Correction to: Overexpression of apelin in Wharton' jelly mesenchymal stem cell reverses insulin resistance and promotes pancreatic ß cell proliferation in type 2 diabetic rats.

The original article [1] contained errors in the presentation of Figure 7.

Overexpression of apelin in Wharton' jelly mesenchymal stem cell reverses insulin resistance and promotes pancreatic ß cell proliferation in type 2 diabetic rats.

BACKGROUND: Apelin plays a key beneficial role in energy metabolism by increasing glucose uptake and insulin sensitivity; however, apelin has a short half-life because it is rapidly cleared from the circulation limiting its therapeutic benefit. The aim of this study is to create a new approach to treat type 2 diabetes by inducing prolonged expression of apelin in Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs). METHODS: A type 2 diabetic rat model was given a high-fat diet combined with low-dose streptozotocin (STZ) injection. The human WJ-MSCs were isolated and subsequently transduced with apelin-expressing lentiviral particles (WJMSCs-apelin), and expression was verified by flow cytometry, Western blot, ELISA, and RT-PCR analysis. Type 2 diabetic rats were infused with either WJMSCs-apelin (2 × 106 cells) or an equivalent dose of saline through the tail vein injection 7 days after STZ injection. The therapeutic effects of each infusion group were evaluated by monitoring plasma glucose levels and performing glucose tolerance tests (OGTTs), insulin tolerance tests (IPITTs), confocal microscopy, and immunocytochemical analysis for quantitating islet beta cells. Plasma inflammatory cytokines IL-6 and TNF-α and anti-inflammatory factors adiponectin were measured as well. RESULTS: Type 2 diabetic rats infused with WJ-MSCs-apelin significantly decreased levels of blood glucose (from 26.03 ± 2.83 to 15.85 ± 2.13 mmol/L on 7 days P < 0.001, and to 9.41 ± 2.05 on 14 days, P < 0.001). Infusion of WJMSCs-apelin not only improved significantly insulin sensitivity and glucose disposal, but also promoted endogenous pancreatic ß cell proliferation (9.6-fold increase compared to the control group). Furthermore, infusion of the WJMSCs-apelin consistently increased insulin and C-peptide levels in the plasma, and the above effects persisted up to 42 days. The inflammatory cytokines IL-6 and TNF-α were significantly decreased, whereas anti-inflammatory factor adiponectin was significantly increased after WJ-MSC-apelin infusion. CONCLUSION: In this study, we report a novel approach to treat type 2 diabetic rats that combines apelin gene therapy with WJ-MSC cell therapy, which could provide a promising therapeutic option for management of type 2 diabetes clinically.

Activation of Endogenous Cardiac Stem Cells by Apelin-13 in Infarcted Rat Heart.

Our previous study demonstrated that the apelin-APJ pathway contributed to myocardial regeneration and functional recovery after bone marrow-derived mesenchymal stem cell (BM-MSC) transplantation during the differentiation of BM-MSCs into cardiomyogenic cells in acute myocardial infarction (AMI) rat models. However, the underlying mechanisms by which apelin promotes cardiac repair and functional recovery have not been completely clarified. In the present study, we investigated whether apelin could mobilize and activate endogenous cardiac stem cells and progenitors, thereby mediating regeneration and repair of the myocardium after AMI in rat models. Six-week-old male Sprague-Dawley rats underwent AMI and received apelin-13 (200 ng, n = 10) or an equivalent volume of saline by intramyocardial injection (n = 10); there was also a sham operation group (n = 8). Proliferation of endogenous cardiac stem cells was analyzed by immunofluorescence staining in rat infarcted myocardium, and heart function was evaluated by echocardiography at 28 days after apelin-13 injection. Treatment with apelin-13 led to a significant increase of Ki-67+-c-kit+/Sca-1+/Flk-1+ endogenous cardiac stem or progenitor cells in the border zone and infarct zone of rat hearts at 28 days after myocardial infarction (MI). Significant increases in the expression of c-kit, Sca-1, and Flk-1 on both levels of transcription and translation were confirmed by real-time polymerase chain reaction (RT-PCR) and Western blot. Treatment of apelin-13 also resulted in a significant reduction of infarct size and improvement of cardiac function post-MI. We conclude that apelin-13 is able to enhance mobilization, survival, and proliferation of endogenous myocardial stem cells in the injured heart, providing a novel mechanistic explanation for how apelin-13 might repair the heart and improve cardiac function. Thus, apelin-13 or pharmacological agonists of the APJ receptor could act as novel therapies for heart regeneration.

Apelin: an endogenous peptide essential for cardiomyogenic differentiation of mesenchymal stem cells via activating extracellular signal-regulated kinase 1/2 and 5.

Growing evidence has shown that apelin/APJ system functions as a critical mediator of cardiac development as well as cardiovascular function. Here, we investigated the role of apelin in the cardiomyogenic differentiation of mesenchymal stem cells derived from Wharton's jelly of human umbilical cord in vitro. In this research, we used RNA interference methodology and gene transfection technique to regulate the expression of apelin in Wharton's jelly-derived mesenchymal stem cells and induced cells with a effective cardiac differentiation protocol including 5-azacytidine and bFGF. Four weeks after induction, induced cells assumed a stick-like morphology and myotube-like structures except apelin-silenced cells and the control group. The silencing expression of apelin in Wharton's jelly-derived mesenchymal stem cells decreased the expression of several critical cardiac progenitor transcription factors (Mesp1, Mef2c, NKX2.5) and cardiac phenotypes (cardiac α-actin, ß-MHC, cTnT, and connexin-43). Meanwhile, endogenous compensation of apelin contributed to differentiating into cells with characteristics of cardiomyocytes in vitro. Further experiment showed that exogenous apelin peptide rescued the cardiomyogenic differentiation of apelin-silenced mesenchymal stem cells in the early stage (1-4 days) of induction. Remarkably, our experiment indicated that apelin up-regulated cardiac specific genes in Wharton's jelly-derived mesenchymal stem cells via activating extracellular signal-regulated kinase (ERK) 1/2 and 5.

Common expression of stemness molecular markers and early cardiac transcription factors in human Wharton's jelly-derived mesenchymal stem cells and embryonic stem cells.

At present, there are still significant barriers that impede the clinical use of hESCs and iPS cells, including ethics, immunorejection, tumorigenesis from hESCs, and teratoma formation from iPS cells. It is therefore necessary to search for alternative sources of stem cells. WJ-MSCs originate from embryonic epiblasts and possess properties intermediate between hESCs and adult stem cells. However, the stemness properties of molecules in WJ-MSCs remain unclear compared to those of hESCs. In the present study, we isolated WJ-MSCs by a nonenzymatic method. Further, using microarray analysis by Affymetrix GeneChip and functional network analyses, we determined the degree of expression of stemness genes exhibited by the Human Stem Cell Pluripotency array. We also defined a wide range of stem cell gene expression in the WJ-MSCs in comparison with hESCs. At the same time, the definitive markers of early cardiac precursor cells and more committed progenitors were further characterized in WJ-MSCs. Our results demonstrated for the first time that WJ-MSCs had significant expression of undifferentiated human embryonic stem cell core markers, such as SOX2, NANOG, LIN28, SSEA1, SSEA3, SSEA4, KLF4, c-MYC, CRIPTO, and REX1, with a relatively lower level of expression than in hESCs. We also found WJ-MSCs have high expression of early cardiac transcription factors, such as Flk-1, Isl-1, and Nkx2.5. Functional analysis revealed signature genes of WJ-MSCs with specific roles involved in immune, cytoskeletal, and chemokine regulation, cell adhesion, and cell signaling. Our study indicated that there is a significant overlap between the stemness genes expressed by hESCs and WJ-MSCs. WJ-MSCs harbor a true stem cell population and are promising cells for stem cell-based therapies.

[Impact analysis of atmospheric state for target detection in hyperspectral radiance image].

Target detection based on hyperspectral radiance images can improve data processing efficiency to meet the requirements of real-time processing. However, the spectral radiance acquired by the remote sensor will be affected by the atmosphere. In the present paper, hyperspectral imaging process is simulated to analyze the effects of the changes in atmospheric state on target detection in hyperspectral radiance image. The results show that hyperspectral radiance image can be directly used for target detection, different atmospheric states have little impacts on the RXD detection, whereas the MF detection is dependent on the accuracy of the input spectrum, and good results can only be obtained by the MF detector when the atmospheric states are similar between the radiance spectrum of the target to be detected and the simulated hyperspectral image.

[A method of endmember extraction in hyperspectral remote sensing images based on discrete particle swarm optimization (D-PSO)].

For the inaccuracy of endmember extraction caused by abnormal noises of data during the mixed pixel decomposition process, particle swarm optimization (PSO), a swarm intelligence algorithm was introduced and improved in the present paper. By re-defining the position and velocity representation and data updating strategies, the algorithm of discrete particle swarm optimization (D-PSO) was proposed, which made it possible to search resolutions in discrete space and ultimately resolve combinatorial optimization problems. In addition, by defining objective functions and feasible solution spaces, endmember extraction was converted to combinatorial optimization problem, which can be resolved by D-PSO. After giving the detailed flow of applying D-PSO to endmember extraction and experiments based on simulative data and real data, it has been verified the algorithm's flexibility to handle data with abnormal noise and the reliability of endmember extraction were verified. Furthermore, the influence of different parameters on the algorithm's performances was analyzed thoroughly.

[Independent component analysis for spectral unmixing in hyperspectral remote sensing image].

Hyperspectral remote sensing plays an important role in earth observation on land, ocean and atmosphere. A key issue in hyperspectral data exploitation is to extract the spectra of the constituent materials (endmembers) as well as their proportions (fractional abundances) from each measured spectrum of mixed pixel in hyperspectral remote sensing image, called spectral un-mixing. Linear spectral mixture model (LSMM) provides an effective analytical model for spectral unmixing, which assumes that there is a linear relationship among the fractional abundances of the substances within a mixed pixel. To be physically meaningful, LSMM is subject to two constraints: the first constraint requires all abundances to be nonnegative and the second one requires all abundances to be summed to one. Independent component analysis (ICA) has been proposed as an advanced tool to un-mix hyperspectral image. However, ICA is based on the assumption of mutually independent sources, which violates the constraint conditions in LSMM. This embarrassment compromises ICA applicability to hyperspectral data. To overcome this problem, the present paper introduces a solution of minimization of total correlation of the components. Interestingly, with the minimization of total correlation of the components, the angle of the direction between each components is invariable. A Parallel oblique-ICA (Pob-ICA) algorithm is proposed to correct the angle of the searching direction between the components. Two novelties result from our proposed Pob-ICA algorithm. First, the algorithm completely satisfies the physical constraint conditions in LSMM and overcomes the limitation of statistical independency assumed by ICA. Second, the last component, which is missed in other existing ICA algorithms, can be estimated by our proposed algorithm. In experiments, Pob-ICA algorithm demonstrates excellent performance in the simulative and real hyperspectral images.

The apelin-APJ pathway exists in cardiomyogenic cells derived from mesenchymal stem cells in vitro and in vivo.

Our previous study demonstrated that apelin level increased significantly after the treatment of intracoronary implantation of bone marrow mononuclear cells (BMMCs), followed by the improvement of cardiac function in patients with severe ischemic heart failure. The present studies both in vivo and in vitro explored whether mesenchymal stem cells derived from bone marrow (BMSCs) activate the apelin-APJ pathway when differentiating into cardiomyogenic cells. Isolated BMSCs from rat femurs and tibias were cultured and expanded for three passages, labeled with DAPI, and treated with 5-azacytidine (5-AZ). BMSCs labeled with ad-EGFP were injected intramyocardially into the peri-infarct area of rat models with acute myocardial infarction. Immunofluorescence staining exposed that CMGs expressed apelin together with myogenic-specific proteins such as α-actin, troponin T, GATA-4, and connexin-43 at 7 days after 5-AZ treatment or EGFP-BMSC injection. RT-PCR revealed that mRNA in CMGs started to express apelin and APJ from day 7 and progressively increased until day 28. Cardiac function, as measured by echocardiography in vivo, was significantly improved in parallel with the extent of apelin expression after BMSC transplantation. Our finding indicated that the expression of the apelin-APJ pathway during differentiation of BMSCs into CMGs may be an important mechanism in regulation of myocardial regeneration and functional recovery after BMSC transplantation.

Increased apelin following bone marrow mononuclear cell transplantation contributes to the improvement of cardiac function in patients with severe heart failure.

We previously reported that intracoronary implantation of bone marrow mononuclear cells (BMMC) into ischemic hearts improved cardiac function after myocardial infarction. However, the mechanisms have not been elucidated. The present study investigates whether apelin, a newly described inotropic peptide with important cardiovascular regulatory properties, contributes to the functional improvement in patients with severe heart failure after cell transplantation. Forty consecutive patients with severe heart failure secondary to myocardial infarction were assigned to the BMMC therapy group or the standard medication group according to each patient's decision on a signed consent document. In 20 patients intracoronary cell infusion was performed, and another 20 patients were matched to receive standard medication as therapeutic controls. An additional 20 healthy subjects were designated as normal controls. Clinical manifestations, echocardiograms, and biochemical assays were recorded. Plasma apelin and brain natriuretic protein (BNP) levels were determined by enzyme immunoassay. Baseline levels of plasma apelin were significantly lower in all heart failure patients compared to normal subjects. In patients who underwent cell transplantation, apelin increased significantly from 3 to 21 days after operation, followed by significant improvement in cardiac function. In parallel, BNP varied inversely with the increase of apelin. In patients receiving standard medical treatment, apelin remained at a lower level. Our findings indicated that increased apelin levels following cell therapy may act as a paracrine mediator produced from BMMCs and play an important role in the treatment of heart failure through autocrine and paracrine mechanisms.

[Transfection of bone marrow mesenchymal stem cells by adeno-associated virus 2/1 vector].

This study was aimed to investigate the transfection efficacy of recombinant adeno-associated virus 2/1 (rAAV2/1) on bone marrow mesenchymal stem cells (BMMSCs) at different multiplicities of infection (MOI) and time, and effect of transfection on growth of rat BMMSCs. The rat BMMSCs cultured in vitro were transfected by using rAAV2/1 with enhanced green fluorescent protein (rAAV2/1-EGFP) at MOI of 1 x 10(4), 1 x 10(5) and 1 x 10(6); the EGFP expression was observed by fluorescent microscopy at 3, 7 and 14 days. The viability, proliferation multiple, differentiation ability of daughter cells were detected for evaluating the effect of rAAV2/1 on survival, proliferation and differentiation of BMMSCs and the fluorescence index (FI) were determined by flow cytometry. The results indicated that after transfection with rAAV2/1 for 24 hours the green fluorescence in BMMSCs were observed, but also the fluorescence gradually was enhanced along with prolonging of time, and reached to steady level after 7 days; the viability, proliferation multiple, differentiation ability of BMMSCs transfected by rAAV2/1-EGFP at different MOI showed no significant changes at 3,7 and 14 days (p > 0.05), meanwhile at same MOI the proliferation multiple obviously increased in comparison between 7 day vs 3 day and 14 days vs 7 days (p < 0.01). The flow cytometric detection showed that the transfection efficacy of rAAV2/1-EGFP on BMMSCs and FI increased significantly as the multiplicity of infection and culture time increased (p < 0.05). It is concluded that rAAV2/1-EGFP is able to transfect into BMMSCs effectively, but the transfection efficiency and fluorescence index increase significantly along with increase of multiplicity of infection and culture time. rAAV2/1-EGFP do not affect viability, proliferation multiple and differentiation ability of BMMSCs. rAAV2/1 is a kind of active vector for gene transfer to reform BMMSCs.

[Autologous mononuclear bone marrow cell transplantation by intracoronary route for patients with ischemic heart disease: observation of 2-years follow-up].

OBJECTIVE: To investigate the long-term effect and safety of intracoronary autologous bone marrow mononuclear cell (BMMC) transplantation in patients with ischemic heart disease (IHD). METHODS: Seventy-six patients with IHD, 26 patients with acute myocardial infarction (AMI) and 26 patients with chronic ischemic heart failure (CIHF), underwent routine treatment plus intracoronary autologous BMMC transplantation, and 24 patients, including 10 patients with AMI and 14 patients with CIHF underwent routine treatment as controls. Autologous BMMC transplantation was performed via a balloon catheter placed into the infarct-related artery during balloon dilatation by high pressure infusion to occlude the artery, which was performed 6 - 8 times for 2 minutes each with 2-minute interval or via a balloon catheter without occluding the infarct-related artery. Follow-up was conducted for 2 years. RESULTS: The surgery was safety without major periprocedural complications. There were no other new arrhythmias found by Holter recorder during the 2-years follow-up. In the AMI patients receiving BNNC transplantation, the left ventricular ejection fraction (LVEF) 1 and 2 years later increased by 5.79% (P < 0.05), 3.79% (P > 0.05) respectively; but there was no change in left ventricular end diastolic volume (LVEDV) and left ventricular end systolic volume (LVESV). The LVEF 1 and 2 years later of the control group increased by 8.8% and 9.2% respectively (both P < 0.01) and the LVESV 1 and 2 years later decreased by 20.4% and 27.8% respectively (both P < 0.05), the myocardium defect area 2 years later was not significantly different from that 3 months later. The heart function of the control group became markedly worse. CONCLUSION: Autologous BMMC intracoronary transplantation is safe and effective, especially in patients with CIHF.

[The autologous bone marrow mononuclear cell transplantation by intracoronary route treat patients with severe heart failure after myocardial infarction].

OBJECTIVE: To investigate the chronic effects of intracoronary autologous bone marrow mononuclear cell (BM-MNCs) transplantation in patients with refractory heart failure (RIHF) after myocardial infarction. METHODS: Thirty patients with RIHF (LVEF < 40%) were enrolled in this nonrandomized study, autologous BM-MNCs (5.0 +/- 0.7) x 10(7) were transplanted with via infarct-related coronary artery in 16 patients and 14 patients received standard medical therapy served as control. Baseline and follow up evaluations included complete clinical evaluations, plasma BNP, ANP, ET-1 measurements, echocardiography, PET, and Holter monitoring. RESULTS: Baseline characteristics were similar between the 2 groups. There were no major periprocedural complications. One patient developed ventricular premature contractions during cell infusion for several seconds and recovered spontaneously. Compared to pre-transplantation, plasma BNP and ET-1 significantly decreased and plasma ANP significantly increased at 7 days post transplantation; 6 minutes walking distance increased from (72.1 +/- 31.5) to (201.6 +/- 23.3) m (P < 0.01), LVEF increased 9.9% (P < 0.001) and FDG-PET revealed vital myocardium area increased (10.3 +/- 3.4)% (P < 0.01) at 3 months after BM-MNCs transplantation. At 6 months follow up, the NYHA class improved from (3.4 +/- 0.1 to 2.4 +/- 0.2, P < 0.001) and no patient died and 1 patient rehospitalized due to lower extremities edema. In control group, LVEF decreased 7.2% compared to baseline (P < 0.001) and was significantly lower than transplantation group at 3 months (P < 0.001). At 6 months follow up, the NYHA class increased from (3.5 +/- 0.1 to 3.9 +/- 0.1, P < 0.05), 2 patients died and 10 patients rehospitalized due to aggravated heart failure. CONCLUSION: Present study demonstrates that intracoronary transplantation of autologous BM-MNCs is safe and effective for treating patients with RIHF after myocardial infarction.

Effect of intracoronary transplantation of autologous bone marrow-derived mononuclear cells on outcomes of patients with refractory chronic heart failure secondary to ischemic cardiomyopathy.

Recent studies have indicated that stem cell implantation increases cardiac function by repairing damaged myocardium. We investigated whether intracoronary transplantation of autologous bone marrow-derived mononuclear cells (BMMCs) confers beneficial effects in patients with refractory chronic heart failure. Twenty-eight patients received standard heart failure medication and BMMC transplantation (BMMC treatment) or standard medication only (controls). BMMCs were harvested from each patient. Clinical manifestations, biochemical assays, rhythm studies, echocardiograms, and positron emission tomograms were recorded. Fourteen patients with cell grafting had symptomatic relief of heart failure within 3 days. Left ventricular ejection fraction increased by 9.2% and 10.5% at 1 week and 3 months after the procedure, respectively, versus baseline (p < 0.01 for the 2 comparisons). Left ventricular end-systolic volume decreased by 30.7% after 3 months (p < 0.01). Brain natriuretic peptide levels at days 3 and 7 after cell infusion significantly decreased by 69.2% and 70.4%, respectively, whereas atrial natriuretic peptide levels increased by 30.1% at day 7. Positron emission tomographic analysis showed a significant increase in cell viability of 10.3% in the infarcted zone. No patient died in the BMMC-treated group at 6-month follow-up. In contrast, heart failure did not improve in any control patient. Left ventricular ejection fraction decreased by 7.2% after 3 months. Two control patients died from heart failure within 6 months. In conclusion, this is the first demonstration in humans that intracoronary BMMC transplantation is a feasible and safe therapeutic strategy to decrease symptoms, increase cardiac function, and possibly prolong life in patients with end-stage heart failure refractory to standard medical therapy.

[Transplantation of fetal cardiomyocyte regenerates infarcted myocardium in rats].

OBJECTIVE: To investigate the feasibility and efficiency of fetal cardiomyocyte transplantation into the rat model of myocardial infarction. METHODS: Cardiomyocytes were isolated from aborted human embryos aged 12 - 16 weeks and cultured for 5 days to confirm their viability. Rat model of extensive myocardial infarction (MI) was established in 18 male Wistar rats by ligating the descending anterior branch of left coronary artery and the 18 rats were randomly divided into 2 groups: transplantation group (n = 7, 2 x 10(6) fetal cardiomyocytes were transplanted into the myocardial scar) and culture medium injection group (n = 6, culture medium was injected into the myocardial scar) 5 days after extensive MI was caused. Another 6 rats undergoing sham operation were used as controls. Echocardiography was performed before and 60 +/- 3 days after the implantation to assess the left ventricular (LV) remodeling and cardiac function. Then the rats were killed and their heart were harvested to undergo HE staining, immunohistochemical examination with antibody against human alpha-actin smooth muscle (SMA) isoform, and light microscopy. RESULTS: Light microscopy revealed the presence of engrafted human fetal cardiomyocytes in the infarcted myocardium and the presence of nascent intercalated disks connecting the engrafted fetal cardiomyocytes and the host myocardium. The engrafted fetal cardiomyocytes were SMA positive. Serial echocardiography revealed that cell transplantation prevented scar thinning, LV further dilatation and dysfunction while the control animals developed scar thinning, significant LV dilatation accompanied by progressive deterioration in LV contractility. CONCLUSION: Fetal cardiomyocytes can be implanted and survive in the infarcted myocardial cells, thus preventing the scar thinning, and LV further dilatation and dysfunction.

Effect of ghrelin on septic shock in rats.

AIM: To study the role of ghrelin in the late stage of septic shock in rats. METHODS: The rat model of septic shock was made by caecal ligation and perforation. At the time of operation ghrelin 10 nmol/kg was infused through femoral vein followed by a sc injection at 8 h after operation. Hemodynamic parameters including heart rate (HR), mean arterial blood pressure (MABP), LVdp/dtmax, and left ventricular end-diastolic pressure (LVEDP) in survival rats were measured at 18 h after surgery. Plasma glucose and lactate concentrations, plasma ghrelin level and myocardial ATP content were assayed. The mortality rate in rats with septic shock was also observed. RESULTS: Compared to that of septic shock group, MABP of rats in ghrelin-treated group increased by 33 % (P <0.01). The values of +LVdp/dtmax and -LVdp/dtmax increased by 27 % and 33 %, respectively (P <0.01), but LVEDP decreased by 33 % (P < 0.01). The plasma glucose concentration and myocardial ATP content increased by 53 % and 22 %, respectively, but plasma lactate concentration decreased by 40 % in ghrelin-treated rats (P < 0.01). The plasma ghrelin level in rats with septic shock was 51 % higher than that of rats in sham group, and was negatively correlated with MABP and blood glucose concentration (r=-0.721 and -0.811, respectively, P <0.01). The mortality rates were 47 % (9/19) in rats with septic shock and 25 % (3/12) in rats of ghrelin-treated group, respectively. CONCLUSION: Treatment with ghrelin could correct partly the abnormalities of hemodynamics and metabolic disturbance in septic shock of rats.