Evidence of disrupted rhombic lip development in the pathogenesis of Dandy-Walker malformation.

Dandy-Walker malformation (DWM) and Cerebellar vermis hypoplasia (CVH) are commonly recognized human cerebellar malformations diagnosed following ultrasound and antenatal or postnatal MRI. Specific radiological criteria are used to distinguish them, yet little is known about their differential developmental disease mechanisms. We acquired prenatal cases diagnosed as DWM and CVH and studied cerebellar morphobiometry followed by histological and immunohistochemical analyses. This was supplemented by laser capture microdissection and RNA-sequencing of the cerebellar rhombic lip, a transient progenitor zone, to assess the altered transcriptome of DWM vs control samples. Our radiological findings confirm that the cases studied fall within the accepted biometric range of DWM. Our histopathological analysis points to reduced foliation and inferior vermian hypoplasia as common features in all examined DWM cases. We also find that the rhombic lip, a dorsal stem cell zone that drives the growth and maintenance of the posterior vermis is specifically disrupted in DWM, with reduced proliferation and self-renewal of the progenitor pool, and altered vasculature, all confirmed by transcriptomics analysis. We propose a unified model for the developmental pathogenesis of DWM. We hypothesize that rhombic lip development is disrupted through either aberrant vascularization and/or direct insult which causes reduced proliferation and failed expansion of the rhombic lip progenitor pool leading to disproportionate hypoplasia and dysplasia of the inferior vermis. Timing of insult to the developing rhombic lip (before or after 14 PCW) dictates the extent of hypoplasia and distinguishes DWM from CVH.

Fetal Urinary Tract Anomalies: Review of Pathophysiology, Imaging, and Management.

OBJECTIVE: Common fetal anomalies of the kidneys and urinary tract encompass a complex spectrum of abnormalities that can be detected prenatally by ultrasound. Common fetal anomalies of the kidneys and urinary tract can affect amniotic fluid volume production with the development of oligohydramnios or anhydramnios, resulting in fetal pulmonary hypoplasia and, potentially, abnormal development of other fetal structures. CONCLUSION: We provide an overview of common fetal anomalies of the kidneys and urinary tract with an emphasis on sonographic patterns as well as pathologic and postnatal correlation, along with brief recommendations for postnatal management. Of note, we render an updated classification of fetal abnormalities of the kidneys and urinary tract based on the presence or absence of associated urinary tract dilation. In addition, we review the 2014 classification of urinary tract dilation based on the Linthicum multidisciplinary consensus panel.

Phenotypic outcomes in Mouse and Human Foxc1 dependent Dandy-Walker cerebellar malformation suggest shared mechanisms.

FOXC1 loss contributes to Dandy-Walker malformation (DWM), a common human cerebellar malformation. Previously, we found that complete Foxc1 loss leads to aberrations in proliferation, neuronal differentiation and migration in the embryonic mouse cerebellum (Haldipur et al., 2014). We now demonstrate that hypomorphic Foxc1 mutant mice have granule and Purkinje cell abnormalities causing subsequent disruptions in postnatal cerebellar foliation and lamination. Particularly striking is the presence of a partially formed posterior lobule which echoes the posterior vermis DW 'tail sign' observed in human imaging studies. Lineage tracing experiments in Foxc1 mutant mouse cerebella indicate that aberrant migration of granule cell progenitors destined to form the posterior-most lobule causes this unique phenotype. Analyses of rare human del chr 6p25 fetal cerebella demonstrate extensive phenotypic overlap with our Foxc1 mutant mouse models, validating our DWM models and demonstrating that many key mechanisms controlling cerebellar development are likely conserved between mouse and human.

Comprehensive Imaging Review of Abnormalities of the Placenta.

The placenta has a fundamental role in fetal health and functions as an important bridge to normal fetal development throughout pregnancy. A complete fetal ultrasound (US) survey should include full assessment of the placenta for any possible abnormalities. Placental diseases range from abnormal morphology, size, location, extent, and degree of placentation, to abruption and the presence of rare placental neoplasms of benign or malignant nature. Some of these conditions are associated with other diseases including aneuploidies, and their discovery should alert the radiologist to perform a very thorough fetal US examination. At times, a fetal karyotype may be needed to provide additional information. Timely detection of placental abnormalities can alert the clinician regarding the need to make important management decisions to reduce fetal and maternal morbidity and mortality. Familiarity with the normal and abnormal imaging appearance of the placenta is therefore necessary for the radiologist. Ultrasound with Doppler is the initial imaging modality of choice for placental assessment. Magnetic resonance imaging serves as a problem-solving examination in instances where the US findings are equivocal or where additional information is needed. Computed tomography has a limited role in the evaluation of placental disease because of its relatively limited tissue characterization and in particular because of the resultant direct radiation exposure of the fetus. However, in specific instances, particularly after trauma, computed tomography can provide invaluable information for patient management.

Development of novel software to generate anthropometric norms at perinatal autopsy.

Fetal and infant autopsy yields information regarding cause of death and the risk of recurrence, and it provides closure for parents. A significant number of perinatal evaluations are performed by general practice pathologists or trainees, who often find them time-consuming and/or intimidating. We sought to create a program that would enable pathologists to conduct these examinations with greater ease and to produce reliable, informative reports. We developed software that automatically generates a set of expected anthropometric and organ weight ranges by gestational age (GA)/postnatal age (PA) and a correlative table with the GA/PA that best matches the observed anthropometry. The program highlights measurement and organ weight discrepancies, enabling users to identify abnormalities. Furthermore, a Web page provides options for exporting and saving the data. Pathology residents utilized the program to determine ease of usage and benefits. The average time using conventional methods (ie, reference books and Internet sites) was compared to the average time using our Web page. Average time for novice and experienced residents using conventional methods was 26.7 minutes and 15 minutes, respectively. Using the Web page program, these times were reduced to an average of 3.2 minutes (P < 0.046 and P < 0.02, respectively). Participants found our program simple to use and the corrective features beneficial. This novel application saves time and improves the quality of fetal and infant autopsy reports. The software allows data exportation to reports and data storage for future analysis. Finalization of our software to enable usage by both university and private practice groups is in progress.

Comprehensive imaging review of abnormalities of the umbilical cord.

A complete fetal ultrasonographic (US) study includes assessment of the umbilical cord for possible abnormalities. Knowledge of the normal appearance of the umbilical cord is necessary for the radiologist to correctly diagnose pathologic conditions. Umbilical cord abnormalities can be related to cord coiling, length, and thickness; the placental insertion site; in utero distortion; vascular abnormalities; and primary tumors or masses. These conditions may be associated with other fetal anomalies and aneuploidies, and their discovery should prompt a thorough fetal US examination. Further workup and planning for a safe fetal delivery may include fetal echocardiography and karyotype analysis. Doppler US is a critical tool for assessment and diagnosis of vascular cord abnormalities. US also can be used for follow-up serial imaging evaluation of conditions that could result in fetal demise. Recent studies suggest that three- or four-dimensional Doppler US of the fetal umbilical cord and abdominal vasculature allows more accurate diagnosis of vascular abnormalities. Doppler US also is invaluable in assessment of fetal growth restriction since hemodynamic changes in the placenta or fetus would appear as a spectral pattern of increased resistance to forward flow in the fetal umbilical artery. Early detection of umbilical cord abnormalities and close follow-up can reduce the risk of morbidity and mortality and assist in decision making.

Microtomographic analysis of lower urinary tract obstruction.

Prenatal obstruction of the lower urinary tract may result in megacystis, with subsequent development of hydroureter, hydronephrosis, and renal damage. Oligo- or anhydramnios, pulmonary hypoplasia, and prune belly syndrome are lethal consequences. Causes and mechanisms responsible for obstruction remain unclear but might be clarified by anatomic study at autopsy. To this end, we employed 2 methods of tomographic imaging-optical projection tomography and contrast-enhanced microCT scanning-to elucidate the anatomy of the intact urinary bladder and urethra in 10 male fetuses with lower urinary tract obstruction. Images were compared with those from 9 age-matched controls. Three-dimensional images, rotated and sectioned digitally in multiple planes, permitted thorough examination while preserving specimens for later study. Both external and internal features of the bladder and urethra were demonstrated; small structures (ie, urethral crest, verumontanum, prostatic utricle, ejaculatory ducts) were seen in detail. Types of obstruction consisted of urethral atresia (n  =  5), severe urethral stenosis (n  =  2), urethral diaphragm (n  =  2), or physical kinking (n  =  1); classic (Young type I) posterior urethral valves were not encountered. Traditional light microscopy was then used to verify tomographic findings. The prostate gland was hypoplastic or absent in all cases; in 1, prostatic tissue was displaced inferior to the verumontanum. Findings support previous views that dissection may produce valve-like artifacts (eg, bisection of an obstructing diaphragm) and that deformation of an otherwise normal urethra may result in megacystis. The designation "posterior urethral valves" should not be used as a generic expression of urethral obstruction unless actual valves are demonstrated.

Novel FOXF1 mutations in sporadic and familial cases of alveolar capillary dysplasia with misaligned pulmonary veins imply a role for its DNA binding domain.

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare and lethal developmental disorder of the lung defined by a constellation of characteristic histopathological features. Nonpulmonary anomalies involving organs of gastrointestinal, cardiovascular, and genitourinary systems have been identified in approximately 80% of patients with ACD/MPV. We have collected DNA and pathological samples from more than 90 infants with ACD/MPV and their family members. Since the publication of our initial report of four point mutations and 10 deletions, we have identified an additional 38 novel nonsynonymous mutations of FOXF1 (nine nonsense, seven frameshift, one inframe deletion, 20 missense, and one no stop). This report represents an up to date list of all known FOXF1 mutations to the best of our knowledge. Majority of the cases are sporadic. We report four familial cases of which three show maternal inheritance, consistent with paternal imprinting of the gene. Twenty five mutations (60%) are located within the putative DNA-binding domain, indicating its plausible role in FOXF1 function. Five mutations map to the second exon. We identified two additional genic and eight genomic deletions upstream to FOXF1. These results corroborate and extend our previous observations and further establish involvement of FOXF1 in ACD/MPV and lung organogenesis.

Fibroblast growth factor-10 signals development of von Brunn's nests in the exstrophic bladder.

von Brunn's nests have long been recognized as precursors of benign lesions of the urinary bladder mucosa. We report here that von Brunn's nests are especially prevalent in the exstrophic bladder, a birth defect that predisposes the patient to formation of bladder cancer. Cells of von Brunn's nest were found to coalesce into a stratified, polarized epithelium which surrounds itself with a capsule-like structure rich in types I, III, and IV collagen. Histocytochemical analysis and keratin profiling demonstrated that nested cells exhibited a phenotype similar, but not identical, to that of urothelial cells of transitional epithelium. Immunostaining and in situ hybridization analysis of exstrophic tissue demonstrated that the FGF-10 receptor is synthesized and retained by cells of von Brunn's nest. In contrast, FGF-10 is synthesized and secreted by mesenchymal fibroblasts via a paracrine pathway that targets basal epithelial cells of von Brunn's nests. Small clusters of 10pRp cells, positive for both FGF-10 and its receptor, were observed both proximal to and inside blood vessels in the lamina propria. The collective evidence points to a mechanism where von Brunn's nests develop under the control of the FGF-10 signal transduction system and suggests that 10pRp cells may be the original source of nested cells.

Increasing the efficiency of autopsy reporting.

CONTEXT: -When autopsy reports are delayed, clinicians and families do not receive information in a timely fashion. OBJECTIVE: -Using lean principles derived from the Toyota Production System, we set out to streamline our autopsy reporting process. DESIGN: -In a formal workshop setting, we identified the steps involved in producing an autopsy report, then sought to eliminate, abbreviate, or reschedule them into a more efficient format. We established intermediate deadlines for each case, taking care to make them visible; we initiated a weekly quality assurance review, giving attention to both scientific issues and approaching deadlines. RESULTS: -By adopting a more standardized approach, eliminating redundancy, and improving the visibility of tasks, we improved the mean completion time of autopsy reports from 53 days (N = 47 cases) to 25 days (N = 47 cases). Previously, 17% of reports were completed by 30 days and 71% by 60 days; in the 15 months following initiation of the program, 72% of reports were completed by 30 days and 100% by 60 days. A follow-up survey of attending physicians revealed continuing appreciation for the autopsy and timely communication, with no perceived diminution in the quality of reports. CONCLUSIONS: -This approach was of great benefit in our laboratory and may assist others in reducing the turnaround time of their autopsy reports. It may also benefit other areas of the laboratory.

Familial recurrence of urethral stenosis/atresia.

BACKGROUND: We report the familial recurrence of urethral stenosis/atresia in two sibling fetuses with bladder outlet obstruction, severe oligohydramnios, and pulmonary hypoplasia. Urethral obstruction in the fetus, when severe, results in a dilated urinary bladder (megacystis) and associated urinary anomalies (hydroureter, hydronephrosis, renal dysplasia). Distention of the fetal abdomen, the result of megacystis or urinary ascites, leads to stretching and eventually hypoplasia or even absence of abdominal muscles. CASES: This constellation of findings, known by a variety of terms including "prune belly" syndrome, is associated with a variety of urethral changes, including posterior urethral valves and urethral stenosis/atresia. One fetus manifested unilateral postaxial polydactyly of the left hand. CONCLUSIONS: A microdeletion of 6p25.3, identified in mother and one fetus, is not associated with a gene known to be involved in urethral development and therefore of unknown significance.

Normal and abnormal anatomy of the cerebellar vermis in midgestational human fetuses.

BACKGROUND: Evaluation of the cerebellar vermis is an important component of fetal autopsy, but lack of an established approach, inadequate normal anatomic data, and the subtle nature of some cerebellar malformations negatively affect concordance between prenatal ultrasound and autopsy diagnoses. METHODS: Gross anatomy and sagittal histologic sections of vermis from 26 midgestation fetuses with no posterior fossa anomalies detected by prenatal ultrasound or autopsy were examined to establish stage-specific norms. These were compared to data from three fetuses with prenatal ultrasound diagnoses of hypoplasia or absence of the cerebellar vermis, each of which had no or equivocal gross cerebellar malformation at autopsy. RESULTS: Two findings segregated cases from controls: (1) The ratio of the rostro-caudal length of the vermis to that of the cerebellar hemispheres was shorter for cases (<0.7), in comparison with controls (0.7-1). (2) The lobules of the vermis, particularly in the posterior lobe, were less arborized, and the nodulus (caudal-most lobule) was elongated. Prenatal sonograms from the three cases predicted more severe vermis hypoplasia than was evident at autopsy. CONCLUSIONS: Prenatal ultrasound images that suggest moderate-to-severe hypoplasia of the cerebellar vermis may reflect relatively subtle malformations, which are recognized histologically by direct comparison with stage-matched control data. The data in this series and others suggest a somewhat consistent pattern of lobular malformation, which affects the caudal cerebellum, particularly the nodulus, most severely. Rotation of the cerebellum, secondary to an enlarged fourth ventricle, may account for discordance between ultrasound and autopsy findings.

Antenatal diagnosis of intestinal malrotation on fetal MRI.

We report a case of intestinal malrotation without any associated GI tract complications diagnosed antenatally by fetal MRI. Antenatal US revealed a midline stomach. Subsequent fetal MRI confirmed the midline stomach and, in addition, revealed all loops of small bowel to the right of the midline and all large bowel to the left. All these features were consistent with intestinal malrotation. There was no abnormal bowel wall thickening, bowel dilatation, ascites or polyhydramnios. To our knowledge, this is a unique case of intestinal malrotation without associated GI tract complications diagnosed antenatally on fetal MRI.

Exposure to environmental tobacco smoke during pregnancy in rats yields less effect on indices of brain cell number and size than does postnatal exposure.

While there is evidence that human perinatal exposure to environmental tobacco smoke (ETS) can result in an increased risk of respiratory disorders and sudden infant death syndrome, evidence linking ETS exposure to neurodevelopmental handicaps is suggestive but less compelling. We previously noted that postnatal ETS exposure, rather than prenatal exposure, resulted in reduced concentration of hindbrain DNA and increased protein/DNA ratio when rat brain tissue was studied at 9 weeks postnatal age. We have now evaluated the effects of ETS exposure during pregnancy on brain development by assaying brain tissue at term. ETS exposure had no detectable effects on regional brain concentrations of DNA, protein and cholesterol or on protein/DNA and cholesterol/DNA ratios. While ETS exposure during pregnancy also had no detectable effects on the weights of the individual fetuses or on the weights of various organs, certain regions of the fetal skeleton demonstrated accelerated ossification. The findings of this study are contrasted to the developmental effects of both nicotine and ETS in Rhesus macaques. Additional studies designed specifically to assess the risk of prenatal ETS exposure on brain development in non-human primates and other precocial species are warranted.

Cyclopia, aprosencephaly, and acardiac twinning: Is hypoxia-ischemia a unifying mechanism?

In a recent case of monochorionic diamniotic twinning we observed one twin with acardia, cyclopia, and aprosencephaly, an association not reported previously. In most cases of acardia, the development of tissues in superior regions of the body is disrupted severely, while inferior structures develop more normally. A common explanation for this disruption is hypoxia-ischemia due to twin reversed arterial perfusion (TRAP). In this condition, arterial-arterial and venous-venous anastomoses in the placenta permit twin-twin transfusion and reversal of blood flow in the umbilical vessels and aorta of the recipient twin. The heart is absent or severely deficient, either by secondary atrophy or possibly a more primary, though currently unknown, mechanism. As a result, cranial tissues are less likely to be perfused with oxygenated blood than caudal tissues. A host of craniocerebral anomalies are observed in acardia, including total absence of the head and brain, rudimentary brain, anencephaly, holoprosencephaly, neuronal migration defects, and near-normal brain. Hypoxia-ischemia could be an important factor in the disruption of tissues in the present case, although a more generalized process affecting heart, head, and brain cannot be excluded. The findings suggest that hypoxia-ischemia may play a role in the pathogenesis of some cases of holoprosencephaly and aprosencephaly. This mechanism has been underreported and requires additional investigation.

Five cases of caudal regression with an aberrant abdominal umbilical artery: Further support for a caudal regression-sirenomelia spectrum.

Sirenomelia and caudal regression have sparked centuries of interest and recent debate regarding their classification and pathogenetic relationship. Specific anomalies are common to both conditions, but aside from fusion of the lower extremities, an aberrant abdominal umbilical artery ("persistent vitelline artery") has been invoked as the chief anatomic finding that distinguishes sirenomelia from caudal regression. This observation is important from a pathogenetic viewpoint, in that diversion of blood away from the caudal portion of the embryo through the abdominal umbilical artery ("vascular steal") has been proposed as the primary mechanism leading to sirenomelia. In contrast, caudal regression is hypothesized to arise from primary deficiency of caudal mesoderm. We present five cases of caudal regression that exhibit an aberrant abdominal umbilical artery similar to that typically associated with sirenomelia. Review of the literature identified four similar cases. Collectively, the series lends support for a caudal regression-sirenomelia spectrum with a common pathogenetic basis and suggests that abnormal umbilical arterial anatomy may be the consequence, rather than the cause, of deficient caudal mesoderm.

Estimating human ovarian non-growing follicle number: the application of modern stereology techniques to an old problem.

BACKGROUND Previous published reports on the number of non-growing follicles (NGFs) in the human ovary have employed model-based methods for number estimates. These methods are time-intensive, and require correction factors and assumptions that ultimately limit their accuracy. Here, we describe the modification, application and validation of a modern fractionator/optical disector technique for the estimation of human ovarian NGF number. METHODS Forty-eight pairs of normal human ovaries were collected from women (age 8-51 years) undergoing elective bilateral oophorectomy, organ donation, or from autopsy. After gross pathologic examination, systematic random sampling was utilized to obtain tissue for analysis by the fractionator/optical disector method. The precision of individual NGF counts was determined by calculating the observed coefficient of error (OCE). Intra-observer variability and variation in NGF number between ovaries within a pair were also determined. RESULTS The mean OCE was 16.6% with larger variations observed at lower follicle counts. In recount experiments of the same ovary, NGF number estimates varied by 15-29%, except at very low follicle counts where variation was greater, but absolute differences were small. There was no significant difference in NGF number between ovaries within a pair (Wilcoxon signed rank test, P = 0.81). CONCLUSIONS Modern stereology methods provide an unbiased, efficient method for estimating NGF number in the human ovary. Both ovaries within a pair contain similar numbers of NGFs.