Microtechnologies for Cardiovascular Tissue Engineering

Cardiovascular disease is a rising epidemic worldwide, and curative therapies remain elusive. Heart and vascular disease remain some of the hardest to cure due to the limited capacity of the heart to repair itself, necessitating a cell or organ based therapy to cure the inevitable descent into heart failure. Tissue engineering is uniquely poised to significantly alter this disease burden though the fabrication of cardiac and vascular tissues in vitro. However, the challenges for achieving these aims are significant - for cardiac tissues, the therapy must adhere to strict requirements of adequate perfusion and functional integration with the damaged heart. Vascular tissues are required to be amenable to surgical anastomosis while at the same time provide nutrient transport on the cellular level. Recently, a new set of technologies based from the semiconductor industry, have enabled micron level control over the cellular environment and cells themselves and may enable novel approaches to fulfill these tissue engineering requirements. In this dissertation, these microtechnologies will be leveraged to address some of the current obstacles that limit the use of tissue engineering approaches for functional therapy. Specifically, microtechnologies were used to screen the effect of electrical stimulation on the function and maturation of human embryonic stem cell derived cardiomyocytes, which resulted in the ability to program specific individual beating frequencies of the cells while improving contractile function and led to the identification of a channel specific effect for frequency modulation. These technologies were also used to distinguish the vasculogenic potential of different mesenchymal stem cell sources for nascent vessel stabilization, and enabled the development of a powerful hydrogel docking platform with the novel capability to spatially pattern any number of cells, cytokines or drugs on the microscale, while permitting scale up for larger tissue generation without the loss of precision. Finally, these technologies were used to create vascular networks with hierarchical branching patterns that could be implanted and used in vivo fulfilling a major criterion of vascular tissue function - surgical compatibility with microscale architecture for tissue perfusion. Therefore, these microtechnologies support novel interrogation of cell function and enable new methods to engineer cardiovascular tissues

Crystal Structure of Di-iso-butylammonium Thiolactatotriphenylstannate

The title compounds, [(iso-C4H9)2NH2][SnPh3(O2CCH(CH3)S)], crystallized in a monoclinic space group P21/n with the following cell parameters: a = 9.8537(2)Å, b = 16.7775(3)Å, c = 17.5845(3)Å, β = 103.7740(10)°, V = 2823.48(9)Å3, Z = 4 and Dx = 1.375 Mg m-3. The structure was refined to a final R value of 0.0222 for 5042 reflections [I \u3e 2σ(I)]. The structure of the complex is ionic consisting of an anionic triphenyltin moiety and a cationic di-iso-butylammonium portion. In addition, a hydrogen bonding network between the cations and anions was observed

Synthesis and Characterization of Some Triphenyltin(IV) Complexes from Sterically Crowded [(( E )-1-{2-Hydroxy-5-[( E )-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]acetate Ligands and Crystal Structure Analysis of a Tetrameric Triphenyltin(IV) Compound

Four new triphenyltin(IV) complexes containing [((E)-1-{2-hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]acetate ligands (L) have been synthesized with formulations of Ph3SnLH. They have been studied by multinuclear (1H, 13C, 119Sn) NMR, 119Sn Mössbauer and IR spectroscopy. A full characterization of one complex, Ph3SnL1H (1), was accomplished by single crystal X-ray crystallography, which revealed the compound to be a macrocyclic tetramer. In the tetramer, the five coordinate tin atoms have distorted trigonal bipyramidal geometries with the three phenyl groups occupying equatorial positions, while an oxygen atom of the carboxylate group of one L ligand and the oxide O-atom (formerly the hydroxy group) of a second L ligand in an apical positions. The carboxylate ligands bridge adjacent tin atoms and coordinate in the zwitterionic form with the phenolic proton moved to the nearby nitrogen atom. 119Sn NMR results indicate that the tetrameric structures of the complexes in the solid state, in which the tin atoms are five-coordinated, dissociate in solution to yield four coordinate monomeric specie

The value of liquid biopsy in the diagnosis and staging of hepatocellular carcinoma : A systematic review

Peer reviewedPublisher PD

Retreatment with anti-EGFR based therapies in metastatic colorectal cancer: impact of intervening time interval and prior anti-EGFR response.

BackgroundThis retrospective study aims to investigate the activity of retreatment with anti-EGFR-based therapies in order to explore the concept of clonal evolution by evaluating the impact of prior activity and intervening time interval.MethodsEighty-nine KRAS exon 2-wild-type metastatic colorectal patients were retreated on phase I/II clinical trials containing anti-EGFR therapies after progressing on prior cetuximab or panitumumab. Response on prior anti-EGFR therapy was defined retrospectively per physician-records as response or stable disease ≥6 months. Multivariable statistical methods included a multiple logistic regression model for response, and Cox proportional hazards model for progression-free survival.ResultsRetreatment anti-EGFR agents were cetuximab (n = 76) or cetuximab plus erlotinib (n = 13). The median interval time between prior and retreatment regimens was 4.57 months (range: 0.46-58.7). Patients who responded to the prior cetuximab or panitumumab were more likely to obtain clinical benefit to the retreatment compared to the non-responders in both univariate (p = 0.007) and multivariate analyses (OR: 3.38, 95 % CI: 1.27, 9.31, p = 0.019). The clinical benefit rate on retreatment also showed a marginally significant association with interval time between the two anti-EGFR based therapies (p = 0.053). Median progression-free survival on retreatment was increased in prior responders (4.9 months, 95 % CI: 3.6, 6.2) compared to prior non-responders (2.5 months, 95 % CI, 1.58, 3.42) in univariate (p = 0.064) and multivariate analysis (HR: 0.70, 95 % CI: 0.43-1.15, p = 0.156).ConclusionOur data lends support to the concept of clonal evolution, though the clinical impact appears less robust than previously reported. Further work to determine which patients benefit from retreatment post progression is needed

High Origin of Radial Arteries: A Report of Two Rare Cases

Variations in the arterial supply of the upper limb are relatively common, with reported prevalence rates ranging from 11 to 24.4%. Of these, the most commonly encountered variation in the arm is a high origin of the radial artery. However, after consecutively dissecting and examining 600 Singaporean Chinese cadavers (1,200 upper limbs), we found only two cases of this. In both cases, the brachioradial artery originated from the upper one-third of the brachial artery and continued distally as the radial artery in the forearm. The local prevalence of 0.33% of this variation is significantly lower compared against populations from other geographical regions. Although rare, recognition of the variation is of fundamental importance to clinical practice

Percutaneous Cell Delivery Into the Heart Using Hydrogels Polymerizing In Situ

Heart disease is the leading cause of death in the US. Following an acute myocardial infarction, a fibrous, noncontractile scar develops, and results in congestive heart failure in more than 500,000 patients in the US each year. Muscle regeneration and the induction of new vascular growth to treat ischemic disorders of the heart can have significant therapeutic implications. Early studies in patients with chronic ischemic systolic left ventricular dysfunction (SLVD) using skeletal myoblasts or bone marrow-derived cells report improvement in left ventricular ejection function (LVEF) and clinical status, without notable safety issues. Nonetheless, the efficacy of cell transfer for cardiovascular disease is not established, in part due to a lack of control over cell retention, survival, and function following delivery. We studied the use of biocompatible hydrogels polymerizable in situ as a cell delivery vehicle, to improve cell retention, survival, and function following delivery into the ischemic myocardium. The study was conducted using human bone marrow-derived mesenchymal stem cells and fibrin glue, but the methods are applicable to any human stem cells (adult or embryonic) and a wide range of hydrogels. We first evaluated the utility of several commercially available percutaneous catheters for delivery of viscous cell/hydrogel suspensions. Next we characterized the polymerization kinetics of fibrin glue solutions to define the ranges of concentrations compatible with catheter delivery. We then demonstrate the in vivo effectiveness of this preparation and its ability to increase cell retention and survival in a nude rat model of myocardial infarction

Geometric Control of Human Stem Cell Morphology and Differentiation

During tissue morphogenesis, stem cells and progenitor cells migrate, proliferate, and differentiate, with striking changes in cell shape, size, and acting mechanical stresses. The local cellular function depends on the spatial distribution of cytokines as well as local mechanical microenvironments in which the cells reside. In this study, we controlled the organization of human adipose derived stem cells using micro-patterning technologies, to investigate the influence of multi-cellular form on spatial distribution of cellular function at an early stage of cell differentiation. The underlying role of cytoskeletal tension was probed through drug treatment. Our results show that the cultivation of stem cells on geometric patterns resulted in pattern- and position-specific cell morphology, proliferation and differentiation. The highest cell proliferation occurred in the regions with large, spreading cells (such as the outer edge of a ring and the short edges of rectangles). In contrast, stem cell differentiation co-localized with the regions containing small, elongated cells (such as the inner edge of a ring and the regions next to the short edges of rectangles). The application of drugs that inhibit the formation of actomyosin resulted in the lack of geometrically specific differentiation patterns. This study confirms the role of substrate geometry on stem cell differentiation, through associated physical forces, and provides a simple and controllable system for studying biophysical regulation of cell function