P5397Mesenchymal stem cells derived from bone marrow promotes cardiomyocytes survival under hypoxia through exosomal miR-210

Background

A paracrine effect was regarded as the key mechanism involved in the MSC (mesenchymal stem cell)-based treatment for myocardial infarction. In our pilot experiments, hypoxia remarkably promotes MSC to paracrine exosomal miR-210, which could significantly enhance the cardiomyocytes survival in hypoxic incubation, suggesting that exosomal miR-210 played critical roles in the favorable paracrine effect of MSC on cardiomyocytes.

Purpose

The aim of this study was to investigate the important mechanism by which MSCs promote the tolerance of cardiomyocytes to hypoxia by secreting exosomal miR-210.

Methods and results

The exosomes were isolated from MSCs conditioned medium through ultracentrifugation, and we detected that miR-210 was the most abundant in MSC-exosome and increased most prominently in the hypoxia. The extracted exosomes were prepared for conditioned medium and the effect on myocardial protection was examined. The viability of control group was much better than the cardiomyocytes treated with hypoxia, but it was further increased in the presence of MSC-exosome, however, measurement was significantly lower in cardiomyocytes in hypoxia with exosomes derived from MSCs treated with GW4869. Subsequently, the co-localization of miR-210 with exosome-specific surface markers CD81 and CD63 were observed by immunofluorescence technique. Continuous magnetic live cell imaging was used to observe the uptake of exosome by cardiomyocytes, and fluorescence localization was used to observe the localization of miR-210 with Cy3 fluorescence in cardiomyocytes. Then, we demonstrated that MSCs exosomal miR-210 exerts the cardioprotective effect by regulating the AIFM3 (apoptosis-inducing factor mitochondria-associated protein 3), and we directly overexpressed miRNA-210 in cardiomyocytes and the results showed that the regulatory activity of the intake of exosomal miR-210 was consistent with that of the biological exosomal miR-210. Finally, we verified the protective effect on the ischemic myocardium by constructing rat myocardial infarction models. The level of apoptosis was detected at 1 week after myocardial infarction. The left ventricular ejection fraction and ventricular remodeling were measured at 4 weeks. In vivo, we demonstrated that explanted miR-210 from transplanted MSCs significantly reduced myocardial necrosis and apoptosis induced by ischemia and improved cardiac function and myocardial remodeling.

Conclusion

Here, we show that the exosomal miR-210 secreted by MSCs significantly increase the viability of cardiomyocytes and cardiac function. These findings suggest that exosomal miR-210 is a key effector that mediates the protection against hypoxia.

Acknowledgement/Funding

National Natural Science Foundation of China (Grant Nos. 81470467)

In situ multiproperty measurements of individual nanomaterials in SEM and correlation with their atomic structures

The relationship between property and structure is one of the most important fundamental questions in the field of nanomaterials and nanodevices. Understanding the multiproperties of a given nano-object also aids in the development of novel nanomaterials and nanodevices. In this paper, we develop for the first time a comprehensive platform for in situ multiproperty measurements of individual nanomaterials using a scanning electron microscope (SEM). Mechanical, electrical, electromechanical, optical, and photoelectronic properties of individual nanomaterials, with lengths that range from less than 200 nm to 20 μm, can be measured in situ with an SEM on the platform under precisely controlled single-axial strain and environment. An individual single-walled carbon nanotube (SWCNT) was measured on the platform. Three-terminal electronic measurements in a field effect transistor structure showed that the SWCNT was semiconducting and agreed with the structure characterization by transmission electron microscopy after the in situ measurements. Importantly, we observed a bandgap increase of this SWCNT with increasing axial strain, and for the first time, the experimental results quantitatively agree with theoretical predictions calculated using the chirality of the SWCNT. The vibration performance of the SWCNT, a double-walled CNT, and a triple-walled CNT were also studied as a function of axial strain, and were proved to be in good agreement with classical beam theory, although the CNTs only have one, two, or three atomic layers, respectively. Our platform has wide applications in correlating multiproperties of the same individual nanostructures with their atomic structures.

A platform for in-situ multi-probe electronic measurements and modification of nanodevices inside a transmission electron microscope

We developed a new platform that enables in-situ four-probe electronic measurements, in-situ three-probe field-effect measurements, nanomanipulation, and in-situ modification of nanodevices inside a transmission electron microscope (TEM). The platform includes a specially designed chip-holder and a silicon (Si) chip with suspended metal electrodes. The chip-holder can hold one Si chip with a size up to 3 mm × 3 mm and provides four electrical connections that can be connected to the micrometer-sized electrodes on the Si chip by wire-bonding. The other side of the electrical connections on the chip-holder is connected to the electronic instruments outside the TEM through a commercial Nanofactory SPM-TEM holder. The Si chip with suspended metal electrodes on one of its edges was fabricated by lithography and wet etching. Carbon nanotubes (CNTs), InAs nanowires, and tungsten disulfide nanowires were placed to stride over and connect to the suspended electrodes on the Si chip by nanomanipulations inside a scanning electron microscope (SEM). By using the platform, I-V curves of an individual single-walled CNT connecting to four electrodes were in-situ measured between any two of the four suspended electrodes, and a high-resolution TEM image of the same CNT was obtained. Furthermore, four-terminal I-V measurement on an InAs nanowire was achieved on this platform, and with a movable probe used as a gate electrode, field-effect measurement on the same InAs nanowire device was accomplished in SEM. In addition, by using the movable probe on the SPM-TEM holder, we could further in-situ modify nanomaterial and nanodevices. The present work demonstrates a method that allows a direct correlation between the atomic-level structure and the electronic property of nanomaterials or nanodevices whose structure can be further modified in-situ.

Transversally and axially tunable carbon nanotube resonators in situ fabricated and studied inside a scanning electron microscope

We report a new design of carbon nanotube (CNT) resonator, whose resonance frequency can be tuned not only transversally by a gate voltage, but also by the axial strain applied through directly pulling the CNT. The resonators are fabricated from individual suspended single-walled CNT (SWCNT) in situ inside a scanning electron microscope. The resonance frequency of a SWCNT resonator can be tuned by more than 20 times with an increase of quality factor when the axial strain of the SWCNT is only increased from nearly zero to 2% at room temperature. The transversal gate-tuning ability is found to be weaker than the axial-tuning ability and decrease with increasing the axial strain. The gate voltage can hardly tune the resonance frequency when the initial axial strain is larger than 0.35% and the CNT acts like a tied string. The relationship among resonance frequency, gate voltage, and initial axial strain of the CNT obtained presently will allow for the designs of CNT resonators with high frequency and large tuning range. The present resonator also shows ultrahigh sensitivity in displacement and force detection, with a resolution being better than 2.4 pm and 0.55 pN, respectively.

An efficacy analysis for nasopharyngeal carcinoma screening of different screening intervals

OBJECTIVE

To evaluate the impact of different screening intervals on screening for nasopharyngeal carcinoma (NPC).

METHODS

A Markov model was constructed, based on the natural history of NPC. The 5-year mortality rate of NPC was the major measurement to evaluate the efficacies of 16 screening strategies. Parameters for the model were derived from published literature.

RESULTS

Screening reduced the 5-year mortality rate for NPC by 20.4 - 43.3%, compared with the equivalent rate without screening. The 5 year mortality rate and the NPC pick-up rate with strategy A1 (annual screening) were 23.6% and 83.9%, respectively. Compared with strategy A1, strategy B1 (annual screening for seropositive subjects; biennial screening for seronegative subjects) had a similar 5-year mortality rate (24.0%) and a slightly smaller NPC pick-up rate (81.7%), but led to a 39.3% reduction in total screenings. Compared with all other strategies excluding strategy A1, strategy B1 achieved the lowest 5-year mortality rate and the largest NPC pick-up rate.

CONCLUSIONS

Strategy B1 had the highest efficacy for NPC screening.