Ventral Bud Research Articles

Presenting embryologically defined peripancreatic compartments and fusion planes in the search for pancreatic cancer fields

BackgroundClinical progress in form of “total mesometrial resection” (TMMR) in cervical cancer and “total mesorectal excision” (TME) in rectal cancer can be traced to a paradigm-shift regarding the extent and range of resection. More significance is bestowed upon embryologically defined borders which define compartments, “morphogenetic units” and “cancer fields”, that have to be addressed in order to avoid incomplete tumor resection. We want to transfer this rationale on the pancreas and define such borders for pancreatic compartments. Material and methodsWe used 26 unfixed body donors (16 male, 10 female) ranging in age from 64 to 98 years. Manual preparation consisted of performing the Cattell-Braasch maneuver to restore embryologic anatomy and define fascial remnants of the borders of the dorsal and ventral mesogastrium with focus on the pancreatic fusion fasciae and peripancreatic spaces. ResultsWe tracked what used to be the dorsal and ventral mesogastrium and assigned their remnants to the bowel and pancreas. Following avascular embryologic fascial fusion planes along the mesogastria we could demonstrate peripancreatic spaces, which were sealed off from bordering surfaces of presumably different morphogenetic units and possible cancer fields. Reverting embryologic development also seemed possible within the pancreas, demonstrating the embryologic fusion plane between the ventral and dorsal pancreatic buds as two distinct compartments. ConclusionsFollowing pancreatic fusion fasciae by separating embryologic fusion planes enables to define the pancreatic compartments which might play a major role in applying the success of TMMR and TME on pancreatic resection and define pancreatic cancer fields.

Exome sequencing findings in children with annular pancreas.

Annular pancreas (AP) is a congenital defect of unknown cause in which the pancreas encircles the duodenum. Theories include abnormal migration and rotation of the ventral bud, persistence of ectopic pancreatic tissue, and inappropriate fusion of the ventral and dorsal buds before rotation. The few reported familial cases suggest a genetic contribution. We conducted exome sequencing in 115 affected infants from the California birth defects registry. Seven cases had a single heterozygous missense variant in IQGAP1, five of them with CADD scores >20; seven other infants had a single heterozygous missense variant in NRCAM, five of them with CADD scores >20. We also looked at genes previously associated with AP and found two rare heterozygous missense variants, one each in PDX1 and FOXF1. IQGAP1 and NRCAM are crucial in cell polarization and migration. Mutations result in decreased motility which could possibly cause the ventral bud to not migrate normally. To our knowledge, this is the first study reporting a possible association for IQGAP1 and NRCAM with AP. Our findings of rare genetic variants involved in cell migration in 15% of our population raise the possibility that AP may be related to abnormal cell migration.

Annulling an Annulled Annular Pancreas: A Case Report

Annular Pancreas (AP) is a rare congenital developmental anomaly which results from failure of the ventral bud to rotate to fuse with the dorsal bud, resulting in a ring of pancreatic parenchyma that surrounds the second portion of the duodenum. This rare entity can be partial or complete and the partial is even rarer. Most cases manifest in the infancy but may remain asymptomatic and various nonspecific clinical manifestations are seen in adults. We report a rare case of partial annular pancreas with atrophy of body and tail of pancreas which presented with upper gastrointestinal bleeding and obstruction. The challenge in this case was the annular pancreas was the only functioning pancreatic tissue.

The sun beside the pancreatic neck: The lymph node gastrinoma (with video).

The sun beside the pancreatic neck: The lymph node gastrinoma (with video).

En1 and Lmx1b do not recapitulate embryonic dorsal-ventral limb patterning functions during mouse digit tip regeneration.

The mouse digit tip regenerates following amputation. How the regenerate is patterned is unknown, but a long-standing hypothesis proposes developmental patterning mechanisms are re-used during regeneration. The digit tip bone exhibits dorsal-ventral (DV) polarity, so we focus on En1 and Lmx1b, two factors necessary for DV patterning during limb development. We investigate whether they are re-expressed during regeneration in a developmental-like pattern and whether they direct DV morphology of the regenerate. We find that both En1 and Lmx1b are expressed in the regenerating digit tip epithelium and mesenchyme, respectively, but without DV polarity. Conditional genetics and quantitative analysis of digit tip bone morphology determine that genetic deletion of En1 or Lmx1b in adult digit tip regeneration modestly reduces bone regeneration but does not affect DV patterning. Collectively, our data suggest that, while En1 and Lmx1b are re-expressed during mouse digit tip regeneration, they do not define the DV axis during regeneration.

TP53 gain-of-function mutations and impact on CDKN2A mutation on prognosis of pancreatic ductal adenocarcinoma.

e16294 Background: Developmentally pancreas head derives from ventral bud while pancreas neck, body and tail derive from dorsal bud. Pancreatic ductal adenocarcinoma (PDAC) frequently harbors multiple mutations including KRAS, TP53, CDKN2A, and others. It is unknown how TP53 gain-of-function (GOF) and non-gain-of-function (non-GOF) mutations affect the prognosis. Methods: We retrospectively examined a cohort of 741 Kaiser Permanente (KP) patients with locally advanced/metastatic PDAC who had NGS performed to determine the association of KRAS (mutKRAS), TP53 (mutp53) and CDKN2A (mutCDKN2A) mutations (individually and in combination) with overall survival (OS). We used Cox modeling to estimate hazard ratios (HR) adjusted for age, sex, ethnicity, performance status, Charlston Comorbidity Index, chemotherapy received, anatomic location and co-mutations. We also analyzed the TCGA PDAC dataset to examine the association of OS with these same mutations. Results: In the KP cohort, patient ages ranged from 36 to 94 years and approximately 50% were female. In 384 patients PDAC was on the head, and 357 patients had PDAC on a non-head location (neck, body, and tail). Those with head PDAC had modestly better OS compared to non-head PDAC (HR = 0.87), and this appeared to be driven by the subsets of patients with wtp53 (HR = 0.68), with wtKRAS (HR = .74) and with wtCDKN2A (HR = .78). Approximately 67.5% of patients had mutp53, 89.2% had mutKRAS and 44.8% had mutCDKN2A. Among all KP patients, OS was similar for patients with mutp53 vs. wtp53 (HR = 1.05); worse for patients with mutKRAS vs. wtKRAS (HR = 1.26), and worse for patients with mutCDKN2 vs. wtCDKN2A (HR = 1.51). Interestingly, among patients with a GOF mutp53, those with mutCDKN2A had substantially worse OS vs patients with wtCDKN2A (HR = 2.56, 95% CI 1.46-4.50). In contrast, among patients with a non-GOF mutp53, patients with mutCDKN2A had only moderately worse OS compared to patients with wtCDKN2A (HR = 1.37, 95% CI 1.06-1.79). Analysis of the TCGA PDAC dataset showed that the number of mutations (0, 1, 2, or 3, of p53, KRAS and CDKN2A) was associated with incrementally worse OS ( p < .001). Conclusions: Better OS of head vs. non-head PDAC was primarily driven by patients with wtp53, wtKRAS, and wtCDKN2A. The adverse effect of mutCDKN2A on OS appears to be most pronounced in patients with GOF mutp53. Our TCGA analysis suggests interactions among TP53, KRAS and CDKN2A mutations in affecting PDAC survival.

Bisection, Disjuncture, Aqueduct: Pancreas Divisum

The conformable congenital anatomic malformation of the pancreas is Pancreas Divisum. Conventionally, the pancreas evolves from the fusion of the dorsal and the ventral pancreatic buds throughout the sixth week of gestation. The dorsal bud structures the head, tail and the body of the pancreas while the ventral bud configures the uncinate process besides the inferior portion of the head. The concurrence of this arrangement permits the amalgamation of the ductal schemata so the major pancreatic duct evacuates the pancreatic secretions into the duodenum through the major duodenal papilla. Comparatively 30% of entities delineate the traditional anatomical derivatives, where the proximal dorsal pancreatic duct prevails as the accessory pancreatic duct and expels through the minor duodenal papilla.

70-Year-Old Man With Chronic Nausea and Vomiting

70-Year-Old Man With Chronic Nausea and Vomiting

An Infundibular Unidentified Object (IUO): a new pituitary stalk marker?

Measurement of the pituitary stalk (PS) diameter does not always solve the issue of minimal PS thickening. A previously undescribed image is found at the infundibular level on high resolution thin section T2W MRI in a large number of normal individuals. We speculate that this image-whose exact origin is still unknown-may serve as a marker of the normal infundibulum. In the last 6months, 350 consecutive adult patients suspected of sellar pathology or controlled after medical or surgical treatment prospectively underwent a pituitary MRI including a sagittal T2W high resolution sequence. One hundred twelwe patients presenting a pituitary mass with suprasellar extension or those whose PS was not entirely visible were excluded. A short focal annular T2 hypointense thickening of the wall of the infundibular recess of the third ventricle, more pronounced anteriorly was found in 151/238 patients. Additionally, a more or less tiny ventral extension was demonstrated on sagittal T2W sequence in 105/151 patients. These images were not identified on T1W or on T1W gadolinium enhanced sequences. The ring-like infundibular thickening and/or its ventral extension were not identified in 87/238 patients; in 43/87 of these patients the PS was found severely stretched mainly in case of primary or secondary empty sella. If patients with empty sella were excluded, our finding was observed in 194/238 cases, i.e. in 82%. A detailed appearance of the PS on T2W MRI is described for the first time. A previously unreported T2W hypointense annular focal image prolonged by a tiny spicular or nodular ventral bud is found at the lower part of the infundibulum in a majority of normal patients, but not if the PS is stretched such as in empty sella. This image has to be recognized as a normal anatomical landmark. The possible origin of this image is discussed but not totally elucidated. An ongoing research will demonstrate or not if this image may serve as a marker to improve the early diagnosis of PS lesions.

A Case of Late Presentation of Pancreatic Divisum in a Patient with Recurrent Pancreatitis

Pancreatic Divisum (PD) is the most common congenital variation of pancreatic duct anatomy, arising when embryological ventral and dorsal endodermal buds fail to fuse (“classic” PD) or only fuse partially (“incomplete” PD). Most patients with PD are asymptomatic, but a subgroup of patients can present with recurrent bouts of pancreatitis. While alcohol and gallstones are the common causes of acquired pancreatitis, PD is a congenital cause of pancreatitis. It is usually suspected in younger individuals with recurrent pancreatitis who also have a family history. Here, we present a rare case of PD in an older individual who presented with recurrent pancreatitis. He underwent cholecystectomy for suspected gallstone pancreatitis but continued to have episodes of pancreatitis. He had a history of alcohol abuse but denied use in the last one year. PD was detected later as the cause. Recurrent pancreatitis led to the development of a pseudocyst and pancreaticopleural fistula (PPF). Medical management improved the pseudocyst and PPF.

Multicolor Labeling and Tracing of Pancreatic Beta-Cell Proliferation in Zebrafish.

During embryogenesis, beta-cells arise from the dorsal and ventral bud originating in the endoderm germ layer. As the animal develops to adulthood, the beta-cell mass dramatically increases. The expansion of the beta-cell population is driven by cell division among the embryonic beta-cells and supplanted by neogenesis from post-embryonic progenitors. Here, we describe a protocol for multicolor clonal analysis in zebrafish to define the contribution of individual embryonic beta-cells to the increase in cell numbers. This technique provides insights into the proliferative history of individual beta-cells in an islet. This insight helps in defining the replicative heterogeneity among individual beta-cells during development. Additionally, the ability to discriminate individual cells based on unique color signatures helps quantify the volume occupied by beta-cells and define the contribution of cellular size to the beta-cell mass.

Role of the Wilms' tumor suppressor gene Wt1 in pancreatic development.

The Wilms tumor suppressor gene (Wt1) encodes a transcription factor involved in the development of a number of organs, but the role played by Wt1 in pancreatic development is unknown. The pancreas contains a population of pancreatic stellate cells (PSC) very important for pancreatic physiology. We described elsewhere that hepatic stellate cells originate from the WT1-expressing liver mesothelium. Thus, we checked if the origin of PSCs was similar. WT1 expression is restricted to the pancreatic mesothelium. Between embryonic day (E) 10.5 and E15.5, this mesothelium gives rise to mesenchymal cells that contribute to a major part of the PSC and other cell types including endothelial cells. Most WT1 systemic mutants show abnormal localization of the dorsal pancreas within the mesentery and intestinal malrotation by E14.0. Embryos with conditional deletion of WT1 between E9.5 and E12.5 showed normal dorsal pancreatic bud and intestine, but the number of acini in the ventral bud was reduced approximately 30% by E16.5. Proliferation of acinar cells was reduced in WT1 systemic mutants, but pancreatic differentiation was not impaired. Thus, mesothelial-derived cells constitute an important subpopulation of pancreatic mesodermal cells. WT1 expression is not essential for pancreas development, although it influences intestinal rotation and correct localization of the dorsal pancreas within the mesogastrium. Developmental Dynamics 247:924-933, 2018. © 2018 Wiley Periodicals, Inc.

Morphometric Study of Pancreas in Human Fetuses.

The pancreas arises from the endoderm as a dorsal and a ventral bud which fuse together to form the single organ. It extends transversely across the posterior abdominal wall from the duodenum to the spleen. Functionally, it is endocrine and exocrine. This study was undertaken to study the morphometry of human pancreas at different gestational age groups of normal, still born fetuses. Forty aborted human fetuses (25 male and 15 female) of 12-40 weeks gestational age with no obvious congenital abnormality were obtained. The fetuses were dissected and pancreas was removed. The length and weight of the pancreas as well as height of its head were noted. It was observed that there was increase in body weight and crown rump length with increasing gestational age. The average length of pancreas was 1.80 cm in 12th week and 4.70 cm in 40th week of gestation. The average height of pancreas head was 0.80 cm in the 12th and 2.70 cm in 40th week of gestation. The knowledge of development of pancreas helps in planning new therapeutic interventions in the treatment of various congenital and functional pancreatic anomalies.

Development of the pancreas in medaka, Oryzias latipes, from embryo to adult.

To address conserved and unique features of fish pancreas development, we performed extensive analyses of pancreatic development in medaka embryos and adults using pdx1- and ptf1a-transgenic medaka, in situ hybridization and immunohistochemistry. The markers used in these analyses included pdx1, nkx6.1, nkx6.2, nkx2.2, Islet1, insulin, Somatostatin, glucagon, ptf1a, ela3l, trypsin, and amylase. The double transgenic (Tg) fish produced in the present study visualizes the development of endocrine (pdx1+) and exocrine (ptf1a+) parts simultaneously in living fishes. Like other vertebrates, the medaka pancreas develops as two (dorsal and ventral) buds in the anterior gut tube, which soon fuse into a single anlagen. The double Tg fish demonstrates that the differential property between the two buds is already established at the initial phase of bud development as indicated by strong pdx1 expression in the dorsal one. This Tg fish also allowed us to examine the gross morphology and the structure of adult pancreas and revealed unique characters of medaka pancreas such as broad and multiple connections with the gut tube along the anterior-posterior axis.

Lnx2 ubiquitin ligase is essential for exocrine cell differentiation in the early zebrafish pancreas

The gene encoding the E3 ubiquitin ligase Ligand of Numb protein-X (Lnx)2a is expressed in the ventral-anterior pancreatic bud of zebrafish embryos in addition to its expression in the brain. Knockdown of Lnx2a by using an exon 2/intron 2 splice morpholino resulted in specific inhibition of the differentiation of ventral bud derived exocrine cell types, with little effect on endocrine cell types. A frame shifting null mutation in lnx2a did not mimic this phenotype, but a mutation that removed the exon 2 splice donor site did. We found that Lnx2b functions in a redundant manner with its paralog Lnx2a. Inhibition of lnx2a exon 2/3 splicing causes exon 2 skipping and leads to the production of an N-truncated protein that acts as an interfering molecule. Thus, the phenotype characterized by inhibition of exocrine cell differentiation requires inactivation of both Lnx2a and Lnx2b. Human LNX1 is known to destabilize Numb, and we show that inhibition of Numb expression rescues the Lnx2a/b-deficient phenotype. Further, Lnx2a/b inhibition leads to a reduction in the number of Notch active cells in the pancreas. We suggest that Lnx2a/b function to fine tune the regulation of Notch through Numb in the differentiation of cell types in the early zebrafish pancreas. Further, the complex relationships among genotype, phenotype, and morpholino effect in this case may be instructive in the ongoing consideration of morpholino use.

A rare congenital anomaly of the pancreas: a cadaveric case report.

The pancreas is formed by ventral and dorsal pancreatic buds which arise from the endodermal lining of the gut. When the duodenum rotates to the right, the ventral pancreatic bud migrates dorsally and finally come and lie below the dorsal pancreatic bud. The developmental errors in the rotation of these components lead to annular pancreas. We report a rare type of the incomplete annular pancreas around the contents of right free margin of lesser omentum. There was an extra pancreatic mass situated horizontally immediately above the superior border of the pancreas, situated behind the lesser omentum. The right end of this mass extended into the epiploic foramen and incompletely encircled the portal vein, bile duct and hepatic artery proper from behind. The left end of the extra pancreatic mass was extended towards the lesser curvature of the stomach. Further, this mass completely surrounded the origin of three branches of the celiac trunk. Its right end was found to be continuous with the head of the pancreas, close to the pylorus. Histology of the extra pancreatic mass revealed the presence of normal pancreatic tissue. preoperative diagnosis of this rare anomaly is of clinical importance during surgeries involving the contents of right free margin of lesser omentum and epiploic foramen.

A relative shift in cloacal location repositions external genitalia in amniote evolution.

The move of vertebrates to a terrestrial lifestyle required major adaptations in their locomotory apparatus and reproductive organs. While the fin-to-limb transition has received considerable attention1,2, little is known about the developmental and evolutionary origins of external genitalia. Similarities in gene expression have been interpreted as a potential evolutionary link between the two anatomical structures3-6, yet without providing any underlying developmental mechanism. Here, we have reexamined this question using micro-Computed Tomography (μCT), lineage tracing in three amniote clades and RNA-Seq transcriptional profiling. We show that the developmental origin of external genitalia has shifted through evolution, and in some taxa limbs and genitals share a common primordium. In squamates, the genitalia develop directly from the budding hindlimbs, or the remnants thereof, whereas in mice the genital tubercle originates from the ventral and tail bud mesenchyme. The recruitment of different cell populations for genital outgrowth follows a change in the relative position of the cloaca, the genitalia organizing center. Ectopic grafting of the cloaca demonstrates the conserved ability of different mesenchymal cells to respond to these genitalia-inducing signals. Our results support a limb-like developmental origin of external genitalia as the ancestral condition. Moreover, it suggests that a change in the relative position of the cloacal signaling center during evolution has led to an altered developmental route of external genitalia in mammals, while preserving parts of the ancestral limb molecular circuitry due to a common evolutionary origin.

Pancreas divisum: a common developmental variant that deserves attention in preclinical medical education.

Clinical literature indicates that pancreas divisum (PD) is present in 3-22% of the population and may be associated with an increased risk of pancreatitis. PD is a developmental variant wherein the duct systems derived from the dorsal and ventral pancreatic buds are not fused. Hence secretions from the head, neck, body, and tail, which develop from the dorsal bud, must pass through the minor duodenal papilla. The smaller uncinate process, derived from the ventral bud, drains through the major duodenal papilla. The purpose of this study was: (1) to do a cadaveric dissection to confirm whether PD is common in donors who had not been selected because they had pancreatitis and (2) to determine the frequency of PD descriptions in anatomy, embryology, pathology, and surgery books in our libraries. For our anatomical study, pancreata of eight human donors were dissected. Dye was injected into the ducts so that any communications between main and accessory ducts could be easily located. For our literature review, 22 anatomy, 14 embryology, 11 pathology, and 26 surgery books were examined for mention of PD. PD was unambiguously identified in two donor cadavers. However, only 14% of the anatomy plus embryology books compared to 70% of the surgery plus pathology books describe PD. Cadaveric dissection confirms that PD is indeed prevalent. The prevalence of PD with its increased risk of pancreatitis merits inclusion of this topic in textbooks of anatomy and embryology.

Budding process during the organogenesis of the ventral prostatic lobe in Mongolian gerbil.

The prostate is a mammalian gland that shows a complex process of organogenesis. Here, a morphological study to characterize the organogenesis of the ventral prostate lobe in male gerbils was conducted. The urogenital sinus (UGS) was dissected out and processed for paraffin embedding. Histological sections were subjected to cytochemical, immunofluorescence, immunohistochemical, and three-dimensional reconstruction techniques. We found that the first ventral buds emerged from the ventral urethral epithelium between the days 20 and 21 of prenatal life, reaching the ventral mesenchymal pad and initiating the branching process on the first day of postnatal life. The buds presented a V-shaped elongation, suggesting that the smooth muscle layer (SML) plays an important role during budding events. Indeed, whereas the androgen receptor (AR) was preferentially found in the UGS mesenchyme (UGM), estrogen receptor alpha (ERα) was localized in both the UGM and in the emerging buds. This study characterized the morphological aspects of the budding process in a different rodent from rat and mice, serving as a new model for future studies on developmental biology of the prostate.

Control of Cell Identity in Pancreas Development and Regeneration

The endocrine and exocrine cells in the adult pancreas are not static, but can change their differentiation state in response to injury or stress. This concept of cells in flux means that there may be ways to generate certain types of cells (such as insulin-producing β-cells) and prevent formation of others (such as transformed neoplastic cells). We review different aspects of cell identity in the pancreas, discussing how cells achieve their identity during embryonic development and maturation, and how this identity remains plastic, even in the adult pancreas.