Postnatal effects of intrauterine treatment of the growth-restricted ovine fetus with intra-amniotic insulin-like growth factor-1

Placental Nanoparticle-mediated IGF1 Gene Therapy Corrects Fetal Growth Restriction in a Guinea Pig Model

Fetal growth restriction (FGR) caused by placental insufficiency is a major contributor to neonatal morbidity and mortality. There is currently no in utero treatment for placental insufficiency or FGR. The placenta serves as the vital communication, supply, exchange, and defense organ for the developing fetus and offers an excellent opportunity for therapeutic interventions. Here we show efficacy of repeated treatments of trophoblast-specific human insulin-like 1 growth factor (IGF1) gene therapy delivered in a non-viral, polymer nanoparticle to the placenta for the treatment of FGR. Using a guinea pig maternal nutrient restriction model (70% food intake) of FGR, nanoparticle-mediated IGF1 treatment was delivered to the placenta via ultrasound guidance across the second half of pregnancy, after establishment of FGR. This treatment resulted in correction of fetal weight in MNR + IGF1 animals compared to sham treated controls on an ad libitum diet, increased fetal blood glucose and decreased fetal blood cortisol levels compared to sham treated MNR, and showed no negative maternal side-effects. Overall, we show a therapy capable of positively impacting the entire pregnancy environment: maternal, placental, and fetal. This combined with our previous studies using this therapy at mid pregnancy in the guinea pig and in two different mouse model and three different human in vitro/ex vivo models, demonstrate the plausibility of this therapy for future human translation. Our overall goal is to improve health outcomes of neonates and decrease numerous morbidities associated with the developmental origins of disease.

Role of Microglial Modulation in Therapies for Perinatal Brain Injuries Leading to Neurodevelopmental Disorders

Neurodevelopmental disorders (NDDs) encompass various conditions stemming from changes during brain development, typically diagnosed early in life. Examples include autism spectrum disorder, intellectual disability, cerebral palsy, seizures, dyslexia, and attention deficit hyperactivity disorder. Many NDDs are linked to perinatal events like infections, oxygen disturbances, or insults in combination. This chapter outlines the causes and effects of perinatal brain injury as they relate to microglia, along with efforts to prevent or treat such damage. We primarily discuss therapies targeting microglia modulation, focusing on those either clinically used or in advanced development, often tested in large animal models such as sheep, non-human primates, and piglets-standard translational models in perinatal medicine. Additionally, it touches on experimental studies showcasing advancements in the field.

Perspectives on frailty as a total life-course disease with consideration of the fetal environment

Frailty attracts research as it represents a significant target for intervention to extend the healthy life span. An unanswered question in this field is the time point during the life-course at which an individual becomes predisposed to frailty. Here, we propose that frailty has a fetal origin and should be regarded as part of the spectrum of the developmental origins of health and disease. The developmental origins of health and disease theory originated from findings linking the fetal environment to lifestyle-related disorders such as hypertension and diabetes. Coincidentally, a recent trend in frailty research also centers on vascular dysfunction and metabolic alterations as the causality of lifestyle-related disorders such as sarcopenia and dementia. Here, we explore the relationship between fetal programming, frailty-related disorders (sarcopenia and dementia), and other age-related diseases mainly based on reports on intrauterine growth restriction. We propose a "total" life-course approach to combat frailty. With this viewpoint, not only physicians and gerontologists but also obstetricians and pediatricians should team up to overcome age-related diseases in the elderly. Geriatr Gerontol Int 2023; ••: ••-••.

Perinatal Origins of Adult Disease and Opportunities for Health Promotion: A Narrative Review

The “developmental origins of health and disease” (DOHaD) hypothesis refers to the influence of early developmental exposures and fetal growth on the risk of chronic diseases in later periods. During fetal and early postnatal life, cell differentiation and tissue formation are influenced by several factors. The interaction between genes and environment in prenatal and early postnatal periods appears to be critical for the onset of multiple diseases in adulthood. Important factors influencing this interaction include genetic predisposition, regulation of gene expression, and changes in microbiota. Premature birth and intrauterine growth restriction (IUGR) are other important factors considered by the DOHaD hypothesis. Preterm birth is associated with impaired or arrested structural or functional development of key organs/systems, making preterm infants vulnerable to cardiovascular, respiratory, and chronic renal diseases during adulthood. Growth restriction, defined as impaired fetal growth compared to expected biological potential in utero, is an additional negative factor increasing the risk of subsequent diseases. Environmental factors implicated in the developmental programming of diseases include exposure to pollution, stress, drugs, toxic agents, nutrition, and exercise. The DOHaD may explain numerous conditions, including cardiovascular, metabolic, respiratory, neuropsychiatric, and renal diseases. Potential antenatal and postnatal preventive measures, interventions, and future directions are discussed.

Sexually dimorphic changes in the endocrine pancreas and skeletal muscle in young adulthood following intra-amniotic IGF-I treatment of growth-restricted fetal sheep

Fetal growth restriction (FGR) is associated with decreased insulin secretory capacity and decreased insulin sensitivity in muscle in adulthood. We investigated whether intra-amniotic IGF-I treatment in late gestation mitigated the adverse effects of FGR on the endocrine pancreas and skeletal muscle at 18 mo of age. Singleton-bearing ewes underwent uterine artery embolization between 103 and 107 days of gestational age, followed by 5 once-weekly intra-amniotic injections of 360-µg IGF-I (FGRI) or saline (FGRS) and were compared with an unmanipulated control group (CON). We measured offspring pancreatic endocrine cell mass and pancreatic and skeletal muscle mRNA expression at 18 mo of age (n = 7-9/sex/group). Total α-cell mass was increased ∼225% in FGRI males versus CON and FGRS males, whereas β-cell mass was not different between groups of either sex. Pancreatic mitochondria-related mRNA expression was increased in FGRS females versus CON (NRF1, MTATP6, UCP2), and FGRS males versus CON (TFAM, NRF1, UCP2) but was largely unchanged in FGRI males versus CON. In skeletal muscle, mitochondria-related mRNA expression was decreased in FGRS females versus CON (PPARGC1A, TFAM, NRF1, UCP2, MTATP6), FGRS males versus CON (NRF1 and UCP2), and FGRI females versus CON (TFAM and UCP2), with only MTATP6 expression decreased in FGRI males versus CON. Although the window during which IGF-I treatment was delivered was limited to the final 5 wk of gestation, IGF-I therapy of FGR altered the endocrine pancreas and skeletal muscle in a sex-specific manner in young adulthood.NEW & NOTEWORTHY Fetal growth restriction (FGR) is associated with compromised metabolic function throughout adulthood. Here, we explored the long-term effects of fetal IGF-I therapy on the adult pancreas and skeletal muscle. This is the first study demonstrating that IGF-I therapy of FGR has sex-specific long-term effects at both the tissue and molecular level on metabolically active tissues in adult sheep.

Pluripotency and Growth Factors in Early Embryonic Development of Mammals: A Comparative Approach

The regulation of early events in mammalian embryonic development is a complex process. In the early stages, pluripotency, cellular differentiation, and growth should occur at specific times and these events are regulated by different genes that are expressed at specific times and locations. The genes related to pluripotency and cellular differentiation, and growth factors that determine successful embryonic development are different (or differentially expressed) among mammalian species. Some genes are fundamental for controlling pluripotency in some species but less fundamental in others, for example, Oct4 is particularly relevant in bovine early embryonic development, whereas Oct4 inhibition does not affect ovine early embryonic development. In addition, some mechanisms that regulate cellular differentiation do not seem to be clear or evolutionarily conserved. After cellular differentiation, growth factors are relevant in early development, and their effects also differ among species, for example, insulin-like growth factor improves the blastocyst development rate in some species but does not have the same effect in mice. Some growth factors influence genes related to pluripotency, and therefore, their role in early embryo development is not limited to cell growth but could also involve the earliest stages of development. In this review, we summarize the differences among mammalian species regarding the regulation of pluripotency, cellular differentiation, and growth factors in the early stages of embryonic development.

Mitochondria antioxidant protection against cardiovascular dysfunction programmed by early-onset gestational hypoxia

Mitochondria-derived oxidative stress during fetal development increases cardiovascular risk in adult offspring of pregnancies complicated by chronic fetal hypoxia. We investigated the efficacy of the mitochondria-targeted antioxidant MitoQ in preventing cardiovascular dysfunction in adult rat offspring exposed to gestational hypoxia, integrating functional experiments in vivo, with those at the isolated organ and molecular levels. Rats were randomized to normoxic or hypoxic (13%-14% O₂ ) pregnancy ± MitoQ (500 μM day^-1 ) in the maternal drinking water. At 4 months of age, one cohort of male offspring was chronically instrumented with vascular catheters and flow probes to test in vivo cardiovascular function. In a second cohort, the heart was isolated and mounted onto a Langendorff preparation. To establish mechanisms linking gestational hypoxia with cardiovascular dysfunction and protection by MitoQ, we quantified the expression of antioxidant system, β-adrenergic signaling, and calcium handling genes in the fetus and adult, in frozen tissues from a third cohort. Maternal MitoQ in hypoxic pregnancy protected offspring against increased α₁ -adrenergic reactivity of the cardiovascular system, enhanced reactive hyperemia in peripheral vascular beds, and sympathetic dominance, hypercontractility and diastolic dysfunction in the heart. Inhibition of Nfe2l2-mediated oxidative stress in the fetal heart and preservation of calcium regulatory responses in the hearts of fetal and adult offspring link molecular mechanisms to the protective actions of MitoQ treatment of hypoxic pregnancy. Therefore, these data show the efficacy of MitoQ in buffering mitochondrial stress through NADPH-induced oxidative damage and the prevention of programmed cardiovascular disease in adult offspring of hypoxic pregnancy.

Prenatal correction of IGF2 to rescue the growth phenotypes in mouse models of Beckwith-Wiedemann and Silver-Russell syndromes

Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS) are imprinting disorders manifesting as aberrant fetal growth and severe postnatal-growth-related complications. Based on the insulator model, one-third of BWS cases and two-thirds of SRS cases are consistent with misexpression of insulin-like growth factor 2 (IGF2), an important facilitator of fetal growth. We propose that the IGF2-dependent BWS and SRS cases can be identified by prenatal diagnosis and can be prevented by prenatal intervention targeting IGF2. We test this hypothesis using our mouse models of IGF2-dependent BWS and SRS. We find that genetically normalizing IGF2 levels in a double rescue experiment corrects the fetal overgrowth phenotype in the BWS model and the growth retardation in the SRS model. In addition, we pharmacologically rescue the BWS growth phenotype by reducing IGF2 signaling during late gestation. This animal study encourages clinical investigations to target IGF2 for prenatal diagnosis and prenatal prevention in human BWS and SRS.

Liao et al. use mouse models to test a prenatal approach for correcting growth anomalies in two imprinting diseases, BWS and SRS. They find that cases where the fetal growth factor IGF2 is misregulated can be diagnosed, and growth can be corrected by prenatally adjusting IGF2 or its signaling output.

Effect of maternal nutrient restriction on expression of glucose transporters (SLC2A4 and SLC2A1) and insulin signaling in skeletal muscle of SGA and Non-SGA sheep fetuses

Maternal nutrient restriction (NR) causes small for gestational age (SGA) offspring, which are at higher risk for accelerated postnatal growth and developing insulin resistance in adulthood. Skeletal muscle is essential for whole-body glucose metabolism, as 80% of insulin-mediated glucose uptake occurs in this tissue. Maternal NR can alter fetal skeletal muscle mass, expression of glucose transporters, insulin signaling, and myofiber type composition. It also leads to accumulation of intramuscular triglycerides (IMTG), which correlates to insulin resistance. Using a 50% NR treatment from gestational day (GD) 35 to GD 135 in sheep, we routinely observe a spectral phenotype of fetal weights within the NR group. Thus, we classified those fetuses into NR(Non-SGA; n = 11) and NR(SGA; n = 11). The control group (n = 12) received 100% of nutrient requirements throughout pregnancy. At GD 135, fetal plasma and gastrocnemius and soleus muscles were collected. In fetal plasma, total insulin was lower in NR(SGA) fetuses compared NR(Non-SGA) and control fetuses (P < 0.01), whereas total IGF-1 was lower in NR(SGA) fetuses compared with control fetuses (P < 0.05). Within gastrocnemius, protein expression of insulin receptor (INSRB; P < 0.05) and the glucose transporters, solute carrier family 2 member 1 and solute carrier family 2 member 4, was higher (P < 0.05) in NR(SGA) fetuses compared with NR(Non-SGA) fetuses; IGF-1 receptor protein was increased (P < 0.01) in NR(SGA) fetuses compared with control fetuses, and a lower (P < 0.01) proportion of type I myofibers (insulin sensitive and oxidative) was observed in SGA fetuses. For gastrocnemius muscle, the expression of lipoprotein lipase (LPL) messenger RNA (mRNA) was upregulated (P < 0.05) in both NR(SGA) and NR(Non-SGA) fetuses compared with control fetuses, whereas carnitine palmitoyltransferase 1B (CPT1B) mRNA was higher (P < 0.05) in NR(Non-SGA) fetuses compared with control fetuses, but there were no differences (P > 0.05) for protein levels of LPL or CPT1B. Within soleus, there were no differences (P > 0.05) for any characteristic except for the proportion of type I myofibers, which was lower (P < 0.05) in NR(SGA) fetuses compared with control fetuses. Accumulation of IMTG did not differ (P > 0.05) in gastrocnemius or soleus muscles. Collectively, the results indicate molecular differences between SGA and Non-SGA fetuses for most characteristics, suggesting that maternal NR induces a spectral phenotype for the metabolic programming of those fetuses.

Effects of intrauterine insulin-like growth factor-1 therapy for fetal growth restriction on adult metabolism and body composition are sex specific

Fetal growth restriction (FGR) is associated with compromised growth and metabolic function throughout life. Intrauterine therapy of FGR with intra-amniotic insulin-like growth factor-1 (IGF1) enhances fetal growth and alters perinatal metabolism and growth in a sex-specific manner, but the adult effects are unknown. We investigated the effects of intra-amniotic IGF1 treatment of FGR on adult growth and body composition, adrenergic sensitivity, and glucose-insulin axis regulation. Placental embolization-induced FGR was treated with four weekly doses of 360 µg intra-amniotic IGF1 (FGRI) or saline (FGRS). Offspring were raised to adulthood (18 mo: FGRI, n = 12 females, 12 males; FGRS, n = 13 females, 10 males) alongside offspring from unembolized and untreated sheep (CON; n = 12 females, 21 males). FGRI females had increased relative lean mass compared with CON but not FGRS (P < 0.05; 70.6 ± 8.2% vs. 61.4 ± 8.2% vs. 67.6 ± 8.2%), decreased abdominal adipose compared with CON and FGRS (P < 0.05; 43.7 ± 1.2% vs. 49.3 ± 0.9% vs. 48.5 ± 1.0%), increased glucose utilization compared with FGRS but not CON (P < 0.05; 9.6 ± 1.0 vs. 6.0 ± 0.9 vs. 7.6 ± 0.9 mg·kg^-1·min^-1), and increased β-hydroxybutyric acid:nonesterified fatty acid ratio in response to adrenaline compared with CON and FGRS (P < 0.05; 3.9 ± 1.4 vs. 1.1 ± 1.4 vs. 1.8 ± 1.4). FGRS males were smaller and lighter compared with CON but not FGRI (P < 0.05; 86.8 ± 6.3 vs. 93.5 ± 6.1 vs. 90.7 ± 6.3 kg), with increased peak glucose concentration (10%) in response to a glucose load but few other differences. These effects of intra-amniotic IGF1 therapy on adult body composition, glucose-insulin axis function, and adrenergic sensitivity could indicate improved metabolic regulation during young adulthood in female FGR sheep.

Postnatal β2 adrenergic treatment improves insulin sensitivity in lambs with IUGR but not persistent defects in pancreatic islets or skeletal muscle

Key points

Previous studies in fetuses with intrauterine growth restriction (IUGR) have shown that adrenergic dysregulation was associated with low insulin concentrations and greater insulin sensitivity.

Although whole‐body glucose clearance is normal, 1‐month‐old lambs with IUGR at birth have higher rates of hindlimb glucose uptake, which may compensate for myocyte deficiencies in glucose oxidation.

Impaired glucose‐stimulated insulin secretion in IUGR lambs is due to lower intra‐islet insulin availability and not from glucose sensing.

We investigated adrenergic receptor (ADR) β2 desensitization by administering oral ADRβ modifiers for the first month after birth to activate ADRβ2 and antagonize ADRβ1/3. In IUGR lambs ADRβ2 activation increased whole‐body glucose utilization rates and insulin sensitivity but had no effect on isolated islet or myocyte deficiencies.

IUGR establishes risk for developing diabetes. In IUGR lambs we identified disparities in key aspects of glucose‐stimulated insulin secretion and insulin‐stimulated glucose oxidation, providing new insights into potential mechanisms for this risk.

Abstract

Placental insufficiency causes intrauterine growth restriction (IUGR) and disturbances in glucose homeostasis with associated β adrenergic receptor (ADRβ) desensitization. Our objectives were to measure insulin‐sensitive glucose metabolism in neonatal lambs with IUGR and to determine whether daily treatment with ADRβ2 agonist and ADRβ1/β3 antagonists for 1 month normalizes their glucose metabolism. Growth, glucose‐stimulated insulin secretion (GSIS) and glucose utilization rates (GURs) were measured in control lambs, IUGR lambs and IUGR lambs treated with adrenergic receptor modifiers: clenbuterol atenolol and SR59230A (IUGR‐AR). In IUGR lambs, islet insulin content and GSIS were less than in controls; however, insulin sensitivity and whole‐body GUR were not different from controls. Of importance, ADRβ2 stimulation with β1/β3 inhibition increases both insulin sensitivity and whole‐body glucose utilization in IUGR lambs. In IUGR and IUGR‐AR lambs, hindlimb GURs were greater but fractional glucose oxidation rates and ex vivo skeletal muscle glucose oxidation rates were lower than controls. Glucose transporter 4 (GLUT4) was lower in IUGR and IUGR‐AR skeletal muscle than in controls but GLUT1 was greater in IUGR‐AR. ADRβ2, insulin receptor, glycogen content and citrate synthase activity were similar among groups. In IUGR and IUGR‐AR lambs heart rates were greater, which was independent of cardiac ADRβ1 activation. We conclude that targeted ADRβ2 stimulation improved whole‐body insulin sensitivity but minimally affected defects in GSIS and skeletal muscle glucose oxidation. We show that risk factors for developing diabetes are independent of postnatal catch‐up growth in IUGR lambs as early as 1 month of age and are inherent to the islets and myocytes.

Previous studies in fetuses with intrauterine growth restriction (IUGR) have shown that adrenergic dysregulation was associated with low insulin concentrations and greater insulin sensitivity.

Although whole‐body glucose clearance is normal, 1‐month‐old lambs with IUGR at birth have higher rates of hindlimb glucose uptake, which may compensate for myocyte deficiencies in glucose oxidation.

Impaired glucose‐stimulated insulin secretion in IUGR lambs is due to lower intra‐islet insulin availability and not from glucose sensing.

We investigated adrenergic receptor (ADR) β2 desensitization by administering oral ADRβ modifiers for the first month after birth to activate ADRβ2 and antagonize ADRβ1/3. In IUGR lambs ADRβ2 activation increased whole‐body glucose utilization rates and insulin sensitivity but had no effect on isolated islet or myocyte deficiencies.

IUGR establishes risk for developing diabetes. In IUGR lambs we identified disparities in key aspects of glucose‐stimulated insulin secretion and insulin‐stimulated glucose oxidation, providing new insights into potential mechanisms for this risk.

The Placental Transcriptome in Late Gestational Hypoxia Resulting in Murine Intrauterine Growth Restriction Parallels Increased Risk of Adult Cardiometabolic Disease

Intrauterine growth restriction (IUGR) enhances risk for adult onset cardiovascular disease (CVD). The mechanisms underlying IUGR are poorly understood, though inadequate blood flow and oxygen/nutrient provision are considered common endpoints. Based on evidence in humans linking IUGR to adult CVD, we hypothesized that in murine pregnancy, maternal late gestational hypoxia (LG-H) exposure resulting in IUGR would result in (1) placental transcriptome changes linked to risk for later CVD, and 2) adult phenotypes of CVD in the IUGR offspring. After subjecting pregnant mice to hypoxia (10.5% oxygen) from gestational day (GD) 14.5 to 18.5, we undertook RNA sequencing from GD19 placentas. Functional analysis suggested multiple changes in structural and functional genes important for placental health and function, with maximal dysregulation involving vascular and nutrient transport pathways. Concordantly, a ~10% decrease in birthweights and ~30% decrease in litter size was observed, supportive of placental insufficiency. We also found that the LG-H IUGR offspring exhibit increased risk for CVD at 4 months of age, manifesting as hypertension, increased abdominal fat, elevated leptin and total cholesterol concentrations. In summary, this animal model of IUGR links the placental transcriptional response to the stressor of gestational hypoxia to increased risk of developing cardiometabolic disease.

Neonatal Morbidities of Fetal Growth Restriction: Pathophysiology and Impact

Being born small lays the foundation for short-term and long-term implications for life. Intrauterine or fetal growth restriction describes the pregnancy complication of pathological reduced fetal growth, leading to significant perinatal mortality and morbidity, and subsequent long-term deficits. Placental insufficiency is the principal cause of FGR, which in turn underlies a chronic undersupply of oxygen and nutrients to the fetus. The neonatal morbidities associated with FGR depend on the timing of onset of placental dysfunction and growth restriction, its severity, and the gestation at birth of the infant. In this review, we explore the pathophysiological mechanisms involved in the development of major neonatal morbidities in FGR, and their impact on the health of the infant. Fetal cardiovascular adaptation and altered organ development during gestation are principal contributors to postnatal consequences of FGR. Clinical presentation, diagnostic tools and management strategies of neonatal morbidities are presented. We also present information on the current status of targeted therapies. A better understanding of neonatal morbidities associated with FGR will enable early neonatal detection, monitoring and management of potential adverse outcomes in the newborn period and beyond.

Knowledge Gaps and Emerging Research Areas in Intrauterine Growth Restriction-Associated Brain Injury

Intrauterine growth restriction (IUGR) is a complex global healthcare issue. Concerted research and clinical efforts have improved our knowledge of the neurodevelopmental sequelae of IUGR which has raised the profile of this complex problem. Nevertheless, there is still a lack of therapies to prevent the substantial rates of fetal demise or the constellation of permanent neurological deficits that arise from IUGR. The purpose of this article is to highlight the clinical and translational gaps in our knowledge that hamper our collective efforts to improve the neurological sequelae of IUGR. Also, we draw attention to cutting-edge tools and techniques that can provide novel insights into this disorder, and technologies that offer the potential for better drug design and delivery. We cover topics including: how we can improve our use of crib-side monitoring options, what we still need to know about inflammation in IUGR, the necessity for more human post-mortem studies, lessons from improved integrated histology-imaging analyses regarding the cell-specific nature of magnetic resonance imaging (MRI) signals, options to improve risk stratification with genomic analysis, and treatments mediated by nanoparticle delivery which are designed to modify specific cell functions.