Low-Intensity Pulsed Ultrasound Enhances Angiogenesis and Ameliorates Left Ventricular Dysfunction in a Mouse Model of Acute Myocardial Infarction

Whole-brain low-intensity pulsed ultrasound therapy markedly improves cognitive dysfunctions in mouse models of dementia - Crucial roles of endothelial nitric oxide synthase

BACKGROUND

Therapeutic focused-ultrasound to the hippocampus has been reported to exert neuroprotective effects on dementia. In the present study, we examined whether the whole-brain LIPUS (low-intensity pulsed ultrasound) therapy is effective and safe in 2 mouse models of dementia (vascular dementia, VaD and Alzheimer's disease, AD), and if so, to elucidate the common underlying mechanism(s) involved.

METHODS

We used bilateral carotid artery stenosis (BCAS) model with micro-coils in male C57BL/6 mice as a VaD model and 5XFAD transgenic mice as an AD model. We applied the LIPUS therapy (1.875 MHz, 6.0 kHz, 32cycles) to the whole brain.

RESULTS

In both models, the LIPUS therapy markedly ameliorated cognitive impairments (Y-maze test and/or passive avoidance test) associated with improved cerebral blood flow (CBF). Mechanistically, the LIPUS therapy significantly increased CD31-positive endothelial cells and Olig2-positive oligodendrocyte precursor cells (OPCs) in the VaD model, while it reduced Iba-1-positive microglias and amyloid-β (Aβ) plaque in the AD model. In both models, endothelium-related genes were significantly upregulated in RNA-sequencing, and expressions of endothelial nitric oxide synthase (eNOS) and neurotrophins were upregulated in Western blotting. Interestingly, the increases in glia cells and neurotrophin expressions showed significant correlations with eNOS expression. Importantly, these beneficial effects of LIPUS were absent in eNOS-knockout mice.

CONCLUSIONS

These results indicate that the whole-brain LIPUS is an effective and non-invasive therapy for dementia by activating specific cells corresponding to each pathology, for which eNOS activation plays an important role as a common mechanism.

Low-intensity pulsed ultrasound enhances angiogenesis and ameliorates contractile dysfunction of pressure-overloaded heart in mice

Introduction

Chronic left ventricular (LV) pressure overload causes relative ischemia with resultant LV dysfunction. We have recently demonstrated that low-intensity pulsed ultrasound (LIPUS) improves myocardial ischemia in a pig model of chronic myocardial ischemia through enhanced myocardial angiogenesis. In the present study, we thus examined whether LIPUS also ameliorates contractile dysfunction in LV pressure-overloaded hearts.

Methods and results

Chronic LV pressure overload was induced with transverse aortic constriction (TAC) in mice. LIPUS was applied to the whole heart three times in the first week after TAC and was repeated once a week for 7 weeks thereafter (n = 22). Animals in the control groups received the sham treatment without LIPUS (n = 23). At 8 weeks after TAC, LV fractional shortening was depressed in the TAC-Control group, which was significantly ameliorated in the TAC-LIPUS group (30.4±0.5 vs. 36.2±3.8%, P<0.05). Capillary density was higher and perivascular fibrosis was less in the LV in the TAC-LIPUS group than in the TAC-Control group. Myocardial relative ischemia evaluated with hypoxyprobe was noted in the TAC-Control group, which was significantly attenuated in the TAC-LIPUS group. In the TAC-LIPUS group, as compared with the control group, mRNA expressions of BNP and collagen III were significantly lower (both P<0.05) and protein expressions of VEGF and eNOS were significantly up-regulated associated with Akt activation (all P<0.05). No adverse effect related to the LIPUS therapy was noted.

Conclusions

These results indicate that the LIPUS therapy ameliorates contractile dysfunction in chronically pressure-overloaded hearts through enhanced myocardial angiogenesis and attenuated perivascular fibrosis. Thus, the LIPUS therapy may be a promising, non-invasive treatment for cardiac dysfunction due to chronic pressure overload.

Low-intensity pulsed ultrasound activates ERK1/2 and PI3K-Akt signalling pathways and promotes the proliferation of human amnion-derived mesenchymal stem cells

OBJECTIVES

This study was to investigate the effect and mechanism of low-intensity pulsed ultrasound (LIPUS) on the proliferation of human amnion-derived mesenchymal stem cells (hAD-MSCs).

METHODS

Human amnion-derived mesenchymal stem cells were isolated from the amnion of term placentas and identified by flow cytometry and differentiation culture. Proliferation of hAD-MSCs was investigated by Cell Counting Kit-8, cell cycle and EdU assays. Western blotting was used to determine the protein expression levels.

RESULTS

Human amnion-derived mesenchymal stem cells were successfully isolated from the amnion and identified as multipotent mesenchymal stem cells. Low-intensity pulsed ultrasound promoted the proliferation of hAD-MSCs. Cell cycle analysis showed that LIPUS promoted cells to enter S and G2/M phases from G0/G1 phase. Western blot results showed that LIPUS promoted the phosphorylation and activation of ERK1/2 and Akt and significantly upregulated expression of cyclin D1, cyclin E1, cyclin A2 and cyclin B1. ERK1/2 inhibitor (U0126) and PI3K inhibitor (LY294002) significantly reduced LIPUS-induced phosphorylation of ERK1/2 and Akt, respectively, which in turn reduced the LIPUS-induced proliferation of hAD-MSCs.

CONCLUSIONS

Low-intensity pulsed ultrasound can promote the proliferation of hAD-MSCs, and ERK1/2 and PI3K-Akt signalling pathways may play important roles in this process.

Endothelial Functions

The endothelium plays important roles in modulating vascular tone by synthesizing and releasing a variety of endothelium-derived relaxing factors, including vasodilator prostaglandins, NO, and endothelium-dependent hyperpolarization factors, as well as endothelium-derived contracting factors. Endothelial dysfunction is mainly caused by reduced production or action of these relaxing mediators. Accumulating evidence has demonstrated that endothelial functions are essential to ensure proper maintenance of vascular homeostasis and that endothelial dysfunction is the hallmark of a wide range of cardiovascular diseases associated with pathological conditions toward vasoconstriction, thrombosis, and inflammatory state. In the clinical settings, evaluation of endothelial functions has gained increasing attention in view of its emerging relevance for cardiovascular disease. Recent experimental and clinical studies in the vascular biology field have demonstrated a close relationship between endothelial functions and cardiovascular disease and the highlighted emerging modulators of endothelial functions, new insight into cardiovascular disease associated with endothelial dysfunction, and potential therapeutic and diagnostic targets with major clinical implications. We herein will summarize the current knowledge on endothelial functions from bench to bedside with particular focus on recent publications in Arteriosclerosis, Thrombosis, and Vascular Biology.