Impaired Postnatal Growth Research Articles

Preeclampsia and Future Implications on Growth and Body Composition in Preterm Infants.

Preeclampsia is associated with intrauterine growth restriction (IUGR), which can lead to impaired postnatal growth and neurodevelopment in preterm infants. Preeclampsia can also occur without IUGR and its impact on postnatal nutrition, growth, and body composition remains not fully investigated to the best of our knowledge. This study included infants born before 37 weeks of gestation who underwent air displacement plethysmography to measure body composition (fat-free mass [FFM] and fat mass [FM]) at term-equivalent age. We compared infants born to mothers with preeclampsia and IUGR (PE-IUGR group) and preeclampsia without IUGR (PE-non-IUGR group) to those born to mothers without preeclampsia (control group). In total, 291 infants were enrolled (control: n = 227; PE-non-IUGR: n = 43; PE-IUGR: n = 21). FFM was significantly lower in the PE-IUGR (mean differences -231 g (IQR: (-373, -88); p < 0.001)) and PE-non-IUGR groups (mean differences -260 g (IQR: (-372, -149); p < 0.001)) in comparison to the control group. FM was not significantly different between the three groups. This study indicates that infants of preeclamptic mothers, even without IUGR, had significantly lower FFM at term-equivalent age compared to the control group. Further research is necessary to determine if these variations can be modified.

Effects of foetal size, sex and developmental stage on adaptive transcriptional responses of skeletal muscle to intrauterine growth restriction in pigs

Intrauterine growth restriction (IUGR) occurs both in humans and domestic species. It has a particularly high incidence in pigs, and is a leading cause of neonatal morbidity and mortality as well as impaired postnatal growth. A key feature of IUGR is impaired muscle development, resulting in decreased meat quality. Understanding the developmental origins of IUGR, particularly at the molecular level, is important for developing effective strategies to mitigate its economic impact on the pig industry and animal welfare. The aim of this study was to characterise transcriptional profiles in the muscle of growth restricted pig foetuses at different gestational days (GD; gestational length ~ 115 days), focusing on selected genes (related to development, tissue injury and metabolism) that were previously identified as dysregulated in muscle of GD90 fetuses. Muscle samples were collected from the lightest foetus (L) and the sex-matched foetus with weight closest to the litter average (AW) from each of 22 Landrace x Large White litters corresponding to GD45 (n = 6), GD60 (n = 8) or GD90 (n = 8), followed by analyses, using RT-PCR and protein immunohistochemistry, of selected gene targets. Expression of the developmental genes, MYOD, RET and ACTN3 were markedly lower, whereas MSTN expression was higher, in the muscle of L relative to AW littermates beginning on GD45. Levels of all tissue injury-associated transcripts analysed (F5, PLG, KNG1, SELL, CCL16) were increased in L muscle on GD60 and, most prominently, on GD90. Among genes involved in metabolic regulation, KLB was expressed at higher levels in L than AW littermates beginning on GD60, whereas both IGFBP1 and AHSG were higher in L littermates on GD90 but only in males. Furthermore, the expression of genes specifically involved in lipid, hexose sugar or iron metabolism increased or, in the case of UCP3, decreased in L littermates on GD60 (UCP3, APOB, ALDOB) or GD90 (PNPLA3, TF), albeit in the case of ALDOB this only involved females. In conclusion, marked dysregulation of genes with critical roles in development in L foetuses can be observed from GD45, whereas for a majority of transcripts associated with tissue injury and metabolism differences between L and AW foetuses were apparent by GD60 or only at GD90, thus identifying different developmental windows for different types of adaptive responses to IUGR in the muscle of porcine foetuses.

STAT5b: A master regulator of key biological pathways.

The Signal Transducer and Activator of Transcription (STAT)-5 proteins are required in immune regulation and homeostasis and play a crucial role in the development and function of several hematopoietic cells. STAT5b activation is involved in the expression of genes that participate in cell development, proliferation, and survival. STAT5a and STAT5b are paralogs and only human mutations in STAT5B have been identified leading to immune dysregulation and hematopoietic malignant transformation. The inactivating STAT5B mutations cause impaired post-natal growth, recurrent infections and immune dysregulation, whereas gain of function somatic mutations cause dysregulated allergic inflammation. These mutations are rare, and they are associated with a wide spectrum of clinical manifestations which provide a disease model elucidating the biological mechanism of STAT5 by studying the consequences of perturbations in STAT5 activity. Further, the use of Jak inhibitors as therapy for a variety of autoimmune and malignant disorders has increased substantially heading relevant lessons for the consequences of Jak/STAT immunomodulation from the human model. This review summarizes the biology of the STAT5 proteins, human disease associate with molecular defects in STAT5b, and the connection between aberrant activation of STAT5b and the development of certain cancers.

Atypical STAT5B deficiency, severe short stature and mild immunodeficiency associated with a novel homozygous STAT5B Variant

STAT5B deficiency, a rare autosomal recessive disorder characterized by severe growth hormone insensitivity (GHI) and immunodeficiency, can manifest as fatal pulmonary complications. We describe atypical STAT5B deficiency associated with a novel homozygous frame-shift STAT5B variant [c.1453delG, p.(Asp485Thrfs*29)] identified in a young 17.6 yr old female subject who had severe postnatal growth impairment, biochemistries typical of GHI, an immune profile notable for hypergammaglobulinaemia and elevated B lymphocytes, and lack of pulmonary disease. Marked elevation of serum prolactin and pathologically diagnosed eczema were evident. In reconstitution studies, the STAT5B p.(Asp485Thrfs*29) was expressed although expression was reduced compared to wild-type STAT5B and a previously identified STAT5B p.(Gln368Profs*9) variant. Both truncated STAT5B peptides could not be activated by GH, nor mobilize to the nucleus. We conclude that an intact, functional, STAT5B is essential for normal GH-mediated growth, while expressed loss-of-function STAT5B variants may alleviate severe immune and pulmonary issues normally associated with STAT5B deficiency.

Growth and risk of adverse neuro-developmental outcome in infants with congenital heart disease: A systematic review.

Congenital heart disease (CHD) is one of the most common birth defects affecting around 1:100 infants. In this systematic review, we aimed to determine impact of growth on neurodevelopmental outcomes of infants with CHD. Studies that reported association of growth with developmental outcomes in infants with CHD who had surgery, were included. The search strategy was prospectively registered. Relevant studies were identified by electronic searches. The Cochrane Central Register of Controlled Trials, MEDLINE and EMBASE were searched from their earliest date to February 2022. Twenty studies met inclusion criteria. Choice of growth measures, developmental assessment tools and timing of assessment varied widely precluding conduct of a meta-analysis. Seventeen studies reported on infants who had cardio-pulmonary bypass. Birth weight was reported in thirteen studies and was associated with adverse outcome in nine. Head circumference at birth and later predicted developmental outcomes in five. Impaired postnatal growth was associated with adverse developmental outcome in seven studies. Growth in infants with congenital heart disease, specifically single ventricle physiology can predict adverse neurodevelopmental outcome. Included studies showed significant clinical heterogeneity. Uniformity should be agreed by various data registries with routine prospective collection of growth and developmental data.

211 Overcoming the Growth Deficits Programmed by Maternofetal Stress

Abstract Prolonged maternofetal stress stunts placental development and causes fetal programming that reduces fetal growth and birthweight. Low birthweight due to intrauterine growth restriction (IUGR) of the fetus increases perinatal mortality. More commonly, however, it results in lifelong impairment of muscle growth capacity and metabolic function. In humans, low birthweight increases risk for obesity, diabetes, and other metabolic disorders by an estimated 18-fold. Similarly, low birthweight livestock exhibit greater early death loss, poor growth efficiency, and lower-quality carcasses at harvest. These animals manifest poor feed-to-gain ratios, less lean mass, and greater fat deposition. Together, these outcomes increase production costs, decrease value, and reduce the amount of meat produced per animal. The fetal programming mechanisms linking stress induced IUGR to impaired postnatal growth and metabolic efficiency are largely unknown. However, recent findings in IUGR fetal and neonatal lambs produced experimentally by maternal heat stress and maternofetal inflammation (and pair-fed controls) indicated skeletal muscle-centric programming of adrenergic and inflammatory pathways. Specifically, studies found reduced β2 adrenergic tone and enriched inflammatory signaling pathways. These changes coincided with intrinsic myoblast dysfunction, reduced muscle fiber hypertrophy, and impaired skeletal muscle glucose metabolism. Additionally, IUGR fetal and neonatal lambs exhibited impaired β cell function that may also be associated with adrenergic and inflammatory programming. Subsequent studies have investigated these mechanisms as potential therapeutic targets for interventions and treatments, which is a fundamental step in developing strategies to improve outcomes in low birthweight humans and livestock.

Growth Patterns of Children With Short Stature in Adulthood According to Auxological Status and Maturity at Birth.

Prematurity carries a risk for impaired postnatal growth and long-term growth restriction. Especially children born SGA seem vulnerable for poor growth, as a persistent short stature can be observed in app 10-15% of these children. In this study we aimed to recognize differences in growth patterns of children according to sex, maturity, and auxological status at birth facilitating earlier identification of small-for-gestational-age (SGA) children with adult short stature. The growth data of 44 791 infants born between January 1, 1980, and December 30, 2012, among 2 pediatric cohorts with follow-up through December 31, 2020, were analyzed. A total of 5698 children with birth data had measurements at near final height (nfh) and at least 2 further points. Preterm children (gestational age < 37 weeks) had a significantly lower mean nfh SDS than term children (preterm, -0.61; term, -0.18) and a higher likelihood of nfh < third percentile (preterm, 20.5%; term, 12.2%). SGA born children also had a lower mean nfh SD score (SDS) than children born appropriate for gestational age (AGA) (SGA, -1.06; AGA, -0.15) and a higher likelihood of nfh < third percentile (SGA, 28.2%; AGA 10.1%). Of 1204 SGA children, 672 (56%) showed successful catch-up growth (CUG) to nfh greater than or equal to the 10th percentile (SGA-CU), and 532 children (44%) did not (SGA-S). The difference in their mean nfh SDS (SGA-CU, -0.12; SGA-S -2.26) can only partly be explained by the differences in mean mid-parental height SDS (SGA-CU, -0.3; SGA-S, -1.19). During the first year, SGA-CU showed higher CUG (SGA-CU, +1.2 SDS; SGA-S, +0.45 SDS), which helps to discriminate between groups earlier. Final growth outcome was influenced by prematurity and auxological status at birth, but not by sex. Height/length SDS increments during year 1 are instrumental to discern SGA children with later normal or short stature. While observing CUG until year 2 and 3 can add specificity, discrimination thereafter becomes difficult.

Macrophages exert homeostatic actions in pregnancy to protect against preterm birth and fetal inflammatory injury.

Macrophages are commonly thought to contribute to the pathophysiology of preterm labor by amplifying inflammation — but a protective role has not previously been considered to our knowledge. We hypothesized that given their antiinflammatory capability in early pregnancy, macrophages exert essential roles in maintenance of late gestation and that insufficient macrophages may predispose individuals to spontaneous preterm labor and adverse neonatal outcomes. Here, we showed that women with spontaneous preterm birth had reduced CD209+CD206+ expression in alternatively activated CD45+CD14+ICAM3– macrophages and increased TNF expression in proinflammatory CD45+CD14+CD80+HLA-DR+ macrophages in the uterine decidua at the materno-fetal interface. In Cd11bDTR/DTR mice, depletion of maternal CD11b+ myeloid cells caused preterm birth, neonatal death, and postnatal growth impairment, accompanied by uterine cytokine and leukocyte changes indicative of a proinflammatory response, while adoptive transfer of WT macrophages prevented preterm birth and partially rescued neonatal loss. In a model of intra-amniotic inflammation–induced preterm birth, macrophages polarized in vitro to an M2 phenotype showed superior capacity over nonpolarized macrophages to reduce uterine and fetal inflammation, prevent preterm birth, and improve neonatal survival. We conclude that macrophages exert a critical homeostatic regulatory role in late gestation and are implicated as a determinant of susceptibility to spontaneous preterm birth and fetal inflammatory injury.

Experience in implementing the International Standards for Assessing Newborn Growth INTERGROWTH-21&lt;sup&gt;st&lt;/sup&gt;

The physical development of newborns and infants is the most important parameter in assessing their health. However, the standards of anthropometric parameters, and most importantly their growth in premature babies, especially those born with low and extremely low body weight, are still controversial.Objective: to apply the methodology for measuring and assessing the main anthropometric indicators of newborns using the international standards of postnatal growth of premature babies INTERGROWTH-21st to resolve the issue of the feasibility of its adaptation and widespread introduction into neonatological and pediatric practice in the Russian Federation. 4876 children were born at Kulakov National Medical Research Center for Obstetrics, Gynecology and Perinatology (participant of the international project for the implementation of INTERGROWTH-21st standards in neonatological and pediatric practice) from 15.05.2018 to 26.11.2018. 439 (9%) of them were born premature, of which 376 children (89,3%) with gestational age confirmed by ultrasound were included in the study. There was a detailed file for each child to assess the environment and health of the mother, the course of pregnancy, childbirth, the state of health of the child from birth to discharge from the hospital. 2.1% of children classified by INTERGROWTH-21st as children with intrauterine growth retardation, according to Fenton charts, had normal intrauterine growth. When comparing the postnatal growth at discharge from hospital on the Fenton scale, more children were classified as children with impaired postnatal growth; the discrepancy between INTERGROWTH-21st and Fenton diagrams was 8%. At discharge, 52% of premature babies were exclusively breastfed, 28.8% of premature babies were at mixed feeding.Conclusion.On the one hand, the use of INTERGROWTH-21st scales helps to correct nutrition in case of delay in physical development, and, on the other hand, it reduces the risk of metabolic disorders associated with an aggressive desire to achieve rapid growth of a premature baby.

Abstract 227: Lack of Beta-carotene 9’,10’ Diooxygenase (Bco2) Impacts Cardiac Postnatal Growth and Energy Metabolism in Female Mice

As the postnatal heart grows it also undergoes critical metabolic adaptations to use mainly lipids rather than carbohydrates as energy-providing substrates. Abnormal growth patterns and lack of metabolic flexibility are pathological responses of the heart that lead to cardiovascular diseases (CVD). Carotenoids, such as β-carotene - the most abundant dietary precursor of vitamin A - have been linked to the prevention of CVD. In the heart, β-carotene can be metabolized to retinoids and other apo-carotenoids by the action of β-carotene 9’,10’-dioxygenase (BCO2). We found that Bco2 -/- female mice have significantly smaller hearts than wild-type (WT), pre- and post-puberty. Echocardiography revealed a significant increase in aortic blood flow velocity with no change in overall cardiac output. This analysis also suggests that the mutant has a smaller left ventricle with thinner walls. In addition, expression of cardiac foetal genes (BNP, α-Skeletal actinin and β-MyHc ), typically upregulated during embryogenesis or under pathological conditions in the adult, were significantly increased in the mutant. Bco2 -/- females showed impaired exercise capacity, displaying a ~40% reduction in running distance compared to WT. These data indicate functional cardiac defects in the mutant under stress conditions. Bco2 -/- females also displayed impaired cardiac metabolic flexibility. We found that Bco2 -/- mice have reduced Pdk4 expression and thus enhanced PDH activity. Cardiac expression of Glut1 and Mct1, key glucose and lactate transporters , were significantly higher in Bco2 -/- females, while triglyceride levels were lower in the heart and serum. These findings suggest preferential use of glucose as a cardiac energy source. Interestingly, the mutants had reduced cardiac retinoic acid levels (by LC-MS analysis) compared to WT. Retinoic acid upregulates Pdk4 , thus we postulated that retinoic acid deficiency contributes to loss of cardiac metabolic flexibility in Bco2 -/- females. Ongoing studies aim to confirm this hypothesis and determine if altered retinoic acid homeostasis is also linked to impaired postnatal heart growth in mutant mice. These findings give new insights into a potential role of the β-carotene metabolic pathway in regulating adult heart function.

Identifying and Pharmacologically Correcting the Molecular Pathophysiology of Contractures in Neonatal Brachial Plexus Injury

Purpose: Neonatal brachial plexus injury (NBPI) causes disabling contractures that cannot be fully prevented or corrected, largely because their pathophysiology is incompletely understood. Research in a mouse model has shown that contractures result at least in part from impaired postnatal muscle growth, but the mechanism of this impaired muscle growth is unknown. The current work uses a mouse model to experimentally assess and correct muscle protein imbalance (synthesis versus degradation) as a mechanism of impaired muscle growth and contractures following NBPI.&#x0D; Methods: Unilateral global (C5-T1) NBPIs were surgically created in 5-day-old mice, which permanently denervates the forelimb and reliably causes shoulder and elbow contractures 4 weeks post-NBPI. Protein synthesis was measured in denervated and contralateral control elbow flexor muscles within 4 weeks post-NBPI by incorporation of puromycin, a nucleoside analog, and by expression of major structural and contractile proteins by RNA-sequencing and Western blot. Protein degradation was similarly measured by K48-linkage specific polyubiquitin, an indicator of protein degradation by the proteasome pathway, and by expression of protein degradation markers by RNA-sequencing. Subsequently, to test the ability of proteasome inhibition to prevent contractures, bortezomib, a 20S proteasome inhibitor, was co-administrated with [Gly14]-Humanin G ([Gly14]-HN, to limit bortezomib toxicity) systemically for 4 weeks post-NBPI. Saline and [Gly14]-HN alone were administered separately as controls. Shoulder and elbow contractures were measured 4 weeks post-NBPI, and denervated and control elbow flexor muscles were assayed for 20S proteasome activity, volume and cross-sectional area (CSA) by microCT, and sarcomere length by DIC microscopy.&#x0D; Results: NBPI did not reduce muscle protein synthesis, measured either by puromycin incorporation or by RNA and protein levels of all major structural and contractile proteins. However, NBPI increased protein degradation, as indicated by a doubling of K48-linkage specific polyubiquitin and increased expression of Trim63/MurF1, a driver of proteasome-mediated protein degradation. Bortezomib + [Gly14]-HN effectively prevented contractures following NBPI compared to saline and [Gly14]-HN alone (p&lt;0.001). Bortezomib blunted the denervation-induced increase in proteasome activity (p&lt;0.001), and rescued muscle growth in volume (p&lt;0.0001), CSA (p&lt;0.001), and sarcomere length (p=0.03).&#x0D; Conclusion: Contractures following NBPI are associated with increased muscle protein degradation counteracting normal protein synthesis. Inhibition of the proteasome pathway of protein degradation improves growth of denervated muscle and prevents contractures following NBPI.&#x0D; Significance: This study identifies a pathophysiologic mechanism of impaired muscle growth and contracture formation following neonatal brachial plexus injury, and demonstrates the first ever successful pharmacologic strategy to prevent these contractures by targeting a causative molecular mechanism.

Mitotic chromosome alignment ensures mitotic fidelity by promoting interchromosomal compaction during anaphase.

Chromosome alignment at the equator of the mitotic spindle is a highly conserved step during cell division; however, its importance to genomic stability and cellular fitness is not understood. Normal mammalian somatic cells lacking KIF18A function complete cell division without aligning chromosomes. These alignment-deficient cells display normal chromosome copy numbers in vitro and in vivo, suggesting that chromosome alignment is largely dispensable for maintenance of euploidy. However, we find that loss of chromosome alignment leads to interchromosomal compaction defects during anaphase, abnormal organization of chromosomes into a single nucleus at mitotic exit, and the formation of micronuclei in vitro and in vivo. These defects slow cell proliferation and are associated with impaired postnatal growth and survival in mice. Our studies support a model in which the alignment of mitotic chromosomes promotes proper organization of chromosomes into a single nucleus and continued proliferation by ensuring that chromosomes segregate as a compact mass during anaphase.

Hypomethylation of HOXA4 promoter is common in Silver-Russell syndrome and growth restriction and associates with stature in healthy children

SRS is a rare congenital disorder, characterized by intrauterine growth restriction, postnatal growth impairment and a wide range of signs and symptoms such as dysmorphic features, severe feeding difficulties, body asymmetry, and neurodevelopmental delay. The molecular etiology is heterogeneous. Loss of methylation on chromosome 11p15 (11p15LOM) is detected in 20-60% and maternal uniparental disomy of chromosome 7 (mUPD7) in approximately 5-10%. Other chromosome abnormalities may occur in single cases. Nevertheless, in 40% of SRS cases the molecular etiology is unknown. SRS is currently a clinical diagnosis based upon the Netchine-Harbison scoring system (NH-CSS) [31].

Zebrafish cdc6 hypomorphic mutation causes Meier-Gorlin syndrome-like phenotype.

Cell Division Cycle 6 (Cdc6) is a component of pre-replicative complex (preRC) forming on DNA replication origins in eukaryotes. Recessive mutations in ORC1, ORC4, ORC6, CDT1 or CDC6 of the preRC in human cause Meier-Gorlin syndrome (MGS) that is characterized by impaired post-natal growth, short stature and microcephaly. However, vertebrate models of MGS have not been reported. Through N-ethyl-N-nitrosourea mutagenesis and Cas9 knockout, we generate several cdc6 mutant lines in zebrafish. Loss-of-function mutations of cdc6, as manifested by cdc6tsu4305 and cdc6tsu7cd mutants, lead to embryonic lethality due to cell cycle arrest at the S phase and extensive apoptosis. Embryos homozygous for a cdc6 hypomorphic mutation, cdc6tsu21cd, develop normally during embryogenesis. Later on, compared with their wild-type (WT) siblings, cdc6tsu21cd mutant fish show growth retardation, and their body weight and length in adulthood are greatly reduced, which resemble human MGS. Surprisingly, cdc6tsu21cd mutant fish become males with a short life and fail to mate with WT females, suggesting defective reproduction. Overexpression of Cdc6 mutant forms, which mimic human CDC6(T323R) mutation found in a MGS patient, in zebrafish cdc6tsu4305 mutant embryos partially represses cell death phenotype, suggesting that the human CDC6(T323R) mutation is a hypomorph. cdc6tsu21cd mutant fish will be useful to detect more tissue defects and develop medical treatment strategies for MGS patients.

Diminished Abundance of Translation Initiation Signaling Components in Skeletal Muscle of Low Birthweight Neonatal Pigs

Low birth weight (LBWT) increases the risk of fetal mortality and neonatal morbidity and is consistently associated with impaired postnatal muscle growth. Our previous data suggested that local insulin‐like growth factor‐I (IGF‐I) expression is lower and mammalian target of rapamycin / ribosomal protein S6 kinase 1 (mTOR/S6K1) signaling is downregulated in skeletal muscle of LBWT neonatal pigs. We hypothesized that protein translation initiation is compromised in skeletal muscle of LBWT pigs as a consequence of dysfunction of IGF‐I signaling cascade, which lead to impaired muscle growth in LBWT pigs. Twelve pairs of newborn male LBWT (816 ± 55 g) and normal birth weight (NBWT; 1,642 ± 55 g) littermates were euthanized to collect longissimus dorsi muscle. Muscle protein abundance and phosphorylation were measured by western blot. There was no difference in abundance of extracellular signal‐regulated kinase 1/2 (ERK1/2) in muscle of LBWT and NBWT groups. In addition, phosphorylation of ERK1/2 did not differ in LBWT pigs compared with their NBWT littermates. However, abundance of both MAPK‐interacting kinase (MNK) 1 and MNK2 was lower (P ≤ 0.05) in muscle of LBWT pigs compared with their NBWT siblings, while phosphorylation of MNKs did not differ between two groups. With decreased abundance of MNKs, protein expression and phosphorylation of eukaryotic initiation factor (eIF) 4E were not different in muscle of LBWT and NBWT pigs. However, abundance and phosphorylation of eIF4G were lower (P ≤ 0.05) in muscle of LBWT pigs compared with their NBWT siblings. In addition, abundance of eIF3e was lower (P ≤ 0.05) in LBWT compared with NBWT group. Lower abundance of eIFs in skeletal muscle of LBWT pigs suggested impaired formation of translation initiation complex, which would contribute to decreased protein synthesis and restricted muscle growth in LBWT neonatal pigs.

Cell-matrix signals specify bone endothelial cells during developmental osteogenesis.

Blood vessels in the mammalian skeletal system control bone formation and support haematopoiesis by generating local niche environments. While a specialized capillary subtype, termed type H, has been recently shown to couple angiogenesis and osteogenesis in adolescent, adult and ageing mice, little is known about the formation of specific endothelial cell populations during early developmental endochondral bone formation. Here, we report that embryonic and early postnatal long bone contains a specialized endothelial cell subtype, termed type E, which strongly supports osteoblast lineage cells and later gives rise to other endothelial cell subpopulations. The differentiation and functional properties of bone endothelial cells require cell-matrix signalling interactions. Loss of endothelial integrin β1 leads to endothelial cell differentiation defects and impaired postnatal bone growth, which is, in part, phenocopied by endothelial cell-specific laminin α5 mutants. Our work outlines fundamental principles of vessel formation and endothelial cell differentiation in the developing skeletal system.

Diminished satellite cell fusion and S6K1 expression in myotubes derived from skeletal muscle of low birth weight neonatal pigs.

Low birth weight (LBWT) is consistently associated with impaired postnatal muscle growth in mammals. Satellite cell (SC)‐mediated myonuclear incorporation precedes protein accumulation in the early stages of postnatal muscle development and growth. The objective of this study was to investigate proliferation and differentiation of SCs and the regulation of protein synthesis signaling in response to insulin‐like growth factor (IGF)‐I stimulation in SC‐derived myotubes of LBWT neonatal pigs. SCs isolated from Longissimus dorsi muscle of LBWT and NBWT pigs (3‐d‐old, n = 8) were cultured and induced to proliferate and differentiate to myotubes in vitro. On day 3 of differentiation, myotubes were fasted in serum‐free media for 3 h and treated with human recombinant R3‐insulin‐like growth factor‐I (rh IGF‐I) at 0, 25, and 50 ng × mL−1 for 30 min. There was no difference in proliferation rates of SCs from LBWT and NBWT pigs. However, LBWT SC fusion was 15% lower (P ≤ 0.05) without a difference in MyoD or myogenin mRNA expression in comparison with NBWT pigs, suggesting SCs are not intrinsically different between the two groups. IGF‐Ι stimulation at physiological concentrations activated downstream effectors of mTOR similarly in myotubes from LBWT and NBWT pigs. However, abundance of ribosomal protein S6 kinase 1(S6K1) was lower in myotubes of LBWT compared to their NBWT siblings (P ≤ 0.05). These results indicate that the modest reduction in SC fusion and S6K1 expression are not the major contributors to the impaired postnatal muscle growth of LBWT pigs.

BRF1 mutations in a family with growth failure, markedly delayed bone age, and central nervous system anomalies

Linear growth failure can be caused by many different genetic abnormalities. In many cases, the genetic defect affects not only the growth plate, causing short stature but also other organs/tissues causing additional clinical abnormalities. A 10-year old boy was evaluated for impaired postnatal linear growth (height 113.3 cm, -4.6 SDS), a bone age that was delayed by 5 years, dysmorphic facies, cognitive impairment, and central nervous system anomalies. His younger brother, presented only with growth failure at 10 months of age. Exome sequencing identified compound heterozygous variants in the gene encoding RNA polymerase III transcription initiation factor 90 kDa subunit (BRF1) in both affected siblings: a missense mutation (c.875 C > G:p.P292R) and a frameshift mutation (c.551delG:p.C184Sfs). The frameshift mutation is expected to lead to nonsense-mediated mRNA decay (NMD) and/or to protein truncation. Expression of BRF1 with the P292R missense mutation failed to rescue yeast lacking BRF1. The findings confirm a previous report showing that biallelic mutations in BRF1 cause cerebellar-facial-dental syndrome. Our findings also help define the growth phenotype, indicating that the linear growth failure can become clinically evident before the neurological abnormalities and that a severely delayed bone age may serve as a diagnostic clue.

Mouse Maternal High-Fat Intake Dynamically Programmed mRNA m⁶A Modifications in Adipose and Skeletal Muscle Tissues in Offspring.

Epigenetic mechanisms have an important role in the pre- and peri-conceptional programming by maternal nutrition. Yet, whether or not RNA m6A methylation—an old epigenetic marker receiving increased attention recently—is involved remains an unknown question. In this study, mouse high-fat feeding prior to conception was shown to induce overweight and glucose intolerant dams, which then continued to be exposed to a high-fat diet during gestation and lactation. The dams on a standard diet throughout the whole experiment were used as a control. Results showed that maternal high-fat intake impaired postnatal growth in male offspring, indicated by decreased body weight and Lee’s index at 3, 8 and 15 weeks old, but the percentages of visceral fat and tibialis anterior relative to the whole body weights were significantly increased at eight weeks of age. The maternal high-fat exposure significantly increased mRNA N6-methyladenosine (m6A) levels in visceral fat at three weeks old, combined with downregulated Fat mass and obesity-associated gene (FTO) and upregulated Methyltransferase like 3 (METTL3) transcription, and these changes were reversed at eight weeks of age. In the tibialis anterior muscle, the maternal high-fat diet significantly enhanced m6A modifications at three weeks, and lowered m6A levels at 15 weeks of age. Accordingly, FTO transcription was significantly inhibited at three weeks and stimulated at 15 weeks of age, and METTL3 transcripts were significantly improved at three weeks. Interestingly, both FTO and METTL3 transcription was significantly elevated at eight weeks of age, and yet the m6A modifications remained unchanged. Our study showed that maternal high-fat intake could affect mRNA m6A modifications and its related genes in offspring in a tissue-specific and development-dependent way, and provided an interesting indication of the working of the m6A system during the transmission from maternal nutrition to subsequent generations.

Heterologous Infection of Pregnant Mice Induces Low Birth Weight and Modifies Offspring Susceptibility to Malaria.

Pregnancy malaria (PM) is associated with poor pregnancy outcomes, and can arise due to relapse, recrudescence or a re-infection with heterologous parasites. We have used the Plasmodium chabaudi model of pregnancy malaria in C57BL/6 mice to examine recrudescence and heterologous infection using CB and AS parasite strains. After an initial course of patent parasitemia and first recrudescence, CB but not AS parasites were observed to recrudesce again in most animals that became pregnant. Pregnancy exacerbated heterologous CB infection of AS-experienced mice, leading to mortality and impaired post-natal growth of pups. Parasites were detected in placental blood without evidence of sequestration, unlike P. falciparum but similar to other malaria species that infect pregnant women. Inflammatory cytokine levels were elevated in pregnant females during malaria, and associated with intensity of infection and with poor outcomes. Pups born to dams during heterologous infection were more resistant to malaria infections at 6–7 weeks of age, compared to pups born to malaria-experienced but uninfected dams or to malaria-naïve dams. In summary, our mouse model reproduces several features of human PM, including recrudescences, heterologous infections, poor pregnancy outcomes associated with inflammatory cytokines, and modulation of offspring susceptibility to malaria. This model should be further studied to explore mechanisms underlying PM pathogenesis.