Investigation of Broadband Optical Nonlinear Absorption and Transient Dynamics in Orange IV Containing Azobenzene.

Broadband reverse saturable absorption is systematically investigated via Z-scan, transient absorption spectrum (TAS). The excited state absorption and negative refraction of Orange IV are observed in the Z-scan experiment at 532 nm. Meanwhile, two-photon-induced excited state absorption and pure two-photon absorption are observed at 600 nm and 700 nm with the pulse width of 190 fs, respectively. An ultrafast broadband absorption in the visible wavelength region is observed via TAS. The different nonlinear absorption mechanisms at multiple wavelengths are discussed and interpreted from the results of TAS. In addition, the ultrafast dynamics of negative refraction in the excited state of Orange IV are investigated via a degenerate phase object pump-probe, from which the weak long-lived excited state is extracted. All studies indicate that Orange IV has the potential to be further optimized into a superior broadband reverse saturable absorption material and also has certain reference significance for the study of optical nonlinearity in organic molecules containing azobenzene groups.

Long noncoding RNA H19 upregulates vascular endothelial growth factor A to enhance mesenchymal stem cells survival and angiogenic capacity by inhibiting miR-199a-5p.

BACKGROUND: Currently, the overall therapeutic efficiency of mesenchymal stem cells (MSCs) transplantation for the treatment of cardiovascular disease is not satisfactory. The low viability and angiogenic capacity of the implanted cells in the local infarct tissues restrict their further application. Evidence shows that long noncoding RNA H19 (lncRNA-H19) mediates cell survival and angiogenesis. Additionally, it is also involved in MSCs biological activities. This study aimed to explore the functional role of lncRNA-H19 in MSCs survival and angiogenic capacity as well as the underlying mechanism. METHODS: MSCs were obtained from C57BL/6 mice and cultured in vitro. Cells at the third passage were divided into the following groups: MSCs+H19, MSCs+H19 NC, MSCs+si-H19, MSCs+si-H19 NC and MSCs. The MSCs+H19 and MSCs+H19 NC groups were transfected with lncRNA-H19 and lncRNA-H19 scramble RNA respectively. The MSCs+si-H19 and MSCs+si-H19 NC groups were transfected with lncRNA-H19 siRNA and lncRNA-H19 siRNA scramble respectively. MSCs were used as the blank control. All groups were exposed to normoxia (20% O2) and hypoxia (1% O2)/serum deprivation (H/SD) conditions for 24 h. Cell proliferation, apoptosis and vascular densities were assessed. Bioinformatics and dual luciferase reporter assay were performed. Relevant biomarkers were detected in different experimental groups. RESULTS: Overexpression of lncRNA-H19 improved survival and angiogenic capacity of MSCs under both normoxia and H/SD conditions, whereas its knockdown impaired cell viability and their angiogenic potential. MicroRNA-199a-5p (miR-199a-5p) targeted and downregulated vascular endothelial growth factor A (VEGFA). MiR-199a-5p was a target of lncRNA-H19. LncRNA-H19 transfection led to a decreased level of miR-199a-5p, accompanied with an elevated expression of VEGFA. However, both miR-199a-5p and VEGFA presented inverse alterations in the condition of lncRNA-H19 knockdown. CONCLUSIONS: LncRNA-H19 enhanced MSCs survival and their angiogenic potential in vitro. It could directly upregulate VEGFA expression by inhibiting miR-199a-5p as a competing endogenous RNA. This mechanism contributes to a better understanding of MSCs biological activities and provides new insights for cell therapy based on MSCs transplantation.

Hypoxia preconditioning promotes cardiac stem cell survival and cardiogenic differentiation in vitro involving activation of the HIF-1α/apelin/APJ axis.

BACKGROUND: Cardiac stem cells (CSCs) transplantation has been regarded as an optimal therapeutic approach for cardiovascular disease. However, inferior survival and low differentiation efficiency of these cells in the local infarct site reduce their therapeutic efficacy. In this study, we investigated the influence of hypoxia preconditioning (HP) on CSCs survival and cardiogenic differentiation in vitro and explored the relevant mechanism. METHODS: CSCs were obtained from Sprague-Dawley rats and cells of the third passage were cultured in vitro and exposed to hypoxia (1% O2). Cells survival and apoptosis were evaluated by MTS assay and flow cytometry respectively. Cardiogenic differentiation was induced by using 5-azacytidine for another 24 h after the cells experienced HP. Normoxia (20% O2) was used as a negative control during the whole process. Cardiogenic differentiation was assessed 2 weeks after the induction. Relevant molecules were examined after HP and during the differentiation process. Anti-hypoxia-inducible factor-1α (HIF-1α) small interfering RNA (siRNA), anti-apelin siRNA, and anti-putative receptor protein related to the angiotensin receptor AT1 (APJ) siRNA were transfected in order to block their expression, and relevant downstream molecules were detected. RESULTS: Compared with the normoxia group, the hypoxia group presented more rapid growth at time points of 12 and 24 h (p < 0.01). Cells exhibited the highest proliferation rate at the time point of 24 h (p < 0.01). The cell apoptosis rate significantly declined after 24 h of hypoxia exposure (p < 0.01). Expression levels of HIF-1α, apelin, and APJ were all enhanced after HP. The percentage of apelin, α-SA, and cTnT positive cells was greatly increased in the HP group after 2 weeks of induction. The protein level of α-SA and cTnT was also significantly elevated at 7 and 14 days (p < 0.01). HIF-1α, apelin, and APJ were all increased at different time points during the cardiogenic differentiation process (p < 0.01). Knockdown of HIF-1α, apelin or APJ by siRNAs resulted in a significant reduction of α-SA and cTnT. HIF-1α blockage caused a remarkable decrease of apelin and APJ (p < 0.01). Expression levels of apelin and APJ were depressed after the inhibition of apelin (p < 0.01). CONCLUSION: HP could effectively promote CSCs survival and cardiogenic differentiation in vitro, and this procedure involved activation of the HIF-1α/apelin/APJ axis. This study provided a new perspective for exploring novel strategies to enhance CSCs transplantation efficiency.

Long noncoding RNA Braveheart promotes cardiogenic differentiation of mesenchymal stem cells in vitro.

BACKGROUND: Mesenchymal stem cells (MSCs) have limited potential of cardiogenic differentiation. In this study, we investigated the influence of long noncoding RNA Braveheart (lncRNA-Bvht) on cardiogenic differentiation of MSCs in vitro. METHODS: MSCs were obtained from C57BL/6 mice and cultured in vitro. Cells were divided into three groups: blank control, null vector control, and lncRNA-Bvht. All three groups experienced exposure to hypoxia (1% O2) and serum deprivation for 24 h, and 24 h of reoxygenation (20% O2). Cardiogenic differentiation was induced using 5-AZA for another 24 h. Normoxia (20% O2) was applied as a negative control during the whole process. Cardiogenic differentiation was assessed, and expressions of cardiac-specific transcription factors and epithelial-mesenchymal transition (EMT)-associated biomarkers were detected. Anti-mesoderm posterior1 (Mesp1) siRNA was transfected in order to block its expression, and relevant downstream molecules were examined. RESULTS: Compared with the blank control and null vector control groups, the lncRNA-Bvht group presented a higher percentage of differentiated cells of the cardiogenic phenotype in vitro both under the normal condition and after hypoxia/re-oxygenation. There was an increased level of cTnT and α-SA, and cardiac-specific transcription factors including Nkx2.5, Gata4, Gata6, and Isl-1 were significantly upregulated (P < 0.01). Expressions of EMT-associated genes including Snail, Twist and N-cadherin were much higher (P < 0.01). Mesp1 exhibited a distinct augmentation following lncRNA-Bvht transfection. Expressions of relevant cardiac-specific transcription factors and EMT-associated genes all presented a converse alteration in the condition of Mesp1 inhibition prior to lncRNA-Bvht transfection. CONCLUSION: lncRNA-Bvht could efficiently promote MSCs transdifferentation into cells with the cardiogenic phenotype in vitro. It might function via enhancing the expressions of cardiac-specific transcription factors and EMT-associated genes. Mesp1 could be a pivotal intermediary in the procedure.

Long noncoding RNAs: Novel molecules in cardiovascular biology, disease and regeneration.

Remarkable breakthroughs made in genomic technologies have facilitated the discovery of thousands of novel transcripts that do not template protein synthesis. Numerous RNAs termed as long noncoding RNAs (lncRNAs) generated from this pervasive transcription function vividly in gene regulatory networks and a variety of biological and cellular processes. Here, we make a brief description of the known and putative functions of lncRNAs in cardiovascular biology and disease. The association between lncRNAs and stem cells mediated cardiomyocytes differentiation and neovascularization is discussed then. It will provide a new clue for further studies on these novel molecules in cardiovascular disease and bring bright prospects for their future applications in cardiac regenerative medicine.

Cardiac stem cells transplantation enhances the expression of connexin 43 via the ANG II/AT1R/TGF-beta1 signaling pathway in a rat model of myocardial infarction.

BACKGROUND: In this study, we hypothesized that CSCs mediated the expression of Cx43 after transplantation post MI via the ANG II/AT1R/TGF-beta1 signaling pathway. METHODS: Myocardial infarction (MI) was induced in twenty male Sprague-Dawley rats. The rats were randomized into two groups and were then received the injection of 5 × 10(6) CSCs labeled with PKH26 in phosphate buffer solution (PBS) or equal PBS alone into the infarct anterior ventricular free wall two weeks after MI. Six weeks later, relevant signaling molecules involved were all examined. RESULTS: In the CSCs group, an increased expression of Cx43 could be observed in different zones of the left ventricle (P<0.01). There was a significant reduction of the angiotensin II (ANG II) level in plasma and different regions of the left ventricular cardiac tissues (P<0.05; P<0.01). The angiotensin II type I receptor (AT1R) was decreased accompanied with an enhanced expression of angiotensin II type II receptor (AT2R) (P<0.01). Transforming growth factor beta-1(TGF-beta1) was downregulated (P<0.01). The expression of mothers against decapentaplegic homolog (SMAD) proteins including SMAD2 and SMAD3 was attenuated whereas SMAD7 was elevated (P<0.01, P<0.01, P<0.05). In addition, the expression of mitogen-activated protein kinases (MAPKs) including extracellular kinases 1/2 (ERK1/2) and p38 was also found to be reduced (P<0.01). CONCLUSION: CSCs transplantation could enhance the level of Cx43 after MI. They might function through intervening the ANGII/AT1R/TGF-beta1 signaling pathway to regulate the expression of Cx43.

Peroxisome Proliferator-Activated Receptor Gamma Promotes Mesenchymal Stem Cells to Express Connexin43 via the Inhibition of TGF-ß1/Smads Signaling in a Rat Model of Myocardial Infarction.

BACKGROUND: In this study, we hypothesized that activation of PPAR-γ enhanced MSCs survival and their therapeutic efficacy via upregulating the expression of Cx43. METHODS: MI was induced in 50 male Sprague-Dawley rats. The rats were randomized into five groups: MI group and four intervention groups, including the MSCs group, combined therapy group (MSCs+ pioglitazone), pioglitazone group and PBS group. Two weeks later, 5 × 10(6) MSCs labeled with PKH26 in PBS were injected into the infarct anterior ventricular free wall in the MSCs and combined therapy groups, and PBS alone was injected into the infarct anterior ventricular free wall in the PBS group. Pioglitazone (3 mg/kg/day) was given to the combined therapy and pioglitazone groups by oral gavage at the same time for another 2 weeks. Myocardial function and relevant signaling molecules involved were all examined thereafter. RESULTS: Heart function was enhanced after MSCs treatment for 2 weeks post MI. A significant improvement of heart function was observed in the combined therapy group in contrast to the other three intervention groups. Compared with the MSCs group, there was a higher level of PPAR-γ in the combined therapy group; Cx43 was remarkably increased in different regions of the left ventricle; TGF-ß1 was decreased in the infarct zone and border zone. To the downstream signaling molecules, mothers against Smad proteins including Smad2 and Smad3 presented a synchronized alteration with TGF-ß1; no differences of the expressions of ERK1/2 and p38 could be discovered in the left ventricular cardiac tissue. CONCLUSIONS: MSCs transplantation combined with pioglitazone administration improved cardiac function more effectively after MI. Activation of PPAR-γ could promote MSCs to express Cx43. Inhibition of TGF-ß1/Smads signaling pathway might be involved in the process.