Gastroschisis in mice lacking aortic carboxypeptidase-like protein is associated with a defect in neuromuscular development of the eviscerated intestine

Development and Validation of a Minimally Invasive Transuterine Experimental Model of Gastroschisis

INTRODUCTION

Perinatal management of gastroschisis remains a subject of substantial research. Current models, including teratogenic, genetic, and surgical approaches, often fail to accurately replicate gastroschisis, exhibiting limitations such as inaccurate phenotyping, low success rates, high mortality, lack of scientific validation, and significant technical challenges. Refined disease models are essential for improving the understanding of GS. This study seeks to develop and validate a minimally invasive transuterine experimental model of GS that overcomes these existing constraints to advance gastroschisis research.

METHODS

A gastroschisis model was surgically created in rat fetuses at E17 (n = 51 fetuses from n = 13 dams). Intestines were harvested at term and divided into herniated gastroschisis (GS-H), intra-abdominal gastroschisis (GS-I), and control (Co) groups. Morphometric analysis, histopathological examination, immunohistochemistry for interstitial cells of Cajal (ICC), double immunofluorescence for ICC and mast cells, TUNEL assay for apoptotic cells, and multiplex cytokine assay were performed to assess intestinal architecture, inflammation, ICC network, apoptosis, and cytokine levels across studied groups.

RESULTS

Histology from GS intestines revealed subchronic inflammation, peel formation, and architectural disruption. Herniated intestines exhibited a significantly increased weight/length ratio and thicker outer layers (p < 0.001) compared with control intestines. Herniated intestines had elevated inflammatory cytokine levels (GS-H vs GS-I and Co, p < 0.05 for G-CSF, GM-CSF, IL-12p70, IL-1beta) and increased apoptotic activity.

CONCLUSIONS

We developed and validated a new surgical model of GS that offers improved survival and feasibility. The key morphological changes and molecular markers observed in this experimental model resemble human gastroschisis.

Ventral body wall closure: Mechanistic insights from mouse models and translation to human pathology

The ventral body wall (VBW) that encloses the thoracic and abdominal cavities arises by extensive cell movements and morphogenetic changes during embryonic development. These morphogenetic processes include embryonic folding generating the primary body wall; the initial ventral cover of the embryo, followed by directed mesodermal cell migrations, contributing to the secondary body wall. Clinical anomalies in VBW development affect approximately 1 in 3000 live births. However, the cell interactions and critical cellular behaviors that control VBW development remain little understood. Here, we describe the embryonic origins of the VBW, the cellular and morphogenetic processes, and key genes, that are essential for VBW development. We also provide a clinical overview of VBW anomalies, together with environmental and genetic influences, and discuss the insight gained from over 70 mouse models that exhibit VBW defects, and their relevance, with respect to human pathology. In doing so we propose a phenotypic framework for researchers in the field which takes into account the clinical picture. We also highlight cases where there is a current paucity of mouse models for particular clinical defects and key gaps in knowledge about embryonic VBW development that need to be addressed to further understand mechanisms of human VBW pathologies.

Inactive metallopeptidase homologs: the secret lives of pseudopeptidases

Inactive enzyme homologs, or pseudoenzymes, are proteins, found within most enzyme families, that are incapable of performing catalysis. Rather than catalysis, they are involved in protein-protein interactions, sometimes regulating the activity of their active enzyme cousins, or scaffolding protein complexes. Pseudoenzymes found within metallopeptidase families likewise perform these functions. Pseudoenzymes within the M14 carboxypeptidase family interact with collagens within the extracellular space, while pseudopeptidase members of the M12 "a disintegrin and metalloprotease" (ADAM) family either discard their pseudopeptidase domains as unnecessary for their roles in sperm maturation or utilize surface loops to enable assembly of key complexes at neuronal synapses. Other metallopeptidase families contain pseudopeptidases involved in protein synthesis at the ribosome and protein import into organelles, sometimes using their pseudo-active sites for these interactions. Although the functions of these pseudopeptidases have been challenging to study, ongoing work is teasing out the secret lives of these proteins.

Cpxm2 as a novel candidate for cardiac hypertrophy and failure in hypertension

Treatment of hypertension-mediated cardiac damage with left ventricular (LV) hypertrophy (LVH) and heart failure remains challenging. To identify novel targets, we performed comparative transcriptome analysis between genetic models derived from stroke-prone spontaneously hypertensive rats (SHRSP). Here, we identified carboxypeptidase X 2 (Cpxm2) as a genetic locus affecting LV mass. Analysis of isolated rat cardiomyocytes and cardiofibroblasts indicated Cpxm2 expression and intrinsic upregulation in genetic hypertension. Immunostaining indicated that CPXM2 associates with the t-tubule network of cardiomyocytes. The functional role of Cpxm2 was further investigated in Cpxm2-deficient (KO) and wild-type (WT) mice exposed to deoxycorticosterone acetate (DOCA). WT and KO animals developed severe and similar systolic hypertension in response to DOCA. WT mice developed severe LV damage, including increases in LV masses and diameters, impairment of LV systolic and diastolic function and reduced ejection fraction. These changes were significantly ameliorated or even normalized (i.e., ejection fraction) in KO-DOCA animals. LV transcriptome analysis showed a molecular cardiac hypertrophy/remodeling signature in WT but not KO mice with significant upregulation of 1234 transcripts, including Cpxm2, in response to DOCA. Analysis of endomyocardial biopsies from patients with cardiac hypertrophy indicated significant upregulation of CPXM2 expression. These data support further translational investigation of CPXM2.

Association of adipocyte enhancer-binding protein 1 with Alzheimer's disease pathology in human hippocampi

Adipocyte enhancer binding protein 1 (AEBP1) activates inflammatory responses via the NF-κB pathway in macrophages and regulates adipogenesis in preadipocytes. Up-regulation of AEBP1 in the hippocampi of patients with Alzheimer's disease (AD) has been revealed by microarray analyses of autopsied brains from the Japanese general population (the Hisayama study). In this study, we compared the expression patterns of AEBP1 in normal and AD brains, including in the hippocampus, using immunohistochemistry. The subjects were 24 AD cases and 52 non-AD cases. Brain specimens were immunostained with antibodies against AEBP1, tau protein, amyloid β protein, NF-κB, GFAP and Iba-1. In normal brains, AEBP1 immunoreactivity mainly localized to the perikarya of hippocampal pyramidal neurons, and its expression was elevated in the pyramidal neurons and some astrocytes in AD hippocampi. Although AEBP1 immunoreactivity was almost absent in neurons containing neurofibrillary tangles, AEBP1 was highly expressed in neurons with pretangles and in the tau-immunopositive, dystrophic neurites of senile plaques. Nuclear localization of NF-κB was also observed in certain AEBP1-positive neurons in AD cases. Comparison of AD and non-AD cases suggested a positive correlation between the expression level of AEBP1 and the degree of amyloid β pathology. These findings imply that AEBP1 protein has a role in the progression of AD pathology.

Heightened Immune Activation in Fetuses with Gastroschisis May Be Blocked by Targeting IL-5

The development of the fetal immune system during pregnancy is a well-orchestrated process with important consequences for fetal and neonatal health, but prenatal factors that affect immune activation are poorly understood. We hypothesized that chronic fetal inflammation may lead to alterations in development of the fetal immune system. To test this hypothesis, we examined neonates with gastroschisis, a congenital abdominal wall defect that leads to exposure of the fetal intestines to amniotic fluid, with resultant intestinal inflammation. We determined that patients with gastroschisis show high systemic levels of inflammatory cytokines and chemokines such as eotaxin, as well as earlier activation of CD4(+) and CD8(+) effector and memory T cells in the cord blood compared with controls. Additionally, increased numbers of T cells and eosinophils infiltrate the serosa and mucosa of the inflamed intestines. Using a mouse model of gastroschisis, we observed higher numbers of eosinophils and both type 2 and type 3 innate lymphoid cells (ILC2 and ILC3), specifically in the portion of organs exposed to the amniotic fluid. Given the role of IL-5 produced by ILC2 in regulating eosinophil development and survival, we determined that maternal or fetal administration of the anti-IL-5 neutralizing Ab, or a depleting Ab against ILCs, can both effectively reduce intestinal eosinophilia. Thus, a congenital anomaly causing chronic inflammation can alter the composition of circulating and tissue-resident fetal immune cells. Given the high rate of prenatal and neonatal complications in these patients, such changes have clinical significance and might become targets for fetal therapy.

Interstitial cells of Cajal are decreased in patients with gastroschisis associated intestinal dysmotility

BACKGROUND

Gastroschisis associated intestinal dysmotility (GAID) is poorly understood. Animal experiments suggest that interstitial cells of Cajal (ICC), play an important role.

METHODS

Infants with gastroschisis (GS) and GAID (time to full feed >42days) were selected. Age matched GS and control (NEC, ileal atresia, malrotation, and volvulus) samples from primary (T1) and secondary (T2) time points underwent standard histopathology and immunohistochemistry for identification of ICC, followed by evaluation of ICC numbers, distribution, morphology, relation to ganglion cells, and myenteric plexus architecture. Groups were compared using parametric and nonparametric tests.

MAIN RESULTS

Twelve patients had samples available for histopathological evaluation. GAID patients had a significantly lower total number of ICCs than controls (3 vs. 8, P<0.0029). ICC number at T1 was 2.5 vs. 6 (P=0.0629) and significantly lower at T2. (3.5 vs. 11, P=0.0124). GAID patients did not show a significant increase of ICC from T1 to T2. Controls showed a significant increase of ICC over time (6 vs. 11, P=0.0408).

CONCLUSION

Intestinal samples from infants with GAID who underwent stoma formation demonstrated fewer ICC than controls. There was no improvement or cell recovery during the study period. The ability to modulate ICC may have significant implications for the management of GAID.

Multidirectional and simultaneous evaluation of gastroschisis-related intestinal damage in chick embryos

PURPOSE

In a chick model of gastroschisis, we aimed to investigate the morphological/cellular, molecular, and ultrastructural changes taking place in gastroschisis-related intestinal damage (GRID).

METHODS

13-Day fertilized eggs were divided into two groups.

CONTROL GROUP

chorio-amnio-allontoic membranes opened and abdominal wall exposed. Gastroschisis group: an anterior abdominal wall defect created after opening membranes. Embryos from both groups were surgically removed on post-fertilization day 19. Intestinal samples were obtained for histopathology, immunohistochemistry, molecular biology, and electron microscopy.

RESULTS

The histopathological grade of intestinal damage which primarily involved mucosal structures was significantly higher in the gastroschisis group when compared to the control group (p<0.001). Immunohistochemically, E-cadherin and synaptophysin immunoreactivity in the gastroschisis group was significantly lower than control group (p<0.05 and p<0.01, respectively), whereas there was no significant difference in laminin and type-4 collagen immunoreactivity between the groups (p>0.05). Molecular analyses indicated a significant decrease in NFκB and IκB expression in the gastroschisis group (p<0.05 and p=0.001, respectively). Electron microscopy showed that the gastroschisis group had considerable ultrastructural damage, manifested by apoptosis in all layers.

CONCLUSIONS

GRID affected all layers but was more prominent in mucosa. The damage may depend on E-cadherin and synaptophysin downregulation. Increased apoptotic activity, associated with decreased NFκB and IκB expression, may be an important component of this multifactorial damaging process.

Dermatan sulfate epimerase 1 deficient mice as a model for human abdominal wall defects

BACKGROUND

Dermatan sulfate (DS) is a highly sulfated polysaccharide with a variety of biological functions in extracellular matrix organization and processes such as tumorigenesis and wound healing. A distinct feature of DS is the presence of iduronic acid, produced by the two enzymes, DS-epimerase 1 and 2, which are encoded by Dse and Dsel, respectively.

METHODS

We have previously shown that Dse knockout (KO) mice in a mixed C57BL/6-129/SvJ background have an altered collagen matrix structure in skin. In the current work we studied Dse KO mice in a pure NFR genetic background.

RESULTS

Dse KO embryos and newborns had kinked tails and histological staining revealed significantly thicker epidermal layers in Dse KO mice when compared with heterozygote (Het) or wild-type (WT) littermates. Immunochemical analysis of the epidermal layers in newborn pups showed increased expression of keratin 5 in the basal layer and keratin 1 in the spinous layer. In addition, we observed an abdominal wall defect with herniated intestines in 16% of the Dse KO embryos. Other, less frequent, developmental defects were exencephaly and spina bifida.

CONCLUSION

We conclude that the combination of defective collagen structure in the dermis and imbalanced keratinocyte maturation could be responsible for the observed developmental defects in Dse KO mice. In addition, we propose that Dse KO mice could be used as a model in pathogenetic studies of human fetal abdominal wall defects.

Carboxypeptidases in disease: insights from peptidomic studies

Carboxypeptidases (CPs) perform many diverse physiological functions by removing C-terminal amino acids from proteins and peptides. Some CPs function in the degradation of proteins in the digestive tract while other enzymes play biosynthetic roles in the formation of neuropeptides and peptide hormones. Another set of CPs modify tubulin by removing amino acids from the C-terminus and from polyglutamyl side chains, thereby altering the properties of microtubules. This review focuses on three CPs: carboxypeptidase E, carboxypeptidase A6, and cytosolic carboxypeptidase 1. Naturally occurring mutations in all three of these enzymes are associated with disease phenotypes, ranging from obesity to epilepsy to neurodegeneration. Peptidomics is a useful tool to investigate the relationship between these mutations and alterations in peptide levels. This technique has also been used to define the function and characteristics of CPs. Results from peptidomics studies have helped to elucidate the function of CPs and clarify the biological underpinnings of pathologies by identifying peptides altered in disease states. This review describes the use of peptidomic techniques to gain insights into the normal function of CPs and the molecular defects caused by mutations in the enzymes.

The contribution of hiatal hernia to severe gastroesophageal reflux disease in patients with gastroschisis

BACKGROUND

A relationship between gastroschisis-associated gastroesophageal reflux (GER) and hiatal hernia (HH) has not been previously reported. In reviewing our experience with gastroschisis-related GER, we noted a surprising incidence of associated HH in patients requiring antireflux procedures.

METHODS

A single center retrospective chart review focused on GER in all gastroschisis patients repaired between January 1, 2000 and December 31, 2012 was performed.

RESULTS

Of the 141 patients surviving initial gastroschisis repair and hospitalization, 16 (11.3%) were noted to have an associated HH (12 Type I, 3 Type II, 1 Type III) on upper gastrointestinal series for severe reflux. Ten of the 13 (76.9%) patients who required an antireflux procedure had an associated HH. The time to initiation of feeds was similar in all patients, 19 and 23 days. However, time to full feedings and discharge was delayed until a median of 80 and 96 days, respectively, in HH patients.

CONCLUSIONS

This study describes a high incidence of associated HH in gastroschisis patients. The presence of large associated HH correlated with severe GER, delayed feeding, requirement for antireflux surgery, and a prolonged hospital stay. Patients with gastroschisis and clinically severe GER should undergo early assessment for associated HH.

Novel exomphalos genetic mouse model: the importance of accurate phenotypic classification

BACKGROUND

Rodent models of abdominal wall defects (AWD) may provide insight into the pathophysiology of these conditions including gut dysfunction in gastroschisis, or pulmonary hypoplasia in exomphalos. Previously, a Scribble mutant mouse model (circletail) was reported to exhibit gastroschisis. We further characterise this AWD in Scribble knockout mice.

METHOD

Homozygous Scrib knockout mice were obtained from heterozygote matings. Fetuses were collected at E17.5-18.5 with intact amniotic membranes. Three mutants and two control fetuses were imaged by in amnio micro-MRI. Remaining fetuses were dissected, photographed and gut length/weight measured. Ileal specimens were stained for interstitial cells of Cajal (ICC), imaged using confocal microscopy and ICC quantified.

RESULTS

127 fetuses were collected, 15 (12%) exhibited AWD. Microdissection revealed 3 mutants had characteristic exomphalos phenotype with membrane-covered gut/liver herniation into the umbilical cord. A further 12 exhibited extensive AWD, with eviscerated abdominal organs and thin covering membrane (intact or ruptured). Micro-MRI confirmed these phenotypes. Gut was shorter and heavier in AWD group compared to controls but morphology/number of ICC was not different.

DISCUSSION

The Scribble knockout fetus exhibits exomphalos (intact and ruptured), in contrast to the original published phenotype of gastroschisis. Detailed dissection of fetuses is essential ensuring accurate phenotyping and result reporting.