Biology subjects

Giussani, D. A.

Publications and source records attributed to Giussani, D. A..

6 recordsLinked to original sources

bioRxiv2026

Hepatic HIF2α modulates extra-hepatic disease-associated phenotypes during metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) afflicts more than one-third of adults globally, contributing significantly to an increased cardiovascular disease risk. Further, patients with severe liver disease experience muscle weakness (sarcopenic obesity) and fatigue. Hypoxia-inducible factor 2 (HIF2) accumulates in the livers of MASLD patients and has been implicated in disease progression. Here we sought to understand the role of hepatic HIF2 in mediating hepatic and extra-hepatic features of MASLD. Using a well-validated obese mouse model of MASLD, we investigated the impact of hepatocyte-specific HIF2 deletion (hHIF2-/-) on hepatic, cardiac and skeletal muscle metabolism, and cardiac function. Over 28 weeks, mice were exposed to a high-fat, high-fructose, high-cholesterol (GAN) diet, which induced obesity alongside hepatic steatosis, fibrosis and inflammation. In contrast to observations in lean mouse models of liver disease, hHIF2-/- did not protect against MASLD, despite greater hepatic NADH-supported mitochondrial respiration and higher intracellular sphingomyelin levels. Instead, in the hearts of GAN-fed mice, hHIF2-/- caused diacylglycerol accumulation independent of diet, accumulation of long-chain acyl-carnitines and exacerbation of ceramide accumulation. Langendorff-perfused hearts from hHIF2-/- mice showed systolic and diastolic dysfunction, including 24% lower left ventricular developed pressure and 34% lower maximal rate of relaxation (dP/dtmin). However, isolated hearts from hHIF2-/- mice were protected against MASLD-associated sympathetic dominance, determined using autonomic receptor agonist stimulation. Both GAN-feeding and hHIF2-/- were associated with lower lean mass (14% and 5.4% lower than respective controls), whilst hHIF2-/- enhanced OXPHOS-associated protein levels in gastrocnemius muscle. Overall, hHIF2-/- resulted in detrimental extra-hepatic effects, including myocardial lipid accumulation, impaired cardiac function, and loss of whole-body lean mass, with no apparent protection against MASLD disease progression.

physiology↗

bioRxiv2026

Developmental Hypoxia Increases Susceptibility to Cardiac Ventricular Arrhythmias in Adult Offspring

Ventricular arrhythmias are the leading cause of sudden cardiac death. It is well-established that environmental factors contribute to the origin and penetrance of ventricular arrhythmic disorders. However, to our knowledge, no studies have considered the role of the intrauterine environment. In this study, we investigated the long-term effects of fetal hypoxia on ventricular arrhythmia susceptibility. Pregnant Wistar rats were assigned to normoxia (21% O2) or hypoxia (13% O2 between gestational days 6-20), and offspring were raised to 6 months. Hearts were isolated and loaded with the fluorescent calcium- and voltage-sensitive indicators, Rhod-2 and RH237, respectively. Optical mapping was performed while the left ventricle was burst paced (10-20hz) to induce arrhythmias. Hearts isolated from adult offspring exposed to fetal hypoxia were more susceptible to arrythmia during burst pacing, compared to controls. This phenotype was associated with prolonged Ca2+ transients and action potentials, an increased frequency of Ca2+ waves and delayed after depolarisations, as well as lower gene and protein expression of the sarcoplasmic reticulum Ca2+ ATPase. Collectively, our data shows that fetal hypoxia can programme ventricular arrhythmia sensitivity in adulthood, driven by abnormalities in excitation-contraction coupling. This is the first evidence that some ventricular arrhythmias may have a developmental origin, highlighting pregnancy as a potential window for early preventive intervention.

developmental biology↗

bioRxiv2026

Maternal cardiometabolic dysfunction and fetal sex-specific alterations to uterine vascular reactivity in an ovine model of diet-induced obesity during pregnancy

Obesity during pregnancy is at pandemic proportions and predisposes women to pre- and postnatal cardiovascular dysfunction. The mechanisms underlying this maternal cardiovascular vulnerability remain unclear, partly due to a lack of translatable models capable of longitudinal in vivo cardiovascular monitoring. Here, we characterise a novel ovine model of maternal diet-induced obesity during pregnancy. Ewes were fed a control (CON) or obesogenic (OB; ad libitum concentrates) diet for 60 days pre-pregnancy and throughout gestation. Pregnant ewes were surgically instrumented with vascular catheters and Transonic flow probes using the wireless CamDAS system, which measured maternal cardiovascular function near term in free-moving ewes. Uterine artery vasoreactivity was assessed ex vivo by in vitro wire myography. OB ewes entered pregnancy 30% heavier than controls (P<0.003) and were hyperglycaemic, hyperinsulinemic, and hyperlipidaemic during pregnancy, relative to CON ewes (all P<0.05). OB ewes had elevated haematocrit and haemoglobin across pregnancy, and were hypertensive near term, with an increase in basal femoral artery blood flow, and elevated peripheral oxygen and glucose delivery (all P<0.05). OB mothers carrying a female fetus showed increased uterine artery vascular resistance in vivo (P<0.005) and reduced smooth muscle-dependent vasorelaxation ex vivo (P<0.05) relative to CON. Conversely, OB mothers carrying a male fetus showed greater NO-independent mechanisms mediating the uterine vasodilator response to methacholine ex vivo (P<0.001). Collectively, this study characterises a robust model of maternal obesity during pregnancy that offers clinical translational potential and highlights fetal sex-specific changes to uterine artery function. Key points summaryO_LIObesity during pregnancy is increasingly common and predisposes women to cardiovascular dysfunction during pregnancy and long after birth, but the specific mechanisms underlying this remain unclear. C_LIO_LIWe developed a novel ovine model of diet-induced obesity during pregnancy that displays maternal hypertension, elevated haemoglobin, metabolic dysfunction and alterations in uterine and peripheral blood flow and nutrient delivery near term. C_LIO_LIMothers with obesity carrying a female fetus had elevated uterine vascular resistance in vivo and reduced uterine artery smooth muscle-dependent vasodilator reactivity ex vivo. C_LIO_LIMothers with obesity carrying a male fetus showed no effect on uterine vascular resistance in vivo, but greater NO-independent mechanisms mediating the uterine vasodilator response to methacholine ex vivo. C_LIO_LIThese findings highlight that fetal sex may influence maternal cardiovascular function during obese pregnancy. C_LI

developmental biology↗

bioRxiv2025

Developmental changes in the carotid body transcriptome accompanying the maturation of chemosensitivity

The carotid body (CB) chemoreceptors mediate rapid cardiorespiratory reflexes to hypoxia, which mature peri-natally and are vital for fetal hypoxia tolerance and post-natal ventilatory control. This maturation is associated with an increase in the sensitivity of the CB electrophysiological response to hypoxia (chemosensitivity): a process that is incompletely understood but critical to systemic oxygen homeostasis. Hypothesizing that perinatal CB gene expression changes would reveal candidate mechanisms for oxygen chemosensitivity, we studied the CB transcriptome in sheep, where peri-natal CB physiology is well-characterised. CB-mediated cardiovascular reflexes are detectable at fetal day 120, and robust by term (day 145), while hypoxic ventilatory responses are established by post-natal day 15. We performed RNA sequencing on sheep CBs at each of these stages, and adults, along with the superior cervical ganglion (SCG) as an oxygen-insensitive control. This allowed us to define tissue-specific changes in the CB transcriptome correlating with chemosensitivity maturation. Striking, progressive CB enrichment is observed in genes implicated in murine CB chemosensitivity, including potassium channels (KCNK9), mitochondrial complex IV regulators (NDUFA4L2, HIGD1C), and HIF-2 (EPAS1). Genes with this expression pattern are also enriched for regulators of diacylglycerol (DAG), particularly the DAG kinase DGKH: one of the most abundant CB transcripts increasing in parallel with chemosensitivity. Across developmental stages, the CB also exhibits marked down-regulation of metabolic pathways and ATP/GTP consuming processes, potentially providing a state permissive to metabolic signal detection. Together, this builds a detailed picture of the CB transcriptional signature, with core features established in fetal life and conserved across species. Key pointsO_LIThe carotid body (CB) chemoreceptors mediate rapid cardiorespiratory responses to hypoxia, which maintain systemic oxygen homeostasis, but CB dysfunction is also implicated in pathologies including hypertension, heart failure and sudden infant death. C_LIO_LICB-mediated chemoreflexes mature during the peri-natal period, with increasing sensitivity of the oxygen chemosensory response. C_LIO_LIWe performed RNA-seq of CBs from sheep across 3 peri-natal stages and adults, enabling us to identify gene expression changes that correlate with functional state. C_LIO_LIWe describe a CB transcriptomic signature that is conserved across species, established in fetal life, and correlates with maturation. This includes features of a unique metabolic phenotype, and up-regulation of genes encoding the extracellular matrix and diacylglycerol signalling. The top transcription factor correlating with functional maturation is EPAS1/ HIF-2. C_LIO_LIWe anticipate that this data set will be a valuable resource in generating novel hypotheses on mechanisms of oxygen chemosensory function, development and CB-associated pathologies. C_LI

physiology↗

bioRxiv2023

An ovine model for investigation of the microenvironment of the male mammary gland

The specific biology of the male breast remains relatively unexplored in spite of the increasing global prevalence of male breast cancer. Delineation of the microenvironment of the male breast is restricted by the low availability of human samples and a lack of characterisation of appropriate animal models. Unlike the mouse, the male ovine gland persists postnatally. We suggest that the male ovine mammary gland constitutes a promising adjunctive model for the male human breast. In this study we evaluate the male ovine mammary gland microenvironment, comparing intact and neutered males. Assessment of the glandular histo-anatomy highlights the resemblance of the male gland to that of the neonatal female sheep and confirms the presence of rudimentary terminal duct lobular units. Irrespective of neutered status, cell proliferation in epithelial and stromal compartments is low in males, and cell proliferation in epithelial cells and in the intralobular stroma is significantly lower than in pubertal female sheep. Between 42% and 72% of the luminal mammary epithelial cells in the male gland express the androgen receptor, and expression is significantly reduced by neutering. Luminal epithelial cells within the intact and neutered male gland also express oestrogen receptor alpha, but minimal progesterone receptor expression is observed. The distrubution of mammary leukocytes within the ducts and stroma is similar in the female mammary gland of sheep and other species. Both macrophages and T lymphocytes are intercalated in the epithelial bilayer and are more abundant in the intralobular stroma than the interlobular stroma, suggesting that they may have a protective immunological function within the vestigial glandular tissue of the male sheep. Mast cells are also observed within the stroma. These cells cluster nearer the glandular tissue and are frequently located adjacent to blood vessels. The abundance of mast cells is significantly higher in intact males compared to neutered males, suggesting that hormone signalling may impact mast cell recruitment. In this study, we demonstrate the utility of the male ovine mammary gland as a model for furthering our knowledge of postnatal male mammary biology.

pathology↗

bioRxiv2018

First evidence that intrinsic fetal heart rate variability exists and is affected by chronic hypoxia

INTRODUCTIONIt is established that normal fetal HRV represents the integration of the autonomic nervous system, components due to fetal body and breathing movements, baroreflex and circadian processes. There is also some evidence of possible intrinsic pacemaker rhythms of the SA node affecting HRV in adult disease.\n\nHowever, whether intrinsic HRV (iHRV) exists in the fetal period and whether this is affected by chronic fetal hypoxia has never been tested. Here, we show iHRV in isolated hearts from fetal sheep in late gestation and significant effects on iHRV of pregnancy complicated by chronic fetal hypoxia.\n\nMETHODSChronically catheterized ewes carrying male singleton fetuses were exposed to normoxia (n=6) or hypoxia (10% inspired O2, n=9) for the last third of gestation (105-138 dG; term~145 dG) in bespoke isobaric chambers, as before. At 138dG, isolated hearts were studied under a Langendorff preparation. CIMVA software was used to calculate basal iHRV matrix indices across five signal-analytical domains from the systolic peaks within 15 min segments in each heart, as before. Data presented as Mean+SEM were compared by the Students t test for unpaired data.\n\nRESULTSThis level of maternal H yields fetal PaO2 values of 11.5{+/-}0.6 relative to controls of 20.9{+/-}0.5 mmHg. Hearts isolated from H pregnancy showed approximately 4-fold increases in the Grid transformation feature as well as the AND similarity index (sgridAND, informational domain) and a 4-fold reduction in the Scale dependent Lyapunov exponent slope (SDLEalpha, invariant domain). We also detected a 2-fold reduction in the Recurrence quantification analysis, the percentage of laminarity and recurrences and maximum diagonal line (pL, pR, dlmax, all from geometric domain) and (AsymI, energetic domain). For dlmax and sgridAND measures, this is also correlated to left ventricular end-diastolic pressure (LVEDP) across both groups.\n\nCONCLUSIONSThe isolated fetal hearts from the hypoxic pregnancy group exhibit a lower complexity in iHRV. This is the first evidence that iHRV originates in fetal life and that chronic fetal hypoxia significantly alters it.\n\nSignificance StatementFetal heart rate variability (fHRV) is an important indicator of health and disease, yet its physiological origins are poorly understood. Both, the heart, intrinsically, and extrinsic systems, such as the brain, are hypothesized to contribute to HRV. In a near-term fetal sheep model of human development, we identified fHRV components reflecting intrinsic contributions to fHRV. In addition, we show that these intrinsic fHRV components carry memory of chronic oxygen deprivation the fetus experienced during the last third of gestation.

physiology↗