Relationship of circulating endothelial progenitor cells to the recurrence of atrial fibrillation after successful conversion and maintenance of sinus rhythm

Metformin Inhibits the Expression of Biomarkers of Fibrosis of EPCs In Vitro

Endothelial progenitor cells (EPCs) are a group of circulating cells with important functions in vascular repair and treatment of cardiovascular diseases. However, in patients with atrial fibrillation (AF), the number and function of EPCs reportedly are decreased. TGF-β is highly expressed in AF patients. In this study, we examined the effect of TGF-β1 on EPCs and the therapeutic outcome of metformin treatment on TGF-β1-induced EPCs. EPCs were induced with TGF-β1 at different concentrations (5 ng/ml, 10 ng/ml, and 20 ng/ml) for 48 h followed by western blot, qPCR, and immunofluorescence analyses to investigate changes in the levels of the fibrosis-related proteins, α-SMA, Col I, Col III, CTGF, and MMP-1. Live-dead cell staining was used to evaluate cell apoptosis. Compared with the control, TGF-β1 treatment significantly (p < 0.05) enhanced the levels of α-SMA, Col I, Col III, CTGF, and MMP-1 in a dose-dependent manner. The most effective concentration of TGF-β1 (20 ng/ml) was then used to induce fibrosis biomarker expression in EPCs, followed by treatment with metformin at different concentrations (0.5, 1, and 2 mmol/l). Metformin treatment suppressed TGF-β-induced expression of all above factors, with the effect at 2 mmol/l being significant (p < 0.05). Live-dead cell staining showed no difference among the control, TGF-β1-treated, and metformin-treated groups. In conclusion, our study showed that TGF-β1 induces the expression of fibrosis biomarkers in EPCs, which is attenuated by treatment with metformin. Thus, metformin may have therapeutic potential for improving EPC function in cardiovascular diseases.

Biological therapies targeting arrhythmias: are cells and genes the answer?

INTRODUCTION

Arrhythmias can cause symptoms ranging from simple dizziness to life-threatening circulatory collapse. Current management includes medical therapy and procedures such as catheter ablation or device implantation. However, these strategies still pose a risk of serious side effects, and some patients remain symptomatic. Advancement in our understanding of how arrhythmias develop on the cellular level has made more targeted approaches possible. In addition, contemporary studies have found that several genes are involved in the pathogenesis of arrhythmias.

AREAS COVERED

In the present review, the authors explore the cellular and genetic mechanisms leading to arrhythmias as well as the progress that has been made in using both gene and cell therapy to treat tachy- and bradyarrhythmias. They also consider why gene and cell therapy has resulted into a few clinical trials with promising results, however still not applicable in routine clinical practice.

EXPERT OPINION

The question currently is whether such biological therapies could replace current established approaches. The contemporary evidence suggests that despite recent advances in this field, it will need more work in experimental models before this is applied into clinical practice. Gene and cell studies targeting conduction and repolarization are promising, but still not ready for use in the clinical setting.

Fluvastatin therapy could not decrease progression of paroxysmal atrial fibrillation in non-valvular disease patients

OBJECTIVE

This study aimed to evaluate whether fluvastatin therapy could decrease the probability of atrial fibrillation (AF) progression from paroxysmal AF to permanent AF and decrease the recurrence frequency of AF.

METHODS

Analyses were performed using two-tailed Student's t test or Mann-Whitney U tests. Categorical variables were compared with the χ2 statistics or Fisher's exact test. Patients with paroxysmal AF were randomized case-control, prospective into either the fluvastatin group (n=61) or control group (n=57). Patients were followed up for 24 months. The primary endpoint event was paroxysmal AF that progressed to permanent AF. Secondary endpoints were AF recurrence, cardiac dysfunction, stroke, or death.

RESULTS

There were no differences in AF progression (fluvastatin group, 8.19% vs. control group, 12.51%; p>0.05) and stroke (fluvastatin group. 6.55% vs.

CONTROL GROUP

8.77%; p>0.05). Patients in the fluvastatin group had a lower rate of AF recurrence (fluvastatin group, 24.59% vs. control group, 49.12%; p<0.05) and a lower rate of cardiac dysfunction (fluvastatin group, 6.55% vs. control group, 19.29%; p<0.05). Death did not occur in both the groups. After 1 week of fluvastatin therapy, C-reactive protein (CRP) and homocysteine (HCY) levels were lower in the fluvastatin group than in the control group. At 24 months of follow-up, CRP and HCY levels remained lower in the fluvastatin group than in the control group. The number of endothelial progenitor cells (EPCs) increased in the fluvastatin group compared with that in the control group (fluvastatin group, 72.27±12.49 counts/105 vs. control group, 57.45±8.24 counts/105, p=0.001).

CONCLUSION

Fluvastatin therapy could not decrease AF progression. However, it could decrease the recurrence frequency of paroxysmal AF and cardiac dysfunction. This may occur because of depressing inflammation and improving circulating EPCs.

Permanent atrial fibrillation impairs the function of circulating endothelial progenitor cells

OBJECTIVE

to determine whether functions of endothelial progenitor cells (EPCs) were impaired in patients with permanent atrial fibrillation (AF).

METHODS

35 patients with permanent AF (AF group) and 35 age and sex matched controls (control group) were collected. The numbers of circulating CD34⁺/KDR⁺ cells were determined with flow cytometry in the two groups. Cell proliferation, tube formation, nitric oxygen (NO) and vascular endothelial growth factor (VEGF) were assayed.

RESULTS

the numbers of CD34⁺/KDR⁺ cells were lower in the AF group than the control group (20.01 ± 12.66 /10⁵ vs 77.93 ± 58.93 /10⁵，p = 0.022). Colony formation unit (CFU) of EPCs were decreased in AF group compared to the control group（1.76 ± 0.59 CFU vs 3.45 ± 0.82 CFU, p = 0.0000). The AF group had lower cell proliferation ability than control group（0.401 ± 0.113 A vs 0.558 ± 0.130 A, p = 0.004). Tube formation ability was decreased in AF patients compared to controls（434.30 ± 96.22μm/mm² vs 568.09 ± 196.17μm/mm²，p = 0.041). AF patients had lower VEGF secretion than controls (27.35 ± 9.93 ng/L vs 41.86 ± 7.31 ng/L，p = 0.001），they also had lower NO secretion than controls（16.55 ± 6.92μmol/l vs 23.65 ± 5.48，p = 0.012).

CONCLUSIONS

proliferation, tube formation and paracrine of EPCs were reduced in patients with permanent AF.

Atrial fibrillation is associated with hematopoietic tissue activation and arterial inflammation

Inflammation is associated with the development of atrial fibrillation (AF). Activity in hematopoietic tissues, which produce inflammatory leukocytes, is closely related to systemic inflammation, arterial inflammation and cardiovascular events, but its relationship to AF is unknown. Using 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging, we examined the relationships between AF, splenic metabolic activity and vascular inflammation. We conducted a cross sectional study of 70 participants: 35 with AF, who were matched (by age, sex and history of active cancer) to 35 controls without AF. Splenic metabolic activity and vascular aortic inflammation were measured by the mean FDG maximum standard uptake values (SUV Max) by PET. We examined (1) the association between AF and splenic activity, and (2) AF and aortic inflammation. The mean age of the population was 68.13 (standard deviation (SD) 8.98) years and 46 (65 %) participants were male. Splenic activity was higher in AF participants [2.31 (SD 0.45) vs. 2.07 (SD 0.37), p = 0.024], and remained significant after adjusting for demographic and clinical covariates. Aortic inflammation was also higher in AF participants [2.22 (SD 0.44) vs. 1.91 (SD 0.44), p = 0.004], and remained significant on multivariable analysis. Aortic inflammation and splenic activity were highly correlated (Pearson R = 0.61, p < 0.001). Atrial fibrillation is associated with higher hematopoietic tissue activation and arterial inflammation. Further studies are needed to clarify the mechanisms by which this cardio-splenic axis is implicated in AF.

Atrial fibrillation following autologous stem cell transplantation in patients with multiple myeloma: incidence and risk factors

Objectives:

Atrial fibrillation (AF) often develops in patients with multiple myeloma following autologous stem cell transplantation (ASCT), but the exact incidence of, and the risk factors for AF have not been described. In this study, we sought to determine the incidence of AF in patients with multiple myeloma undergoing ASCT.

Methods:

Patients who received ASCT for multiple myeloma between January 2000 and December 2009 were identified using the ICD-9 codes for multiple myeloma and ASCT, and formed the basis of this report.

Results:

The study included 278 patients (mean age, 63 ± 9.5 years). A total of 75 (27%) patients developed AF at a mean duration of 14.8 days following ASCT. On multiple regression analysis, baseline renal dysfunction (odds ratio 15.2 [confidence interval 5.08–45.6]), left ventricular systolic dysfunction (9.55 [2.78–32.79]), dilated left atrium on echocardiogram (4.97 [1.8–13.78]), and hypertension (3.6 [1.36–9.52]) were significantly associated with the development of AF after ASCT. The presence of light-chain secretion (0.21 [0.07–0.6]) was associated with a lower incidence of AF. Age, gender, and race were not significantly associated with the development of AF after ASCT.

Conclusions:

AF is very frequent in patients with multiple myeloma when they receive ASCT. The presence of abnormal renal function, left ventricular systolic dysfunction, dilated left atrium, or hypertension at baseline identifies patients at high risk of developing AF following ASCT.