Bacteraemia of oral origin in children-A Systematic review and network meta-analysis.

OBJECTIVES: To systematically review the prevalence of bacteraemia, triggered by dental intervention and home oral hygiene practices, in children. The network meta-analysis (NMA) quantitatively compared the risk of bacteraemia triggered by dental extractions and home and professional cleaning procedures. MATERIALS AND METHODS: Clinical trials with the outcome "bacteraemia in children" were searched. The NMA was performed using the frequentist weighted least-squares approach comparing the odds ratios (OR) of different interventions. RESULTS: Among 11 of 13 studies, dental treatment was performed under general anaesthesia. In 2,381 patients, bacteraemia occurred in 38.7%-56% patients following single-tooth extractions, in 22%-46% after manual toothbrushing (MTB), and in 26%-78% after power toothbrushing (PTB). When MTB was set as the reference (OR 1), rubber cup polishing showed a slightly higher risk (OR 1.26) of bacteraemia. PTB presented a higher risk (OR 1.79-2.27) than with single-tooth extractions (OR 1.55) but lower than that with multiple extractions (OR 2.55). CONCLUSION: Daily use of MTB and routine professional cleaning were associated with the lowest risk of developing bacteraemia in children with gingivitis, almost as much as with a single-tooth extractions. Improved plaque control with PTB increased the risk of bacteraemia. There is limited evidence on gingivitis-free and systemically-diseased children.

In Vitro Grown Micro-Tissues for Cardiac Cell Replacement Therapy in Vivo.

BACKGROUND/AIMS: Different approaches have been considered to improve heart reconstructive medicine and direct delivery of pluripotent stem cell-derived cardiomyocytes (PSC-CMs) appears to be highly promising in this context. However, low cell persistence post-transplantation remains a bottleneck hindering the approach. Here, we present a novel strategy to overcome the low engraftment of PSC-CMs during the early post-transplantation phase into the myocardium of both healthy and cryoinjured syngeneic mice. METHODS: Adult murine bone marrow mesenchymal stem cells (MSCs) and PSC-CMs were co-cultured on thermo-responsive polymers and later detached through temperature reduction, resulting in the protease-free generation of cell clusters (micro-tissues) composed of both cells types. Micro-tissues were transplanted into healthy and cryo-injured murine hearts. Short term cell retention was quantified by real-time-PCR. Longitudinal cell tracking was performed by bioluminescence imaging for four weeks. Transplanted cells were further detected by immunofluorescence staining of tissue sections. RESULTS: We demonstrated that in vitro grown micro-tissues consisting of PSC-CMs and MSCs can increase cardiomyocyte retention by >10fold one day post-transplantation, but could not fully rescue a further cell loss between day 1 and day 2. Neutrophil infiltration into the transplanted area was detected in healthy hearts and could be attributed to the cellular implantation rather than tissue damage exerted by the transplantation cannula. Injected PSC-CMs were tracked and successfully detected for up to four weeks by bioluminescence imaging. CONCLUSION: This approach demonstrated that in vitro grown micro-tissues might contribute to the development of cardiac cell replacement therapies.

Engineering of cardiac microtissues by microfluidic cell encapsulation in thermoshrinking non-crosslinked PNIPAAm gels.

Multicellular agglomerates in form of irregularly shaped or spherical clusters can recapitulate cell-cell interactions and are referred to as microtissues. Microtissues gain increasing attention in several fields including cardiovascular research. Cardiac microtissues are evolving as excellent model systems for drug testingin vitro(organ-on-a-chip), are used as tissue bricks in 3D printing processes and pave the way for improved cell replacement therapiesin vivo. Microtissues are formed for example in hanging drop culture or specialized microwell plates; truly scalable methods are not yet available. In this study, a novel method of encapsulation of cells inpoly-N-isopropylacrylamid(PNIPAAm) spheres is introduced. Murine induced pluripotent stem cell-derived cardiomyocytes and bone marrow-derived mesenchymal stem cells were encapsulated in PNIPAAm by raising the temperature of droplets formed in a microfluidics setup above the lower critical solute temperature (LCST) of 32 °C. PNIPAAM precipitates to a water-insoluble physically linked gel above the LCST and shrinks by the expulsion of water, thereby trapping the cells in a collapsing polymer network and increasing the cell density by one order of magnitude. Within 24 h, stable cardiac microtissues were first formed and later released from their polymer shell by washout of PNIPAAm at temperatures below the LCST. Rhythmically contracting microtissues showed homogenous cell distribution, age-dependent sarcomere organizations and action potential generation. The novel approach is applicable for microtissue formation from various cell types and can be implemented into scalable workflows.

The influence of physiological matrix conditions on permanent culture of induced pluripotent stem cell-derived cardiomyocytes.

Cardiomyocytes (CMs) from induced pluripotent stem (iPS) cells mark an important achievement in the development of in vitro pharmacological, toxicological and developmental assays and in the establishment of protocols for cardiac cell replacement therapy. Using CMs generated from murine embryonic stem cells and iPS cells we found increased cell-matrix interaction and more matured embryoid body (EB) structures in iPS cell-derived EBs. However, neither suspension-culture in form of purified cardiac clusters nor adherence-culture on traditional cell culture plastic allowed for extended culture of CMs. CMs grown for five weeks on polystyrene exhibit signs of massive mechanical stress as indicated by α-smooth muscle actin expression and loss of sarcomere integrity. Hydrogels from polyacrylamide allow adapting of the matrix stiffness to that of cardiac tissue. We were able to eliminate the bottleneck of low cell adhesion using 2,5-Dioxopyrrolidin-1-yl-6-acrylamidohexanoate as a crosslinker to immobilize matrix proteins on the gels surface. Finally we present an easy method to generate polyacrylamide gels with a physiological Young's modulus of 55 kPa and defined surface ligand, facilitating the culture of murine and human iPS-CMs, removing excess mechanical stresses and reducing the risk of tissue culture artifacts exerted by stiff substrates.

Perioperative placement of stents for relief of proximal pulmonary arterial stenoses in infants.

INTRODUCTION: Stenoses in the pulmonary arterial system can have a significant negative impact on the early postoperative course in infants. Early recognition and aggressive management are mandatory. PATIENTS AND METHODS: We describe our experience with 8 infants, with ages ranging from 3 to 9 months, weighing from 4.5 to 7.7 kilograms, who presented in the up to 18 days following construction of a shunt from the superior caval vein to the pulmonary arteries with clinical symptoms of obstructed pulmonary flow. We include also 2 infants in whom pulmonary arterial stents were implanted in the operating room. Cardiac catheterization showed significant stenoses or occlusion of the left pulmonary arteries in 9 infants, the right pulmonary arteries in 2, or the superior caval vein in 1, the investigation being prompted by the findings of supraphysiological superior caval venous pressures and systemic hypoxaemia. We implanted a variety of stents mounted on balloons ranging in diameter from 6 to 13 millimetres, with 7 placed across a newly created surgical anastomotic site. RESULTS: All stenoses were crossed successfully, and stents implanted satisfactorily in all patients, albeit that 1 infant suffered an acute tear of the left pulmonary artery, requiring immediate reoperation. This patient died 72 hours later due to a diffuse coagulopathy. All other patients demonstrated sustained clinical improvement following the procedure. At follow-up, 7 of the 9 survivors have progressed to completion of the Fontan circulation. Redilation of the stents was required in the interim, prior to completion of the Fontan circulation, in 4 of them. In 2 patients, the previously implanted stents were incised during the Fontan completion, permitting placement of the extracardiac Goretex conduit from the inferior caval vein to the pulmonary arteries. CONCLUSIONS: Stents can successfully be implanted perioperatively in the pulmonary arterial system during infancy, and redilated, with improvement in clinical outcome in the majority of those with clinically relevant obstruction.

Microelectrode arrays: a new tool to measure embryonic heart activity.

The analysis of the sequential excitation of cardiac tissue is of high relevance, both for clinical pathophysiological purposes, eg, detection of sustained ventricular arrhythmias, as well as for experimental electrophysiology. Clinically, different technical approaches such as single electrode measurements and bipolar mapping electrode catheters have been used. In experimental setups several techniques to record cardiac activity have been proposed. Beside the well-established intracellular current-clamp recordings of action potentials, recent studies have performed extracellularly activation sequence mapping or simultaneous multichannel action potential electrode array measurements. Measurement of extracellularly recorded field potentials (FPs) hereby especially provides detailed information about the origin and spread of excitation in the heart. A similar analytical approach for cardiac FPs advanced the analysis of excitation spread and arrhythmic activity in multicellular preparations like developmental differentiation tissue of mouse embryonic stem cells, multicellular preparations of isolated native embryonic cardiomyocytes or the embryonic heart in toto. The use of substrate-integrated Microelectrode Arrays (MEAs, Multi Channel Systems, Reutlingen, Germany) with 60 electrodes of 10-30 microm diameters on a 100-200 microm grid, coated with porous titanium nitride to minimize the impedance allows recording of FPs at a high signal to noise ratio. The possibility to electrically stimulate the tissue further expands the range of applications and bioassays. It may thus facilitate the evaluation of drug research providing detailed information about the interplay of the complex cardiac network, and might improve the predictability of physiological and pathophysiological conditions or drug effects in embryonic heart tissue.