Cardiac tissue engineering using tissue printing technology and human cardiac progenitor cells.

Tissue engineering is emerging as a potential therapeutic approach to overcome limitations of cell therapy, like cell retention and survival, as well as to mechanically support the ventricular wall and thereby prevent dilation. Tissue printing technology (TP) offers the possibility to deliver, in a defined and organized manner, scaffolding materials and living cells. The aim of our study was to evaluate the combination of TP, human cardiac-derived cardiomyocyte progenitor cells (hCMPCs) and biomaterials to obtain a construct with cardiogenic potential for in vitro use or in vivo application. With this approach, we were able to generate an in vitro tissue with homogenous distribution of cells in the scaffold. Cell viability was determined after printing and showed that 92% and 89% of cells were viable at 1 and 7 days of culturing, respectively. Moreover, we demonstrated that printed hCMPCs retained their commitment for the cardiac lineage. In particular, we showed that 3D culture enhanced gene expression of the early cardiac transcription factors Nkx2.5, Gata-4 and Mef-2c as well as the sarcomeric protein TroponinT. Printed cells were also able to migrate from the alginate matrix and colonize a matrigel layer, thereby forming tubular-like structures. This indicated that printing can be used for defined cell delivery, while retaining functional properties.

Genes in congenital heart disease: atrioventricular valve formation.

Through the use of animal studies, many candidate genes (mainly encoding transcriptional factors and receptors) have been implicated in the development of congenital heart disease. Thus far, only a minority of these genes have been shown to carry mutations associated with congenital disease in humans, e.g., GATA 4, TBX-5, NOTCH1 and NKX2-5. Mutations in these genes can cause a variety of cardiac defects even within the same family. Conversely, similar phenotypes are observed for different gene mutations suggesting a common pathway. Multiple genes and genetic pathways have been related to atrioventricular valve formation, although most of these genes have not yet been demonstrated as causative in human atrioventricular valve defects. Key pathways include the epidermal growth factor receptor pathway and related interacting pathways, most importantly the pathway of UDP-glucose dehydrogenase, resulting ultimately in activation of Ras. Other examples of interacting pathways include that of Nodal/Cited2/Pitx2, Wnt, Notch and ECE. Further studies are needed to investigate the pathways which are crucial for atrioventricular valve formation in humans. Understanding the underlying molecular process of abnormal atrioventricular valve formation in patients with congenital heart disease may provide important insight, in the etiology and possibly into preventive or treatment regimes.

Constitutively overexpressed erythropoietin reduces infarct size in a mouse model of permanent coronary artery ligation.

In view of the emerging role of recombinant human erythropoietin (rhEPO) as a novel therapeutical approach in myocardial ischemia, we performed the first two-way parallel comparison to test the effects of rhEPO pretreatment (1000 U/kg, 12h before surgery) versus EPO transgenic overexpression in a mouse model of myocardial infarction. Unlike EPO transgenic mice who doubled their hematocrit, rhEPO pretreated mice maintained an unaltered hematocrit, thereby offering the possibility to discern erythropoietic-dependent from erythropoietic-independent protective effects of EPO. Animals pretreated with rhEPO as well as EPO transgenic mice underwent permanent left anterior descending (LAD) coronary artery ligation. Resulting infarct size was determined 24h after LAD ligation by hematoxylin/eosin staining, and morphometrical analysis was performed by computerized planimetry. A large reduction in infarction size was observed in rhEPO-treated mice (-74% +/- 14.51; P = 0.0002) and an even more pronounced reduction in the EPO transgenic group (-87% +/- 6.31; P < 0.0001) when compared to wild-type controls. Moreover, while searching for novel early ischemic markers, we analyzed expression of hypoxia-sensitive Wilms' tumor suppressor gene (WT1) in infarcted hearts. We found that its expression correlated with the infarct area, thereby providing the first demonstration that WT1 is a useful early marker of myocardial infarction. This study demonstrates for the first time that, despite high hematocrit levels, endogenously overexpressed EPO provides protection against myocardial infarction in a murine model of permanent LAD ligation.

The Glu298Asp polymorphism of the NOS 3 gene as a determinant of the baseline production of nitric oxide.

RATIONALE: The endothelial nitric oxide synthase Glu298Asp polymorphism has been suggested to play a role in the development of hypertension, atherosclerosis and coronary artery disease. OBJECTIVE: To investigate functional differences between the various genotypes with respect to basal nitric oxide (NO) production, we estimated the response to endothelial NO synthase (ecNOS) inhibition by infusion of increasing doses of N(G)-monomethyl-L-arginine (L-NMMA) into the brachial artery during venous occlusion plethysmography. METHODS: In 41 healthy subjects forearm blood flow responses to intra-arterial infusion of increasing doses of L-NMMA (0.05, 0.1 and 0.2 mg/min per dl) and norepinephrine (10, 20 and 40 ng/min per dl) were measured. The genotype of the ecNOS Glu298Asp polymorphism was assessed. RESULTS: Nineteen subjects had the Glu/Glu genotype, 19 subjects had the Glu/Asp genotype and three subjects had the Asp/Asp genotype. Groups were comparable concerning demographic, hemodynamic and possible confounding factors. Subjects with the Asp allele showed a reduced response to infusion of L-NMMA as compared to subjects with the Glu/Glu genotype (ANOVA, = 0.01). There was no significant difference in the response to infusion of the NO-independent vasoconstrictor, norepinephrine, between both groups. CONCLUSIONS: The ecNOS Glu298Asp polymorphism is associated with reduced basal NO production and might therefore have functional implications in the development of atherosclerosis or hypertension.