Nox2 and Nox4 influence neonatal c-kit(+) cardiac precursor cell status and differentiation.

Redox status has emerged as critical in modulating stemness and lineage commitment in several precursor cell types. However, a role for redox genes, specifically NADPH oxidases (Nox), in cardiac precursor cells (CPCs) has not been established. We tested whether CPCs marked by type III receptor tyrosine kinase c-kit (c-kit(+)) exhibit a unique NADPH oxidase signature that confers precursor status and whether alterations in this profile are functionally linked to changes in lineage specification. Dihydroethidium (DHE) microfluorography indicated reduced basal reactive oxygen species (ROS) formation within early postnatal c-kit(+) CPCs. Real-time quantitative PCR revealed downregulation of ROS generator Nox2 and its subunit p67(phox) in c-kit(+) CPCs under basal conditions but upregulation of Nox2 and Nox4 over the course of differentiation. Adenoviral silencing of Nox2 and Nox4 increased expression of CPC markers c-kit and Flk-1 and blunted smooth and cardiac muscle differentiation, respectively, while overexpression of Nox2 and Nox4 significantly reduced c-kit expression. These changes were accompanied by altered expression of transcription factors regulating cardiac lineage commitment, Gata6 and Gata4, and cytokine transforming growth factor (TGF)-ß1. Similar to other precursor cell types, RT(2)Profiler PCR Arrays revealed that c-kit(+) CPCs also exhibit enhanced antioxidant capacity at the mRNA level. In conclusion, we report that c-kit(+) CPCs demonstrate reduced Nox2 expression and ROS levels and that increases in Nox2 and Nox4 influence their differentiation into mature cells. We speculate that ROS generators Nox2 and Nox4, along with the antioxidant genes identified by PCR Arrays, may be novel targets in CPCs that could prove useful in cell-based therapy of the heart.

c-kit+ precursors support postinfarction myogenesis in the neonatal, but not adult, heart.

We examined the myogenic response to infarction in neonatal and adult mice to determine the role of c-kit(+) cardiovascular precursor cells (CPC) that are known to be present in early heart development. Infarction of postnatal day 1-3 c-kit(BAC)-EGFP mouse hearts induced the localized expansion of (c-kit)EGFP(+) cells within the infarct, expression of the c-kit and Nkx2.5 mRNA, myogenesis, and partial regeneration of the infarction, with (c-kit)EGFP(+) cells adopting myogenic and vascular fates. Conversely, infarction of adult mice resulted in a modest induction of (c-kit)EGFP(+) cells within the infarct, which did not express Nkx2.5 or undergo myogenic differentiation, but adopted a vascular fate within the infarction, indicating a lack of authentic CPC. Explantation of infarcted neonatal and adult heart tissue to scid mice, and adoptive transfer of labeled bone marrow, confirmed the cardiac source of myogenic (neonate) and angiogenic (neonate and adult) cells. FACS-purified (c-kit)EGFP(+)/(αMHC)mCherry(-) (noncardiac) cells from microdissected infarcts within 6 h of infarction underwent cardiac differentiation, forming spontaneously beating myocytes in vitro; cre/LoxP fate mapping identified a noncardiac population of (c-kit)EGFP(+) myocytes within infarctions, indicating that the induction of undifferentiated precursors contributes to localized myogenesis. Thus, adult postinfarct myogenic failure is likely not due to a context-dependent restriction of precursor differentiation, and c-kit induction following injury of the adult heart does not define precursor status.

Behçet disease presenting with frosted branch angiitis.

The authors present a case of Behçet disease presenting with frosted branch angiitis. Frosted branch angiitis is a rare clinical finding and there are only two reported cases in the literature associated with Behçet disease.

c-kit expression identifies cardiovascular precursors in the neonatal heart.

Directed differentiation of embryonic stem cells indicates that mesodermal lineages in the mammalian heart (cardiac, endothelial, and smooth muscle cells) develop from a common, multipotent cardiovascular precursor. To isolate and characterize the lineage potential of a resident pool of cardiovascular progenitor cells (CPcs), we developed BAC transgenic mice in which enhanced green fluorescent protein (EGFP) is placed under control of the c-kit locus (c-kit(BAC)-EGFP mice). Discrete c-kit-EGFP(+) cells were observed at different stages of differentiation in embryonic hearts, increasing in number to a maximum at about postnatal day (PN) 2; thereafter, EGFP(+) cells declined and were rarely observed in the adult heart. EGFP(+) cells purified from PN 0-5 hearts were nestin(+) and expanded in culture; 67% of cells were fluorescent after 9 days. Purified cells differentiated into endothelial, cardiac, and smooth muscle cells, and differentiation could be directed by specific growth factors. CPc-derived cardiac myocytes displayed rhythmic beating and action potentials characteristic of multiple cardiac cell types, similar to ES cell-derived cardiomyocytes. Single-cell dilution studies confirmed the potential of individual CPcs to form all 3 cardiovascular lineages. In adult hearts, cryoablation resulted in c-kit-EGFP(+) expression, peaking 7 days postcryolesion. Expression occurred in endothelial and smooth muscle cells in the revascularizing infarct, and in terminally differentiated cardiomyocytes in the border zone surrounding the infarct. Thus, c-kit expression marks CPc in the neonatal heart that are capable of directed differentiation in vitro; however, c-kit expression in cardiomyocytes in the adult heart after injury does not identify cardiac myogenesis.

mCLCA4 ER processing and secretion requires luminal sorting motifs.

Ca(+)-activated Cl(-) channel (CLCA) proteins are encoded by a family of highly related and clustered genes in mammals that are markedly upregulated in inflammation and have been shown to affect chloride transport. Here we describe the cellular processing and regulatory sequences underlying murine (m) CLCA4 proteins. The 125-kDa mCLCA4 gene product is cleaved to 90- and 40-kDa fragments, and the NH(2)- and COOH-terminal fragments are secreted, where they are found in cell media and associated with the plasma membrane. The 125-kDa full-length protein is only found in the endoplasmic reticulum (ER), and specific luminal diarginine retention and dileucine forward trafficking signals contained within the CLCA4 sequence regulate export from the ER and proteolytic processing. Mutation of the dileucine luminal sequences resulted in ER trapping of the immaturely glycosylated 125-kDa peptide, indicating that proteolytic cleavage occurs following recognition of the trafficking motifs. Moreover, the mutated dileucine and diarginine signal sequences directed processing of a secreted form of enhanced green fluorescent protein in a manner consistent with the effects on mCLCA4.

Smooth muscle persists in the muscularis externa of developing and adult mouse esophagus.

Following initial patterning as differentiated smooth muscle (SM) cells, the muscularis externa of the murine esophagus is replaced by skeletal muscle, but the mechanism underlying this process is controversial. The hypothesis that committed SM cells transdifferentiate into striated muscle is not consistent with fate mapping studies. Similarly, apoptosis does not fully explain the process. Using immunohistochemical techniques and transgenic mice that express eGFP and Cre-recombinase exclusively in SM, we have identified a population of remnant SM cells that persist throughout the developing and mature murine esophagus. These cells display an atypical phenotype, are not associated with microvasculature, but are often apposed to cKit positive, interstitial cells of Cajal. The absolute length of the SM component of the developing esophagus remains constant during a period when total esophageal length increases 4-fold, resulting in a small maintained distal segment of smooth muscle. Esophageal SM cells fail to express myogenin during development, and striated muscle cell precursors expressing myogenin fail to express specific SM cell markers, indicating that they did not transdifferentiate from SM cells. Moreover, smooth muscle-specific myogenin inactivation has no effect on esophageal skeletal myogenesis. Taken together, our results provide an alternative hypothesis regarding the fate of SM cells in the developing murine esophagus, which does not invoke apoptosis or transdifferentiation.

Randomized controlled clinical trial of beta irradiation as an adjunct to trabeculectomy in open-angle glaucoma.

OBJECTIVE: To assess the effect of a single intraoperative application of 750 cGy of beta irradiation on the outcome of trabeculectomy for uncontrolled open-angle glaucoma. DESIGN: A prospective, randomized, double-blind, placebo-controlled clinical trial. PARTICIPANTS: Sixty-one eyes of 61 Caucasian patients at low risk of filtering surgery failure, with poorly controlled primary or secondary open-angle glaucoma undergoing routine trabeculectomy. METHOD: Patients were randomly assigned to control or beta irradiation groups. All patients underwent standard trabeculectomy with fornix-based conjunctival incision. Eyes assigned to beta irradiation received 750 cGy of beta irradiation directly over the sclerostomy site on completion of conjunctival suturing. An identical but inactive applicator was applied to control eyes, delivering no radiation. Both operator and patient remained masked to the assignment for the 12-month follow-up period. MAIN OUTCOME MEASURES: The main outcome measure was intraocular pressure (IOP) control. Complete success of IOP control was defined as an IOP less than 21 mmHg at 12 months without need for additional medication. Qualified success was defined as an IOP less than 21 mmHg at 12 months where additional medication was required. RESULTS: Complete success of IOP control was achieved in 19 (86%) control eyes and 35 (90%) irradiated eyes (P = 1.0). Qualified success of IOP control was achieved in 21 (95%) control eyes and 39 (100%) irradiated eyes at 12 months follow-up (P = 1.0) CONCLUSIONS: We experienced a very high success rate of filtration surgery in this select population without adjunctive irradiation. Our sample size was too small to show any improvement in success with use of beta irradiation in this group. Other studies would have to be done to determine whether it may have measurable benefit in cases with a high risk of filtration failure.