Hippo pathway deficiency reverses systolic heart failure after infarction.

Mammalian organs vary widely in regenerative capacity. Poorly regenerative organs, such as the heart are particularly vulnerable to organ failure. Once established, heart failure commonly results in mortality. The Hippo pathway, a kinase cascade that prevents adult cardiomyocyte proliferation and regeneration, is upregulated in human heart failure. Here we show that deletion of the Hippo pathway component Salvador (Salv) in mouse hearts with established ischaemic heart failure after myocardial infarction induces a reparative genetic program with increased scar border vascularity, reduced fibrosis, and recovery of pumping function compared with controls. Using translating ribosomal affinity purification, we isolate cardiomyocyte-specific translating messenger RNA. Hippo-deficient cardiomyocytes have increased expression of proliferative genes and stress response genes, such as the mitochondrial quality control gene, Park2. Genetic studies indicate that Park2 is essential for heart repair, suggesting a requirement for mitochondrial quality control in regenerating myocardium. Gene therapy with a virus encoding Salv short hairpin RNA improves heart function when delivered at the time of infarct or after ischaemic heart failure following myocardial infarction was established. Our findings indicate that the failing heart has a previously unrecognized reparative capacity involving more than cardiomyocyte renewal.

Pitx2 promotes heart repair by activating the antioxidant response after cardiac injury.

Myocardial infarction results in compromised myocardial function and heart failure owing to insufficient cardiomyocyte self-renewal. Unlike many vertebrates, mammalian hearts have only a transient neonatal renewal capacity. Reactivating primitive reparative ability in the mature mammalian heart requires knowledge of the mechanisms that promote early heart repair. By testing an established Hippo-deficient heart regeneration mouse model for factors that promote renewal, here we show that the expression of Pitx2 is induced in injured, Hippo-deficient ventricles. Pitx2-deficient neonatal mouse hearts failed to repair after apex resection, whereas adult mouse cardiomyocytes with Pitx2 gain-of-function efficiently regenerated after myocardial infarction. Genomic analyses indicated that Pitx2 activated genes encoding electron transport chain components and reactive oxygen species scavengers. A subset of Pitx2 target genes was cooperatively regulated with the Hippo pathway effector Yap. Furthermore, Nrf2, a regulator of the antioxidant response, directly regulated the expression and subcellular localization of Pitx2. Pitx2 mutant myocardium had increased levels of reactive oxygen species, while antioxidant supplementation suppressed the Pitx2 loss-of-function phenotype. These findings reveal a genetic pathway activated by tissue damage that is essential for cardiac repair.

Mucin production during prenatal and postnatal murine lung development.

Mucus is a protective gel that lines respiratory tract surfaces. To identify potential roles for secreted gel--forming mucins in lung development, we isolated murine lungs on embryonic days (E) 12.5-18.5, and postnatal days (PN) days 5, 14, and 28. We measured the mucin gene expression by quantitative RT-PCR, and localization by histochemical and immunohistochemical labeling. Alcian blue/periodic acid--Schiff--positive cells are present from E15.5 through PN28. Muc5b transcripts were abundant at all time points from E14.5 to PN28. By contrast, transcript levels of Muc5ac and Muc2 were approximately 300 and 85,000 times lower, respectively. These data are supported by immunohistochemical studies demonstrating the production and localization of Muc5ac and Muc5b protein. This study indicates that mucin production is prominent in developing murine lungs and that Muc5b is an early, abundant, and persistent marker of bronchial airway secretory cells, thereby implicating it as an intrinsic component of homeostatic mucosal defense in the lungs.

Expression of the intestinal transcription factor CDX2 in carcinoid tumors is a marker of midgut origin.

CONTEXT: Carcinoid tumors are classified according to their site of origin into foregut, midgut, or hindgut carcinoids, which have different presentations and prognosis. The intestinal transcription factor CDX2 has been found to be expressed in most intestinal adenocarcinomas but in less than one half of the gastrointestinal carcinoids according to 1 study. OBJECTIVE: To determine whether CDX2 expression in carcinoid tumors varies by the site of origin and whether CDX2 expression is retained in metastatic disease. Design.-Sections of formalin-fixed and paraffin-embedded tissue from 36 primary carcinoid tumors and 5 cases of metastatic carcinoid to the liver were immunohistochemically stained for CDX2. The percent of cells with nuclear immunoreactivity and the intensity of staining were assessed. RESULTS: All 18 foregut carcinoids (10 pulmonary and 8 gastric) were negative (0%) for CDX2. All 11 midgut carcinoids (100%) were positive for CDX2 with moderate to strong staining in more than 50% of the cells. Only 2 (29%) of 7 of hindgut carcinoids were CDX2-positive with the 2 positive cases showing weak to moderate staining intensity in less than 10% of the cells. Expression of CDX2 in more than 50% of tumor cells was seen only in midgut carcinoids (P < .001). CDX2 expression in metastatic tumors was consistent with the site of origin. CONCLUSIONS: Midgut carcinoid tumors and their metastases are distinct from foregut and hindgut carcinoids in that they express high levels of CDX2. Additional studies are needed to determine whether CDX2 immunostaining may be helpful in determining the primary site of metastatic carcinoid tumors of unknown origin.

Functional expression of TRAIL receptors TRAIL-R1 and TRAIL-R2 in esophageal adenocarcinoma.

The tumour necrosis factor (TNF) related apoptosis-inducing ligand (TRAIL/Apo2L) is a member of the TNF superfamily that preferentially induces apoptosis in cancer cells, while sparing normal cells. TRAIL induces apoptosis by interacting with its receptors TRAIL-R1 and TRAIL-R2. Recently, new humanized agonistic anti-TRAIL-R1 and anti-TRAIL-R2 antibodies have been developed, and are undergoing phase I/II clinical trails. Esophageal adenocarcinoma (EA) is associated with significantly poor outcome and is rapidly increasing in incidence in the United States and Western Europe, with virtually no effective non-surgical treatment. The aim of this study was to determine whether human EA tissue express TRAIL-R1 and/or TRAIL-R2, and whether EA cell lines Bic-1 and Seg-1 expresses functional TRAIL-R1 and/or TRAIL-R2. The expression of TRAIL-R1 and TRAIL-R2 was determined in sections from 18 human EA by immunohistochemistry (IHC). Sixteen (89%) of the EA expressed TRAIL-R1 and 17 (94%) expressed TRAIL-R2. Both cell lines were found to express TRAIL-R1 and TRAIL-R2 by western blot analysis, IHC, and flow cytometry. The fully human agonistic TRAIL-R1 (HGS-ETR1) and TRAIL-R2 (HGS-ETR2) antibodies induced apoptosis in Bic-1 and Seg-1 cells in a time and dose dependent manner. Our results show that the vast majority of primary human EA express TRAIL-R1 and TRAIL-R2 and that EA cells lines express functional TRAIL-R1 and TRAIL-R2. Targeting of these receptors by agonist monoclonal antibodies may be of therapeutic value in patients with EA.