P1936Selective inhibition of the Mek1/2-Erk1/2 signalling pathway induces the differentiation of human cardiac pericyte-like cells into contractile vascular smooth muscle cells

Background

Arteriogenesis is key for tissue repair but whether myocardial stromal cells contribute to this phenomenon remains unknown.

Purpose

Investigate if cardiac pericytes are a druggable target for therapeutic arteriogenesis.

Methods and results

The localization of pericyte-like cells (PCs) was assessed in the human and murine heart by immunohistochemistry of typical antigenic markers. CD34+ PCs co-expressing NG2 and PDGFRβ but not endothelial cell (EC) or vascular smooth muscle cell (VSMC) antigens were identified in peri-arterial position in normal hearts. Interestingly, we also found rare PCs co-expressing αSMA in the peri-infarct myocardium, suggesting these cells could represent a transitory phenotype between PCs and VSMCs. Next, we isolated human cardiac PCs by immunosorting for CD31 and CD34 and established the purity of the isolated CD34+CD31- fraction by flow cytometry. Following culture expansion, cardiac PCs maintain the typical antigenic profile except for CD34. Moreover, we confirmed the PCs' ability to promote angiogenesis in-vitro. The withdrawal of EGF and bFGF from the culture media for 10 days induced the differentiation of PCs into mature VSMCs, as documented by a massive upregulation of contractile genes MYH11, CNN1 and ACTA2 (200-, 35- and 15-folds increase versus naïve PCs, p<0.01), which was followed by the induction of SM-MHC, Smoothelin B, αSMA, Calponin and SM22α proteins (p<0.05 versus PCs). In addition, PC-derived cells lost migratory capacity, secreted elastin, and responded to endothelin-1 in a contraction assay, thus phenocopying the behaviour of control coronary artery-derived VSMCs. We excluded contamination of the PC preparation by verifying similar phenomena occur in PCs expanded from single cell clonogeneic assays. Moreover, the process is partially reversible, with PC-derived VSMCs being able to reacquire some intermediate markers following EGF/bFGF re-challenge. ECs secrete EGF and bFGF, with this GF signalling being enhanced by hypoxia, suggesting ECs may control the PC phenotype in a paracrine fashion. Mechanistic studies revealed the Mek1/2-Erk1/2-Elk1 signalling is accountable for the transcriptional repression of VSMC genes in PCs. Accordingly, a selective Mek1/2 inhibitor (PD0325901) was able to switch the definitive VSMC phenotype of PCs maintained in full media. The drug prevented the phosphorylation of Erk1/2 and its downstream target Elk1. This likely relieves the complex SRF/MyocD and abolishes the transcriptional repression at the gene promoter.

Conclusions

Cardiac PCs have a VSMC potential which is under the inhibitory control of the Mek1/2-Erk1/2-Elk1 signalling. Mek1/2 inhibitors showed promises for the treatment of melanoma and solid tumours. A novel application of this class of compounds to improve arteriogenesis in myocardial ischemia is fascinating. The caveat about their potential cardiotoxicity could be less relevant with short duration treatments of myocardial ischemia.

Acknowledgement/Funding

British Heart Foundation Centre for Regenerative Medicine Award (II) - “Centre for Vascular Regeneration” (RM/17/3/33381)

P6309Impaired secretion of clusterin in pericardial fluid of diabetics, a deleterious outcome for the cardiac micro-vasculature

Background

Extracellular vesicles are vital mediators of cell-to-cell communications. We previously demonstrated that in the adult heart, exosomes released in the pericardial fluid (PF) have the functional capability to induce cell survival and angiogenesis in recipient endothelial cells. It has previously been shown that PF exosomes from patients with an existing myocardial infarction (MI) contain clusterin (CLU). Remarkably, secreted CLU is cardio-protective as evidenced by enhanced arteriogenesis and reduced apoptosis in animal models of MI. We hypothesize that type 2 Diabetes Mellitus (T2DM) along with ischemic heart disease (IHD) alters PF EV content impairing its reparative angiogenic potential.

Aim

To investigate the role of T2DM in modulating human PF exosomal content and its vascular action.

Methods and results

PF samples were collected from 3 different groups of patients (N=3): 1) Ischemic heart disease (IHD) with or 2) without T2DM, and 3) non-ischaemic, non-diabetic controls operated for mitral valve repair.

The impact of PF exosomes on human coronary microvascular ECs (HCMECs) was evaluated by cell based functional assays for measuring apoptosis, proliferation and angiogenesis. Interestingly, unlike PF exosomes from control patients, PF exosomes from DM patients with IHD promoted EC apoptosis and impaired angiogenesis.

To investigate the effect of T2DM on PF content, we performed high throughput proteomic and metabolomic analysis of whole PF and PF EVs. We identified proteins and metabolites that were differentially expressed under T2DM condition by using the R package Limma. Employing a network approach, protein and metabolic data were integrated by using our newly developed inhouse R package Metabosignal. This networks approach revealed an interesting interaction circuit involving protein CLU. The T2DM-associated reduction of CLU level in the PF, identified from the “omics” analyses was confirmed by ELISA (n=8 patients per group).

To examine the effects of DM and ischemia on CLU intracellular expression and secretion, HCMECs were exposed to high D-glucose (HG, 25 mM) and hypoxia (1%O2). In line with our PF data, HCMECs exposed to HG and hypoxia showed lower levels of both CLU mRNA and secreted CLU (ELISA). Importantly, recombinant CLU (rCLU) treatment on HCMECs rescued their angiogenic potential, induced cell proliferation and protected them from apoptosis under both HG and hypoxia conditions. In addition, silencing of endogenous levels of CLU in HCMECs impaired angiogenesis, suggesting that CLU might be an inherent component of the angiogenesis machinery in ECs.

Conclusions

This study suggests that DM reduces the level of secreted CLU in the PF, depriving myocardial micro-vessels of this protective and regenerative mediator. Restoring diminished CLU levels in the diabetic heart could be a possible therapeutic approach for contrasting diabetic micro-angiopathy.

Acknowledgement/Funding

British Heart Foundation Program Grant

P712Non-neuronal cholinergic system prevents coronary vascular dysfunction in diabetic heart

Background

Diabetic individuals suffer extensive myocardial damage during ischemia due to impaired ATP production and coronary vascular dysfunction. The cardiomyocytes possess a non-neuronal cholinergic system (NNCS) as it has choline acetyltransferase (ChAT) to synthesize acetylcholine (ACh). ACh released from cardiomyocytes activates hypoxia-inducible factor-1 pathway in an auto/paracrine manner under non-hypoxic condition. Activation of this pathway via NNCS promotes angiogenesis and is a promising mechanism to target ischemia in diabetes.

Aim

To investigate if activation of NNCS could improve the coronary vasculature in diabetic heart.

Methods

Type-2 diabetic db/db mice with ventricle-specific ChAT transgene (db/db-ChAT-tg) and control db/db mice of 12- and 24-weeks old were used. Catheterization of the jugular vein and carotid artery was performed in combination with synchrotron radiation microangiography to visualize the in-vivo coronary circulation. Changes of the coronary circulation to ACh (10μg/kg/min) and sodium nitroprusside (SNP, 10μg/kg/min) were assessed. Immunofluorescence analysis was performed to measure the density of arterioles and capillaries ex-vivo.

Results

In comparison to db/db mice, the number of second and third order vessels was higher in the db/db-ChAT-tg mice of 12- and 24-weeks old under baseline condition. In response to ACh and SNP, number of third order vessels were further increased in the db/db-ChAT-tg mice of both ages. However, the magnitude of the diameter changes in db/db-ChAT-tg mice was comparable to that in db/db mice of both ages. Besides, the db/db-ChAT-tg mice had increased density of arterioles and capillaries compared to the db/db mice of both ages.

Conclusion

NNCS-induced angiogenesis prevents coronary vascular dysfunction in diabetic heart.

WITHDRAWN: GLP-1 Has an Anti-Inflammatory Effect on Adipose Tissue Expression of Cytokines, Chemokines, and Receptors in Obese Women

The above-named article by Manning PJ, Dixit P, Satthenapalli VR, Katare R, and Sutherland WHF (J Clin Endocrinol Metab. [published online ahead of print 21 May 2019]; doi: 10.1210/jc.2018-00197) has been withdrawn by the authors. The authors report, "The reason for this decision is that the statistical methodology we used did not adequately limit the impact of outlier data points on our findings. This was evident after reanalysis of the data using a different method." doi: 10.1210/jc.2019-01393.

Preparation, characterization and microhardness study of semi interpenetrating polymer networks of polyvinyl alcohol and crosslinked polyacrylamide

Semi-IPNs based on polyvinyl alcohol (PVA) and crosslinked polyacrylamide (PAM) were prepared and characterized. Various compositions of semi-interpenetrating polymer networks (semi-IPNs) were prepared by varying concentrations of PVA, acrylamide (AM) and crosslinker N,N'-methylene bis acrylamide (MBA) in the feed mixtures and polymerized using a suitable redox system comprising of potassium persulphate and metabisulphite. The prepared semi-IPNs were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. The prepared semi-IPNs were also investigated for microhardness measurements.