Hongmei Xia

Myocardium-targeted transplantation of mesenchymal stem cells by diagnostic ultrasound-mediated microbubble destruction improves cardiac function in myocardial infarction of New Zealand rabbits.

BACKGROUND Therapeutic ultrasound-mediated microbubble destruction has been applied in the targeted delivery of genes, drugs and stem cells. We intended to study whether diagnostic US irradiating lipid-coated microbubble destruction combined with bone-marrow derived MSC infusion could enable the targeted delivery of MSCs into the myocardium and improve cardiac function of the myocardial infarction of New Zealand rabbits. METHODS Diagnostic ultrasound was applied to the anterior chest for 10 min after intravenous injection of lipid-coated microbubble followed by infusion of BM-MSCs. Echocardiography, histological examination, and western blotting were performed 4 weeks after cell transplantation. RESULTS The cardiac function (assessed by fractional shortening and ejection fraction) was markedly improved by US+Microbubble+MSC treatment. The number of capillaries stained by HE in US+Microbubble+MSC group (47+/-23) was much greater than that of the MSCs infusion group (26+/-7), US+Microbubble group(22+/-5) and PBS infusion group (19+/-10), P<0.01. US+Microbubble stimulation induced the expression of adhesion molecule (VCAM-1) in capillaries and enhanced the myocardial permeability of microvessels. US+Microbubble-mediated supply of MSCs increased the level of VEGF in ischemic myocardium. Area of cardiac fibrosis in the US+Microbubble+MSC group was significantly decreased by 25.6%,40.1% and 46.8% when compared with MSC infusion group, US+Microbubble group and PBS infusion group, respectively. CONCLUSIONS This non-invasive cell delivery system may be useful as a novel and efficient approach for angiogenic cell therapy to the infarcted myocardium.

Kidney-Targeted Transplantation of Mesenchymal Stem Cells by Ultrasound-Targeted Microbubble Destruction Promotes Kidney Repair in Diabetic Nephropathy Rats

We test the hypothesis that ultrasound-targeted microbubble destruction (UTMD) technique increases the renoprotective effect of kidney-targeted transplantation of bone-marrow-derived mesenchymal stem cells (BM-MSCs) in diabetic nephropathy (DN) rats. Diabetes was induced by streptozotocin injection (60 mg/Kg, intraperitoneally) in Sprague-Dawley rats. MSCs were administered alone or in combination with UTMD to DN rats at 4 weeks after diabetes onset. Random blood glucose concentrations were measured at 1, 2, 4, and 8 weeks, and plasma insulin levels, urinary albumin excretion rate (UAER) values, the structures of pancreas and kidney, the expressions of TGF-β1, synaptopodin, and IL-10 were assessed at 8 weeks after MSCs transplantation. MSCs transplantation decreased blood glucose concentrations and attenuated pancreatic islets/β cells damage. The permeability of renal interstitial capillaries and VCAM-1 expression increased after UTMD, which enhanced homing and retention of MSCs to kidneys. MSCs transplantation together with UTMD prevented renal damage and decreased UAER values by inhibiting TGF-β1 expression and upregulating synaptopodin and IL-10 expression. We conclude that MSCs transplantation reverts hyperglycemia; UTMD technique noninvasively increases the homing of MSCs to kidneys and promotes renal repair in DN rats. This noninvasive cell delivery method may be feasible and efficient as a novel approach for personal MSCs therapy to diabetic nephropathy.

Ultrasound-targeted stromal cell-derived factor-1-loaded microbubble destruction promotes mesenchymal stem cell homing to kidneys in diabetic nephropathy rats

Mesenchymal stem cell (MSC) therapy has been considered a promising strategy to cure diabetic nephropathy (DN). However, insufficient MSCs can settle in injured kidneys, which constitute one of the major barriers to the effective implementation of MSC therapy. Stromal cell-derived factor-1 (SDF-1) plays a vital role in MSC migration and involves activation, mobilization, homing, and retention, which are presumably related to the poor homing in DN therapy. Ultrasound-targeted microbubble destruction has become one of the most promising strategies for the targeted delivery of drugs and genes. To improve MSC homing to DN kidneys, we present a strategy to increase SDF-1 via ultrasound-targeted microbubble destruction. In this study, we developed SDF-1-loaded microbubbles (MBSDF-1) via covalent conjugation. The characterization and bioactivity of MBSDF-1 were assessed in vitro. Target release in the targeted kidneys was triggered with diagnostic ultrasound in combination with MBSDF-1. The related bioeffects were also elucidated. Early DN was induced in rats with streptozotocin. Green fluorescent protein-labeled MSCs were transplanted intravenously following the target release of SDF-1 in the kidneys of normal and DN rats. The homing efficacy was assessed by detecting the implanted exogenous MSCs at 24 hours. The in vitro results showed an impressive SDF-1 loading efficacy of 79% and a loading content of 15.8 μg/mL. MBSDF-1 remained bioactive as a chemoattractant. In the in vivo study, SDF-1 was successfully released in the targeted kidneys. The homing efficacy of MSCs to DN kidneys after the target release of SDF-1 was remarkably ameliorated at 24 hours compared with control treatments in normal rats and DN rats. In conclusion, ultrasound-targeted MBSDF-1 destruction could promote the homing of MSCs to early DN kidneys and provide a novel potential therapeutic approach for DN kidney repair.

Molecular imaging of vulnerable plaques in rabbits using contrast-enhanced ultrasound targeting to vascular endothelial growth factor receptor-2

Increased neovascularization has been identified as a feature of atherosclerotic plaque vulnerability and can be traced by microbubble ultrasound contrast agents (UCA). We investigated the relationship between retention of a vascular endothelial growth factor receptor 2 (VEGFR‐2) targeted UCA and VEGFR‐2 expression in a vulnerable plaque model in rabbits.

Investigation Into the Impact of Diagnostic Ultrasound with Microbubbles on the Capillary Permeability of Rat Hepatomas

Ultrasound-targeted microbubble destruction (UTMD) takes advantage of transiently increased capillary permeability to enhance the release of tumor-specific drugs from blood vessels into sonicated tumor tissues. However, the application of focused ultrasound is limited because of the lack of an appropriate image-monitoring system. In this study, hepatoma-bearing Sprague-Dawley rats were insonicated with low-frequency diagnostic ultrasound and injected with Evans Blue (EB) dye and microbubbles through their tail veins to test changes in capillary permeability. We studied how the mechanical index, sonication duration and the injected microbubble (MB) concentration affect the hepatoma vascular permeability by quantitatively evaluating the EB delivery efficiency. Confocal laser scanning microscopy was used to observe the deposition of red fluorescence-dyed EB in tumor tissues. In addition, P-selectin, a type of biochemical marker that reflects vascular endothelial cell activation, was identified using an immunoblotting analysis. The experimental results reveal that EB delivery efficiency in tumor tissues was greater in groups with the diagnostic ultrasound-mediated UTMD (8.40 ± 0.71 %ID/g) than in groups without UTMD (1.73 ± 0.19 %ID/g) and EB delivery efficiency could be affected by MI, sonication duration and MB dose. The immunoblotting analysis indicates that diagnostic ultrasound-induced UTMD results in the vascular endothelial cell activation to increase capillary permeability, justifying the high quantity of EB deposited in tumor tissues.

Ultrasound-Targeted Microbubble Destruction Improves the Migration and Homing of Mesenchymal Stem Cells after Myocardial Infarction by Upregulating SDF-1/CXCR4: A Pilot Study

Mesenchymal stem cell (MSC) therapy shows considerable promise for the treatment of myocardial infarction (MI). However, the inefficient migration and homing of MSCs after systemic infusion have limited their therapeutic applications. Ultrasound-targeted microbubble destruction (UTMD) has proven to be promising to improve the homing of MSCs to the ischemic myocardium, but the concrete mechanism remains unclear. We hypothesize that UTMD promotes MSC homing by upregulating SDF-1/CXCR4, and this study was aimed at exploring this potential mechanism. We analyzed SDF-1/CXCR4 expression after UTMD treatment in vitro and in vivo and counted the number of homing MSCs in MI areas. The in vitro results demonstrated that UTMD not only led to elevated secretion of SDF-1 but also resulted in an increased proportion of MSCs that expressed surface CXCR4. The in vivo findings show an increase in the number of homing MSCs and higher expression of SDF-1/CXCR4 in the UTMD combined with MSCs infusion group compared to other groups. In conclusion, UTMD can increase SDF-1 expression in the ischemic myocardium and upregulate the expression of surface CXCR4 on MSCs, which provides a molecular mechanism for the homing of MSCs assisted by UTMD via SDF-1/CXCR4 axis.

Assessment of left ventricular function by three-dimensional speckle-tracking echocardiography in well-treated type 2 diabetes patients with or without hypertension.

The aims of this study were to investigate the myocardial deformation in well‐treated type 2 diabetes patients with or without hypertension using three‐dimensional speckle‐tracking echocardiography and to explore variables that could affect myocardial deformation.

Speckle tracking echocardiography predicts early subclinical anthracycline cardiotoxicity in patients with breast cancer.

This study aimed to assess the early changes of left ventricular (LV) and right ventricular (RV) mechanics associated with anthracycline treatment for breast cancer and to determine whether two‐dimensional speckle tracking echocardiography (2D‐STE) analysis could predict chemotherapy‐induced cardiotoxicity.

Unilateral Opening of Rat Blood-Brain Barrier Assisted by Diagnostic Ultrasound Targeted Microbubbles Destruction

Objective. Blood-brain barrier (BBB) is a key obstacle that prevents the medication from blood to the brain. Microbubble-enhanced cavitation by focused ultrasound can open the BBB and proves to be valuable in the brain drug delivery. The study aimed to explore the feasibility, efficacy, and safety of unilateral opening of BBB using diagnostic ultrasound targeted microbubbles destruction in rats. Methods. A transtemporal bone irradiation of diagnostic ultrasound and intravenous injection of lipid-coated microbubbles were performed at unilateral hemisphere. Pathological changes were monitored. Evans Blue extravasation grades, extraction from brain tissue, and fluorescence optical density were quantified. Lanthanum nitrate was traced by transmission electron microscopy. Results. After diagnostic ultrasound mediated microbubbles destruction, Evans Blue extravasation and fluorescence integrated optical density were significantly higher in the irradiated hemisphere than the contralateral side (all p < 0.01). Erythrocytes extravasations were demonstrated in the ultrasound-exposed hemisphere (4 ± 1, grade 2) while being invisible in the control side. Lanthanum nitrate tracers leaked through interendothelial cleft and spread to the nerve fiber existed in the irradiation side. Conclusions. Transtemporal bone irradiation under DUS mediated microbubble destruction provides us with a more accessible, safer, and higher selective BBB opening approach in rats, which is advantageous in brain targeted drugs delivery.

Enhanced Homing Ability and Retention of Bone Marrow Stromal Cells to Diabetic Nephropathy by Microbubble-Mediated Diagnostic Ultrasound Irradiation

Bone marrow stromal cell (BMSC) transplantation can successfully treat diabetic nephropathy (DN), but the lack of a specific homing place for intravenously injected cells limits the effective implementation of stem cell therapies. The migration and survival of transplanted BMSCs are determined by inflammatory reactions in the local kidney micro-environment. We tested the hypothesis that microbubble-mediated diagnostic ultrasound irradiation could provide a suitable micro-environment for BMSC delivery and retention in DN therapy. In this study, red fluorescent protein-labeled BMSCs were administered combined with microbubbles to streptozotocin-induced DN rats 4 wk after diabetes onset. We observed enhanced BMSC homing and retention in microbubble-mediated diagnostic ultrasound-irradiated kidneys compared with the contralateral kidneys on days 1 and 3 post-treatment. The results from immunohistochemical analysis, Western blot and enzyme-linked immunosorbent assay indicated that the local and transient expression of various chemo-attractants (i.e., cytokines, integrins and trophic factors) found to promote BMSC homing was much higher than observed in non-treated kidneys. The local capillary endothelium rupture observed by transmission electron microscopy may account for local micro-environment changes. Histopathologic analysis revealed no signs of kidney damage. These results confirmed that renal micro-environment changes caused by appropriate microbubble-mediated diagnostic ultrasound irradiation may promote BMSC homing ability to the diabetic kidney without renal toxicity and cell damage. This non-invasive and effective technique may be a promising method for BMSC transplantation therapy.