Effects of constitutively active IKKß on cardiac development.

NF-κB is a major transcription factor regulating cell survival, organ development and inflammation, but its role in cardiac development has been inadequately explored. To examine this function, we generated mice in which IKKß, an essential kinase for NF-κB activation, was constitutively activated in embryonic cardiomyocytes. For this purpose, we used smooth muscle-22α (SM22α)-Cre mice, which are frequently used for gene recombination in embryonic cardiomyocytes. Embryonic hearts of SM22αCre-CA (constitutively active) IKKßflox/flox mice revealed remarkably thin, spongy and hypoplastic myocardium. In exploring the mechanism, we found that the expression of bone morphogenetic protein 10 (BMP10) and T-box transcription factor 20 (Tbx20), major regulators of cardiac development, was significantly downregulated and upregulated, respectively, in the SM22αCre-CAIKKßflox/flox mice. We also generated NK2 homeobox 5 (Nkx2.5) Cre-CAIKKßflox/wt mice since Nkx2.5 is also expressed in embryonic cardiomyocytes and confirmed that the changes in these genes were also observed. These results implicated that the activation of NF-κB affects cardiac development.

Concomitant Mitral Regurgitation in Severe Aortic Stenosis　- A Report From the CURRENT AS Registry.

BACKGROUND: The clinical significance of concomitant mitral regurgitation (MR) has not been well addressed in patients with severe aortic stenosis (AS).Methods and Results:We analyzed 3,815 patients from a retrospective multicenter registry of severe AS in Japan (CURRENT AS registry). We compared the clinical outcomes between patients with moderate/severe MR and with none/mild MR according to the initial treatment strategy (initial aortic valve replacement [AVR] or conservative strategy). The primary outcome measure was a composite of aortic valve-related death or heart failure hospitalization. At baseline, moderate/severe MR was present in 227/1,197 (19%) patients with initial AVR strategy and in 536/2,618 (20%) patients with a conservative strategy. The crude cumulative 5-year incidence of the primary outcome measure was significantly higher in patients with moderate/severe MR than in those with none/mild MR, regardless of the initial treatment strategy (25.2% vs. 14.4%, P<0.001 in the initial AVR strategy, and 63.3% vs. 40.7%, P<0.001 in the conservative strategy). After adjusting confounders, moderate/severe MR was not independently associated with higher risk for the primary outcome measure in the initial AVR strategy (hazard ratio [HR] 1.11, 95% confidence interval [CI] 0.67-1.83, P=0.69), and in the conservative strategy (HR 1.13, 95% CI 0.93-1.37, P=0.22). CONCLUSIONS: Concomitant moderate/severe MR was not independently associated with higher risk for the primary outcome measure regardless of the initial treatment strategy.

Smooth muscle protein 22α-Cre recombination in resting cardiac fibroblasts and hematopoietic precursors.

The Cre-loxP system has been widely used for cell- or organ-specific gene manipulation, but it is important to precisely understand what kind of cells the recombination takes place in. Smooth muscle 22α (SM22α)-Cre mice have been utilized to alter genes in vascular smooth muscle cells (VSMCs), activated fibroblasts or cardiomyocytes (CMs). Moreover, previous reports indicated that SM22α-Cre is expressed in adipocytes, platelets or myeloid cells. However, there have been no report of whether SM22α-Cre recombination takes place in nonCMs in hearts. Thus, we used the double-fluorescent Cre reporter mouse in which GFP is expressed when recombination occurs. Immunofluorescence analysis demonstrated that recombination occurred in resting cardiac fibroblasts (CFs) or macrophages, as well as VSMCs and CMs. Flow cytometry showed that some CFs, resident macrophages, neutrophils, T cells, and B cells were positive for GFP. These results prompted us to analyze bone marrow cells, and we observed GFP-positive hematopoietic precursor cells (HPCs). Taken together, these results indicated that SM22α-Cre-mediated recombination occurs in resting CFs and hematopoietic cell lineages, including HPCs, which is a cautionary point when using SM22α-Cre mice.