Ultrasound contrast agents affect the angiogenic response

Therapeutic Angiogenesis for Ovarian Transplantation through Ultrasound-Targeted Microbubble Destruction

Timely angiogenesis and effective microcirculation perfusion are essential for the survival and functional recovery of transplanted ovaries. Ultrasound-targeted microbubble destruction (UTMD) can lead to angiogenesis and increase flow perfusion by causing transient inflammation. The purpose of this study was to evaluate the effects of UTMD on transplanted ovarian revascularization and survival. In vitro, for the criteria of cell viability and tube formation capability, the optimal exposure parameters were determined to be a microbubble concentration of 1 × 10⁸/mL, mechanical index of 1 and exposure time of 30 s. After ovarian transplantation, 40 female Sprague Dawley rats were divided into four groups: transplantation alone, ultrasound alone, microbubbles alone and ultrasound and microbubbles (UTMD). At 7 d after transplantation, ovarian perfusion was assessed using qualitative and quantitative methods. The effect of angiogenesis was assessed by contrast-enhanced ultrasound, laser Doppler perfusion imaging and histologic analysis. The results, in which ovarian perfusion was highest in the UTMD group, suggest that UTMD can effectively improve ovarian perfusion. Compared with the other three groups, the number of follicles, microvascular density and rate of Ki-67-positive cells increased significantly in the UTMD group, while apoptosis decreased significantly (p < 0.05). The study indicates that UTMD promoted ovarian re-vascularization after ovarian transplantation and maintained follicular reserve.

Contrast Ultrasound Imaging of the Aorta Does Not Affect Progression of Atherosclerosis or Cardiovascular Biomarkers in ApoE-/- Mice

OBJECTIVES

Ultrasound contrast agents (UCAs) enhance cardiovascular ultrasound imaging. Adverse biological effects have occurred after administration of UCAs, and more research is needed for a comprehensive understanding of the risks involved. We used the ApoE(-/-) mouse model of atherosclerosis to characterize the effects of ultrasound and UCAs on atherosclerosis and plasma biomarkers.

METHODS

Male ApoE(-/-) mice (8 weeks old; n = 24) were intravenously infused with a UCA (2 × 10(10) Definity microbubbles per hour; Lantheus Medical Imaging, North Billerica, MA) and exposed to 2.8-MHz center frequency ultrasound (10 Hz pulse repetition frequency, 1.4 microseconds pulse duration, 2 minutes exposure duration, and 2 sites) at 1 of 3 derated peak rarefactional pressure amplitudes (0, 1.9, or 3.8 MPa), and then consumed either a chow or Western diet for 4 weeks (n = 4 per group). Blood plasma samples were collected before ultrasound exposure and at 2 and 4 weeks after exposure and assayed for total cholesterol and von Willebrand Factor (vWF). A pathologist measured atheroma thickness in formalin-fixed, hematoxylin-eosin-stained transverse aorta sections and scored them for severity of atherosclerosis.

RESULTS

Plasma total cholesterol initially averaged 286 mg/dL in the Western diet group and increased to 861 mg/dL after 4 weeks on the diet (P < .0001). Total cholesterol did not increase significantly in the chow diet group. Plasma vWF increased after 2 weeks on the Western diet (P < .0001). Atheroma thickness was greater in animals consuming the Western diet than in chow-fed animals (P < .05). Ultrasound had no significant effect on plasma total cholesterol, plasma vWF, or atheroma thickness.

CONCLUSIONS

Contrast ultrasound did not increase the severity of atherosclerosis or alter cardiovascular biomarkers in the ApoE(-/-) mouse model.

Quantitative analysis of ultrasound contrast agent postexcitation collapse

An empirically based peak-detection technique is described for statistically analyzing single ultrasound contrast agent collapses. It is shown that microbubbles with postexcitation collapse initially exhibit a stronger principal response on average than those without postexcitation, and that lower insonifying frequencies lead to postexcitation signals which have greater separation from their principal response and persist through more rebounds.

New progress in angiogenesis therapy of cardiovascular disease by ultrasound targeted microbubble destruction

Angiogenesis plays a vital part in the pathogenesis and treatment of cardiovascular disease and has become one of the hotspots that are being discussed in the past decades. At present, the promising angiogenesis therapies are gene therapy and stem cell therapy. Besides, a series of studies have shown that the ultrasound targeted microbubble destruction (UTMD) was a novel gene delivery system, due to its advantages of noninvasiveness, low immunogenicity and toxicity, repeatability and temporal and spatial target specificity; UTMD has also been used for angiogenesis therapy of cardiovascular disease. In this review, we mainly discuss the combination of UTMD and gene therapy or stem cell therapy which is applied in angiogenesis therapy in recent researches, and outline the future challenges and good prospects of these approaches.

Bubble liposomes and ultrasound exposure improve localized morpholino oligomer delivery into the skeletal muscles of dystrophic mdx mice

Duchenne muscular dystrophy (DMD) is a genetic disorder that is caused by mutations in the DMD gene that lead to an absence of functional protein. The mdx dystrophic mouse contains a nonsense mutation in exon 23 of the dystrophin gene; a phosphorodiamidate morpholino oligomer (PMO) designed to skip this mutated exon in the mRNA induces dystrophin expression. However, an efficient PMO delivery method is needed to improve treatment strategies for DMD. We previously developed polyethylene glycol (PEG)-modified liposomes (Bubble liposomes) that entrap ultrasound contrast gas and demonstrated that the combination of Bubble liposomes with ultrasound exposure is an effective gene delivery tool in vitro and in vivo. In this study, to evaluate the ability of Bubble liposomes as a PMO delivery tool, we tested the potency of the Bubble liposomes combined with ultrasound exposure to boost the delivery of PMO and increase the skipping of the mutated exon in the mdx mouse. The results indicated that the combination of Bubble liposomes and ultrasound exposure increased the uptake of the PMO targeting a nonsense mutation in exon 23 of the dystrophin gene and consequently increased the PMO-mediated exon-skipping efficiency compared with PMO injection alone, leading to significantly enhanced dystrophin expression. This increased efficiency indicated the potential of the combination of Bubble liposomes with ultrasound exposure to enhance PMO delivery for treating DMD. Thus, this ultrasound-mediated Bubble liposome technique may provide an effective, noninvasive, nonviral method for PMO therapy for DMD muscle as well as for other muscular dystrophies.

Early detection of ovarian cancer with conventional and contrast-enhanced transvaginal sonography: recent advances and potential improvements

Recently, there have been several major technical advances in the sonographic diagnosis of ovarian cancer in its early stages. These include improved assessment of tumor morphology with transvaginal sonography (TVS), and detection and characterization of tumor neovascularity with transvaginal color Doppler sonography (TV-CDS) and contrast-enhanced transvaginal sonography (CE-TVS). This paper will discuss and illustrate these improvements and describe how they enhance detection of early-stage ovarian cancer. Our initial experience with parametric mapping of CE-TVS will also be mentioned.