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.

Prenatal Diagnosis and Postnatal Outcome of Fetuses with Pulmonary Atresia and Ventricular Septal Defect.

PURPOSE: To assess the intrauterine course, associated conditions and postnatal outcome of fetuses with pulmonary atresia with ventricular septal defect (PAVSD). METHODS: All cases of PAVSD diagnosed prenatally over a period of 10 years with a minimum follow-up of 6.5 years were retrospectively collected in 3 tertiary referral centers. RESULTS: 50 cases of PAVSD were diagnosed prenatally. 44.0 % of fetuses had isolated PAVSD, 4.0 % had associated cardiac anomalies, 10.0 % had extra-cardiac anomalies, 38.0 % had chromosomal anomalies, 4.0 % had non-chromosomal syndromes. Among the 32 liveborn children, 56.3 % had reverse flow in the patent arterial duct, 25.0 % had major aortopulmonary collateral arteries (MAPCAs) with ductal agenesis and 18.7 % had a double supply. 17 pregnancies were terminated (34.0 %), there was 1 intrauterine fetal death (2.0 %), 1 neonatal death (2.0 %), and 6 deaths (12.0 %) in infancy. 25 of 30 (83.3 %) liveborn children with an intention to treat were alive at the latest follow-up. The mean follow-up among survivors was 10.0 years (range 6.5-15.1). 56.0 % of infants underwent staged repair, 44.0 % had one-stage complete repair. After exclusion of infants with additional chromosomal or syndromal anomalies, 88.9 % were healthy, and 11.1 % had mild limitations. The presence of MAPCAs did not differ significantly between survivors and non-survivors (p = 0.360), between one-stage or staged repair (p = 0.656) and healthy and impaired infants (p = 0.319). CONCLUSION: The prognosis in cases without chromosomal or syndromal anomalies is good. MAPCAs did not influence prognosis or postoperative health. The incidence of repeat interventions due to recurrent stenoses is significantly higher after staged compared with single-stage repair.

Severe Pulmonary Stenosis or Atresia with Intact Ventricular Septum in the Fetus: The Natural History.

PURPOSE: To assess the intrauterine course, the outcome, and to establish a new prenatal echocardiographic scoring system to predict biventricular (BV) versus univentricular (UV) outcome of fetuses with severe pulmonary stenosis or atresia with intact ventricular septum (PSAIVS). METHODS: All cases of PSAIVS diagnosed prenatally over a period of 14years were retrospectively collected in 2 tertiary referral centers. RESULTS: Forty-nine fetuses with PSIVS (n = 11) or PAIVS (n = 38) were identified prenatally. Nineteen (38.8%) fetuses had additional ventriculocoronary connections (VCCs) and 21 (42.9%) fetuses had right ventricular hypoplasia. Four (8.2%) pregnancies were terminated, 2 (4.1%) ended in intrauterine fetal death, 4 (8.2%) in neonatal death, and 5 (10.2%) children died in infancy or childhood, including one case with compassionate care. Thirty-four of 44 (77.3%) fetuses with the intention-to-treat were alive at latest follow-up, 25 (73.5%) with BV, and 9 (26.5%) with UV circulation. Most significant predictive markers of UV circulation were Vmax of tricuspid regurgitation (TR) <2 m/s, right ventricle/left ventricle length ratio ≤0.6, and presence of VCC. A scoring system including these 3 markers had 100% sensitivity and 100% specificity predicting an UV outcome if more than one of these criteria was fulfilled. All 25 liveborn infants that were suitable for BV repair survived, whereas only 9 out of 14 candidates for UV repair survived. None of the 14 fetuses with predicted UV outcome would have met the inclusion criteria for fetal intervention, as 10 of them had VCC and the remaining 4 had absent TR or Vmax <2 m/s. CONCLUSION: The prognosis of prenatally diagnosed PSAIVS is good if BV circulation can be achieved, while postnatal mortality in UV circulation is high within the first 4 months of life. Postnatal outcome can be predicted prenatally with high accuracy using a simple scoring system. This information is mandatory for parental counseling and may be useful in selecting fetuses for intrauterine valvuloplasty.

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.

Use of whole exome sequencing in the NICU: Case of an extremely low birth weight infant with syndromic features.

Single gene (Mendelian) disorders are one of the leading causes of neonatal morbidity and mortality. However, in the setting of preterm birth phenotypic features of genetic diseases are often undifferentiated and are clinically very difficult to interpret based on the wide range of differential diagnoses. We report an extremely low birth weight infant (ELBW) born prematurely at 23 + 0 gestational weeks after twin pregnancy with a novel clinical manifestation with persistent hyperglycaemia as well as the known manifestations of disease-associated hypokinesia, renal salt wasting, and multifocal atrial tachycardia. The patient died of heart failure on the 72nd day of life. Whole exome sequencing (WES) revealed a previously well established, disease-causing heterozygous likely pathogenic variant in the Harvey rat sarcoma viral oncogene homolog (HRAS)-gene (c.35G > C, p. G12A, rs104894230), which implied the clinical diagnosis of Costello syndrome (CS; OMIM#190020.0004). The twin brother merely had complications related to preterm birth and did not show any CS symptoms. In conclusion, our case illustrated that CS should be considered in ELBW infants showing a life-threatening combination of complex cardiac arrhythmia and hypokinesia. If a syndromic disorder is suspected in the neonatal intensive care unit (NICU) setting, rapid WES is a useful, non-invasive diagnostic tool in critically ill ELBW infants.

Aortic Coarctation a Systemic Vessel Disease-Insights from Magnetic Resonance Imaging.

BACKGROUND: Even after successful aortic coarctation (CoA) repair, hypertension causes premature morbidity and mortality. The mechanisms are not clear. The aim was to evaluate elastic wall properties and aortic morphology and to correlate these results with severity of restenosis, hypertension, aortic arch geometry, noninvasive pressure gradients, and time and kind of surgical procedure. METHODS: Eighty-nine patients (17 ± 6.3 years) and 20 controls (18 ± 4.9 years) were examined using magnetic resonance imaging (MRI). In addition to contrast-enhanced MR angiography and flow measurements, CINE MRI was performed to assess the relative change of aortic cross-sectional areas at diaphragm level to calculate aortic compliance (C). RESULTS: Fifty-four percent of all patients showed hypertension (> 95th percentile), but more than half of them had no significant stenosis (defined as ≥30%). C was lower in CoA than in controls (3.30 ± 2.43 vs. 4.67 ± 2.21 [10-5 Pa-1 m-2]; p = 0.024). Significant differences in compliance were found between hyper- and normotensive patients (2.61 ± 1.60 vs. 4.11 ± 2.95; p = 0.01), and gothic and Romanesque arch geometry (2.64 ± 1.58 vs. 3.78 ± 2.81; p = 0.027). There was a good correlation between C and hypertension (r = 0.671; p < 0.01), but no correlation between C (and hypertension) and time or kind of repair, restenosis, or pressure gradients. CONCLUSION: The decreased compliance, a high rate of hypertension without restenosis, and independency of time and kind of repair confirm the hypothesis that CoA may not be limited to isthmus region but rather be a widespread (systemic) vascular anomaly at least in some of the CoA patients. Therefore, aortic compliance should be assessed in these patients to individually tailor treatment of CoA patients with restenosis and/or hypertension.

Prenatal diagnosis, associated findings and postnatal outcome of fetuses with double outlet right ventricle (DORV) in a single center.

Objective To assess the spectrum of associated anomalies, the intrauterine course, postnatal outcome and management of fetuses with double outlet right ventricle (DORV). Methods All cases of DORV diagnosed prenatally over a period of 8 years were retrospectively collected in a single tertiary referral center. All additional prenatal findings were assessed and correlated with the outcome. The accuracy of prenatal diagnosis was assessed. Results Forty-six cases of DORV were diagnosed prenatally. The mean gestational age at first diagnosis was 21+4 weeks (range, 13-37). A correct prenatal diagnosis of DORV was made in 96.3% of the cases. If the relation of the great arteries, the position of the ventricular septal defect (VSD) and additional cardiac anomalies are taken into account, the prenatal diagnosis was correct in 92.6% of the cases. One case was postnatally classified as transposition of the great arteries with subpulmonary VSD and was excluded from further analysis. A total of 41 (91.1%) fetuses with DORV had major additional cardiac anomalies, 30 (66.7%) had extracardiac anomalies and 13 (28.9%) had chromosomal or syndromal anomalies. Due to their complex additional anomalies, five (11.1%) of our 45 fetuses had multiple malformations and were highly suspicious for non-chromosomal genetic syndromes, although molecular diagnosis could not be provided. Disorders of laterality occurred in 10 (22.2%) fetuses. There were 17 terminations of pregnancy (37.8%), two (4.4%) intrauterine and seven (15.6%) postnatal deaths. Nineteen of 22 (86.4%) live-born children with an intention to treat were alive at last follow-up. The mean follow-up among survivors was 32 months (range, 2-72). Of 21 children who had already undergone postnatal surgery, eight (38.1%) achieved biventricular repair and 13 (61.9%) received univentricular palliation. One recently born child is still waiting for surgery. All children predicted prenatally to need a single ventricle palliation, and all children predicted to achieve biventricular repair, ultimately received the predicted type of surgery. After surgery, 14 of 18 (77.8%) children were healthy without any impairment. Conclusion DORV is a rare and often complex cardiac anomaly that can be diagnosed prenatally with high precision. DORV is frequently associated with major additional anomalies, leading to a high intrauterine and postnatal loss rate due to terminations or declined postnatal therapy. Without additional anomalies, the prognosis is good, although approximately 60% of children will have single ventricle palliation.

Bubble Formation in Children and Adolescents after Two Standardised Shallow Dives.

Circulating venous bubbles after dives are associated with symptoms of decompression sickness in adults. Up to now it is not known to what extent children and adolescents are subjected to a bubble formation during their shallow dives and if there are possible indications for that. The aim of this pilot study is to investigate whether bubbles and/or symptoms occur after standardised repeated dives performed by young divers. 28 children and adolescents (13.5±1.1 years) carried out two 25 min dives to a depth of 10 m with a 90 min surface interval. Before and after, echocardiographic data were recorded and evaluated with regard to circulating bubbles with an extended Eftedal-Brubakk-Scale by 2 different examiners. Bubbles were observed for a total of 6 subjects, Grade I (n=5) and Grade III (n=1). None of them showed any symptoms of decompression sickness. No differences were established regarding potential influencing factors on bubble formation between the groups with and without bubbles. The results indicate that even relatively shallow and short dives can generate venous bubbles in children and adolescents. To what extent this relates to the decompression sickness or clinical symptoms cannot be validated at this point.

The electrocardiogram of the neonate and infant.

The ECG in children has a number of characteristic differences compared to the ECG of the adult. The transition of the ECG in neonates after birth represents dynamic changes of the circulatory system due to the postnatal adaptation, different physiologic properties of the fetal and neonatal myocardium, the location and orientation of the heart in the chest and influence of body mass during that period and later on in childhood. The complexity of the changes implies a broad variation of ECG changes during the first days and weeks of life, whose interpretation requires expert knowledge. The ECG is an obligatory diagnostic tool in childhood arrhythmias. The long QT syndrome is an inherited rhythm disorder with risk of sudden cardiac death in early childhood. Electrocardiographic screening in neonates for the early detection of LQTS might identify individuals with an abnormal repolarization and prevent sudden death. The potential benefits of a universal screening program, even if achievable logistically and in a cost-effective manner, are however highly debatable.

Secular trends in pregnancy weight gain in German women and their influences on foetal outcome: a hospital-based study.

BACKGROUND: Increasing rates of overweight have been reported. In Germany, women of childbearing age are especially affected. Those women are at increased risks of several peri- and postnatal complications. The purpose of this study was to carry out Germany's first study in terms of secular trends of overweight and weight gain during pregnancy related to foetal clinical outcomes (birth weight, Apgar score and umbilical blood pH). METHODS: A database maintained by a large regional university hospital in Cologne, Germany was used to evaluate clinical routine data from 1996 to 2012. 11771 women (23.5 ± 5.4 years; 18-48 years), who gave birth to a live singleton child (>2000 gram) were included. Recommended weight gain during pregnancy was based on IOM guidelines: Total weight gain range for underweight (initial BMI < 18.5 kg/m2) is 12.5-18 kg/ 28-40 lbs respectively, for normal-weight (initial BMI 18.5 -24.9 kg/m2) is 11.5-16 kg/ 25-35 lbs respectively, for overweight (initial BMI 25.0-29.9 kg/m2) is 7-11.5 kg/ 15-25 lbs respectively and for obese (initial BMI ≥ 30.0 kg/m2) is 5-9 kg/ 11-20 lbs respectively.A one-way variance analysis was employed to test for differences in particular factors in various groups. Multiple linear regression analysis was used to model impact factors. RESULTS: Over the second analysed period (2005-2012), the number of women with high weight gain increased from 33.8% to 42.9% (p <0.001). 54.5% overweight and 57.7% obese women were affected (p <0.001). Women with high weight gain were 54.5% significantly more likely to give birth to an infant ≥ 4000 grams than women with normal (31.7%) or low weight gain (13.8%, p < 0.001). Women with normal weight gain had significantly better foetal outcomes in terms of the Apgar score at 5 min and umbilical cord blood pH. CONCLUSION: These data confirm an increase in maternal weight gain before and during pregnancy. An excessive weight gain is accompanied by macrosomia, lower Apgar scores and pH-value. Women should therefore be advised about the risks of obesity before and during pregnancy as well as excessive maternal weight gain during pregnancy.

The pathophysiologic aspects and clinical implications of electrocardiographic parameters of ventricular conduction delay in repaired tetralogy of Fallot.

The 12-lead surface electrocardiogram is a valuable and feasible clinical tool in the management of patients following tetralogy of Fallot (TOF) repair. The importance of QRS duration in TOF patients has long been acknowledged. A prolonged QRS complex has been associated with increased risk for subsequent life-threatening ventricular arrhythmia and sudden cardiac death. Our current ability to risk-stratify TOF patients for malignant arrhythmogenic events primarily on the basis of QRS duration is rather limited. Nevertheless, increasing evidence suggests that QRS morphology and duration may be useful as surrogate markers of infundibular and regional right ventricular myocardial disease. The aim of this review is to provide a critical appraisal of the clinical implications of established and new electrocardiographic markers of ventricular conduction delay in TOF patients following surgical correction with a particular focus on QRS duration, lengthening, and fragmentation. In addition, the pathophysiological background of these parameters is addressed.

A new model to perform electrophysiological studies in the early embryonic mouse heart.

BACKGROUND: The first electrocardiograms (ECGs) have been recorded with a capillary electrometer in the late 19(th) century by John Burdon Sanderson and Augustus Waller. In 1903 Willem Einthoven used the much more sensitive string galvanometer and was awarded Nobel Price in Medicine for this discovery. Though the physical principles of that era are still in use, there have been many advances but also challenges in cardiac electrophysiology over the last decades. One challenge is to record electrocardiograms of rather small animals such as mice and even smaller organisms such as their embryos. As mice belong to the most routinely used laboratory animals it is important to better understand their physiology and specific diseases. We therefore aimed to study whether it is feasible to measure electrical activities of embryonic mouse hearts. METHODS AND RESULTS: For our studies we used substrate-integrated Microelectrode Arrays combined with newly developed stimulation electrodes to perform electrophysiological studies in these hearts. The system enabled us to perform ECG-like recordings with atrio-ventricular (anterograde) and ventriculo-atrial (retrograde) stimulation. The functional separation of atria and ventricles, indicated by a stable atrio-ventricular conduction time, occurred clearly earlier than the morphological separation. Electrical stimulation induced a reversible prolongation of the anterograde and retrograde conduction up to atrio-ventricular conduction blocks at higher frequencies. CONCLUSION: These results yield new insight into functional aspects of murine cardiac development, and may help as a new diagnostic tool to uncover the functional and electrophysiological background of embryonic cardiac phenotypes of genetically altered mice.

Fast diastolic swinging motion of the mitral valve as a clinical marker of familial hypertrophic cardiomyopathy in genetically affected young children without left ventricular hypertrophy: a new role for noninvasive imaging?

Structural mitral valve (MV) abnormalities are common in patients with hypertrophic cardiomyopathy (HCM). This is the first report demonstrating MV abnormalities in very young children as the sole overt clinical feature of a known HCM-causing sarcomere protein gene mutation. Due to MV leaflet elongation, we also noticed a typical fast diastolic swinging motion of the MV in our patients. This novel echocardiographic feature may be used as a clinical marker of HCM disease in the absence of left ventricular hypertrophy.

Effect of Lifestyle Interventions during Pregnancy on Maternal Leptin, Resistin and Offspring Weight at Birth and One Year of Life.

Lifestyle during pregnancy impacts the health of the mother and child. However, the extent to which physical activity affects maternal biomarkers and factors that might influence birth weight remains unclear. We analysed data from two lifestyle interventions in which the effects of an exercise programme (2x/week, 60-90 min) on the course of pregnancy with regard to adipokines and offspring were evaluated. A total of 70 women participated in this study (45, intervention group; 25, control group). Anthropometric data and maternal fasting serum leptin and resistin levels were measured at three time points (approximately 14th (T1), 24th (T2), and 36th (T3) weeks of gestation). Neonatal/child data were retrieved from screening examinations. Independent of the intervention, we found a positive correlation between the fat mass at T1 and both leptin and resistin levels at all time points. Leptin level was significantly higher in the control group at T3; however, no differences between the groups were found for resistin. The birth weight was influenced by the birth length, fat mass at T1/T3, and resistin level at T2. The BMI-SDS at one year of age was influenced by maternal fat-free mass at T3 and resistin at T1/T2. Even if these results can only be interpreted cautiously, lifestyle interventions during pregnancy are important in promoting maternal and child health. Further randomised controlled trials and translational studies are warranted to clarify the underlying mechanisms.

Maternal Exercise during Pregnancy Impacts Motor Performance in 9-Year-Old Children: A Pilot Study.

The benefits of maternal physical activity during pregnancy are well documented, but long-term effects on the child have been less studied. Therefore, we conducted a pilot follow-up study of a lifestyle intervention during pregnancy that aimed to investigate whether exercise (endurance and strength training) during pregnancy affects motor performance and body composition of children up to 9 years of age, as well as possible influencing factors like brain-derived neurotrophic factor (BDNF) and lifestyle. Eleven mother-child pairs from the intervention and eight mother-child pairs from the control group were included. From birth up to 9 years of age, no differences in body mass index (BMI) or body mass index standard deviation scores (BMI-SDS) were found between the groups. Lifestyle intervention was one of the influencing factors for children's cardiorespiratory endurance capacity and coordination. Moreover, maternal BDNF in the last trimester was significantly associated with running performance, which may be due to better neuronal development. This is the first study evaluating the effects of a lifestyle intervention during pregnancy on the motor performance 9 years after birth. Children's participation in exercise programs over the past 9 years was not continuously recorded and therefore not included in the analysis. Even a cautious interpretation of these results indicates that a healthy lifestyle during pregnancy is essential in promoting child health. Larger studies and randomized control trials are necessary to confirm our results, especially those pertaining to the role of BDNF.

High-efficient serum-free differentiation of endothelial cells from human iPS cells.

INTRODUCTION: Endothelial cells (ECs) form the inner lining of all blood vessels of the body play important roles in vascular tone regulation, hormone secretion, anticoagulation, regulation of blood cell adhesion and immune cell extravasation. Limitless ECs sources are required to further in vitro investigations of ECs' physiology and pathophysiology as well as for tissue engineering approaches. Ideally, the differentiation protocol avoids animal-derived components such as fetal serum and yields ECs at efficiencies that make further sorting obsolete for most applications. METHOD: Human induced pluripotent stem cells (hiPSCs) are cultured under serum-free conditions and induced into mesodermal progenitor cells via stimulation of Wnt signaling for 24 h. Mesodermal progenitor cells are further differentiated into ECs by utilizing a combination of human vascular endothelial growth factor A165 (VEGF), basic fibroblast growth factor (bFGF), 8-Bromoadenosine 3',5'-cyclic monophosphate sodium salt monohydrate (8Bro) and melatonin (Mel) for 48 h. RESULT: This combination generates hiPSC derived ECs (hiPSC-ECs) at a fraction of 90.9 ± 1.5% and is easily transferable from the two-dimensional (2D) monolayer into three-dimensional (3D) scalable bioreactor suspension cultures. hiPSC-ECs are positive for CD31, VE-Cadherin, von Willebrand factor and CD34. Furthermore, the majority of hiPSC-ECs express the vascular endothelial marker CD184 (CXCR4). CONCLUSION: The differentiation method presented here generates hiPSC-ECs in only 6 days, without addition of animal sera and at high efficiency, hence providing a scalable source of hiPSC-ECs.

Psychosocial well-being and quality of life in siblings of children with congenital heart disease: A systematic review.

Congenital heart disease (CHD) is a major global health problem. Until recently, the siblings of this group did not receive much attention. This review, conducted from November 2019 to October 2020, aims to summarize knowledge about psychosocial well-being and quality of life (QoL), associated factors, and interventions for siblings of children with CHD. Systematic searches were conducted in PubMed, PsycINFO, PsycARTICLES, Web of Science via EBSCOhost, and CENTRAL. Twelve articles were included. Results showed that psychosocial well-being was impaired in 14% to 40% of siblings. Negative impact of illness was highest for CHD siblings compared to siblings of children with cancer, cystic fibrosis, or diabetes. QoL was impaired in up to one-third. Siblings of children with CHD and cancer rated their QoL lower than those of siblings of children with cystic fibrosis or type-1 diabetes. Associated factors were sibling age, gender, socioeconomic status, miscarriage, previous sibling death, visibility of illness, and severity of condition. Only one of two interventions focused on siblings of CHD children. Although data are scarce and inhomogeneous, it indicates that siblings of CHD children suffer from lower psychosocial well-being and QoL than siblings of children with other chronic conditions. Interventions to improve their situation should be developed.

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.

Direct contact of umbilical cord blood endothelial progenitors with living cardiac tissue is a requirement for vascular tube-like structures formation.

The umbilical cord blood derived endothelial progenitor cells (EPCs) contribute to vascular regeneration in experimental models of ischaemia. However, their ability to participate in cardiovascular tissue restoration has not been elucidated yet. We employed a novel coculture system to investigate whether human EPCs have the capacity to integrate into living and ischaemic cardiac tissue, and participate to neovascularization. EPCs were cocultured with either living or ischaemic murine embryonic ventricular slices, in the presence or absence of a pro-angiogenic growth factor cocktail consisting of VEGF, IGF-1, EGF and bFGF. Tracking of EPCs within the cocultures was performed by cell transfection with green fluorescent protein or by immunostaining performed with anti-human vWF, CD31, nuclei and mitochondria antibodies. EPCs generated vascular tube-like structures in direct contact with the living ventricular slices. Furthermore, the pro-angiogenic growth factor cocktail reduced significantly tubes formation. Coculture of EPCs with the living ventricular slices in a transwell system did not lead to vascular tube-like structures formation, demonstrating that the direct contact is necessary and that the soluble factors secreted by the living slices were not sufficient for their induction. No vascular tubes were formed when EPCs were cocultured with ischaemic ventricular slices, even in the presence of the pro-angiogenic cocktail. In conclusion, EPCs form vascular tube-like structures in contact with living cardiac tissue and the direct cell-to-cell interaction is a prerequisite for their induction. Understanding the cardiac niche and micro-environmental interactions that regulate EPCs integration and neovascularization are essential for applying these cells to cardiovascular regeneration.

Integration properties of Wharton's jelly-derived novel mesenchymal stem cells into ventricular slices of murine hearts.

Wharton's jelly (WJ) is a rich source of multiple-lineage differentiating cells, recently proposed for cell replacement therapy. However, their ability to integrate into the cardiac tissue has not been elucidated, yet. We employed in vitro cardiac transplantation models to investigate the capacity of a novel population of human WJ-derived mesenchymal stem cells (nMSCs) to integrate into both living and ischemic cardiac tissue. NMSCs were characterized for the expression of stem/progenitor cell genes and proteins, as well as for multi-lineage differentiation potential. To assess their integration properties, nMSCs were cocultured with either living or ischemic embryonic murine ventricular slices. Immunohistochemical analyses were performed on cryosections of cocultured preparations to allow human cells tracking within the cocultures. Results showed that nMSCs shared MSC and endothelial colony-forming cell characteristics at gene, protein, and functional levels. NMSCs were markedly chemoattracted towards the ventricular slices, integrating robustly into the depth of both living and ischemic cardiac tissue. In conclusion, the functional ability of WJ-derived cells to populate the cardiac tissue could be validated in vitro. The transplantation models described could be further used to depict the mechanisms of WJ-derived cells integration into the cardiac tissue, contributing to optimization of reliable cell therapies for cardiac repair.