Means for high-density multiparametric physiological mapping and stimulation are critically important in both basic and clinical cardiology. Current conformal electronic systems are essentially 2D sheets, which cannot cover the full epicardial surface or maintain reliable contact for chronic use without sutures or adhesives. Here we create 3D elastic membranes shaped precisely to match the epicardium of the heart via the use of 3D printing, as a platform for deformable arrays of multifunctional sensors, electronic and optoelectronic components. Such integumentary devices completely envelop the heart, in a form-fitting manner, and possess inherent elasticity, providing a mechanically stable bioti-/abiotic interface during normal cardiac cycles. Component examples range from actuators for electrical, thermal and optical stimulation, to sensors for pH, temperature and mechanical strain. The semiconductor materials include silicon, gallium arsenide and gallium nitride, co-integrated with metals, metal oxides and polymers, to provide these and other operational capabilities. Ex vivo physiological experiments demonstrate various functions and methodological possibilities for cardiac research and therapy.

Rationale: Although an age-related decrease in NO bioavailability contributes to vascular stiffness, the underlying molecular mechanisms remain incompletely understood. We hypothesize that NO constrains the activity of the matrix crosslinking enzyme tissue transglutaminase (TG2) via S-nitrosylation in young vessels, a process that is reversed in aging. Objective: We sought to determine whether endothelium-dependent NO regulates TG2 activity by S-nitrosylation and whether this contributes to age-related vascular stiffness. Methods and Results: We first demonstrate that NO suppresses activity and increases S-nitrosylation of TG2 in cellular models. Next, we show that nitric oxide synthase (NOS) inhibition leads to increased surface and extracellular matrix-associated TG2. We then demonstrate that endothelium-derived bioactive NO primarily mediates its effects through TG2, using TG2 ؊/؊ mice chronically treated with the NOS inhibitor L-N Gnitroarginine methyl ester (L-NAME). We confirm that TG2 activity is modulated by endothelium-derived bioactive NO in young rat aorta. In aging rat aorta, although TG2 expression remains unaltered, its activity increases and S-nitrosylation decreases. Furthermore, TG2 inhibition decreases vascular stiffness in aging rats. Finally, TG2 activity and matrix crosslinks are augmented with age in human aorta, whereas abundance remains unchanged. Conclusions: Decreased S-nitrosylation of TG2 and increased TG activity lead to enhanced matrix crosslinking and contribute to vascular stiffening in aging. TG2 appears to be the member of the transglutaminase family primarily contributing to this phenotype. Inhibition of TG2 could thus represent a therapeutic target for age-associated vascular stiffness and isolated systolic hypertension. (Circ Res. 2010;107:117-125.)Key Words: tissue transglutaminase Ⅲ S-nitrosylation Ⅲ S-nitrosation Ⅲ aging Ⅲ vascular stiffness A ging is associated with alterations in the properties of all elements of the vascular wall including endothelium, vascular smooth muscle, and matrix. 1 These changes result in increased vascular stiffness and isolated systolic hypertension. In addition, increased vascular stiffness promotes atherosclerosis at various sites in the vascular tree, such as the carotid artery. 2,3 Both dynamic changes (alterations in endothelial function and effects on vascular smooth muscle contractility), as well as structural alterations (eg, fracturing of elastin, increased collagen content, and accumulation of advanced glycation end products) have been described in aging. Vessel structure can additionally be regulated by alterations in matrix crosslinking. 1 Transglutaminases (TGs) are enzymes that catalyze a transamidation reaction, leading to the crosslinking of proteins through the formation of the stable N--(␥-glutamyl)lysine isopeptide bonds. 4,5 At least 3 of the 9 members of the TG superfamily are expressed in vascular systems. Tissue transglutaminase (TG2) in particular is ubiquitously expressed in vasculature, including in endothelial ce...

Advanced materials and fractal design concepts form the basis of a 3D conformal electronic platform with unique capabilities in cardiac electrotherapies. Fractal geometries, advanced electrode materials, and thin, elastomeric membranes yield a class of device capable of integration with the entire 3D surface of the heart, with unique operational capabilities in low power defibrillation. Co‐integrated collections of sensors allow simultaneous monitoring of physiological responses. Animal experiments on Langendorff‐perfused rabbit hearts demonstrate the key features of these systems.