Intestinal microcirculation and necrotizing enterocolitis: The vascular endothelial growth factor system

Hope on the horizon: promising novel therapies for necrotizing enterocolitis

Necrotizing enterocolitis (NEC) remains among the most common and devastating diseases in neonates. Despite advances in neonatal clinical care, specific treatment strategies and diagnostic modalities remain lacking. As a result, morbidity and mortality remain high. Improved understanding of the pathogenesis of NEC has the potential for improved therapeutics. Some of the areas of research leading to promising discoveries include inhibition of Toll-like receptor signaling, modulation of vascular endothelial growth factor signal pathways, defining metabolomic alterations in NEC to discover potential biomarkers, probing for genetic predispositions to NEC susceptibility, determining mechanistic relations between anemia and NEC, and microflora modulation through the use of probiotics. All of these areas may represent novel promising approaches to the prevention and treatment of NEC. This review will focus on these current and possible therapeutic perspectives.

Developmental 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure of either parent enhances the risk of necrotizing enterocolitis in neonatal mice

BACKGROUND

Necrotizing enterocolitis (NEC) is a rare, but potentially fatal intestinal inflammatory condition most often arising in premature infants. Infants provided formula are also at greater risk of developing this disease. Although the majority of formula-fed, preterm infants do not develop NEC, up to 30% of infants with the disease do not survive. Thus, identifying additional, currently unrecognized factors, which may predispose a specific infant to NEC development would be a significant clinical advancement. In this regard, we have previously reported that offspring of female or male mice with a history of developmental exposure to the environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exhibit altered sensitivity to inflammatory challenges and are frequently born premature. Herein, we examined the possibility that, compared to unexposed mice (F1_NONE ), developmental TCDD exposure of either parent (maternal, F1M_TCDD , or paternal, F1P_TCDD ) would enhance the risk of NEC in offspring (F2_TCDD mice) in association with supplemental formula feeding.

METHODS

Beginning on postnatal day 7, all neonates were randomized to maternal milk only or maternal milk with up to 20 supplemental formula feedings. All pups remained with the Dams and were additionally allowed to nurse ad libitum.

RESULTS

Formula-fed F2_NONE pups rarely developed NEC while this disease was common in formula-fed F2M_TCDD and F2P_TCDD mice. Unexpectedly, 50% of F2M_TCDD pups that were not provided supplemental formula also developed NEC.

CONCLUSIONS

Our studies provide evidence that a history of parental TCDD exposure enhances the risk of NEC in offspring and suggest exposure to environmental immunotoxicants such as TCDD may also contribute to this inflammatory disease in humans.

Recent Advances in Necrotizing Enterocolitis Research: Strategies for Implementation in Clinical Practice

Necrotizing enterocolitis (NEC) is a complex inflammatory necrosis of the neonatal intestine, which is likely to require a multipronged approach for prevention and treatment. Despite identifying and defining NEC as a disease entity several decades back, no major progress has been made toward its early identification, treatment, or prevention. This article reviews the latest research strategies that are currently ongoing for early diagnosis and monitoring and prevention of the disease.

Transfusion-related Gut Injury and Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) accounts for 10% of deaths in neonatal intensive care units. Several causal mechanisms are likely to lead to a final common disease phenotype. This article summarizes recent data on NEC following red blood cell (RBC) transfusion, with a focus on the most recent literature and ongoing trials. It highlights potential mechanisms from preclinical and human physiologic studies. It also discusses the role of feeding during RBC transfusion and the risk of NEC. Ongoing randomized trials will provide important data on how liberal or conservative approaches to RBC transfusion influence the risk of NEC.

Gut Injury and the Microbiome in Neonates

The causes of neonatal gut injury are multifactorial and include ischemia, tissue hypoxia due to anemia, excessive inflammation, deficiency of growth factors, and food protein sensitivity. The developing intestinal microbiome plays a role in some of these forms of intestinal injury but knowledge of its relative role in each remains poorly understood. Commensal bacteria are required for normal immune development and immune tolerance. Dysbiosis in the neonatal gut that alters the patterns of commensal and pathogenic bacteria may accentuate gut injury.

Human Mesenchymal Stem Cell Hydrogen Sulfide Production Critically Impacts the Release of Other Paracrine Mediators After Injury

BACKGROUND

The use of mesenchymal stem cells (MSCs) for treatment during ischemia is novel. Hydrogen sulfide (H₂S) is an important paracrine mediator that is released from MSCs to facilitate angiogenesis and vasodilation. Three enzymes, cystathionine-beta-synthase (CBS), cystathionine-gamma-lyase (CSE), and 3-mercaptopyruvate-sulfurtransferase (MPST), are mainly responsible for H₂S production. However, it is unclear how these enzymes impact the production of other critical growth factors and chemokines. We hypothesized that the enzymes responsible for H₂S production in human MSCs would also critically regulate other growth factors and chemokines.

MATERIALS AND METHODS

Human MSCs were transfected with CBS, MPST, CSE, or negative control small interfering RNA. Knockdown of enzymes was confirmed by polymerase chain reaction. Cells were plated in 12-well plates at 100,000 cells per well and stimulated with tumor necrosis factor-α (TNF-α; 50 ng/mL), lipopolysaccharide (LPS; 200 ng/mL), or 5% hypoxia for 24 h. Supernatants were collected, and cytokines measured by multiplex beaded assay. Data were compared with the Mann-Whitney U-test, and P < 0.05 was significant.

RESULTS

TNF-α, LPS, and hypoxia effectively stimulated MSCs. Granulocyte colony-stimulating factor (GCSF), epidermal growth factor, fibroblast growth factor, granulocyte/monocyte colony-stimulating factor (GMCSF), vascular endothelial growth factor, and interferon gamma-inducible protein 10 were all significantly elevated when CSE was knocked down during TNF-α stimulation (P < 0.05). Knockdown of MPST during LPS stimulation more readily increased GCSF and epidermal growth factor but decreased GMCSF (P < 0.05). CBS knockdown decreased production of GCSF, fibroblast growth factor, GMCSF, and vascular endothelial growth factor (P < 0.05) after hypoxia.

CONCLUSIONS

The enzymes that produce H₂S in MSCs are also responsible for the production of other stem cell paracrine mediators under stressful stimuli. Therefore, reprogramming MSCs to endogenously produce more H₂S as a therapeutic intervention could also critically impact other paracrine mediators, which may alter the desired beneficial effects.

Birthweight determines intestinal microvasculature development and alters endothelial nitric oxide synthase density in young piglets

Blood supply to enterocytes dictates intestinal health and nutrient absorption. These two aspects are impaired in low birthweight (LBW) piglets, but whether the perfusion to intestinal tissues is implicated as well is still unknown. Thus, structural changes in the microvasculature of LBW and normal birthweight (NBW) piglets were investigated during early postnatal development. Additionally, the presence of endothelial nitric oxide synthase (eNOS) in the intestinal mucosa was assessed given its important role to assure perfusion. A total of 22 pigs (11 LBW and 11 NBW) were sacrificed at days 0, 3, 8 and 19 of life. Body weight and intestinal length were recorded and a piece of the small intestine was sampled for immunohistochemical analysis of von Willebrand Factor (vWF, an endothelial cell marker) and eNOS. LBW piglets had a relatively (to body weight) longer intestine than their NBW counterparts. Age did not affect microvasculature, which was more abundant (85% larger vWF-positive area) in NBW than LBW pigs. However, an interaction age*BW was observed for eNOS-IR, showing that eNOS presence peaked in NBW piglets on the first day of life and subsequently decreased. This pattern was not observed in LBW piglets. The less abundant intestinal endothelial mass and the different pattern of eNOS expression observed in LBW piglets suggests microcirculation as a contributing factor in the impaired digestive functioning and gut health of LBW pigs. However, revealing whether the origin of this alteration is prenatal or postnatal, for example due to a lower milk intake, needs further study.

Risk of Necrotizing Enterocolitis Associated With the Single Nucleotide Polymorphisms VEGF C-2578A, IL-18 C-607A, and IL-4 Receptor α-Chain A-1902G: A Validation Study in a Prospective Multicenter Cohort

The etiology of necrotizing enterocolitis (NEC) is multifactorial and an underlying genetic predisposition to NEC is increasingly being recognized. A growing number of studies identified single nucleotide polymorphisms (SNPs) of selected genes with potential biological relevance in the development of NEC. However, few of these genetic studies have been replicated in validation cohorts. We aimed to confirm in a cohort of 358 preterm newborns (gestational age <30 weeks, 26 cases of NEC ≥ Bell stage II) the association with NEC of three candidate SNPs: the vascular endothelium growth factor (VEGF) C-2578A polymorphism (rs699947), the interleukin (IL)-18 C-607A polymorphism (rs1946518), and the IL-4 receptor α-chain (IL-4Rα) A-1902G polymorphism (rs1801275). We observed that allele and genotype frequencies of the three SNPs did not significantly differ between the infants with and without NEC. In contrast, the minor G-allele of the IL-4Rα A-1902G polymorphism was significantly less frequent in the group of 51 infants with the combined outcome NEC or death before 34 weeks postmenstrual age than in the infants without the outcome (0.206 vs. 0.331, P = 0.01). In addition, a significant negative association of the G-allele with the combined outcome NEC or death was found using the dominant (adjusted odds ratio, aOR: 0.44, 95% CI 0.21-0.92), recessive (aOR 0.15, 95% CI 0.03-0.74), and additive (aOR 0.46, 95% CI 0.26-0.80) genetic models. In conclusion our study provides further evidence that a genetic variant of the IL-4Rα gene may contribute to NEC.

The impact of placental massive perivillous fibrin deposition on neonatal outcome in pregnancies complicated by fetal growth restriction

INTRODUCTION

Massive perivillous fibrin deposition (MPDD) is an uncommon placental lesion which has been associated with an increased risk of adverse pregnancy outcome in retrospective series. The purpose of the study was to evaluate the frequency and consequences of MPFD in pregnancies complicated by fetal growth restriction (FGR).

MATERIALS AND METHODS

A cohort study of 355 pregnancies complicated by FGR diagnosed according to standard ultrasonographic criteria, enrolled, followed and delivered at a single obstetric unit. Pathological placental lesions were classified according to the Amsterdam Placental Workshop Consensus. Penalized logistic regression models were used to evaluate the association of MPFD with maternal risk factors, other pathological lesions and neonatal outcome.

RESULTS

The rates of moderate (25-50% of villi) and severe (>50% of villi) MPFD were 8.7% (31/355) and 3.1% (11/355), respectively. Compared to other FGR cases, MPFD pregnancies were characterized by higher placental volume (450 ± 144.5 SD as compared to 412.2 ± 151 cm³,p < 0.001) and lower birthweight/placental weight ratio (5.32 ± 1.53 compared to 6.1 ± 1.52,p < 0.001). The rates of abnormal Doppler ultrasound studies of umbilical and middle cerebral artery were similar in MPFD subjects and controls. After correction for gestational age and birthweight, MPFD was associated with an increased risk of neonatal intraventricular hemorrhage (>grade II) (OR = 5.66,95% CI = 1.69-18.97), sepsis (OR = 5.9, 95% CI = 1.27-27.12), proven necrotizing enterocolitis (OR = 9.84,95% CI = 2.49-38.8) and overall severe adverse neonatal outcome (OR = 5.71,95% CI = 2.05-15.87).

CONCLUSIONS

Moderate-to-severe MPFD was relatively common among FGR pregnancies and was associated with morphometric modifications of placenta and with an increased risk of severe adverse neonatal outcome.