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A disturbed inflammatory response following myocardial infarction (MI) is associated with poor prognosis and increased tissue damage. Monocytes are key players in healing after MI, but little is known about the role of the cardiac niche in monocyte activation. This study investigated microenvironment‐dependent changes in inflammatory monocytes after MI. RNA sequencing analysis of murine Ly6Chigh monocytes on day 3 after MI revealed differential regulation depending on location. Notably, the local environment strongly impacted components of the WNT signaling cascade. Analysis of WNT modulators revealed a strong upregulation of WNT Inhibitory Factor 1 (WIF1) in cardiomyocytes—but not fibroblasts or endothelial cells—upon hypoxia. Compared to wild‐type (WT) littermates, WIF1 knockout mice showed severe adverse remodeling marked by increased scar size and reduced ejection fraction 4 weeks after MI. While FACS analysis on day 1 after MI revealed no differences in neutrophil numbers, the hearts of WIF1 knockouts contained significantly more inflammatory monocytes than hearts from WT animals. Next, we induced AAV‐mediated cardiomyocyte‐specific WIF1 overexpression, which attenuated the monocyte response and improved cardiac function after MI, as compared to control‐AAV‐treated animals. Finally, WIF1 overexpression in isolated cardiomyocytes limited the activation of non‐canonical WNT signaling and led to reduced IL‐1β and IL‐6 expression in monocytes/macrophages. Taken together, we investigated the cardiac microenvironment's interaction with recruited monocytes after MI and identified a novel mechanism of monocyte activation. The local initiation of non‐canonical WNT signaling shifts the accumulating myeloid cells toward a pro‐inflammatory state and impacts healing after myocardial infarction.

Background: Smooth muscle cells (SMC) are a preferential target for gene therapeutic approaches in atherosclerosis and restenosis. However, the undesirable expression of putative therapeutic genes in tissues other than the vascular wall is a considerable safety limitation for clinical trials, thus requiring the identification of a smooth-muscle-specific promoter sequence. Since the 2.3 kb rabbit Smooth Muscle Myosin Heavy Chain (SMHC) promoter was shown to be transcriptionally active in primary vascular but not visceral or other non-SMC in vitro, this fragment was chosen for in vivo analysis. Methods and Results: Transgenic mice and rabbits were established expressing a luciferase reporter gene under control of the 2.3 kb rabbit SMHC promoter. In contrast to the endogenous expression pattern of the SMHC gene both species revealed light emission predominantly in the arterial system including coronary arteries. Low activities were measured in large veins and the gastrointestinal system. In situ hybridization of murine embryos using a luciferase riboprobe confirmed reporter gene expression in large arteries with no detectable mRNA in the viscera. Unlike adult animals, ectopic luciferase activities were found in ventricular myocardium during murine development ceasing 1 week post partum. Conclusions: In two animal species, the 2.3 kb SMHC promoter appeared to be effective in discriminating between the pathways regulating vascular and visceral smooth muscle gene expression. The vascular-specific expression profile of the 2.3 kb SMHC promoter suggests that the 2.3 kb SMHC promoter contains the regulatory elements necessary for selective gene targeting into vascular SMC of large arteries including coronary arteries in vivo. [ABSTRACT FROM PUBLISHER]

Introduction: Despite advances in therapy, heart failure (HF) patients continue to experience high rates of hospitalization & death and poor quality of life. There is a high need for treatments to improve the clinical course of HF patients. The ~20,000-25,000 protein-coding genes harbor a reservoir for new drug targets. However, the extensive use of this source remains challenging. The metabolome represents the endpoint of the omics-cascade and the closest link to the phenotype. Most diseases result in metabolic changes which play a causative role in disease progression. By identifying pathological metabolic alterations, metabolomics can point to novel sites for therapeutic Intervention. Hypothesis: We propose a streamlined systems biology approach with integration of metabolomics as valuable key component for fast and efficient drug target identification. Methods: Metabolomics data from myocardium of a mouse model of HF (transversal aortic constriction, TAC) were collected by untargeted liquid chromatography- and gas chromatography-coupled mass spectrometry and integrated with transcriptomics data from the same mouse samples by relating metabolites to protein-function of the corresponding gene. A representative potential target was chosen and overexpressed in TAC mice using adeno-associated virus (AAV) vectors. Mice were analyzed using serial echocardiography and histology. Results: For myocardium, 209 metabolites and >45 000 transcripts were measured. 161 metabolites and 2559 transcripts could be integrated into a systems biology dataset. Using different filter approaches, 16 transcripts were nominated as potential new HF drug targets. To prove the value of this approach, numbers of known HF drug targets identified from systems biology data were compared to numbers from transcriptomics data when applying the same filter strategy, and a significant enrichment (p<0.05) with the systems biology pipeline was obtained. As proof-of-concept hit, OCTN2 and its relevance in HF was further investigated by OCTN2 overexpression in TAC mice using AAV vectors. OCTN2 gene transfer resulted in a significant amelioration of left ventricular function and reduced fibrosis compared to control-treated mice. Conclusions: Data integration of two omics methods reduces the time and the number of potential candidates needed to be screened in order to find promising therapeutic targets. The opportunity to apply metabolomics-based systems to drug target discovery is as broad as the scope of diseases where metabolic changes play a causative role. [ABSTRACT FROM AUTHOR]