Invasive meningococcal disease in three siblings with hereditary deficiency of the 8th component of complement: Evidence for the importance of an early diagnosis

Deficiency of the eighth component of complement (C8) is a very rare primary immunodeficiency, associated with invasive, recurrent infections mainly caused by Neisseria species. We report functional and immunochemical C8 deficiency diagnosed in three Albanian siblings who presented with severe meningococcal infections at the age of 15 years, 4 years and 17 months, respectively. The youngest suffered serious complications (necrosis of fingers and toes requiring amputation). METHODS: Functional activity of the classical, alternative and mannose-binding lectin complement pathways was measured in serum from the 3 siblings and their parents (37-year-old woman and 42-year-old man). Forty healthy subjects (20 males and 20 females aged 4-38 years) served as normal controls. Serum complement factors were measured by haemolytic assays and immunoblotting. Sequence DNA analysis of the C8B gene was performed. RESULTS: Analyses of the three complement pathways revealed no haemolytic activity and also absence of C8beta in serum samples from all three siblings. The genetic analysis showed that the three siblings were homozygous for the p.Arg428* mutation in the C8B gene on chromosome 1p32 (MIM 120960). The parents were heterozygous for the mutation and presented normal complement activities. A 2-year follow-up revealed no further infective episodes in the siblings after antibiotic prophylaxis and meningococcal vaccination. CONCLUSIONS: Complement deficiencies are rare and their occurrence is often underestimated. In presence of invasive meningococcal infection, we highlight the importance of complement screening in patients and their relatives in order to discover any genetic defects which would render necessary prophylaxis to prevent recurrent infections and severe complications

Embedding physical activity in the heart of the NHS: the need for a whole-system approach

Solutions to the global challenge of physical inactivity have tended to focus on interventions at an individual level, when evidence shows that wider factors, including the social and physical environment, play a major part in influencing health-related behaviour. A multidisciplinary perspective is needed to rewrite the research agenda on physical activity if population-level public health benefits are to be demonstrated. This article explores the questions that this raises regarding the particular role that the UK National Health Service (NHS) plays in the system. The National Centre for Sport and Exercise Medicine in Sheffield is put forward as a case study to discuss some of the ways in which health systems can work in collaboration with other partners to develop environments and systems that promote active lives for patients and staff

Novel Echocardiographic Biomarkers in the Management of Atrial Fibrillation

Purpose of Review: Atrial fibrillation (AF) is the most common arrhythmia in adults. The number of patients with AF is anticipated to increase annually, mainly due to the aging population alongside improved arrhythmia detection. AF is associated with a significantly elevated risk of hospitalization, stroke, thromboembolism, heart failure, and all-cause mortality. Echocardiography is one of the key components of routine assessment and management of AF. Therefore, the aim of this review is to briefly summarize current knowledge on “novel” echocardiographic parameters that may be of value in the management of AF patients. Recent Findings: Novel echocardiographic biomarkers and their clinical application related to the management of AF have been taken into consideration. Both standard parameters such as atrial size and volume but also novels like atrial strain and tissue Doppler techniques have been analyzed. Summary: A number of novel echocardiographic parameters have been proven to enable early detection of left atrial dysfunction along with increased diagnosis accuracy. This concerns particularly experienced echocardiographers. Hence, these techniques might improve the prediction of stroke and thromboembolic events among AF patients and need to be further developed and disseminated. Nonetheless, even the standard imaging parameters could be of significant value and should not be discontinued in everyday clinical practice. © 2019, The Author(s)

Increased frequency rate and alteration of If current in iPSC-derived atrial fibrillation human cardiomyocytes.

Atrial fibrillation (AF) is the most common sustained arrhythmia worldwide. The mechanisms underlying AF are not fully understood, but multiple pathophysiological pathways have been suggested. On the contrary, the well-established AF risk factors include male sex, advancing age, diabetes, hypertension, heart failure, myocardial infarction, and valvular heart disease. Nevertheless, much of the AF risk variability remains unexplained, leading investigators to look for novel and genetic risk factors. Since 1940, a number of reports have described rare inherited AF disorders mainly associated with cardiac channel mutations. Recently several GWAS studies have shown the association of AF with peculiar chromosomal loci, and, nowadays, parental AF is considered as one of the main risk factor in offspring. We started characterizing a family where three siblings suffered a common persistent AF. The consanguinity, the variability in risk factors, and the young age of onset of AF in these patients (from 44 to 52 years old) strongly suggested a genetic basis for this form of arrhythmia. Since an extensive single candidate gene analysis, comprising several known AF-associated genes, did not reveal any mutation, we approached the entire exome analysis to identify other sequence abnormalities. Preliminary results show that the three siblings are carrying two different single nucleotide mutations in cellular filaments. These mutations, further confirmed by Sanger sequence analysis, are absent in the rest of the family and have not been described in human exome sequence databases. In parallel, we built the cellular-based human in vitro AF model, starting from patients-derived primary cultures of dermal fibroblasts. These cells were transduced with Yamanaka’s factors OCT4, KLF4, SOX2 and c-MYC, using two different systems: either a mix of retroviruses each of them carrying a single gene, or a single lentiviral particle carrying an omni-comprehensive polycistronic RNA. Colonies of pluripotent stem cells (iPSC) were generated using both systems, but the lentiviral infection showed a higher reprogramming efficiency. Nevertheless, karyotype analysis of five independent clones showed a common chromosomal translocation (t17;19) that was absent in fibroblast primary culture, as well as in retroviral infected iPS clones. Following the assessment of pluripotency, we have differentiated AF-derived iPSC into cardiomyocytes (CMs) by a standard differentiation protocol through embryoid bodies formation. The presence of beating cells allowed us to identify and to isolate clusters of CMs whose electrophysiological properties have been analyzed. Cellular spontaneous action potentials were recorded revealing different traces and frequencies in AF-derived CMs versus the normal counterpart. Moreover, after single CM isolation, we measured funny current (If), strongly related to pacemaker activity. We found that the activation of HCN channels in AF-derived CMs is reached before the normal counterpart, thus suggesting a higher cellular excitability. In conclusion we obtained iPSC-derived human CMs that, as shown, represent a valuable and reliable model of AF. We are presently using our model to understand the link between the identified mutations and the recorded functional alterations. Using this tool we will ultimately be able to identify novel therapeutic targets for this form of cardiac arrhythmia

Generation and characterization of human cardiomyocytes derived from pluripotent stem cells

In vitro development has been widely studied using murine ESCs (mESCs), whose differentiation procedure in culture implies the initial leukemia inhibitory factor (LIF) removal and the formation of cellular aggregates using the “hanging drop” method. These three dimensional (3D) structures, called embryoid bodies (EBs), replicate in vitro the different stages of murine embryonic development. Around differentiation day (dd) 8, clusters of spontaneously beating cells appear in culture; these cells express several transcriptional and structural cardiac markers and were therefore classified generically as cardiomyocytes. Since their isolation, human ESCs have shown different culturing needs from the murine counterpart, and their behavior revealed also minor differentiation plasticity. Cardiac differentiation is the most glaring example of this statement: only a modest proportion of EBs derived from either hESC or hiPSC contains contracting cells. This occurrence leads to the setup of different methods aimed to increase cardiac differentiation during in vitro development of pluripotent stem cells. While some of these procedures retain an initial 3D EB formation, others start from a confluent monolayer. However, CMs differentiated in vitro vary considerably from cells isolated from a mature human heart, because of the absence of humoral factors and organized mechanical and electrical stress. In general, many of the features of hPSC-CMs are reminiscent of normal fetal cells. hPSC-CMs are spontaneously beating cells co-expressing atrial-, ventricular-, and nodal- markers, with unorganized sarcomeres, immature mitochondria, and an expression profile different from adult CMs. The CMs that arise during early hESC or hiPSC in vitro differentiation exhibit spontaneous AP, with a relatively depolarized resting membrane potential, probably due to the temporary absence of the inward rectifier potassium current. The expression of the ion channels and, consequently, the ionic currents will undergo developmental maturation over time, as assessed by modifications in current density and property. hPSC-CMs immaturity is also reflected in their excitation–contraction machinery, lacking clear T-tubuli, disorganized sarcomeric striations, and immature Ca2+ handling. Then the possibility to obtain human CMs in a culture dish is a powerful technique that will allow identification of new drugs in pharmacological studies as well as the identification of new causative genes in modeling genetic pathologies. Nevertheless, newly differentiated human CMs show a low degree of maturation that must be considered and, eventually, overcome by physical, mechanical or cultural stimuli