The systemic renin-angiotensin system in COVID-19.

SARS-CoV-2 gains cell entry via angiotensin-converting enzyme (ACE) 2, a membrane-bound enzyme of the "alternative" (alt) renin-angiotensin system (RAS). ACE2 counteracts angiotensin II by converting it to potentially protective angiotensin 1-7. Using mass spectrometry, we assessed key metabolites of the classical RAS (angiotensins I-II) and alt-RAS (angiotensins 1-7 and 1-5) pathways as well as ACE and ACE2 concentrations in 159 patients hospitalized with COVID-19, stratified by disease severity (severe, n = 76; non-severe: n = 83). Plasma renin activity (PRA-S) was calculated as the sum of RAS metabolites. We estimated ACE activity using the angiotensin II:I ratio (ACE-S) and estimated systemic alt-RAS activation using the ratio of alt-RAS axis metabolites to PRA-S (ALT-S). We applied mixed linear models to assess how PRA-S and ACE/ACE2 concentrations affected ALT-S, ACE-S, and angiotensins II and 1-7. Median angiotensin I and II levels were higher with severe versus non-severe COVID-19 (angiotensin I: 86 versus 30 pmol/L, p < 0.01; angiotensin II: 114 versus 58 pmol/L, p < 0.05), demonstrating activation of classical RAS. The difference disappeared with analysis limited to patients not taking a RAS inhibitor (angiotensin I: 40 versus 31 pmol/L, p = 0.251; angiotensin II: 76 versus 99 pmol/L, p = 0.833). ALT-S in severe COVID-19 increased with time (days 1-6: 0.12; days 11-16: 0.22) and correlated with ACE2 concentration (r = 0.831). ACE-S was lower in severe versus non-severe COVID-19 (1.6 versus 2.6; p < 0.001), but ACE concentrations were similar between groups and correlated weakly with ACE-S (r = 0.232). ACE2 and ACE-S trajectories in severe COVID-19, however, did not differ between survivors and non-survivors. Overall RAS alteration in severe COVID-19 resembled severity of disease-matched patients with influenza. In mixed linear models, renin activity most strongly predicted angiotensin II and 1-7 levels. ACE2 also predicted angiotensin 1-7 levels and ALT-S. No single factor or the combined model, however, could fully explain ACE-S. ACE2 and ACE-S trajectories in severe COVID-19 did not differ between survivors and non-survivors. In conclusion, angiotensin II was elevated in severe COVID-19 but was markedly influenced by RAS inhibitors and driven by overall RAS activation. ACE-S was significantly lower with severe COVID-19 and did not correlate with ACE concentrations. A shift to the alt-RAS axis because of increased ACE2 could partially explain the relative reduction in angiotensin II levels.

Cysto-Vaginoscopy of a 3D-Printed Cloaca Model: A Step toward Personalized Noninvasive Preoperative Assessment in Patients with Complex Anorectal Malformations.

INTRODUCTION: For the classification of the complexity of cloacal malformations and the decision on the operative approach, an exact anatomical assessment is mandatory. To benefit from using three-dimensional (3D)-printed models in preoperative planning and training, the practicability of these models should be guaranteed. The aim of this study was to evaluate the quality and feasibility of a real-size 3D-printed cloaca model for the purpose of cysto-vaginoscopic evaluation. MATERIALS AND METHODS: We performed a 3D reconstruction and printed a real-size, rubber-like 3D model of an infant pelvis with a cloacal malformation and asked invited pediatric surgeons and pediatric urologists to perform a cysto-vaginoscopy on the model and to complete a brief questionnaire to rate the quality and feasibility of the model and to indicate whether they would recommend the model for preoperative planning and training. RESULTS: Overall, 41 participants rated the model quality as good to very good (M = 3.28, standard deviation [SD] = 0.50, on a scale from 1 to 4). The model was rated as feasible for preoperative training (M = 4.10, SD = 0.75, on a scale from 1 to 5) and most participants (85.4%) would recommend the model for preoperative training. The cysto-vaginoscopy of the model was considered as a valid training tool for real-life cases and improved the confidence on the anatomy of a cloaca. CONCLUSION: The results of our study indicate that patient-specific 3D-printed models might be a useful tool in the preoperative evaluation of complex anorectal malformations by simulation of cysto-vaginoscopy with an excellent view on anatomical structures to assess the whole spectrum of the individual cloacal malformation. Our model might be a valuable add-on tool for specialty training in pediatric colorectal surgery.