Pathogenesis Of Spina Bifida Research Articles

Research progress on the etiology and pathogenesis of spina bifida

To review the research progress on etiology and pathogenesis of spina bifida. By consulting relevant domestic and foreign research literature on spina bifida, the classification, epidemic trend, pathogenesis, etiology, prevention and treatment of it were analyzed and summarized. Spina bifida, a common phenotype of neural tube defects, is classified based on the degree and pattern of malformation associated with neuroectodermal involvement and is due to the disturbance of neural tube closure 28 days before embryonic development. The prevalence of spina bifida varies greatly among different ethnic groups and regions, and its etiology is complex. Currently, some spina bifida patients can be prevented by folic acid supplements, and with the improvement of treatment technology, the short-term and long-term survival rate of children with spina bifida has improved. The research on the pathogenesis of spina bifida will be based on the refined individual information on exposure, genetics, and complex phenotype, and will provide a theoretical basis for improving prevention and treatment strategies through multidisciplinary cooperation.

CD200-CD200R imbalance correlates with microglia and pro-inflammatory activation in rat spinal cords exposed to amniotic fluid in retinoic acid-induced spina bifida

Spina bifida aperta is a congenital malformation characterized by the failure of neural tube closure resulting in an unprotected fetal spinal cord. The spinal cord then undergoes progressive damage, likely due to chemical and mechanical factors related to exposure to the intrauterine environment. Astrogliosis in exposed spinal cords has been described in animal models of spina bifida during embryonic life but its relationship with neuroinflammatory processes are completely unknown. Using a retinoic acid-induced rat model of spina bifida we demonstrated that, when exposed to amniotic fluid, fetal spinal cords showed progressive astrogliosis with neuronal loss at mid-gestation (E15) compared to unexposed spinal cords. The number of microglial cells with a reactive phenotype and activation marker expression increased during gestation and exhibited progressive disruption in the inhibitory immune ligand-receptor system. Specifically we demonstrate down-regulation of CD200 expression and up-regulation of CD200R. Exposed spinal cords demonstrated neuroinflammation with increased tissue water content and cytokine production by the end of gestation (E20), which correlated with active Caspase3 expression in the exposed layers. Our findings provide new evidence that microglia activation, including the disruption of the endogenous inhibitory system (CD200-CD200R), may participate in the pathogenesis of spina bifida through late gestation.

Rare deleterious variants in GRHL3 are associated with human spina bifida

Neural tube defects, including spina bifida, are among the most common birth defects caused by failure of neural tube closure during development. They have a complex etiology involving largely undetermined environmental and genetic factors. Previous studies in mouse models have implicated the transcription factor Grhl3 as an important factor in the pathogenesis of spina bifida. In the present study, we conducted a resequencing analysis of GRHL3 in a cohort of 233 familial and sporadic cases of spina bifida. We identified two novel truncating variants: one homozygous frameshift variant, p.Asp16Aspfs*10, in two affected siblings and one heterozygous intronic splicing variant, p.Ala318Glyfs*26. We also identified five missense variants, one of which was demonstrated to reduce the activation of gene targets in a luciferase reporter assay. With the previously identified p.Arg391Cys variant, eight variants were found in GRHL3. Comparison of the variant rate between our cohort and the ExAC database identified a significant enrichment of deleterious variants in GRHL3 in the whole gene and the transactivation region in spina bifida patients. These data provide strong evidence for a role of GRHL3 as a predisposing factor to spina bifida and will help dissect the complex etiology and pathogenic mechanisms of these malformations.

Altered microRNA expression profiles in a rat model of spina bifida.

MicroRNAs (miRNAs) are dynamically regulated during neurodevelopment, yet few reports have examined their role in spina bifida. In this study, we used an established fetal rat model of spina bifida induced by intragastrically administering olive oil-containing all-trans retinoic acid to dams on day 10 of pregnancy. Dams that received intragastric administration of all-trans retinoic acid-free olive oil served as controls. The miRNA expression profile in the amniotic fluid of rats at 20 days of pregnancy was analyzed using an miRNA microarray assay. Compared with that in control fetuses, the expression of miRNA-9, miRNA-124a, and miRNA-138 was significantly decreased (> 2-fold), whereas the expression of miRNA-134 was significantly increased (> 4-fold) in the amniotic fluid of rats with fetuses modeling spina bifida. These results were validated using real-time quantitative reverse-transcription polymerase chain reaction. Hierarchical clustering analysis of the microarray data showed that these differentially expressed miRNAs could distinguish fetuses modeling spina bifida from control fetuses. Our bioinformatics analysis suggested that these differentially expressed miRNAs were associated with many cytological pathways, including a nervous system development signaling pathway. These findings indicate that further studies are warranted examining the role of miRNAs through their regulation of a variety of cell functional pathways in the pathogenesis of spina bifida. Such studies may provide novel targets for the early diagnosis and treatment of spina bifida.

An Integrative Computational Approach for Prioritization of Genomic Variants

An essential step in the discovery of molecular mechanisms contributing to disease phenotypes and efficient experimental planning is the development of weighted hypotheses that estimate the functional effects of sequence variants discovered by high-throughput genomics. With the increasing specialization of the bioinformatics resources, creating analytical workflows that seamlessly integrate data and bioinformatics tools developed by multiple groups becomes inevitable. Here we present a case study of a use of the distributed analytical environment integrating four complementary specialized resources, namely the Lynx platform, VISTA RViewer, the Developmental Brain Disorders Database (DBDB), and the RaptorX server, for the identification of high-confidence candidate genes contributing to pathogenesis of spina bifida. The analysis resulted in prediction and validation of deleterious mutations in the SLC19A placental transporter in mothers of the affected children that causes narrowing of the outlet channel and therefore leads to the reduced folate permeation rate. The described approach also enabled correct identification of several genes, previously shown to contribute to pathogenesis of spina bifida, and suggestion of additional genes for experimental validations. The study demonstrates that the seamless integration of bioinformatics resources enables fast and efficient prioritization and characterization of genomic factors and molecular networks contributing to the phenotypes of interest.

Maternal periconceptional factors affect the risk of spina bifida-affected pregnancies: an Italian case–control study

Neural tube defects, including spina bifida and anencephaly, are the second most common birth defects with an incidence in Italy of 0.4-1/1,000. Information on factors playing a role in the pathogenesis of spina bifida is based on populations with different exposures, lifestyle, social and cultural habits compared to Italian people. Our objective was to fill this gap by using data from a case-control interview study carried out at the G. Gaslini Children's Hospital, Genoa, from 2000 to 2008. We surveyed questionnaires from 133 case mothers and 273 control women providing information on periconceptional risk factors. Univariate and multivariate logistic regression analyses were used to estimate risks by odds ratios (ORs) and 95% confidence intervals (95% CIs). Univariate results suggest that birth order, low maternal educational level, age, smoking habits, alcohol consumption, high caffeine intake, lack of folate supplementation, low and high calorie diet, occasional consumption of fruit and vegetables, high emotional stress, and environmental pollution are associated with an increased spina bifida risk. Nevertheless, high caffeine intake (OR = 10.82; 95% CI, 3.78-31), low calorie diet (OR = 5.15; 95%CI, 1.79-14), occasional consumption of fruit and vegetables (OR = 3.38; 95% CI, 1.67-6.82), alcohol consumption (OR = 3.05; 95% CI, 1.24-7.50) and, above all, lack of folate supplementation at any time of pregnancy (OR = 20.54; 95% CI, 5.41-77) mainly determined spina bifida risk in the multivariate analysis. Our findings point out that a common underlying mechanism, a disturbed folate/homocysteine metabolism, may be causative for the burden of spina bifida in the Italian population.

Estimation and correlation of serum folic acid levels in spina bifida babies and their mothers

Spina bifida is a common neural tube defect. The relative deficiency of folic acid (FA) in mother during periconceptional period is an important factor. We measured the serum FA levels in spina bifida babies and their mothers and compared the result with the FA level in normal babies. The blood samples were collected at the time of admission to hospital. Enquiry made about the age, sex, and birth order, problem in siblings and FA supplementation and detailed examination done to access the severity of the problem. Folic acid estimation was done by enzyme-linked immunosorbent assay method. Antenatal FA supplementation was found in 40% of cases and 80% of control group. In the study group, the mean FA level in babies and mothers of FA supplemented group was 21.73 ± 5.64 ng/dl and 15.02 ± 3.02 ng/dl and in non-supplemented group were 7.41 ± 1.48 ng/dl and 4.12 ± 0.81 ng/dl, respectively. In control group mean FA level in babies and mothers of FA supplemented group were 16.88 ± 3.2 ng/dl and 14.70 ± 2.30 ng/dl and in nonsupplemented group were 14.33 ± 1.74 ng/dl and 10.75 ± 1.34 ng/dl, respectively. The serum FA levels in spina bifida babies as well as in their mothers were significantly low as compared to control group. This study suggests that the low serum FA levels in a lady at the time of pregnancy may be a causative factor in the pathogenesis of spina bifida and low levels in affected babies.

Evidence for a functional genetic polymorphism of the human retinoic acid–metabolizing enzyme CYP26A1, an enzyme that may be involved in spina bifida

CYP26A1, together with CYP26B1 and CYP26C1, are key enzymes of all-trans retinoic acid (RA) inactivation and their specific and restricted expression in developing embryos participate in the fine tuning RA levels. As RA is a critical regulator of gene expression during embryonic development, the imbalance between the synthesis and degradation of RA during embryogenesis could contribute to malformations and developmental defects. A PCR-single strand conformation polymorphism (PCR-SSCP) strategy was developed to screen for CYP26A1 sequence variations that could affect the enzyme expression and/or activity and applied to DNA samples from 80 unrelated Caucasians, comprising 40 French healthy volunteers and 40 Italian patients with spina bifida. The consequence of the 1-bp deletion identified in the coding sequence was investigated by an in vitro functional assay using COS-7 cells. A total of 7 polymorphisms were identified, comprising 1 nucleotide deletion in the coding sequence (g.3116delT) that results in a frameshift and consequently in the creation of a premature stop codon. The g.3116delT mutation is of particular interest because it was identified in a patient with spina bifida and likely encodes a truncated protein with no enzymatic activity, as demonstrated by our preliminary in vitro data. Despite the fact that our findings could not show any evidence that the CYP26A1 genetic polymorphism has implications in the pathogenesis of spina bifida, this work represents the first description of a functional genetic polymorphism affecting the coding sequence of the human CYP26A1 gene.

Are myo-inositol, glucose and zinc concentrations in amniotic fluid of fetuses with spina bifida different from controls?

Associations are reported between myo-inositol, glucose, zinc and the occurrence of spina bifida. To gain more insight into the pathogenesis of spina bifida, the concentrations of myo-inositol, glucose and zinc were determined in amniotic fluids from pregnancies with a spina bifida or unaffected control fetus. Amniotic fluids of 27 pregnancies complicated by spina bifida and 49 controls were collected at the Department of Obstetrics and Gynecology of the University Medical Center Nijmegen in the Netherlands. Myo-inositol, glucose and zinc concentrations were determined. By indication, the samples were taken at different gestational ages. Therefore, the data were evaluated using multiple linear regression analysis to adjust for gestational age. Amniocentesis was performed at a more advanced gestational age in the spina bifida group than in controls. In the spina bifida group, amniotic fluid myo-inositol, glucose and zinc concentrations gradually declined throughout pregnancy. At a gestational age of 15 weeks, the estimated mean amniotic fluid glucose and zinc concentrations in the spina bifida group were, respectively, significantly lower (p< or =0.5) and higher (p< or =0.5) compared with the control group. At the same gestational age, the estimated mean myo-inositol concentrations were comparable in both groups. At a gestational age of 38 weeks, the estimated mean myo-inositol, glucose and zinc concentrations were not significantly different in the spina bifida compared with the control group. This study may suggest that a derangement in zinc and glucose transfer or metabolism is associated with spina bifida. Since compounds in amniotic fluid are only a very crude marker of the actual fetal condition, studies that focus on the metabolism of these compounds on tissue or even cellular level should be performed to clarify their role in the pathogenesis and future prevention of spina bifida.

OBSERVATIONS ON THE PATHOGENESIS OF SPINA BIFIDA IN CHICK EMBRYOS: FORKING OF THE NEURAL TUBE

Observations on the pathogenesis of spina bifida in chick embryos: forking of the neural tubeForking is an early malformation in which the neural tube is split into 2–6 tubules, walled off by neuroepithelium. Occasionally the undivided tube proximal to forking of the neural tube (FNT) or some of the secondary tubules, may show marked cystic dilatation. FNT may occur at any level of the cord and hence its development is not related to the caudal cell mass (‘tail node’). It is important that FNT may be covered by intact ectoderm or may occur simultaneously with myeloschisis. Spina bifida (SB) probably develops in those cases of FNT in which marked increase in volume of the malformed tube, due either to cystic dilatation or to presence of multiple tubules, prevents the mesoderm from growing between the ectoderm and the neural tissue. FNT seems to result from primary damage to the neural tissue around the posterior neuropore, followed by formation of supernumerary tubules from fragmented neuroepithelium. This process does not interfere with normal growth of the ectoderm. The likely consequences of FNT are deduced tentatively from a comparison with cases of fully developed spontaneous human SB associated with diastematomyelia (DM). FNT is related to variable degree of myelodysplasia, diplomyelia, myelocystocele and meningocele. The hypothesis (Rokos, 1975) that meningocele is a manifestation of anteroposterior FNT (anteroposterior DM) is supported by the present findings.

The pathogenesis of spina bifida: a study of the relationship between observation, hypothesis, and surgical incentive.

SUMMARYThe growth of medical literature concerned with spina bifida since the seventeenth century reveals a stimulating relationship between factual observations upon the complex nature of the malformation, conflicting hypotheses upon its pathogenesis, and changing therapeutic possibilities as a result of advances in surgical technique.This study endeavours to account for this relationship in the particular context of the current renewal of surgical interest in spina bifida.RÉSUMÉPathogénie du spina bifida: étude de la relation entre l'observation, l'hypothèse et les tentatives chírurgicalesLe développement de la littérature médicale concernant le spina bifida depuis le XVIIème siècle révèle une relation stimulante entre les faits d'observation sur la nature complexe de la malformation, des hypothèses contradictoires sur sa pathogénie et des possibilités thérapeutiques évoluant en fonction des progrès de la technique chirurgicale.Cette étude s'efforce de replacer cette relation dans le contexte particulier de l'actuel courant d'intérêts sur la chirurgie dans le spina bifida.ZUSAMMENFASSUNGDie Pathogenese der Spina bifida: Eine Untersuchung über das Verhältnis zwischen Beobachtung, Hypothese und chirwgischem ImpetusDas Anwachsen der medizinischen Literatur über die Spina bifida seit dem 17 Jahrhundert deckt ein stimulierendes Verhältnis zwischen tatsächlichen Beobachtungen über die komplexe Natur der Mißbildung, gegensätzliche Hypothesen über ihre Pathogenese und weehselnde therapeutische Möglichkeiten als Ergebnis fortgeschrittener chirurgischer Techniken auf.Diese Untersuchung bemüht sich, dieses Verhältnis unter der besonderen Berücksichtigung des gegenwärtigen neuen Interesses der Chirurgen an der Spina bifida zu erläutern.RESUMEN Patogenia de la espina bifida: estudio de la relatión entre la observation, la hipótesis y el incentivo quirúrgicoEl aumento de la literatura médica acerca de la espina bífida desde el siglo XVII revela una estimulante relación entre los hechos observados acerca de su patogénesis y loscambios en las posibilidades terapeuticas como resultado de los adelantos en la técnica quirúrgica.Este estudio engloba esta relación en el contexto particular del interés quirúrgico constantemente renovado de la espina bífida.