB cavitation activity. The results indicate that the decrease in the efficiency of extraction of calcein molecules from Chinese hamster ovary cells, as well as cell viability, is associated with MB cavitation activity and can be accurately predicted using inertial cavitation doses up to 0.18 V × s (R² > 0.9, p < 0.0001). No decrease in additional calcein release or cell viability was observed after complete MB sonodestruction was achieved. This indicates that the optimal exposure duration within which maximal sono-extraction efficiency is obtained coincides with the time necessary to achieve complete MB destruction. These results illustrate the importance of MB inertial cavitation in the sono-extraction process. To our knowledge, this study is the first to (i) investigate small molecule extraction from cells via sonoporation and (ii) relate the extraction process to the quantitative characteristics of MB cavitation acoustic spectra.

Patient-Specific Therapy via Cell-Reprogramming Technology: a Curative Potential for Patients with Diabetes

Gene therapeutics provides great opportunities for curing diabetes. Numerous attempts have been made to establish a safe and high-efficiency gene delivery strategy, but all of them are unsuccessful. To achieve an ideal transfection, a novel gene delivery strategy was presented in this research. The novel system proposed was transfection mediated by the combination of ultrasound with microbubbles and cross-linked polyethylenimines (PEIs). Ultrasound with microbubbles enhances the permeability of target cells; moreover, cross-linked PEIs enabled DNA to escape from endosomes into the cytoplasm. If the proposed method is feasible and effective, the endogenous secretion system of insulin would be re-established in patients with diabetes.

Analysis of Metrics for Molecular Sonotransfer in Vitro

Ultrasound induced microbubble (MB) cavitation is used to significantly enhance cell membrane permeabilization, thereby allowing delivery of various therapeutic agents into cells. In order to monitor and quantitatively control the extent of cavitation the uniform dosimetry model is needed. In present study we have simultaneously performed quantitative evaluation of three main sonoporation factors: (1) MB concentration, (2) MB cavitation extent, and (3) doxorubicin (DOX) sonotransfer into Chinese hamster ovary cells. MB concentration measurement results and passively recorded MB cavitation signals were used for MB sonodestruction rate and spectral root-mean-square (RMS) calculations, respectively. Subsequently, time to maximum value of RMS and inertial cavitation dose (ICD) quantifications were performed for every acoustic pressure value. This comprehensive research has led not only to explanation of relation of ICD and MB sonodestruction rate but also to the development of a new sonoporation metric: the inverse of time to maximum value of RMS (1/time to maximum value of RMS). ICD and MB sonodestruction rate intercorrelation and correlation with DOX sonotransfer suggest inertial cavitation to be the key mechanism for cell sonoporation. All these metrics were successfully used for doxorubicin sonotransfer prediction (R(2) > 0.9, p < 0.01) and therefore shows feasibility to be applied for future dosimetric applications for ultrasound-mediated drug and gene delivery.

The dual effect of ultrasound-targeted microbubble destruction in mediating recombinant adeno-associated virus delivery in renal cell carcinoma: transfection enhancement and tumor inhibition

BACKGROUND

Recombinant adeno-associated virus (rAAV) is recognized as a promising vector for cancer gene therapy, although its low transfer efficiency in less permissive cells limits extensive application. Our previous studies reported that ultrasound-targeted microbubble (MB) destruction (UTMD) enhanced rAAV transfer in its permissive retinal cells. In the present study, we investigated whether UTMD increased rAAV transfer in less permissive human renal cell carcinoma (hRCC) cells and tumors.

METHODS

hRCC cells were treated with rAAV2 under different conditions of UTMD, and the viral transfer efficiency and cell viability were analyzed. Fifty-two male nude mice (BALB/c) implanted with hRCC cells were randomly assigned to four groups consisting of rAAV, rAAV + ultrasound and rAAV + UTMD (20 µl and 40 µl of MBs). UTMD was initiated immediately after intratumoral viral injection, and viral transfer efficiency and tumor volumes were analyzed at 12 weeks after infection.

RESULTS

The efficiency of non-augmented transfer of rAAV2 into hRCC cells was low (17.28 ± 2.44%). The use of UTMD enhanced viral transfer efficiency by two- to three-fold, and enhanced viral genomic DNA by more than nine-fold, without decreasing cell viability. In vivo studies also showed that UTMD increased rAAV2 transfer in tumor. The enhancements were maintained for a period of 12 weeks. Tumor growth in mice was inhibited by UTMD treatment, and UTMD treatment augmented by MBs (40 µl) produced an even stronger effect.

CONCLUSIONS

UTMD enhanced rAAV2 transfer into less permissive RCC cells and tumors, resulting in inhibition of tumor growth, which suggests that UTMD may be a useful delivery tool for cancer gene therapy.

Ultrasound enhanced PEI-mediated gene delivery through increasing the intracellular calcium level and PKC-δ protein expression

PURPOSE

Polyethylenimine (PEI), a cationic polymer, has been shown to aggregate plasmid DNA and facilitate its internalization. It has also been shown that combining ultrasound (US) with PEI could enhance and prolong in vitro and in vivo transgene expression. However, the role US in the enhancement of PEI uptake is poorly understood. This study investigates the impact of US on PEI-mediated gene transfection.

METHODS

Specific endocytosis pathway siRNA, including clathrin HC siRNA, caveolin-1 siRNA and protein kinase C-delta (PKC-δ) siRNA, are used to block the corresponding endocytosis pathways prior to the transfection of luciferase DNA/PEI polyplexes to cultured cells by 1-MHz pulsed US with ultrasound contrast agent SonoVue®.

RESULTS

Transgene expression was found not to be enhanced by US treatment in the presence of the PKC-δ siRNA. We further demonstrated that PKC-δ protein could be enhanced at 6 h after US exposure. Moreover, intracellular calcium levels were found to be significantly increased at 3 h after US exposure, while transgene expressions were significantly reduced in the presence of calcium channel blockers both in vitro and in vivo.

CONCLUSIONS

Our results suggest that US enhanced PEI-mediated gene transfection specifically by increasing PKC-δ related fluid phase endocytosis, which was induced by increasing the intracellular calcium levels.

Enhancement of chitosan nanoparticle-facilitated gene transfection by ultrasound both in vitro and in vivo

In recent years, inefficiency of transfection and the lack of safe gene vectors have limited the feasibility of gene therapy. Fabrication of a vector that is safe and has high transfection efficiency is crucial for the development of successful gene therapies. Herein, we complexed chitosan to plasmids at various N/P ratios, the molar ratios of the amino groups of chitosan to the phosphate groups of DNA, to create chitosan-DNA nanoparticles (CDNs), and then measured CDNs size, zeta-potential, efficiency of plasmid complexation, and plasmid integrity from enzyme digestion. We also used flow cytometry and fluorescence microscopy to examine the effect of an ultrasound (US) regimen on the efficiency of transfection of HeLa cells. The results revealed that the average size, zeta-potential, and loading efficiency of plasmid DNA in CDNs were 180-200 nm, 26-35 mV, and greater than 80%, respectively. Moreover, the transgene expression could be enhanced efficiently while HeLa cells or tumor tissues were given CDNs and then treated with US. Therefore, the use of chitosan nanoparticles and an US regimen shows great promise as an effective method of gene therapy.

Adjustment of ultrasound exposure duration to microbubble sonodestruction kinetics for optimal cell sonoporation in vitro

Cell sonoporation enables the delivery of various exogenous molecules into the cells. To maximize the percentage of reversibly sonoporated cells and to increase cell viability we propose a model for implicit dosimetry for adjustment of ultrasound (US) exposure duration. The Chinese hamster ovary cell suspension was supplemented with microbubbles (MB) and exposed to US, operating at the frequency of 880kHz, with a 100% duty cycle and with an output peak negative pressure (PNP) of 500kPa for durations ranging from 0.5 to 30s. Using diagnostic B-scan imaging we showed that the majority of the MB at 500kPa US peak negative pressure undergo sonodestruction in less than a second. During this time maximal number of reversibly sonoporated cells was achieved. Increase of US exposure duration did not increase sonoporated cell number, however it induced additional cell viability decrease. Therefore aiming to achieve the highest level of reversibly sonoporated cells and also to preserve the highest level of cell viability, the duration of US exposure should not exceed the duration needed for complete MB sonodestruction.

Sonoporation-mediated anti-angiogenic gene transfer into muscle effectively regresses distant orthotopic tumors

Ultrasound (US) is an effective tool for local delivery of genes into target tumors or organs. In combination with microbubbles, US can temporarily change the permeability of cell membranes by cavitation and facilitate entry of plasmid DNA into cells. Here, we demonstrate that repeated US-mediated delivery of anti-angiogenic genes, endostatin or calreticulin, into muscle significantly inhibits the growth of orthotopic tumors in the liver, brain or lung. US-mediated anti-angiogenic gene therapy also seems to function as an adjuvant therapy that significantly enhances the antitumor effects of the chemotherapeutic drug doxorubicin and adenovirus-mediated cytokine gene therapy. Significantly higher levels of tumor apoptosis or tumor-infiltrating lymphocytes were observed after combined therapy consisting of either anti-angiogenic therapy and chemotherapy, or anti-angiogenic therapy and immunotherapy. Taken together, our experiments demonstrate that intramuscular delivery of anti-angiogenic genes by US exposure can effectively treat distant orthotopic tumors, and thus has great therapeutic potential in terms of clinical treatment.

Sonoporation delivery of interleukin-27 gene therapy efficiently reduces prostate tumor cell growth in vivo

We have examined the potential of a novel cytokine, interleukin-27 (IL-27), for gene therapy of prostate cancer. IL-27 is the most recently characterized member of the family of heterodimeric IL-12-related cytokines and has shown promise in halting tumor growth and mediating tumor regression in several cancer models. In the present study, we examined the efficacy of a new mode of gene delivery to prostate tumors: low-frequency ultrasound irradiation or "sonoporation." We also examined the potential of IL-27 gene delivery by sonoporation to treat and reduce the growth of prostate cancer in vivo. We used three models of immune-competent prostate adenocarcinoma and characterized the tumor-growth reduction, gene-profile expression, and effector cellular profiles. Our results suggest that IL-27 can be effective in reducing tumor growth and can help enhance accumulation of effector cells in prostate tumors in vivo. These results are promising, because they are potentially relevant to developing novel therapies that can be translated by using the novel and effective sonoporation gene-therapy delivery strategy.

A simple method for quantifying ultrasound-triggered microbubble destruction

Ultrasound-triggered microbubble destruction (UTMD) is essential for targeted drug delivery but currently there is no agreed gold standard for its real-time monitoring. This study used a clinical diagnostic ultrasound scanner to quantify the destruction effects of different values of mechanical index (MI) on microbubble. This was achieved by measuring the signal intensity of peripheral vessels, which is representative of systemic microbubble concentration. Twenty-four male Sprague-Dawley rats and SonoVue contrast agent were used for this study, six for the determination of signal saturation and 18 for the study of microbubble destruction. In the first part of the experiment, four different SonoVue doses (200, 400, 600 and 800 μL/kg) were injected into each of six rats and the signal intensity in their right femoral arteries were recorded using a diagnostic ultrasound scanner. This data was used to plot time-intensity curves (TIC) to determine at which concentration the signal reaches saturation. Then UTMD studies were performed using the 400 μL/kg dose as its peak signal intensity (PSI) was safely within the linear portion of the intensity-concentration curve. The remaining 18 rats were divided into three MI groups (0.2, 0.6 and 1.0) and for each rat, the following was performed: TIC recording of a sham exposure without sonication was performed first using the same scanner from signal saturation study. Simultaneously, another ultrasound scanner was applied to the adductor muscles of left hind limb for sonication later. Then, a sonication TIC recording was performed, with both ultrasound scanners activated. A TIC recording of second sonication was also obtained for comparison. The TICs showed that the area under the curve and the enhancement duration were reduced after sonication in the groups MI = 0.6 and MI = 1.0 but not for the group MI = 0.2. The PSI in the groups with MI of 0.6 and 1.0 were slightly lowered after sonication, although it is not statistically significant. No significant difference of TIC exists between the first and the second sonication for each group. Pharmacokinetic analysis was performed with estimated concentration-time curve derived from TIC curve and found that SonoVue had faster clearance and decreased half-life in the groups MI = 0.6 and MI = 1.0. In conclusion, this study shows that sonographic signal measured from peripheral vessels is a feasible indicator of systemic microbubble concentration and may be used to quantify ultrasound-triggered microbubble destruction at target site.

Exploiting ultrasound-mediated effects in delivering targeted, site-specific cancer therapy

Although the concept of employing ultrasound for the treatment of cancer is not a new one, virtually all existing ultrasound-based clinical cancer treatments are based on hyperthermic ablation. This review seeks to highlight the potential offered by more subtle ultrasound-triggered phenomena such as sonoporation in delivering novel targeted cancer treatment modalities.

Sonoporation-mediated gene transfer into adult rat dorsal root ganglion cells

Background

Gene transfer into many cell types has been successfully used to develop alternative and adjunct approaches to conventional medical treatment. However, effective transfection of postmitotic neurons remains a challenge. The aim of this study was to develop a method for gene transfer into rat primary dorsal root ganglion neurons using sonoporation.

Methods

Dissociated cells from adult rat dorsal root ganglion (DRG) cells were sonicated for 1-8 s at 2.5-10 W to determine the optimal ultrasound duration and power for gene transfection and cell survival. Transfection efficiency was compared between sonoporation, liposome and lentiviral vector gene transfer techniques.

Results

The optimum ultrasound intensity was 5 W for 2 s and yielded an efficiency of gene transfection of 31% and a survival rate of 35%.

Conclusions

Sonoporation can be optimized to minimize cell death and yield a high percentage of transfected neurons and that this technique can be easily applied to primary cultures of rat dorsal root ganglion neurons.