Discovering Networks of Perturbed Biological Processes in Hepatocyte Cultures

The liver plays a vital role in glucose homeostasis, the synthesis of bile acids and the detoxification of foreign substances. Liver culture systems are widely used to test adverse effects of drugs and environmental toxicants. The two most prevalent liver culture systems are hepatocyte monolayers (HMs) and collagen sandwiches (CS). Despite their wide use, comprehensive transcriptional programs and interaction networks in these culture systems have not been systematically investigated. We integrated an existing temporal transcriptional dataset for HM and CS cultures of rat hepatocytes with a functional interaction network of rat genes. We aimed to exploit the functional interactions to identify statistically significant linkages between perturbed biological processes. To this end, we developed a novel approach to compute Contextual Biological Process Linkage Networks (CBPLNs). CBPLNs revealed numerous meaningful connections between different biological processes and gene sets, which we were successful in interpreting within the context of liver metabolism. Multiple phenomena captured by CBPLNs at the process level such as regulation, downstream effects, and feedback loops have well described counterparts at the gene and protein level. CBPLNs reveal high-level linkages between pathways and processes, making the identification of important biological trends more tractable than through interactions between individual genes and molecules alone. Our approach may provide a new route to explore, analyze, and understand cellular responses to internal and external cues within the context of the intricate networks of molecular interactions that control cellular behavior

Assessment of stunned and viable myocardium using manganese-enhanced MRI

Objective In a proof-of-concept study, to quantify myocardial viability in patients with acute myocardial infarction using manganese-enhanced MRI (MEMRI), a measure of intracellular calcium handling. Methods Healthy volunteers (n=20) and patients with ST-elevation myocardial infarction (n=20) underwent late gadolinium enhancement (LGE) using gadobutrol and MEMRI using manganese dipyridoxyl diphosphate. Patients were scanned ≤7 days after reperfusion and rescanned after 3 months. Differential manganese uptake was described using a two-compartment model. Results After manganese administration, healthy control and remote non-infarcted myocardium showed a sustained 25% reduction in T1 values (mean reductions, 288±34 and 281±12 ms). Infarcted myocardium demonstrated less T1 shortening than healthy control or remote myocardium (1157±74 vs 859±36 and 835±28 ms; both p0.1) myocardium. Conclusions Through visualisation of intracellular calcium handling, MEMRI accurately differentiates infarcted, stunned and viable myocardium, and correlates with myocardial dysfunction better than LGE. MEMRI holds major promise in directly assessing myocardial viability, function and calcium handling across a range of cardiac diseases. Trial registration numbers NCT03607669; EudraCT number 2016-003782-25.</p

Manganese-enhanced magnetic resonance imaging in dilated cardiomyopathy and hypertrophic cardiomyopathy.

AimsThe aim of this study is to quantify altered myocardial calcium handling in non-ischaemic cardiomyopathy using magnetic resonance imaging.Methods and resultsPatients with dilated cardiomyopathy (n = 10) or hypertrophic cardiomyopathy (n = 17) underwent both gadolinium and manganese contrast-enhanced magnetic resonance imaging and were compared with healthy volunteers (n = 20). Differential manganese uptake (Ki) was assessed using a two-compartment Patlak model. Compared with healthy volunteers, reduction in T1 with manganese-enhanced magnetic resonance imaging was lower in patients with dilated cardiomyopathy [mean reduction 257 ± 45 (21%) vs. 288 ± 34 (26%) ms, P ConclusionThe rate of manganese uptake in both dilated and hypertrophic cardiomyopathy provides a measure of altered myocardial calcium handling. This holds major promise for the detection and monitoring of dysfunctional myocardium, with the potential for early intervention and prognostication.</div

Impaired Myocardial Calcium Uptake in Patients With Diabetes Mellitus: A Manganese-Enhanced Cardiac Magnetic Resonance Study

The pathophysiology of diabetic cardiomyopathy is complex and may involve dysregulated myocardial calcium uptake, which has been demonstrated in animal models.1 Manganese is a paramagnetic calcium analog for voltage-gated L-type calcium channels on cardiac myocytes, and manganese-enhanced cardiac magnetic resonance (CMR) provides a novel method of assessing myocardial calcium uptake in vivo.2 We aimed to determine whether myocardial calcium uptake is altered in people with type 1 or type 2 diabetes without cardiac disease. This was a prospective, 2-center, case-control study. We enrolled subjects with type 1 or type 2 diabetes, 18 to 75 years of age, with no prior history or symptoms of cardiac disease. Age-matched control volunteers without diabetes or known cardiac disease were recruited for comparison. Ethical approval was granted by the United Kingdom National Research Ethics Service (17/WM/0192, 20/NS/0037 and 20/WM/0304). Where applicable, subjects taking calcium-channel blockers withheld these medications 48 hours prior to study entry. All participants underwent manganese-enhanced CMR, performed using standardized imaging protocols on 3.0-T scanners. Initial imaging assessment of cardiac structure and function was performed with cine imaging. T1 mapping was then performed precontrast in a mid–short-axis slice position using a modified Look-Locker inversion recovery sequence (Siemens MyoMaps). An intravenous infusion of manganese dipyridoxyl diphosphate (5 μmol/kg [0.1 mL/kg] at 1 mL/min; Exova SL Pharma) was commenced and repeated T1 maps at the same location were performed every 2.5 minutes for 30 minutes. Image analysis was performed at a core laboratory blinded to all participant details. Cardiac chamber volumes, mass, and function were assessed using cvi42 software (v5.13.5; Circle CVI) as described previously.3 Participants with regional wall motion abnormalities or reduced left ventricular ejection fraction were excluded. For analysis of manganese uptake, regions of interest were drawn in the midventricular inferoseptal segment and the myocardial blood pool for all T1 maps from 0 to 30 minutes (Figure 1A).</p

Impaired Myocardial Calcium Uptake in Patients With Diabetes Mellitus: A Manganese-Enhanced Cardiac Magnetic Resonance Study

The pathophysiology of diabetic cardiomyopathy is complex and may involve dysregulated myocardial calcium uptake, which has been demonstrated in animal models.1 Manganese is a paramagnetic calcium analog for voltage-gated L-type calcium channels on cardiac myocytes, and manganese-enhanced cardiac magnetic resonance (CMR) provides a novel method of assessing myocardial calcium uptake in vivo.2 We aimed to determine whether myocardial calcium uptake is altered in people with type 1 or type 2 diabetes without cardiac disease. This was a prospective, 2-center, case-control study. We enrolled subjects with type 1 or type 2 diabetes, 18 to 75 years of age, with no prior history or symptoms of cardiac disease. Age-matched control volunteers without diabetes or known cardiac disease were recruited for comparison. Ethical approval was granted by the United Kingdom National Research Ethics Service (17/WM/0192, 20/NS/0037 and 20/WM/0304). Where applicable, subjects taking calcium-channel blockers withheld these medications 48 hours prior to study entry. All participants underwent manganese-enhanced CMR, performed using standardized imaging protocols on 3.0-T scanners. Initial imaging assessment of cardiac structure and function was performed with cine imaging. T1 mapping was then performed precontrast in a mid–short-axis slice position using a modified Look-Locker inversion recovery sequence (Siemens MyoMaps). An intravenous infusion of manganese dipyridoxyl diphosphate (5 μmol/kg [0.1 mL/kg] at 1 mL/min; Exova SL Pharma) was commenced and repeated T1 maps at the same location were performed every 2.5 minutes for 30 minutes. Image analysis was performed at a core laboratory blinded to all participant details. Cardiac chamber volumes, mass, and function were assessed using cvi42 software (v5.13.5; Circle CVI) as described previously.3 Participants with regional wall motion abnormalities or reduced left ventricular ejection fraction were excluded. For analysis of manganese uptake, regions of interest were drawn in the midventricular inferoseptal segment and the myocardial blood pool for all T1 maps from 0 to 30 minutes (Figure 1A).</p