Cytotoxic response of tumor-infiltrating lymphocytes of head and neck cancer slice cultures under mitochondrial dysfunction

Background

Head and neck squamous cell carcinomas (HNSCC) are highly heterogeneous tumors. In the harsh tumor microenvironment (TME), metabolic reprogramming and mitochondrial dysfunction may lead to immunosuppressive phenotypes. Aerobic glycolysis is needed for the activation of cytotoxic T-cells and the absence of glucose may hamper the full effector functions of cytotoxic T-cells. To test the effect of mitochondrial dysfunction on cytotoxic T cell function, slice cultures (SC) of HNSCC cancer were cultivated under different metabolic conditions.

Methods

Tumor samples from 21 patients with HNSCC were collected, from which, SC were established and cultivated under six different conditions. These conditions included high glucose, T cell stimulation, and temporarily induced mitochondrial dysfunction (MitoDys) using FCCP and oligomycin A with or without additional T cell stimulation, high glucose and finally, a control medium. Over three days of cultivation, sequential T cell stimulation and MitoDys treatments were performed. Supernatant was collected, and SC were fixed and embedded. Granzyme B was measured in the supernatant and in the SC via immunohistochemistry (IHC). Staining of PD1, CD8/Ki67, and cleaved-caspase-3 (CC3) were performed in SC.

Results

Hematoxylin eosin stains showed that overall SC quality remained stable over 3 days of cultivation. T cell stimulation, both alone and combined with MitoDys, led to significantly increased granzyme levels in SC and in supernatant. Apoptosis following T cell stimulation was observed in tumor and stroma. Mitochondrial dysfunction alone increased apoptosis in tumor cell aggregates. High glucose concentration alone had no impact on T cell activity and apoptosis. Apoptosis rates were significantly lower under conditions with high glucose and MitoDys (p=0.03).

Conclusion

Stimulation of tumor-infiltrating lymphocytes in SC was feasible, which led to increased apoptosis in tumor cells. Induced mitochondrial dysfunction did not play a significant role in the activation and function of TILs in SC of HNSCC. Moreover, high glucose concentration did not promote cytotoxic T cell activity in HNSCC SC.

Optimizing culturing conditions in patient derived 3D primary slice cultures of head and neck cancer

Background

Three-dimensional primary slice cultures (SC) of head and neck squamous cell carcinomas (HNC) are realistic preclinical models. Until now, preserving structure and viability ex vivo for several days has been difficult. The aim of this study was to optimize cultivation conditions for HNC SC and analyze the added effects of platelet rich fibrin (PRF) on these conditions.

Methods

SC were prepared from the tumor biopsies of 9 HNC patients. Cultures were incubated for 1 and 7 days in three different media- Keratinocyte serum-free medium (SFM), RPMI-1640i, and 1:1 mix of both, with and without addition of PRF. After culturing, SC were fixated, embedded, and stained with Hematoxylin-Eosin (HE) and cleaved caspase-3. In addition, triple immune fluorescence staining for cytokeratin, vimentin and CD45 was performed. Outcome parameters were cell count and cell density, viability and apoptosis, SC total area and proportions of keratinocytes, mesenchymal and immune cells. The effects of culture time, medium, and addition of PRF were calculated in an SPSS generalized linear model and using the Wald Chi-Squared test.

Results

Ninety-four slice cultures were analyzed. Viability remained stable for 7 days in culture. After addition of PRF, cell viability increased (p=0.05). SC total area decreased (0.44 ± 0.04 mm² on day 1 (95% CI: 0.35 to 0.56) to 0.29 ± 0.03 mm² on day 7 (95% CI: 0.22 to 0.36), but cell density and cell proportions remained stable. Differences in cultivation media had no significant impact on outcome parameters.

Conclusion

HNC SC can be preserved for up to 7 days using the tested cultivation media. Cell viability was best preserved with addition of PRF. HNC SC are a versatile experimental tool to study physiology and drug actions. Autologous PRF can help simulate realistic conditions in vitro.

Fibrosis inhibits ablation lesion formation in muscle tissue

Introduction

Myocardial fibrosis is a trigger for both atrial and ventricular arrhythmia. Ventricular fibrosis correlates with ventricular tachycardia, ventricular fibrillation, and sudden death. Besides medical therapy, radiofrequency (RF) ablation is an important therapeutical option to treat ventricular arrhythmia. Our study gains insights into effectivity of RF ablation depending on the degree of fibrosis.

Methods

Using a wet lab, we created with radiofrequency (RF) ablation lesions in parts of restructured beef with a defined, homogenous content of 0, 10, 20 and 50% fiber. We calculated the volume of ablation zones (called lesion volume below). Both common ablation modes low-power long-duration (LPLD: 30 W, 30 s) and high-power short-duration (HPSD: 70 W, 10 s) were tested. Lesion volumes of fibrotic beef were compared to lesion volumes of fibrotic-free beef using an ordinary ANOVA. The effect and interaction of fibrosis and ablation mode to the lesion volume was tested by a two-way ANOVA.

Results

Higher degrees of fibrosis create smaller lesion volumes (M = mean volume ablation zone): M (0%) = 322 mm3 (SD 187 mm3), M (10%) = 226 mm3 (SD 94.8), M (20%) = 217 mm3 (SD 103 mm3) and M (50%) = 186 mm3 (SD 92.7 mm2). Lesion volumes in fibrotic tissue differ significantly from lesion volumes in fibrotic-free tissue (F(3,124) = 6.94, p<0.001). There is a significant difference in lesion volumes for all degrees of fibrosis compared to fibrosis-free tissue (MD = mean difference of ablation zone volumes between 0% fibrosis and 10, 20 and 50% fibrosis): MD (0, 10%) = 95.6 mm3 (95% confidence interval (20.8–170), p=0.008), MD (0, 20%) = 105 mm3 (95% confidence interval (30.4–180), p=0.003) and MD (0, 50%) = 135 mm3 (95% confidence interval (60.7–210), p<0.001). We also found a significant difference in lesion volumes related to the content of fiber in a comparison of all groups (F(3,120) = 7,49, p≪0.001). There is no significant difference in lesion volumes related to the used ablation mode (F(1,120) = 2.89, p=0.09). There is also no significant difference in lesion volumes related to the interaction between the content of fiber and the ablation mode (F(3,120) = 1.23, p=0.3).

Conclusion

Lesions created by RF ablation are influenced by fibrosis. A higher content of fibrosis is associated with smaller lesion volumes. Neither LPLD nor HPSD ablation mode shows an advantage in fibrotic tissue.

Funding Acknowledgement

Type of funding sources: None.

Chronic heart failure as a sequel of severe burn injury: first insight into a novel pathological heart-skin axis

Research question

Our clinical research unveiled chronic heart failure with preserved ejection fraction (HFpEF) as a long-term sequel in survivors of severe pediatric burn injury due to a yet unknown molecular pathomechanism (1). Applying a standardized scald injury rat model, which is widely used in burn research, we systematically determined the pathophysiological impact of burn injury on cardiac performance to uncover systemic and molecular pathomechanisms that may cause post-burn injury HFpEF development.

Methods

Male adolescent SD-rats were subjected to a 60% total body surface area (TBSA) full-thickness burn- or sham-trauma and subsequently characterized by serial transthoracic echocardiography, bulk myocardial next-generation sequencing and proteomics as well as RT-PCR, immuno-blotting (IB), histology and plasma proteomics for cardiac performance and molecular alterations, for up to 90 days (3, 7, 30 and 90d).

Results

In comparison to the sham-group (SG, n=10), animals from the burn-group (BG, n=10; survival rate 100%) recapitulated typical post-burn clinical traits, such as significant loss in body weight (BG 27% less than SG at 30d, p<0.05) or skeletal muscle wasting (i.e., 27% less at 30d, p<0.05) in accord with elevated molecular atrophy markers throughout the observation period. Our focus on the heart revealed for the first-time post-burn cardiac muscle wasting (BG 22% less at 30d, p<0.05) and persistent markers of cardiac dysfunction in accord with significant histological cardiomyocyte hypotrophy (BG −8% at 30d, p<0.05) and significantly diminished left ventricular (LV) global longitudinal strain and isovolumic relaxation time in BGs, while LV-EF remained unchanged. Subsequent IB analysis uncovered diminished protein synthesis activity and diminished mTOR pathway activity in BG hearts. Weighted gene network correlation analysis i.e., from bulk myocardial NGS and clinical traits related activation of immunological and pro-fibrotic pathways in post-burn injury hearts to cardiac dysfunction in BGs. Subsequent RT-PCR and histology confirmed significant myocardial accumulation of cardio-depressive damage associated molecular patterns (i.e., S100A8 and A9) and infiltration by granulocytes (myeloperoxidase+) and monocytes (CD 68+) as well as significant LV fibrosis. Serial plasma proteomic analysis indicated elevated plasma levels i.e., of S100A8 and A9 and other heart failure markers that mirrored similar changes in human post-burn injury plasma samples.

Conclusion

Here we report for the first time the development of HFpEF as a novel systemic consequence of severe burn injury in a rodent model, which prepares the ground for further mechanistic and translational studies. The initial observation of cardiac inflammation and fibrosis, which are known to negatively impact cardiac performance, may be mechanistic key findings that will guide further therapeutic studies and subsequent validation of post-burn heart failure biomarkers.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Rolf-Schwiete Stiftung

Multicenter, international observational study on quality of life and acceptability of a vaginal contraceptive ring containing etonogestrel/ethinylestradiol 11.00/3.474 mg over six months of use

OBJECTIVE

The current post-market study aimed at analyzing women's menstrual bleeding intensity, vaginal infections, and quality of life parameters using the contraceptive vaginal ring Ornibel®.

PATIENTS AND METHODS

In Germany and Spain, a multicenter study of healthy female adults (n=211) aged 18 to 45 used the vaginal ring Ornibel® for at least six months. Data collection was conducted using a patient questionnaire. The menstrual bleeding intensity was analyzed using visual analog scales (VAS). A Chi-square linear trend test assessed associations between quality-of-life parameters and continuation and recommendation of vaginal ring use.

RESULTS

Three out of four women experienced six menstrual bleedings during the first six months of using the vaginal ring, with a median duration of four days during the study. The use of the vaginal ring led to a significant reduction in menstrual flow intensity (from 60 VAS points to 40 VAS points, p<0.001). In the German cohort, it was shown that dysmenorrhea and unscheduled bleeding and spotting were reduced with the use of Ornibel® as well. Most women (93.7%) agreed or strongly agreed that the vaginal ring was easy to insert, and its use was rated as comfortable or very comfortable by 97.5%. Both parameters were significantly associated with the continuation of the ring (easy to insert p=0.01, feeling comfortable: p=0.002) or its recommendation (easy to insert p=0.002, feeling comfortable: p=0.002).

CONCLUSIONS

The observational data demonstrate that the contraceptive vaginal ring provides high acceptability and comfort. It is a well-accepted contraceptive method characterized by high efficacy and positive effects on cycle control.

Multiplexed apolipoprotein profiling advances the assessment of residual lipid-related cardiovascular risk

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation

Background and Purpose

Low-density lipoprotein cholesterol (LDL-C) is among the conventional lipid parameters used to predict risk of cardiovascular disease (CVD). Statins lower blood levels of pro-atherogenic LDL-C, but a residual cardiovascular risk remains in some individuals with therapeutically optimised LDL-C levels. Although the metabolism of LDL-C and other lipoprotein particles is governed by a range of different apolipoproteins, only apolipoproteins A-I and B are measured in clinical assays. Using a more comprehensive apolipoprotein panel in a large epidemiological cohort, this study aimed to determine the association of individual apolipoprotein levels with risk of coronary heart disease (CHD).

Methods

Bottom-up multiple reaction monitoring–mass spectrometry (MRM–MS) was used in conjunction with stable isotope-labelled peptide standards to quantify plasma levels of 13 apolipoproteins in participants of the Precocious Coronary Artery Disease (PROCARDIS) study (N = 1916; 941 cases of CHD, 975 controls). The relationship between apolipoprotein levels and CHD was assessed after adjusting for established risk factors for CVD and correcting for statin use.

Results

The strongest positive associations with CHD in the PROCARDIS study were seen for triglyceride-related apolipoproteins C-I (odds ratio [OR] 2.38, 95% confidence interval [CI] 1.63–3.46), C-III (OR 2.95, 95% CI 1.85–4.71) and E (OR 2.35, 95% CI 1.54–3.58), as well as for apolipoprotein (a) (kringle IV type 2 repeat, OR 2.84, 95% CI 2.04–3.95). Comparing these with associations of apolipoproteins with CVD in the Bruneck study (N = 688) revealed consistency across the two cohorts. Robust inverse associations with CHD were observed for apolipoproteins A-IV (OR 0.45, 95% CI 0.31–0.65) and M (OR 0.29, 95% CI 0.19–0.44).

Conclusion

Analysing two large epidemiological cohorts, Bruneck and PROCARDIS, demonstrated that multiplexed apolipoprotein profiling improves the understanding of cardiovascular risk independent of conventional lipid parameters. Most prominently, triglyceride-related apolipoproteins were shown to positively associate with residual cardiovascular risk. The findings of this study support the need for development and implementation of standardised, MRM–MS-based apolipoprotein profiling assays to guide novel lipid-modifying therapies beyond statins.

A proteomic atlas of atherosclerosis: regional proteomic signatures for plaque inflammation and calcification

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): This study was mainly supported from the British Heart Foundation (BHF) supporting Prof. Manuel Mayr as a Chair Holder (CH/16/3/32406) with BHF programme grant support (RG/16/14/32397) and Dr. Theofilatos with BHF programm grant support (G/20/10387).

Background

Using proteomics, we strove to reveal novel molecular subtypes of human atherosclerotic lesions, study their associations with histology and imaging and relate them to long-term cardiovascular outcomes.

Methods

219 samples were obtained from 120 patients undergoing carotid endarterectomy. Sequential protein extraction was combined with multiplexed, discovery proteomics. Parallel reaction monitoring for 135 proteins was deployed for targeted validation. A combination of statistical, bioinformatics and machine learning methods was used to perform differential expression, network, pathway enrichment analysis and train and evaluate prognostic models.

Results

Our extensive proteomics analysis from the core and periphery of plaques doubled the coverage of the plaque proteome compared to the largest proteomics study on atherosclerosis thus far. Plaque inflammation and calcification signatures were inversely correlated and validated with targeted proteomics. The inflammation signature was enriched with neutrophil-derived proteins, including calprotectin (S100A8/9) and myeloperoxidase. The calcification signature contained fetuin-A, osteopontin, and gamma-carboxylated proteins. Sex differences in the proteome of atherosclerosis were explained by a higher proportion of calcified plaques in women. Single-cell RNA sequencing data attributed the inflammation signature predominantly to neutrophils and macrophages and the calcification signature to smooth muscle cells, except for certain plasma proteins that were not expressed but retained in the plaque, i.e., fetuin-A. Echogenic lesions reflect the collagen content and calcification of plaque but carotid Duplex ultrasound fails to capture the extent of inflammatory protein changes in symptomatic plaques. Applying dimensionality reduction and machine learning on the proteomics data defined 4 distinct plaque phenotypes and revealed key protein signatures linked to smooth muscle cell content, plaque calcification and structural extracellular matrix, which improved the 9-year prognostic AUC by 25% compared to ultrasound and histology. A biosignature of four proteins (CNN1, PROC, SERPH, and CSPG2) independently predicted the progression of atherosclerosis and cardiovascular mortality with an AUC of 75%

Conclusion

We combined discovery and targeted proteomics with network reconstruction and clustering techniques to provide molecular insights into protein changes in atherosclerotic plaques. The application of proteomics and machine learning techniques revealed distinct clusters of plaques that inform on disease progression and future adverse cardiovascular events.

Proteomics to assess myocardial remodelling in human heart failure and explore the effect of medications and comorbidities

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation

Background

Myocardial remodelling is a hallmark of heart failure (HF). Our previous proteomics analyses demonstrated a profound effect of beta blockers on cardiac extracellular matrix composition in ischaemic HF patients (1). No comprehensive proteomics characterizations has been performed in non-ischaemic HF patients.

Methods

Mass spectrometry was used to analyze intracellular and extracellular protein extracts from left ventricular samples obtained from patients with ischemic (n=65) and non-ischaemic (n=114) HF after heart transplantation, as well as non-failing controls (n=19). All HF patients had ventricular dilatation and reduced ejection fraction (EF%).

Results

The proteomics comparison across 198 cardiac samples with two tissue extracts revealed hallmarks of HF in both groups of patients compared to controls, including elevated levels of atrial natriuretric peptides and the fibroblast marker vimentin, as well as decreases in creatine kinase M/B, troponin C, and myosin light chain 2 (Figure 1). In comparison to ischaemic HF patients, non-ischaemic HF patients showed elevated levels of proteins involved in proteasome activation, consistent with the notion of increased protein degradation in cardiomyocytes even at the end stage of the disease (2). Despite similar clinical characteristics, myocardial remodelling in response to HF medications and the presence of comorbidities was different between the two HF groups. In ischaemic HF patients the use of β-blockers resulted in reduced proteoglycan deposition. In non-ischaemic patients, few protein changes were associated with medication. Instead, comorbidities such as atrial fibrillation and hypertension were critical determinants of myocardial protein remodelling in these HF patients (Figure 2). Notably, hypertensive HF patients showed a marked reduction in angiotensin converting enzyme 2 (ACE2) compared to normotensive patients, and this was accompanied by a reduction in Cysteine And Glycine Rich Protein 3 (CSRP3), a key player in the organization of cytosolic structures in cardiomyocytes, and the nuclear lamina proteins lamin A/C and B. The inflammation-related galectin 3-binding protein was reduced in hypertensive patients as were the extracellular proteases matrix metalloprotease 2, cathepsin G and chymase 1.

Conclusion

Our study constitutes the largest proteomics analysis of HF to date. We observed distinct protein remodelling processes in ischaemic and non-ischaemic HF patients and discerned the myocardial effects of medications and comorbidities such as hypertension.

MicroRNA biomarkers of platelet function

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation (BHF), VASCage (Centre for Promoting Vascular Health in the Ageing Community) of the Austrian Research Promotion Agency FFG (COMET program - Competence Centers for Excellent Technologies)

Introduction

Antiplatelet therapy (APT) leads to reduced morbidity and mortality in patients with cardiovascular disease but some still have thrombotic events. Tailoring APT to platelet function is currently limited by a lack of suitable platelet function tests. It has been previously shown that different circulating microRNAs (miRNAs) are derived from platelets and their measurement could provide new markers of platelet reactivity.

Purpose

To compare the release of different platelet miRNAs in response to different platelet agonists.

Methods

Measurements of platelet function were performed by light transmission aggregometry (LTA) in participants of the 2015 follow-up of the Bruneck study (n=338), using the following agonists: arachidonic acid (1mM), adenosine diphosphate (5µM, 20µM), collagen (0.4 µg/ml, 4 µg/ml, 10µg/ml), TRAP-6 amide (25µM) and U46619 (10µM). LTA platelet releasates were then used for RT-qPCR measurements of five platelet-enriched miRNAs (miR-21, miR-126, miR-150, miR-197, miR-223). Platelet-poor plasma (PPP) served as negative control.

Results

Platelet activation led to aggregation and extracellular release of miRNAs, with aspirin users (n=155) showing significantly lower miRNA release than non-aspirin users (n=183). Agonist responsiveness differed among miRNAs, with miR-21 being hyperresponsive to arachidonic acid and miR-150 being hyperresponsive to adenosine diphosphate, whilst release of miR-126, miR-197 and miR-223 was strongest to collagen (10µg/ml). In non-aspirin users, inflammation markers such as granulocyte counts or C-reactive protein correlated positively with platelet-derived miRNAs measured in PPP, whilst they correlated negatively with platelet-derived miRNAs measured in releasates. These effects were absent in aspirin users.

Conclusions

MiRNAs released from activated platelets can be reliably detected in PPP and platelet releasates. Preferential release of miRNAs in response to specific agonists suggests a selective release mechanism. Elevated PPP levels and decreased releasate levels of platelet-derived miRNAs in inflammatory environments suggest platelet exhaustion ex vivo due to platelet pre-activation.

Assessing compartmentalisation of small non-coding RNAs by fractionation of lipoproteins and extracellular vesicles of human plasma

Funding Acknowledgements

Type of funding sources: None.

Background/Introduction

Circulating small non-coding RNAs (ncRNAs), such as microRNAs (miRNAs) and YRNAs, have been implicated in intercellular communication and as biomarkers for cardiometabolic diseases. The putative carriers of ncRNAs are lipoproteins, extracellular vesicles (EVs) and RNA-binding proteins. However, the lack of reliable separation methods for EVs and lipoproteins from human blood hampers the assignment of small ncRNA signatures to different carriers.

Purpose

To study which classes of ncRNAs are carried by EVs or lipoproteins in the circulation.

Methods & Results

In order to minimise the co-isolation of lipoproteins and EVs, size-exclusion chromatography (SEC) was established to improve resolution of nanoparticles from plasma. Mass spectrometry and immunoblotting for EV markers (syntenin-1 and CD9) and apolipoproteins (ApoA1 and ApoB for high- and low-density lipoproteins, respectively) were used to characterise the isolated preparations and identify co-isolating species. Quantitative real-time PCR of each carrier-rich fraction after SEC showed that miRNAs were mainly detected in the late-eluting fractions, enriched in ApoA1-containing lipoproteins. Only a small proportion of miRNAs was associated with fractions rich in albumin or in EVs. On the other hand, YRNAs were predominantly found in the albumin-rich and ApoB-containing fractions. To assess whether lipoproteins are key carriers for ncRNAs, HDL and ApoB immuno-depletion methods were employed. Both lipoprotein depletion methods failed to substantially deplete small ncRNAs from plasma.

Conclusion

We studied the distribution of circulating ncRNAs amongst different SEC fractions from human plasma. We have observed a minor role for lipoproteins as carriers of ncRNAs. Further investigation will focus on using SEC fractionation to assess EVs and RNA-binding proteins and their role as ncRNA carriers in plasma.

Comparative secretome analysis of obese perivascular adipose tissue reveals impaired adipose-neuronal crosstalk

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): BHF Programme Grant (RG/16/14/32397)

VASCage-Research Center on Vascular Ageing and Stroke (No. 868624)

Background

While canonical adipose tissue (AT) depots have been extensively characterised in health and disease, comparatively little is known about the pathological changes affecting the perivascular AT’s (PVAT) physiology during obesity.

Purpose

The aim of this study was to study the impact of obesity on the secretory activity of the murine PVAT.

Methods

We exploited proteomics to profile the secretome of peri-aortic and canonical AT depots in wild-type (wt) and obese (ob/ob) mice. In parallel, fat tissues were processed for biochemical and histological analysis and mechanistical experiments were performed in vitro on primary neuronal cultures.

Results

Proteomics on ATs conditioned media from wt mice revealed that each fat depot displays a unique secretory profile. The enrichment of neuronal cell-adhesion molecules detected in PVAT secretomes reflected a higher content of intra-parenchymal sympathetic projections compared to non-perivascular ATs. A significant decrease of the same neuronal proteins in PVAT conditioned media from ob/ob mice was found to be associated with a substantial reduction of the perivascular sympathetic innervation. Intriguingly, a similar decrease of sympathetic markers was detected in the epicardial AT from obese patients. Mechanistically, the conditioned media from ob/ob AT explants was found to exert a deleterious effect on the axons of primary sympathetic neurons in vitro, indicating that this neuropathy is due to local alterations of the PVAT secretome that detrimentally impact on the embedded sympathetic neurites. Among proteins significantly down-regulated in the secretomes of ob/ob PVAT samples, neuronal growth regulator 1 (Negr1) was found to promote axonal elongation and branching on sympathetic neurons in vitro. Administration of recombinant Negr1 also partially restored the neurotrophic effect of ob/ob AT secretomes on sympathetic axons both in vitro and in vivo.

Conclusions

Obesity-related alterations in the secretome of PVAT severely affect the homeostasis of the perivascular environment, leading to a loss of perivascular sympathetic innervation. A novel neurotrophic role is unveiled for Negr1, whose locus has been associated with human obesity.

Precision Medicine Approach for Cardiometabolic Risk Factors in Therapeutic Apheresis

Lipoprotein apheresis (LA) is currently the most powerful intervention possible to reach a maximal reduction of lipids in patients with familial hypercholesterolemia and lipoprotein(a) hyperlipidemia. Although LA is an invasive method, it has few side effects and the best results in preventing further major cardiovascular events. It has been suggested that the highly significant reduction of cardiovascular complications in patients with severe lipid disorders achieved by LA is mediated not only by the potent reduction of lipid levels but also by the removal of other proinflammatory and proatherogenic factors. Here we performed a comprehensive proteomic analysis of patients on LA treatment using intra-individually a set of differently sized apheresis filters with the INUSpheresis system. This study revealed that proteomic analysis correlates well with routine clinical chemistry in these patients. The method is eminently suited to discover new biomarkers and risk factors for cardiovascular disease in these patients. Different filters achieve reduction and removal of proatherogenic proteins in different quantities. This includes not only apolipoproteins, C-reactive protein, fibrinogen, and plasminogen but also proteins like complement factor B (CFAB), protein AMBP, afamin, and the low affinity immunoglobulin gamma Fc region receptor III-A (FcγRIIIa) among others that have been described as atherosclerosis and metabolic vascular diseases promoting factors. We therefore conclude that future trials should be designed to develop an individualized therapy approach for patients on LA based on their metabolic and vascular risk profile. Furthermore, the power of such cascade filter treatment protocols may improve the prevention of cardiometabolic disease and its complications.

Detection and abundance of SARS-CoV-2 in wastewater in Liechtenstein, and the estimation of prevalence and impact of the B.1.1.7 variant

The new coronavirus 2 (SARS-CoV-2) is known to be also shed through feces, which makes wastewater-based surveillance possible, independent of symptomatic cases and unbiased by any testing strategies and frequencies. We investigated the entire population of the Principality of Liechtenstein with samples from the wastewater treatment plant Bendern (serving all 39,000 inhabitants). Twenty-four-hour composite samples were taken once or twice a week over a period of 6 months from September 2020 to March 2021. Viral RNA was concentrated using the PEG centrifugation method followed by reverse transcription quantitative PCR. The aim of this research was to assess the suitability of SARS-CoV-2 fragments to relate the viral wastewater signal to the incidences and assess the impact of the emerging B.1.1.7. variant. The viral load in the wastewater peaked at almost 9 × 10⁸ viral fragments per person equivalent (PE) and day on October 25, and showed a second peak on December 22 reaching a viral load of approximately 2 × 10⁸ PE^-1d^-1. Individual testing showed a lag of 4 days and a distinct underestimation of cases at the first peak when testing frequency was low. The wastewater signal showed an immediate response to the implementation of non-pharmaceutical interventions. The new virus variant B.1.1.7. was first detected in wastewater on December 23, while it was first observed with individual testing on January 13, 2021. Further, our data indicate that the emergence of new virus variant may change the wastewater signal, probably due to different shedding patterns, which should be considered in future models.

Nichtrauchen ist clever: a smoking prevention program for schoolchildren and what we learn from the kids

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): PFIZER: unrestricted medical grant

Background

Tobacco consumption is an important preventable cause of premature death worldwide. Nevertheless, smoking is still common, globally. Smoking in adulthood is closely associated with smoking during adolescence. Therefore, as a global epidemic, tobacco consumption must not only be tackled in adults, but it is particularly important to focus on smoking prevention among young people.

Purpose

In 2014, a hospital-based smoking prevention program "Nichtrauchen ist clever!" (NIC!) for adolescents was initiated, consisting of three parts: namely a workshop, a film, and a patient interview. The aim of the study was to evaluate the acceptance of the program, and to explore participants’ awareness on smoking related diseases and factors that promote smoking initiation.

Methods

We performed an observational study to evaluate students’ acceptance of the program and their smoking habits, and a qualitative approach, to assess their view on reasons for smoking initiation and their knowledge about smoking-related diseases.

Results

Between January 2016 and December 2019, 1658 students participated our observational study with a mean age of 13.3 years (SD ±0.9). Twenty-six percent (429/1658) have already tried tobacco products (so called triers), specifically cigarettes, electronic (e)-cigarettes, and shisha. Use of e-cigarettes was most popular among triers 58% (252/429). All parts of the program were widely rated as good and excellent, and 88% (1408/1604) of participants reported they had acquired good or excellent knowledge about smoking.

Particularly lung cancer, cancer in general and heart diseases were frequently mentioned to be smoking related; peer pressure, stress and coolness were identified as reasons for smoking initiation. The influence of marketing and multimedia on smoking behaviour in the young was barely noticed.

Conclusion

NIC!" had a high acceptance among the participants and a large number of students reported relevant knowledge gain. We identified important knowledge-gaps relating smoking initiation and smoking related diseases, helping to improve further smoking prevention approaches.

O15: DISRUPTION OF THE BLOOD-SPINAL CORD BARRIER PREDICTS PERMANENT PARAPLEGIA AFTER THORACOABDOMINAL AORTIC ANEURYSM REPAIR

Introduction

Paraplegia post-thoracoabdominal aortic aneurysm (TAAA) repair remains both a devastating and poorly understood complication. We related temporal changes in cellular and protein composition of cerebrospinal fluid (CSF) to neurological outcomes after TAAA repair to gain mechanistic insights driving paraplegia.

Method

Patients undergoing TAAA repair (open or endovascular) with a CSF drain were prospectively recruited between 2016-2018. CSF was collected pre-operatively and 24-hourly until removal. Daily neurological examinations were performed by blinded neurologists to the study. CSF cell content was characterised by flow cytometry and proteome analysed by tandem-mass-tag proteomics. An in-vivo rat model was modified using 15 minutes of aortic occlusion to produce consistent paraplegia. Rats were analysed neuro-behaviourally and histologically.

Result

CSF was analysed from 52 patients (age: 70.27+/-11.4; 66% male; open (n=9), endovascular (n=43)). 12 developed paraplegia of whom 5 remained permanently-paraplegic. Demographics were comparable between paraplegics, those who recovered and without post-op neurology. Permanent paraplegia was associated with a significant infiltration of CSF CD45+ leucocytes (P&lt;0.0001). Levels of ADVS-1 was &gt;3-fold higher in permanent-paraplegics CSF versus those who recovered (P=0.0008). ADVS-1 &gt;15ng/ml predicted permanent paraplegia with 100% specificity. Pre-treatment with ADVS-1 inhibition significantly improved walking (&lt;0.001) and increased astrocytic staining in the lateral corticospinal, reticulospinal and rubrospinal tracts versus controls (P=0.03, 0.04, 0.04 respectively).

Conclusion

Permanent paraplegia is associated with shedding of ADVS-1 from parenchymal cord into CSF and blood/spinal-cord barrier disruption leading to cord oedema/leucocyte infiltration. Pre-treatment with ADVS-1 inhibition led to neurobehavioural and histological improvements offering translational hope for this devastating complication.

Take-home message

ADVS-1 is a novel biomarker of paraplegia where accurate biomarkers have proven challenging but more importantly it has proven a therapeutic target with genuine translational potential.

The transCampus Metabolic Training Programme Explores the Link of SARS-CoV-2 Virus to Metabolic Disease

Currently, we are experiencing a true pandemic of a communicable disease by the virus SARS-CoV-2 holding the whole world firmly in its grasp. Amazingly and unfortunately, this virus uses a metabolic and endocrine pathway via ACE2 to enter our cells causing damage and disease. Our international research training programme funded by the German Research Foundation has a clear mission to train the best students wherever they may come from to learn to tackle the enormous challenges of diabetes and its complications for our society. A modern training programme in diabetes and metabolism does not only involve a thorough understanding of classical physiology, biology and clinical diabetology but has to bring together an interdisciplinary team. With the arrival of the coronavirus pandemic, this prestigious and unique metabolic training programme is facing new challenges but also new opportunities. The consortium of the training programme has recognized early on the need for a guidance and for practical recommendations to cope with the COVID-19 pandemic for the community of patients with metabolic disease, obesity and diabetes. This involves the optimal management from surgical obesity programmes to medications and insulin replacement. We also established a global registry analyzing the dimension and role of metabolic disease including new onset diabetes potentially triggered by the virus. We have involved experts of infectious disease and virology to our faculty with this metabolic training programme to offer the full breadth and scope of expertise needed to meet these scientific challenges. We have all learned that this pandemic does not respect or heed any national borders and that we have to work together as a global community. We believe that this transCampus metabolic training programme provides a prime example how an international team of established experts in the field of metabolism can work together with students from all over the world to address a new pandemic.

PLK2 is a novel regulator of osteopontin-driven fibrosis and diastolic dysfunction in permanent atrial fibrillation

Background and aim

Atrial fibrillation (AF) is frequently accompanied by cardiac fibrosis and diastolic heart failure. Due to the heterogeneous nature and complexity of fibrosis, the knowledge of the underlying pathomechanisms is limited. Thus, effective antifibrotic pharmacotherapy is missing. The objective of this study was to decipher the role of polo-like kinase 2 (PLK2) in the pathogenesis of cardiac fibrosis and left ventricular diastolic dysfunction. We put particular emphasis on the identification of profibrotic downstream targets of PLK2, which can serve as therapeutic targets.

Methods and results

This study was based on human atrial tissue biopsies and peripheral blood samples, a PLK2 knockout mouse model, a canine tachy-pacing model and specific pharmacological interventions on cardiac fibroblasts. In human atrial AF tissue samples, PLK2 was 50% downregulated by hypoxia-induced promoter methylation compared to sinus rhythm (SR) control. Confirmatory analysis of a canine tachy-pacing model showed PLK2 downregulation exclusively in the atria but not in the ventricles. Specific pharmacological inhibition as well as genetic deletion of PLK2 led to a striking myofibroblast phenotype. Discovery proteomics revealed that the global knockout of PLK2 resulted in de novo secretion of the inflammatory cytokine osteopontin (OPN) in cardiac fibroblasts and concomitant ventricular fibrosis in the PLK2 knockout mouse model. An ELISA analysis of peripheral blood samples of AF patients with electrophysiologically proven fibrosis, confirmed significantly increased OPN plasma concentrations compared to SR and non-fibrosis AF controls. Consequently, echocardiography on PLK2 KO mice revealed left ventricular diastolic dysfunction, tachycardia and fibrosis-typical surface ECG anomalies (PQ and QRS prolongation). Mechanistically, we identified the ERK1/2 signaling pathway as the molecular link between reduced expression of PLK2 and elevated osteopontin transcription. In a reverse translational attempt, we successfully tested the capability of 5-amino-salicylic acid (5-ASA) to inhibit osteopontin transcription and to reverse a TGF-β-induced myofibroblast phenotype in vitro. Currently the long-term administration of 5-ASA is tested in PLK2 knockout mice to evaluate the therapeutic potential to prevent cardiac fibrosis and diastolic heart failure development.

Conclusion and clinical impact

We identified PLK2 as an epigenetically regulated kinase involved in the pathophysiology of fibrosis in AF. PLK2 knockout mice can serve as a model of diastolic heart failure wherein OPN is a promising therapeutic target. Our results strengthen the current hypothesis that atrial fibrillation is not only an ion channel disease but a complex systemic disorder. Restoration of physiological PLK2 expression and blockade of osteopontin release with 5-ASA may constitute valuable new drug targets for the prevention and treatment of fibrosis and diastolic heart failure in AF.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Faculty of Medicine, Carl Gustav Carus, Dresden, “MeDDrive Start” Grant

444Plasma levels of microfibrillar associated protein type 4 (MFAP4) are predictive for aortic dissection in patients with Marfan Syndrome

Aim

Marfan syndrome is a disorder with mutations in the fibrillin-1 gene, leading to elastic fiber degradation and increased TGF-beta signaling. The life-threatening feature of Marfan is aneurysm formation with a risk of fatal aortic dissections. In a proteomics screen, we identified MFAP4, a protein involved in fibrillin-1 and elastic fiber formation, to be increased in the Marfan aorta. We aim to study the role of MFAP4 in Marfan aortic disease.

Methods and results

MFAP4 co-localizes in the aorta with elastin and collagen fibers.

In vitro experiments show that MFAP4 expression is upregulated by TGF-beta, which could explain the increased MFAP4 protein levels in the Marfan aorta.

In a substudy of 96 Marfan patients from the COMPARE trial, MFAP4 levels correlate with aortic root diameter (r=0.30, p=0.01). Patients previously enrolled in the COMPARE trial were retrospectively analyzed. Cardiovascular events, including aortic dissection, were assessed. Plasma samples were prospectively collected at time of inclusion in the study and analyzed retrospectively on MFAP4. In the 7 years of follow up, 5 Type B dissections occurred, all of them in patients in the upper tertile of plasma MFAP4. High plasma MFAP4 associates with poor dissection-free survival (Figure 1).

Moreover, the aortic distensibility as measure for aortic stiffness and damage, was calculated throughout the aorta from available MRI images of these patients. Interestingly, in the descending thoracic aorta where type B dissections occur, the aortic distensibility is significantly lower (indicating decreased aortic elasticity) in Marfan patients with high plasma MFAP4, thus associating with aortic damage.

Figure 1

Conclusion

MFAP4, a protein involved in extracellular matrix assembly, is elevated in the Marfan aorta. High plasma MFAP4 seems to reflect aortic damage and predicted type B aortic dissections in up to 7 years follow up.

Orbital Angular Momentum Coupling in Elastic Photon-Photon Scattering

In this Letter, we investigate the effect of orbital angular momentum (OAM) on elastic photon-photon scattering in a vacuum for the first time. We define exact solutions to the vacuum electromagnetic wave equation which carry OAM. Using those, the expected coupling between three initial waves is derived in the framework of an effective field theory based on the Euler-Heisenberg Lagrangian and shows that OAM adds a signature to the generated photons thereby greatly improving the signal-to-noise ratio. This forms the basis for a proposed high-power laser experiment utilizing quantum optics techniques to filter the generated photons based on their OAM state.

Synergistic effects of dendritic cell targeting and laser-microporation on enhancing epicutaneous skin vaccination efficacy

Due to its unique immunological properties, the skin is an attractive target tissue for allergen-specific immunotherapy. In our current work, we combined a dendritic cell targeting approach with epicutaneous immunization using an ablative fractional laser to generate defined micropores in the upper layers of the skin. By coupling the major birch pollen allergen Bet v 1 to mannan from S. cerevisiae via mild periodate oxidation we generated hypoallergenic Bet-mannan neoglycoconjugates, which efficiently targeted CD14⁺ dendritic cells and Langerhans cells in human skin explants. Mannan conjugation resulted in sustained release from the skin and retention in secondary lymphoid organs, whereas unconjugated antigen showed fast renal clearance. In a mouse model, Bet-mannan neoglycoconjugates applied via laser-microporated skin synergistically elicited potent humoral and cellular immune responses, superior to intradermal injection. The induced antibody responses displayed IgE-blocking capacity, highlighting the therapeutic potential of the approach. Moreover, application via micropores, but not by intradermal injection, resulted in a mixed TH1/TH17-biased immune response. Our data clearly show that applying mannan-neoglycoconjugates to an organ rich in dendritic cells using laser-microporation is superior to intradermal injection. Due to their low IgE binding capacity and biodegradability, mannan neoglycoconjugates therefore represent an attractive formulation for allergen-specific epicutaneous immunotherapy.

Vascular proteomics in metabolic and cardiovascular diseases

The vasculature is essential for proper organ function. Many pathologies are directly and indirectly related to vascular dysfunction, which causes significant morbidity and mortality. A common pathophysiological feature of diseased vessels is extracellular matrix (ECM) remodelling. Analysing the protein composition of the ECM by conventional antibody-based techniques is challenging; alternative splicing or post-translational modifications, such as glycosylation, can mask epitopes required for antibody recognition. By contrast, proteomic analysis by mass spectrometry enables the study of proteins without the constraints of antibodies. Recent advances in proteomic techniques make it feasible to characterize the composition of the vascular ECM and its remodelling in disease. These developments may lead to the discovery of novel prognostic and diagnostic markers. Thus, proteomics holds potential for identifying ECM signatures to monitor vascular disease processes. Furthermore, a better understanding of the ECM remodelling processes in the vasculature might make ECM-associated proteins more attractive targets for drug discovery efforts. In this review, we will summarize the role of the ECM in the vasculature. Then, we will describe the challenges associated with studying the intricate network of ECM proteins and the current proteomic strategies to analyse the vascular ECM in metabolic and cardiovascular diseases.

Lung assist devices influence cardio-energetic parameters: Numerical simulation study

We aim at an analysis of the effects mechanical ventilators (MVs) and thoracic artificial lungs (TALs) will have on the cardiovascular system, especially on important quantities, such as left and right ventricular external work (EW), pressure-volume area (PVA) and cardiac mechanical efficiency (CME). Our analyses are based on simulation studies which were carried out by using our CARDIOSIM(©) software simulator. At first, we carried out simulation studies of patients undergoing mechanical ventilation (MV) without a thoracic artificial lung (TAL). Subsequently, we conducted simulation studies of patients who had been provided with a TAL, but did not undergo MV. We aimed at describing the patient's physiological characteristics and their variations with time, such as EW, PVA, CME, cardiac output (CO) and mean pulmonary arterial/venous pressure (PAP/PVP). We were starting with a simulation run under well-defined initial conditions which was followed by simulation runs for a wide range of mean intrathoracic pressure settings. Our simulations of MV without TAL showed that for mean intrathoracic pressure settings from negative (-4 mmHg) to positive (+5 mmHg) values, the left and right ventricular EW and PVA, right ventricular CME and CO decreased, whereas left ventricular CME and the PAP increased. The simulation studies of patients with a TAL, comprised all the usual TAL arrangements, viz. configurations "in series" and in parallel with the natural lung and, moreover, hybrid configurations. The main objective of the simulation studies was, as before, the assessment of the hemodynamic response to the application of a TAL. We could for instance show that, in case of an "in series" configuration, a reduction (an increase) in left (right) ventricular EW and PVA values occurred, whereas the best performance in terms of CO can be achieved in the case of an in parallel configuration.

Fold stability during endolysosomal acidification is a key factor for allergenicity and immunogenicity of the major birch pollen allergen

BACKGROUND

The search for intrinsic factors, which account for a protein's capability to act as an allergen, is ongoing. Fold stability has been identified as a molecular feature that affects processing and presentation, thereby influencing an antigen's immunologic properties.

OBJECTIVE

We assessed how changes in fold stability modulate the immunogenicity and sensitization capacity of the major birch pollen allergen Bet v 1.

METHODS

By exploiting an exhaustive virtual mutation screening, we generated mutants of the prototype allergen Bet v 1 with enhanced thermal and chemical stability and rigidity. Structural changes were analyzed by means of x-ray crystallography, nuclear magnetic resonance, and molecular dynamics simulations. Stability was monitored by using differential scanning calorimetry, circular dichroism, and Fourier transform infrared spectroscopy. Endolysosomal degradation was simulated in vitro by using the microsomal fraction of JAWS II cells, followed by liquid chromatography coupled to mass spectrometry. Immunologic properties were characterized in vitro by using a human T-cell line specific for the immunodominant epitope of Bet v 1 and in vivo in an adjuvant-free BALB/c mouse model.

RESULTS

Fold stabilization of Bet v 1 was pH dependent and resulted in resistance to endosomal degradation at a pH of 5 or greater, affecting presentation of the immunodominant T-cell epitope in vitro. These properties translated in vivo into a strong allergy-promoting TH2-type immune response. Efficient TH2 cell activation required both an increased stability at the pH of the early endosome and efficient degradation at lower pH in the late endosomal/lysosomal compartment.

CONCLUSIONS

Our data indicate that differential pH-dependent fold stability along endosomal maturation is an essential protein-inherent determinant of allergenicity.

Renal involvement in a patient with cobalamin A type (cblA) methylmalonic aciduria: a 42-year follow-up

Chronic renal failure is a well-known long-term complication of methylmalonic aciduria (MMA-uria), occurring even under apparently optimal metabolic management. The onset of renal dysfunction seems to be dependent on the type of defect and vitamin B12-responsiveness. We report on a patient with a vitamin B12-responsive cobalamin A type (cblA) MMA-uria caused by a homozygous stop mutation (p.R145X) in the cobalamin A gene (MMAA). She was diagnosed with chronic kidney disease (CKD) stage III at the age of 12 years. Following re-evaluation, the patient received vitamin B12 (hydroxocobalamin) treatment, resulting in a significant decrease in the concentration of methylmalonic acid (MMA) in urine and plasma. Until age 29 years glomerular filtration rate remained stable probably due to hydroxocobalamin treatment slowing down progression to end-stage renal failure. Kidney biopsies showed non-specific manifestations of chronic interstitial inflammation. The patient received a renal transplant at age 35 years. Under continuous treatment with hydroxocobalamin there is no evidence of kidney damage due to MMA-uria until the last follow-up 6 years after transplantation. This case report illustrates (i) a long-term follow-up of a patient with MMA-uria due to cblA deficiency, (ii) the involvement of the kidney as a target organ and (iii) the importance of early and adequate vitamin B12 substitution in responsive patients. Further investigation will be necessary to prove the protective effect of hydroxocobalamin in the kidney in vitamin B12-responsive patients.

Pathology of resolving polyomavirus-associated nephropathy

Control of polyomavirus BK (BKV) is achieved by reducing immunosuppression allowing an effective BKV-specific T-cell response. The morphology of resolving BKV-associated nephropathy (PyVAN) has not been systematically investigated. Ninety-nine surveillance biopsies of 35 patients with BKV viremia treated exclusively by immunosuppression reduction were scored according to Banff criteria and grouped relative to BKV viremia as pre-, increasing, decreasing and post-BKV viremia. Thirty-four of 35 patients (97%) cleared BKV viremia after a median of 9 months posttransplantation. The tubulitis score, extent of tubules with intraepithelial lymphocytes, and interstitial inflammation significantly increased from the time of increasing to decreasing viremia. Tubulointerstitial inflammation, to a lower extent, persisted after clearance. The number of SV40+ tubules correlated with the BKV load in plasma, but SV40 immunohistochemistry was frequently negative (60%). During decreasing viremia, 31% of PyVAN cases were plasma cell-rich and 40% showed tubular HLA-DR expression. Compared to baseline 1 month posttransplantation, allograft function remained stable or improved in 29/35 patients (83%) after a median follow-up of 48 months. Within 1 year after clearance of BKV viremia, clinical rejection occurred in 2/35 patients (6%). Our data suggest that resolving PyVAN is typically characterized by a self-limiting acute interstitial nephritis, morphologically indistinguishable from interstitial rejection.

Pathology of resolving polyomavirus-associated nephropathy

Control of polyomavirus BK (BKV) is achieved by reducing immunosuppression allowing an effective BKV-specific T-cell response. The morphology of resolving BKV-associated nephropathy (PyVAN) has not been systematically investigated. Ninety-nine surveillance biopsies of 35 patients with BKV viremia treated exclusively by immunosuppression reduction were scored according to Banff criteria and grouped relative to BKV viremia as pre-, increasing, decreasing and post-BKV viremia. Thirty-four of 35 patients (97%) cleared BKV viremia after a median of 9 months posttransplantation. The tubulitis score, extent of tubules with intraepithelial lymphocytes, and interstitial inflammation significantly increased from the time of increasing to decreasing viremia. Tubulointerstitial inflammation, to a lower extent, persisted after clearance. The number of SV40+ tubules correlated with the BKV load in plasma, but SV40 immunohistochemistry was frequently negative (60%). During decreasing viremia, 31% of PyVAN cases were plasma cell-rich and 40% showed tubular HLA-DR expression. Compared to baseline 1 month posttransplantation, allograft function remained stable or improved in 29/35 patients (83%) after a median follow-up of 48 months. Within 1 year after clearance of BKV viremia, clinical rejection occurred in 2/35 patients (6%). Our data suggest that resolving PyVAN is typically characterized by a self-limiting acute interstitial nephritis, morphologically indistinguishable from interstitial rejection.

CO₂ versus air insufflation for private practice routine colonoscopy: results of a randomized double blind trial

BACKGROUND

Pain and bloating following colonoscopy are an underestimated problem, with 30 - 60 % of patients complaining of such symptoms. The use of CO₂ has been shown to significantly decrease pain after colonoscopy in academic hospital-based studies. The aim of the present study was to evaluate whether such an effect can also be seen during private practice routine colonoscopy.

PATIENTS AND METHODS

In a prospective double-blind randomized trial, one experienced colonoscopist (> 12,000 examinations) used either air or CO₂ insufflation for diagnostic or screening colonoscopy in consecutive patients presenting for diagnostic and screening colonoscopy in private practice. Outcome parameters were occurrence and duration of pain and bloating after colonoscopy based on a patient questionnaire.

RESULTS

Of 180 randomized patients, 156 replies were analyzed (43.3 % male, mean age 61.7 ± 9.7 years). There were no significant differences between the two groups with respect to age and sex distribution, indication, sedation, examination times and polypectomy rates. Both pain and abdominal bloating were significantly lower in the CO₂ group. Abdominal pain and bloating in the CO₂ vs. air group were absent in 84.4 vs. 64.6 % (p = 0.005) and 66.2 vs. 32.9 % (p < 0.001). Moderate/strong symptoms were also significantly lower with CO₂.

CONCLUSIONS

The use of CO₂ appears to be as effective in daily routine in private practice colonoscopy as reported in previous hospital-based studies.