Exosomes Derived from Mesenchymal Stem Cells Suppress Angiogenesis by Down-Regulating VEGF Expression in Breast Cancer Cells

Exosomes are small membrane vesicles released by a variety of cell types. Exosomes contain genetic materials, such as mRNAs and microRNAs (miRNAs), implying that they may play a pivotal role in cell-to-cell communication. Mesenchymal stem cells (MSCs), which potentially differentiate into multiple cell types, can migrate to the tumor sites and have been reported to exert complex effects on tumor progression. To elucidate the role of MSCs within the tumor microenvironment, previous studies have suggested various mechanisms such as immune modulation and secreted factors of MSCs. However, the paracrine effects of MSC-derived exosomes on the tumor microenvironment remain to be explored. The hypothesis of this study was that MSC-derived exosomes might reprogram tumor behavior by transferring their molecular contents. To test this hypothesis, exosomes from MSCs were isolated and characterized. MSC-derived exosomes exhibited different protein and RNA profiles compared with their donor cells and these vesicles could be internalized by breast cancer cells. The results demonstrated that MSC-derived exosomes significantly down-regulated the expression of vascular endothelial growth factor (VEGF) in tumor cells, which lead to inhibition of angiogenesis in vitro and in vivo. Additionally, miR-16, a miRNA known to target VEGF, was enriched in MSC-derived exosomes and it was partially responsible for the anti-angiogenic effect of MSC-derived exosomes. The collective results suggest that MSC-derived exosomes may serve as a significant mediator of cell-to-cell communication within the tumor microenvironment and suppress angiogenesis by transferring anti-angiogenic molecules.     

Overexpression of alfalfa mitochondrial HSP23 in prokaryotic and eukaryotic model systems confers enhanced tolerance to salinity and arsenic stress

The cloning and characterization of a gene (MsHSP23) coding for a heat shock protein in alfalfa in a prokaryotic and model plant system is described. MsHSP23 contains a 633 bp ORF encoding a polypeptide of 213 amino acids and exhibits greater sequence similarity to mitochondrial sHSPs from dicotyledons than to those from monocotyledons. When expressed in bacteria, recombinant MsHSP23 conferred tolerance to salinity and arsenic stress. Furthermore, MsHSP23 was cloned in a plant expressing vector and transformed into tobacco, a eukaryotic model organism. The transgenic plants exhibited enhanced tolerance to salinity and arsenic stress under ex vitro conditions. In comparison to wild type plants, the transgenic plants exhibited significantly lower electrolyte leakage. Moreover, the transgenic plants had superior germination rates when placed on medium containing arsenic. Taken together, these overexpression results imply that MsHSP23 plays an important role in salinity and arsenic stress tolerance in transgenic tobacco. This approach could be useful to develop stress tolerant crops including forage crops.     

Comparative proteomic approach to identify proteins involved in flooding combined with salinity stress in soybean

Salinity together with waterlogging or flooding, a condition that occurs frequently in the field, can cause severe damage to crops. Combined flooding and salinity decreases the growth and survival of plants more than either stress alone. We report here the first proteomic analysis to investigate the global effects of saline flooding on multiple metabolic pathways. Soybean seedlings at the emergence (VE) stage were treated with 100 mM NaCl and flooded with water or 100 mM sodium chloride solution for 2 days. Proteins were extracted from hypocotyl and root samples and analyzed by two-dimensional gel electrophoresis followed by MALDI-TOF, MALDI-TOF/TOF mass spectrometry or immunoblotting. A total of 43 reproducibly resolved, differentially expressed protein spots visualized by Coomassie brilliant blue staining were identified by MALDI-TOF MS. Identities of several proteins were also validated by MS/MS analysis or immunoblot analysis. Twenty-nine proteins were upregulated, eight proteins were downregulated and six spots were newly induced. The identified proteins include well-known salt and flooding induced proteins as well as novel proteins expressed by the salinity-flooding combined stress. The comparative analysis identified changes at the proteome level that are both specific and part of a common or shared response. The identification of such differentially expressed proteins provides new targets for future studies that will allow assessment of their physiological roles and significance in the response of glycophytes to a combination of flooding and salinity.     

Overexpression of a chloroplast-localized small heat shock protein OsHSP26 confers enhanced tolerance against oxidative and heat stresses in tall fescue

Small heat shock proteins are involved in stress tolerance. We previously isolated and characterized a rice cDNA clone, Oshsp26, encoding a chloroplast-localized small heat shock protein that is expressed following oxidative or heat stress. In this study, we transferred this gene to tall fescue plants by an Agrobacterium-mediated transformation system. The integration and expression of the transgene was confirmed by PCR, Southern, northern, and immunoblot analyzes. Compared to the control plants, the transgenic plants had significantly lower electrolyte leakage and accumulation of thiobarbituric acid-reactive substances when exposed to heat or methyl viologen. The photochemical efficiency of photosystem II (PSII) (Fv/Fm) in the transgenic tall fescue plants was higher than that in the control plants during heat stress (42°C). These results suggest that the OsHSP26 protein plays an important role in the protection of PSII during heat and oxidative stress in vivo.     

In vitro propagation of Trichosanthes kirilowii Maxim. through nodal segment shoot proliferation

Trichosanthes kirilowii Maxim. is a vital traditional herbal medicinal plant found in northeastern Asia. Its roots, fruits, and seeds are used as food and medicine. Roots harvested for medicinal use take over 3 yr to mature when the plant is grown in a traditional way through cultivation in the field. This coupled with uncertainty in identification of the plant when collected from the wild calls for a standard in vitro propagation system to meet the increasing demand for it. The purpose of this study was to develop a standard protocol for the in vitro micropropagation of T. kirilowii. Ten different media supplemented with different concentrations of plant growth regulators were evaluated. At 5 wk, De Greef and Jacobs medium supplemented with 0.1 mg L⁻¹ kinetin led to optimal shoot growth, while the same medium supplemented with 0.5 mg L⁻¹ indole 3-butyric acid induced optimal root growth, also at 5 wk. The micropropagated plants that were acclimatized for 8 wk in the greenhouse produced mature root tubers after planted in the field for 3 mo. Therefore, these findings provide a basis for future large-scale in vitro propagation of T. kirilowii.

     

Identification of MsHsp23 gene using annealing control primer system

To identify potential candidates for acquiring stress tolerance, a new annealing control primer (ACP) system was used to identify the differentially expressed genes. Alfalfa (Medicago sativa L.) seedlings were exposed to various abiotic stresses such as cold (4°C for 6 h), heat (42°C for 6 h), salt (300 mM for 6 h), drought (withdrawing irrigation for 48 h), copper (500 μM for 6 h), cadmium (500 μM for 6 h), and arsenic (500 μM for 6 h). Primer sets 41 and 93 were differentially expressed and identified as same sequence, which represents a mitochondrial small heat-shock protein encoding gene, MsHsp23. This band was markedly increased or induced in alfalfa under heat, salt, and arsenic stresses. Differential expression of MsHsp23 was further evaluated by Northern blot analysis. Temporal expression analysis showed that mRNA pool was altered as early as 1 h of treatment. Thus, differential accumulation of MsHsp23 under heat, salt, and arsenic stresses suggests its potential involvement in diverse abiotic stress tolerance, and thereby making a target for further molecular analysis.