New insights into lipid raft function regulating myocardial vascularization competency in human idiopathic dilated cardiomyopathy

The lipid rafts in cancer stem cell: a target to eradicate cancer

Cancer stem cells (CSCs) are a subpopulation of cancer cells with stem cell properties that sustain cancers, which may be responsible for cancer metastasis or recurrence. Lipid rafts are cholesterol- and sphingolipid-enriched microdomains in the plasma membrane that mediate various intracellular signaling. The occurrence and progression of cancer are closely related to lipid rafts. Emerging evidence indicates that lipid raft levels are significantly enriched in CSCs compared to cancer cells and that most CSC markers such as CD24, CD44, and CD133 are located in lipid rafts. Furthermore, lipid rafts play an essential role in CSCs, specifically in CSC self-renewal, epithelial-mesenchymal transition, drug resistance, and CSC niche. Therefore, lipid rafts are critical regulatory platforms for CSCs and promising therapeutic targets for cancer therapy.

Diagnostic biomarkers of dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is a condition involving dilation of cardiac chambers, which results in contraction impairment. Besides invasive and non-invasive diagnostic procedures, cardiac biomarkers are of great importance in both diagnosis and prognosis of the disease. These biomarkers are categorized into three groups based on their site; cardiomyocyte biomarkers, microenvironmental biomarkers and macroenvironmental biomarkers.

AIMS

In this review, an overview of characteristics, epidemiology, etiology and clinical manifestations of DCM is provided. In addition, the most important biomarkers, of all three categories, and their diagnostic and prognostic values are discussed.

CONCLUSION

Considering the association of DCM with conditions such as infections and autoimmunity, which are prevalent among the population, introducing efficient diagnostic tools is of high value for the early detection of DCM to prevent its severe complications. The three discussed classes of biomarkers are potential candidates for the detection of DCM. However, further studies are necessary in this regard.

Extracellular vesicles do not contribute to higher circulating levels of soluble LRP1 in idiopathic dilated cardiomyopathy

Idiopathic dilated cardiomyopathy (IDCM) is a frequent cause of heart transplantation. Potentially valuable blood markers are being sought, and low‐density lipoprotein receptor‐related protein 1 (LRP1) has been linked to the underlying molecular basis of the disease. This study compared circulating levels of soluble LRP1 (sLRP1) in IDCM patients and healthy controls and elucidated whether sLRP1 is exported out of the myocardium through extracellular vesicles (EVs) to gain a better understanding of the pathogenesis of the disease. LRP1 α chain expression was analysed in samples collected from the left ventricles of explanted hearts using immunohistochemistry. sLRP1 concentrations were determined in platelet‐free plasma by enzyme‐linked immunosorbent assay. Plasma‐derived EVs were extracted by size‐exclusion chromatography (SEC) and characterized by nanoparticle tracking analysis and cryo‐transmission electron microscopy. The distributions of vesicular (CD9, CD81) and myocardial (caveolin‐3) proteins and LRP1 α chain were assessed in SEC fractions by flow cytometry. LRP1 α chain was preferably localized to blood vessels in IDCM compared to control myocardium. Circulating sLRP1 was increased in IDCM patients. CD9‐ and CD81‐positive fractions enriched with membrane vesicles with the expected size and morphology were isolated from both groups. The LRP1 α chain was not present in these SEC fractions, which were also positive for caveolin‐3. The increase in circulating sLRP1 in IDCM patients may be clinically valuable. Although EVs do not contribute to higher sLRP1 levels in IDCM, a comprehensive analysis of EV content would provide further insights into the search for novel blood markers.

Umbilical cord blood-derived mesenchymal stem cells: new therapeutic weapons for idiopathic dilated cardiomyopathy?

Dilated cardiomyopathy is the most frequent etiology of non-ischemic heart failure. In a majority of cases the causal mechanism is unknown, giving rise to the term 'idiopathic' dilated cardiomyopathy (IDCM). Major pathological derangements include patchy interstitial fibrosis, degenerated cardiomyocytes, and dilatation of the cardiac chambers, but recent evidence suggests that disease progression may also have the signature of cardiac endothelial dysfunction. As we better understand the molecular basis of IDCM, novel therapeutic approaches, mainly gene transfer and cell-based therapies, are being explored. Cells with regenerative potential have been extensively tested in cardiac diseases of ischemic origin in both pre-clinical and clinical settings. However, whether cell therapy has any clinical value in IDCM patients is still being evaluated. This article is a concise summary of cell therapy studies for IDCM, with a focus on recent advances that highlight the vascular potential exhibited by umbilical cord blood-derived mesenchymal stem cells (UCBMSCs). We also provide an overview of cardiac vasculature as a key regulator of subjacent myocardial integrity and function, and discuss the potential mechanisms of UCBMSC amelioration of IDCM myocardium. Consideration of these issues shows that these cells are conceivably new therapeutic agents for this complex and elusive human disorder.

Inverse relationship between raft LRP1 localization and non-raft ERK1,2/MMP9 activation in idiopathic dilated cardiomyopathy: potential impact in ventricular remodeling

BACKGROUND

Idiopathic dilated cardiomyopathy (IDCM) is characterized by adverse ventricular remodeling attributed to altered activity of extracellular matrix metalloproteinase (MMP). MMP overactivation is linked to changes in extracellular signal-regulated kinases (ERK), reportedly modulated by the low-density lipoprotein receptor-related protein 1 (LRP1) receptor. The aim of this work was to compare the levels, membrane distribution and interactions of LRP1, ERK1,2 and MMP2/9 in control and IDCM myocardium.

METHODS

Left ventricle samples from IDCM patients and control subjects were collected to analyze gene and protein expression by Real-time PCR and Western blot, respectively. Fractions enriched in cholesterol, Flotillin-1 and Caveolin-3 (rafts) were isolated from the remaining membrane (non-rafts) by sucrose gradient ultracentrifugation. We assessed the formation of LRP1-ERK1,2 complexes and MMP activity by immunoprecipitation and zymography, respectively.

RESULTS

In control myocardium, LRP1 was exclusively found in non-rafts while activation of ERK1,2 was preferentially detected in rafts. LRP1/p-ERK1,2 complexes were almost undetectable in rafts and non-rafts. In contrast, in IDCM myocardium, LRP1 moved to rafts and ERK1,2 activation was found in raft and non-raft fractions. Moreover, LRP1/p-ERK1,2 complexes were also found in both membrane fractions, although the amount was higher in non-rafts where MMP9 overactivation was exclusively detected.

CONCLUSIONS

The presented findings demonstrate a differential membrane compartmentalisation of ERK signaling in IDCM myocardium. The movement of LRP1 to rafts and the concomitant increase in non-raft-related ERK1,2/MMP9 activation may have crucial clinical implications in the progression of disease.