Targeting endoglin, an auxiliary transforming growth factor β coreceptor, to prevent fibrosis and heart failure

Mechanism of miR-30b-5p-Loaded PEG-PLGA Nanoparticles for Targeted Treatment of Heart Failure

Objective: Exploring the effectiveness of miR-30b-5p-loaded PEG-PLGA nanoparticles (NPs) for the treatment of heart failure and the underlying mechanism.

Methods: PEG-PLGA characteristics with different loading amounts were first examined to determine the loading, encapsulation, and release of miR-30b-5p from NPs. The effects of miR-30b-5p NPs on cardiac function and structure were assessed by immunofluorescence, echocardiography, HE/Masson staining, and TUNEL staining. The effects of NPs on the expression of factors related to cardiac hypertrophy and inflammation were examined by RT-PCR and western blotting, and the mechanism of miR-30b-5p treatment on heart failure was explored by dual luciferase reporter assay and RT-PCR.

Results: The size of PEG-PLGA NPs with different loading amounts ranged from 200 to 300 nm, and the zeta potential of PEG-PLGA NPs was negative. The mean entrapment efficiency of the NPs for miR-30b-5p was high (81.8 ± 2.1%), and the release rate reached 5 days with more than 90% release. Distribution experiments showed that NPs were mainly distributed in the heart and had a protective effect on myocardial injury and cardiac function. Compared with a rat model of cardiac failure and miR-30b-5p-non-loaede NP groups, the expression of cardiac hypertrophy markers (ANP, BNPβ-MHC) and inflammatory factors (IL-1β, IL-6) were significantly decreased. Dual luciferase reporter assay assays indicated that miR-30b-5p exerted its effects mainly by targeting TGFBR2.

Conclusion: PEG-PLGA NPs loaded with miR-30b-5p improved cardiac function, attenuated myocardial injury, and regulated the expression of factors associated with cardiac hypertrophy and inflammation by targeting TGFBR2.

Circulating Connective Tissue Growth Factor Is Associated with Diastolic Dysfunction in Patients with Diastolic Heart Failure

Background: Connective tissue growth factor (CTGF) and transforming growth factor β1 (TGF-β1) are emerging biomarkers for tissue fibrosis. The aim of this study was to investigate the association between circulating CTGF, TGF-β1 levels and cardiac diastolic dysfunction in patients with diastolic heart failure (DHF). Methods: Admitted subjects were screened for heart failure and those with left ventricular (LV) ejection fraction <45% were excluded. Diastolic dysfunction was defined as functional abnormalities that exist during LV relaxation and filling by echocardiographic criteria. Totally 114 patients with DHF and 72 controls were enrolled. Plasma levels of CTGF, TGF-β1, and B-type natriuretic peptide (BNP) were determined. Results: The plasma CTGF and TGF-β1 levels increased significantly in patients with DHF. Circulating CTGF and TGF-β1 levels were correlated with echocardiographic parameter E/e’ and diastolic dysfunction grading in DHF patients. In multivariate logistic analysis, CTGF was significantly associated with diastolic dysfunction (odds ratio: 1.027, p < 0.001). Plasma CTGF (AUC: 0.770 ± 0.036, p < 0.001) and CTGF/BNP (AUC: 0.839 ± 0.036, p < 0.001) showed good predictive power to the diagnosis of DHF. Conclusions: This finding suggested CTGF could be involved in the pathophysiology of diastolic heart failure and CTGF/BNP might have auxiliary diagnostic value on diastolic heart failure.

MicroRNA-208a Increases Myocardial Endoglin Expression and Myocardial Fibrosis in Acute Myocardial Infarction

BACKGROUND

MicroRNAs (miRs) play a role in cardiac remodelling, and acute myocardial infarction (AMI) can regulate miR expression. MiR-208a is essential for the expression of the genes involved in cardiac hypertrophy and fibrosis. MiR-208a activates endoglin expression and may result in cardiac fibrosis. The role of miR-208a and endoglin in AMI is not known. We sought to investigate the regulation of miR-208a and endoglin in AMI.

METHODS

Ligation of the proximal left anterior descending artery was performed in adult Sprague-Dawley rats to induce AMI. Echocardiography was used to measure heart size and left ventricular function. The TaqMan miR real-time quantitative assay was used to quantitate miR-208a. Myocardial fibrosis was detected by Masson trichrome staining.

RESULTS

AMI and overexpression of miR-208a in the sham group without infarction significantly increased myocardial miR-208a, endoglin, and β-myosin heavy chain (β-MHC) expression. Overexpression of antagomir-208a significantly inhibited the increase of myocardial endoglin and β-MHC protein expression induced by infarction. Overexpression of mutant miR-208a in the sham group did not induce myocardial endoglin and β-MHC expression. Pretreatment with atorvastatin and the angiotensin-receptor antagonist valsartan significantly attenuated the increase of endoglin and β-MHC induced by infarction. AMI and overexpression of miR-208a in the sham group significantly increased the area of myocardial fibrosis compared with the sham group. Overexpression of antagomir-208a and pretreatment with atorvastatin and valsartan in the AMI group significantly decreased the area of myocardial fibrosis induced by infarction.

CONCLUSIONS

MiR-208a increases endoglin expression to induce myocardial fibrosis in rats with AMI. Treatment with atorvastatin and valsartan can decrease myocardial fibrosis induced by AMI through attenuating miR-208a and endoglin expression.

MicroRNA-208a increases myocardial fibrosis via endoglin in volume overloading heart

MicroRNA-208a (mir-208a) is essential for cardiac hypertrophy and fibrosis. Endoglin, a co-receptor of transforming growth factor-β is also essential for cardiac fibrosis. Endoglin has been shown to be a target of mir-208a in the in vitro mechanical stress model. Volume overload can lead to heart failure and cardiac fibrosis. The role of mir-208a and endoglin in volume overload heart failure is well known. We sought to investigate the mechanism of regulation of mir-208a and endoglin in volume overload-induced heart failure. Aorta-caval (AV) shunt was performed in adult Sprague-Dawley rats to induce volume overload. Heart weight and heart weight/body weight ratio significantly increased in AV shunt animals. AV shunt significantly increased left ventricular end-diastolic dimension as compared to sham group. Mir-208a was significantly induced by AV shunt from 3 to 14 days. Endoglin, myosin heavy chain-β and brain natriuretic peptide were significantly induced by AV shunt from 3 to 14 days. Overexpression of mir-208a in the sham group without AV shunt significantly increased endoglin expression similar to the AV shunt group. Antagomir-208a attenuated the endoglin expression induced by AV shunt. Pretreatment with atorvastatin also attenuated the endoglin expression induced by AV shunt. AV shunt significantly increased myocardial fibrosis as compared to sham group. Overexpression of mir-208a in the sham group significantly increased myocardial fibrosis. Antagomir-208a and atorvastatin significantly attenuated the myocardial fibrosis induced by AV shunt. In conclusion, mir-208a increased endoglin expression to induce myocardial fibrosis in volume overloaded heart failure. Treatment with atorvastatin can attenuate the myocardial fibrosis induced by volume overload through inhibition of endoglin expression.

Connective tissue growth factor and cardiac diastolic dysfunction: human data from the Taiwan diastolic heart failure registry and molecular basis by cellular and animal models

AIMS

Connective tissue growth factor (CTGF) is an emerging marker for tissue fibrosis. We investigated the association between CTGF and cardiac diastolic function using cellular and animal models and clinical human data.

METHODS AND RESULTS

A total of 125 patients with a diagnosis of diastolic heart failure (DHF) were recruited from 1283 patients of the Taiwan Diastolic Heart Failure Registry. The severity of DHF was determined by tissue Doppler imaging (E/e'). Cardiac magnetic resonance imaging (CMRI) was used to evaluate myocardial fibrosis in some of the patients (n = 25). Stretch of cardiomyocytes on a flexible membrane base serves as a cellular phenotype of cardiac diastolic dysfunction (DD). A canine model of DD was induced by aortic banding. A significant correlation was found between plasma CTGF and E/e' in DHF patients. The severity of cardiac fibrosis evaluated by CMRI also correlated with CTGF. In the cell model, stretch increased secretion of CTGF from cardiomyocytes. In the canine model, myocardial tissue CTGF expression and fibrosis significantly increased after 2 weeks of aortic banding. Notably, the expression of CTGF paralleled the severity of LV DD (r = 0.40, P < 0.001 for E/e') and haemodynamic changes (r = 0.80, P < 0.001). After adjusting for confounding factors, CTGF levels still correlated with diastolic parameters in both human and canine models (human plasma CTGF, P < 0.001; canine tissue CTGF, P = 0.04).

CONCLUSION

Plasma CTGF level correlated with the severity of DD and tissue fibrosis in DHF patients. The mechanism may be through myocardial stretch. Our study indicated that CTGF may serve as an early marker for DHF.

Oxidative stress, fibrosis, and early afterdepolarization-mediated cardiac arrhythmias

Animal and clinical studies have demonstrated that oxidative stress, a common pathophysiological factor in cardiac disease, reduces repolarization reserve by enhancing the L-type calcium current, the late Na, and the Na-Ca exchanger, promoting early afterdepolarizations (EADs) that can initiate ventricular tachycardia and ventricular fibrillation (VT/VF) in structurally remodeled hearts. Increased ventricular fibrosis plays a key facilitatory role in allowing oxidative-stress induced EADs to manifest as triggered activity and VT/VF, since normal non-fibrotic hearts are resistant to arrhythmias when challenged with similar or higher levels of oxidative stress. The findings imply that antifibrotic therapy, in addition to therapies designed to suppress EAD formation at the cellular level, may be synergistic in reducing the risk of sudden cardiac death.

Quantification of active and total transforming growth factor-β levels in serum and solid organ tissues by bioassay

BACKGROUND

Transforming growth factor-β (TGF-β) is a multi-factorial peptide growth factor that has a vital role in the regulation of cell growth, differentiation, inflammation, and tissue repair. Quantification of biologically active TGF-β levels in tissues is crucial to illustrate mechanisms involved in various physiological and pathological processes, but direct measurement of bioactive TGF-β level in the tissue has been hampered by lack of reliable methods. Here, we introduced mink lung epithelial cell bioassay to quantify both active and total TGF-β levels in serum and protein lysates from solid organs in the mouse model.

FINDINGS

Mink lung epithelial cells were stably transfected with plasminogen activator inhibitor-1 promoter/luciferase construct, in which bioactive TGF-β level was represented by luciferase activity. Serum total TGF-β levels were comparable between the bioassay and enzyme-linked immunosorbent assay (ELISA), but active TGF-β levels measured by ELISA were significantly lower than those obtained by the bioassay. Active and total TGF-β levels in the solid organs including heart, liver, and kidney were also measured. Total TGF-β levels were relatively comparable among these organs, but active TGF-β levels were slightly higher in hearts and kidneys than in livers. Positive luciferase activities in the bioassay were almost completely inhibited by adding pan-TGF-β neutralizing antibodies, suggesting its high specificity to bioactive TGF-β. We also measured myocardial TGF-β levels after myocardial infarction and sham control by the bioassay, and compared the values with those obtained by ELISA. The bioassay demonstrated that both active and total tissue TGF-β levels were significantly higher in post-myocardial infarction than in sham myocardium. ELISA was markedly less sensitive in detecting both active and total TGF-β levels than our bioassay and failed to show any statistically significant difference in TGF-β levels between myocardial infarction and sham myocardium.

CONCLUSIONS

Our data suggested that the bioassay was significantly more sensitive than ELISA in detecting active TGF-β in serum and both active and total TGF-β in solid organ tissues. The bioassay will be useful in investigating TGF-β profile in various solid organs in physiological and pathological conditions.