Fetal Pancreas Research Articles

Correlation between Expression of KLF5 and ZEB1 Transcription Factor Genes in Pancreatic Cancer.

The mRNA content of the transcription factors KLF5 and ZEB1 was studied in pancreatic tumor tissues and in fetal and normal pancreas. Transcription of these factors was not high and similar in normal and fetal pancreatic tissues but greatly increased in the pancreatic ductal adenocarcinoma tissues. A significant positive correlation between the KLF5 and ZEB1 transcription levels in the pancreatic tumor tissues was observed.

Fetal pancreatic Langerhans islets size in pregnancies with metabolic disorders

Objective: Metabolic disorders are a pandemic and increasing health problem. Women of childbearing age may also be affected, thus an abnormal metabolism may interfere with pregnancy short- and long-term outcomes, harming both mother and child. In the context of an abnormal maternal and intrauterine metabolic milieu the development of fetal organs, including pancreas, may be affected.Aim: To investigate the effects of pregnancy metabolic disorders on the morphology of pancreatic Langerhans islets in human late-third trimester stillborn fetuses.Methods: Samples from fetal pancreas underwent a quantitative histological evaluation to detect differences between pregnancy with (cases, n = 9) or without (controls, n = 6) abnormal metabolism.Results: Results show that the islets size increases in fetuses from dysmetabolic pregnancies and that this increment is related to both beta-cell hyperplasia and hypertrophy. Moreover, according to pregnancy and fetal metabolic disorders, a threshold of abnormal size of the islets has been identified. Above this threshold the size of fetal pancreatic Langerhans islets should be considered excessively increased.Conclusion: The study suggests that an accurate fetal pancreas analysis supplies an important tool in stillborn fetus, to discover metabolic disturbances that should be kept in mind and managed in future pregnancies.

Trefoil factor 3 in perinatal pancreas is increased by gestational low protein diet and associated with accelerated β-cell maturation

ABSTRACTThe endocrine pancreas expands markedly in the first postnatal days and the insulin producing β-cells initiate a functional maturation preceded by a morphological change of the islets of Langerhans. Trefoil factor 3 (TFF3) is a secreted peptide expressed in intestinal epithelia, where it promotes migration, but its role in the pancreas is not characterized. The aim of this study was to examine the expression and function of TFF3 in perinatal rat pancreas, ex vivo cultured fetal rat pancreas and in the rat β-cell line INS-1E.Control or gestational low-protein diet perinatal rat pancreas was harvested at embryonic day 20 (E20), day of birth (P0) and postnatal day 2 (P2). TFF3 mRNA was upregulated 4.5-fold at P0 vs. E20 and downregulated again at P2. In protein-undernourished pups induction of TFF3 at P0 was further increased to 9.7-fold and was increased at P2. TFF3 caused tyrosine phosphorylation of EGFR in INS-1E β-cells, and purified recombinant TFF3 increased both attachment and spreading of INS-1E β-cells. In ex vivo cultures of collagenase digested fetal rat pancreas, a model of perinatal β-cell maturation, TFF3 increased cellular spreading as well as insulin mRNA levels. TFF3 also increased the expression of Pref1/Dlk1 that shares similarities in expression and regulation with TFF3.These results suggest that TFF3 may promote adhesion and spreading of cells to accelerate β-cell maturation. This study indicates a functional role for TFF3 in pancreatic β-cell maturation in the perinatal period, which is altered by low protein diet during gestation.

The effect of aspartame ingestion in pregnant female albino rats on placental and fetal weights, umbilical cord length, and histology of fetal pancreas

Background and aim Sugar is one of the commonest causes of weight gain and diabetes. Aspartame is one of the most commonly used artificial sweeteners worldwide to replace sugar. This study aimed to study the effects of aspartame in pregnant female albino rats on fetal and placental weights, length of umbilical cord, and possible histological changes in fetal pancreas. Materials and methods Thirty-six adult female albino rats and nine adult male albino rats weighing between 220 and 250 g were used. Each four female rats were housed with one male rat to allow mating. Pregnant rats were divided into three groups (n=12 each): control group (group І), low-dose-treated group (group ІІ), and high-dose-treated group (group ІІІ). The low-dose-treated group received 14 mg/kg aspartame and the high-dose-treated group received 40 mg/kg aspartame daily from the first day of pregnancy to the 20th day of pregnancy. Results This study showed a highly significant reduction of maternal weight gain, placental weight, fetal weight, and umbilical cord length in both aspartame-treated groups. Fetal pancreas showed histopathological changes in both aspartame-treated groups as evidenced by light and electron microscopy. All the results in this study were dose related. Conclusion The use of aspartame during pregnancy might reduce fetal and placental weights and umbilical cord length and alter the histology of fetal pancreas.

Understanding human fetal pancreas development using subpopulation sorting, RNA sequencing and single-cell profiling.

To decipher the populations of cells present in the human fetal pancreas and their lineage relationships, we developed strategies to isolate pancreatic progenitors, endocrine progenitors and endocrine cells. Transcriptome analysis of the individual populations revealed a large degree of conservation among vertebrates in the drivers of gene expression changes that occur at different steps of differentiation, although notably, sometimes, different members of the same gene family are expressed. The transcriptome analysis establishes a resource to identify novel genes and pathways involved in human pancreas development. Single-cell profiling further captured intermediate stages of differentiation and enabled us to decipher the sequence of transcriptional events occurring during human endocrine differentiation. Furthermore, we evaluate how well individual pancreatic cells derived in vitro from human pluripotent stem cells mirror the natural process occurring in human fetuses. This comparison uncovers a few differences at the progenitor steps, a convergence at the steps of endocrine induction, and the current inability to fully resolve endocrine cell subtypes in vitro.

Characterization and Differentiation of Sorted Human Fetal Pancreatic ALDHhi and ALDHhi/CD133+ Cells Toward Insulin-Expressing Cells.

The enzyme aldehyde dehydrogenase (ALDH) is found in developing and multipotent cell populations, and is important for the production and regulation of retinoic acid, which controls β-cell differentiation in the pancreas. The role of ALDH-expressing cells in the formation of endocrine-like cells and co-localization with the putative stem cell marker CD133 has not been examined during human pancreatic development. This study focuses on the co-expression of CD133 on ALDH+ cells from the human fetal pancreas (18-22 weeks of fetal age) with transcription factors (TFs) central to endocrine cell development. Fluorescence-activated cell sorting demonstrated that cells with high ALDH activity (ALDHhi) had increased co-expression of CD133 and endocrine-lineage TFs when compared with cells with low ALDH (ALDHlo) expression. Hormone-expressing (insulin, somatostatin) and ductal cells (CK19) were noted in the ALDHhi population, while mesenchymal (vimentin) and endothelial (CD31) markers were predominantly found in ALDHlo cells. Culture of sorted ALDHhi or ALDHhi/CD133+ cells resulted in loss of endocrine TF, insulin, and CK19 expression. The formation of cell clusters from cultured ALDHhi or ALDHhi/CD133+ cells led to restored CK19 expression and showed endocrine TFs and insulin expression. In summary, pancreatic ALDHhi cells contain a heterogeneous CD133-enriched population with a subset of β-cell associated markers in the developing human pancreas.

Fetal liver injury ameliorated by migration inhibitory factor inhibition in a rat model of acute pancreatitis in pregnancy.

This study was designed to investigate and assess fetal liver injury in a rat model of acute pancreatitis in pregnancy (APIP) as well as its possible mechanisms and potential therapeutic targets. The APIP model was induced by sodium taurocholate in Sprague-Dawley rats during the third trimester. ISO-1, a macrophage migration inhibitory factor (MIF) antagonist, was given before the induction of APIP. In addition, sham-operated rats at later gestation were set as controls. Histological changes in the fetal liver and maternal pancreas were assessed. Amylase and lipase activity as well as the levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β were examined. The expression of MIF in fetal liver was determined by immunochemistry and the expression of NF-κB, IκBα, high mobility group box-1 protein (HMGB1), TNF-α, and IL-1β in fetal liver was determined by Western blot analysis. Ultrastructures of hepatic cells in fetal rats were observed under transmission electron microscopy. ISO-1 ameliorated the following: (i) pathological injuries in maternal pancreas and fetal liver; (ii) levels of TNF-α and IL-1β in maternal serum; and (iii) levels of MIF, myeloperoxidase, NF-κB, HMGB1, TNF-α, and IL-1β in fetal liver. Pathological damage and an inflammatory response in fetal liver were induced by APIP, and MIF inhibition ameliorated fetal liver injury by inhibiting the inflammatory cascade.

Leptin receptors localise to [beta]-cells in the fetal ovine pancreas, but do not appear to influence [beta]-cell mass in utero

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

IGF2 stimulates fetal growth in a sex- and organ-dependent manner.

BackgroundInsulin-like growth factor 2 (IGF2) is a key determinant of fetal growth, and the altered expression of IGF2 is implicated in fetal growth disorders and maternal metabolic derangements including gestational diabetes. Here we studied how increased levels of IGF2 in late pregnancy affect fetal growth.MethodsWe employed a rat model of repeated intrafetal IGF2 administration in late pregnancy, i.e., during GD19-GD21, and measured the consequences on fetal organ weight and expression of insulin/IGF-axis components.ResultsIGF2 treatment tended to increase fetal weight, but only weight increase of the fetal stomach reached significance (+33±9%; P<0.01). Sex-dependent data analysis revealed a sexual dimorphism of IGF2 action. In male fetuses, IGF2 administration significantly increased fetal weight (+13±3%; P<0.05) and weight of fetal stomach (+42±10%; P<0.01), intestine (+26±5%; P<0.05), liver (+13±4%; P<0.05), and pancreas (+25±8%; P<0.05). Weights of heart, lungs, and kidneys were unchanged. In female fetuses, IGF2 increased only stomach weight (+26±9%; P<0.05). Furthermore, gene expression of insulin/IGF axis in the heart, lungs, liver, and stomach was more sensitive toward IGF2 treatment in male than in female fetuses.ConclusionData suggest that elevated circulating IGF2 in late pregnancy predominantly stimulates organ growth of the digestive system, and male fetuses are more susceptible toward the IGF2 effects than female fetuses.

The impact of IUGR on pancreatic islet development and β-cell function.

Placental insufficiency is a primary cause of intrauterine growth restriction (IUGR). IUGR increases the risk of developing type 2 diabetes mellitus (T2DM) throughout life, which indicates that insults from placental insufficiency impair β-cell development during the perinatal period because β-cells have a central role in the regulation of glucose tolerance. The severely IUGR fetal pancreas is characterized by smaller islets, less β-cells, and lower insulin secretion. Because of the important associations among impaired islet growth, β-cell dysfunction, impaired fetal growth, and the propensity for T2DM, significant progress has been made in understanding the pathophysiology of IUGR and programing events in the fetal endocrine pancreas. Animal models of IUGR replicate many of the observations in severe cases of human IUGR and allow us to refine our understanding of the pathophysiology of developmental and functional defects in islet from IUGR fetuses. Almost all models demonstrate a phenotype of progressive loss of β-cell mass and impaired β-cell function. This review will first provide evidence of impaired human islet development and β-cell function associated with IUGR and the impact on glucose homeostasis including the development of glucose intolerance and diabetes in adulthood. We then discuss evidence for the mechanisms regulating β-cell mass and insulin secretion in the IUGR fetus, including the role of hypoxia, catecholamines, nutrients, growth factors, and pancreatic vascularity. We focus on recent evidence from experimental interventions in established models of IUGR to understand better the pathophysiological mechanisms linking placental insufficiency with impaired islet development and β-cell function.

The Normal Fetal Pancreas.

The aim of the study was to assess the sonographic feasibility of measuring the fetal pancreas and its normal development throughout pregnancy. We conducted a cross-sectional prospective study between 19 and 36 weeks' gestation. The study included singleton pregnancies with normal pregnancy follow-up. The pancreas circumference was measured. The first 90 cases were tested to assess feasibility. Two hundred ninety-seven fetuses of nondiabetic mothers were recruited during a 3-year period. The overall satisfactory visualization rate was 61.6%. The intraobserver and interobserver variability had high interclass correlation coefficients of of 0.964 and 0.967, respectively. A cubic polynomial regression described best the correlation of pancreas circumference with gestational age (r = 0.744; P < .001) and significant correlations also with abdominal circumference and estimated fetal weight (Pearson r = 0.829 and 0.812, respectively; P < .001). Modeled pancreas circumference percentiles for each week of gestation were calculated. During the study period, we detected 2 cases with overgrowth syndrome and 1 case with an annular pancreas. In this study, we assessed the feasibility of sonography for measuring the fetal pancreas and established a normal reference range for the fetal pancreas circumference throughout pregnancy. This database can be helpful when investigating fetomaternal disorders that can involve its normal development.

Gestational diabetes affects fetal autophagy

Autophagy is a catabolic process involved in the preservation of energy homeostasis and its dysregulation has been implicated in the development of metabolic disorders, including diabetes mellitus. Gestational diabetes mellitus represents a risk for fetal morbidity and mortality. The present study focuses on the autophagy process in human diabetic placenta and fetal pancreas, compared with controls. Analysis of the autophagy markers LC3, Beclin-1 and p62 suggests an impairment of the autophagy process in diabetic placentas. Results indicate an association between gestational diabetes and autophagy, emphasizing the importance of unravelling the mechanisms regulating this relationship.

Antenatal blockade of N-methyl-D-aspartate receptors by Memantine reduces the susceptibility to diabetes induced by a high-fat diet in rats with intrauterine growth restriction.

Intrauterine growth retardation (IUGR) is closely related to the later development of type 2 diabetes in adulthood. Excessive activation of N-methly-D-aspartate receptors (NMDARs) causes excitatory neurotoxicity, resulting in neuronal injury or death. Inhibition of NMDARs enhances the glucose-stimulated insulin secretion and survival of islet cells in type 2 diabetic mouse and human islets. Here, we examined whether antenatal blockade of NMDARs by Memantine could decrease the risk of diabetes induced by a high-fat (HF) diet at adulthood in IUGR rats. Pregnant SD rats were assigned to four groups: control, IUGR, Memantine, and Memantine + IUGR. The pregnant rats were exposed to hypoxic conditions (FiO2 = 0.105) for 8 h/day (IUGR group) or given a daily Memantine injection (5 mg/kg, i.p.) before hypoxia exposure from embryonic day (E) 14.5 to E 20.5 (Memantine + IUGR). The offspring were fed an HF diet with 60% of the calories from age 4 to 12 weeks. We found that NMDAR mRNAs were expressed in the fetal rat pancreas. An HF diet resulted in a high rate of diabetes at adulthood in the IUGR group. Antenatal Memantine treatment decreased the risk of diabetes at adulthood of rats with IUGR, which was associated with rescued glucose tolerance, increased insulin release, improved the insulin sensitivity, and increased expression of genes related to beta-cell function in the pancreas. Together, our results suggest that antenatal blockade of NMDARs by Memantine in pregnant rats improves fetal development and reduces the susceptibility to diabetes at adulthood in offspring.

213 - Effect of different culture conditions on nestin expression in fetal pancreas derived mesenchymal stem cells

213 - Effect of different culture conditions on nestin expression in fetal pancreas derived mesenchymal stem cells

Вплив трансплантації культур клітин на перебіг експериментального цукрового діабету у тварин

As we know from the literature data, type 1 diabetes mellitus occurs due to the loss of β-cells of island of Langerhans, manufacturing insulin, by the organism, which causes its deficiency. The treatment of this type of diabetes, even at early stages, lies in the substitution therapy together with a careful control of blood glucose which may last for life. It is for this reason that the cellular technologies as an alternative method of treatment of this pathology are growing more and more relevant.Objective of the study: to study the impact of allogenic transplantation of the cultures of bone marrow, lipid tissue and pancreas cells on the course of experimentally generated diabetes mellitus in animals.Task: 1. To obtain the cultures of bone marrow, lipid tissue and pancreas cells in rats. 2. To compare the impact of allogenic transplantation of the cultures of bone marrow, lipid tissue and pancreas cells in the course of experimentally generated diabetes mellitus in rats. 3. To study the impact of pancreas cells culture on the course of experimental diabetes mellitus in cats.The studies were conducted using clinically healthy animals (30 males of white non-pedigree rats with body weight of 200–250 g, aged 4–5 months; 9 white non-pedigree junior rats aged 12 days; 4 mongrel cats aged 15–17 months) and missed fetuses of cats remained after obstetric aid.Alloxan diabetes was generated by means of single subcutaneous injection of alloxane monohydrate in the dose of 150 mg/kg in the form of 5% solution on citrate buffer (pH 4.5) after preliminary 24-hour absolute diet with free access to water.The cultures of bone marrow and pancreas cells were obtained from the bone marrow of tubular bones and pancreas of puppies aged 12 days correspondingly, lipid tissue – from rats aged 4–5 months. The culture of cats’ pancreas cells was obtained from the pancreas of cat fetuses. Cell culture process was carried out according the standard method in CO2- incubator. Glucose level in blood serum was determined by means of electrochemical analysis.The results of the study. The authors studied the impact of allogenic transplantation cells culture of bone marrow, lipid tissue and pancreas on the course of experimentally generated diabetes mellitus in rats. The study revealed the decrease of glucose level in the blood of the animals under investigation at cell material transplantation. The most efficient culture for experimental diabetes mellitus therapy is the culture of pancreas cells which has become the cause of its further study in cats.During allogenic transplantation cells culture of pancreas in cats the authors observed abrupt decrease of glucose level in the blood of the animals under investigation immediately after cell transplantation with the further approximation to the initial state.The experimental models presented the positive effect of cell culture transplantation providing the grounds for the further implementation of this diabetes mellitus therapy method in the clinical practice.

Efficient Generation of Glucose-Responsive Beta Cells from Isolated GP2+ Human Pancreatic Progenitors

Stem cell-based therapy for type 1 diabetes would benefit from implementation of a cell purification step at the pancreatic endoderm stage. This would increase the safety of the final cell product, allow the establishment of an intermediate-stage stem cell bank, and provide a means for upscaling βcell manufacturing. Comparative gene expression analysis revealed glycoprotein 2 (GP2) as a specific cell surface marker for isolating pancreatic endoderm cells (PECs) from differentiated hESCs and human fetal pancreas. Isolated GP2+ PECs efficiently differentiated into glucose responsive insulin-producing cells invitro. We found that invitro PEC proliferation declines due to enhanced expression of the cyclin-dependent kinase (CDK) inhibitors CDKN1A and CDKN2A. However, we identified a time window when reducing CDKN1A or CDKN2A expression increased proliferation and yield of GP2+ PECs. Altogether, our results contribute tools and concepts toward the isolation and use of PECs as a source for the safe production of hPSC-derived β cells.

Hypothyroidism in utero stimulates pancreatic beta cell proliferation and hyperinsulinaemia in the ovine fetus during late gestation.

Key points Thyroid hormones are important regulators of growth and maturation before birth, although the extent to which their actions are mediated by insulin and the development of pancreatic beta cell mass is unknown.Hypothyroidism in fetal sheep induced by removal of the thyroid gland caused asymmetric organ growth, increased pancreatic beta cell mass and proliferation, and was associated with increased circulating concentrations of insulin and leptin.In isolated fetal sheep islets studied in vitro, thyroid hormones inhibited beta cell proliferation in a dose‐dependent manner, while high concentrations of insulin and leptin stimulated proliferation.The developing pancreatic beta cell is therefore sensitive to thyroid hormone, insulin and leptin before birth, with possible consequences for pancreatic function in fetal and later life.The findings of this study highlight the importance of thyroid hormones during pregnancy for normal development of the fetal pancreas. Development of pancreatic beta cell mass before birth is essential for normal growth of the fetus and for long‐term control of carbohydrate metabolism in postnatal life. Thyroid hormones are also important regulators of fetal growth, and the present study tested the hypotheses that thyroid hormones promote beta cell proliferation in the fetal ovine pancreatic islets, and that growth retardation in hypothyroid fetal sheep is associated with reductions in pancreatic beta cell mass and circulating insulin concentration in utero. Organ growth and pancreatic islet cell proliferation and mass were examined in sheep fetuses following removal of the thyroid gland in utero. The effects of triiodothyronine (T3), insulin and leptin on beta cell proliferation rates were determined in isolated fetal ovine pancreatic islets in vitro. Hypothyroidism in the sheep fetus resulted in an asymmetric pattern of organ growth, pancreatic beta cell hyperplasia, and elevated plasma insulin and leptin concentrations. In pancreatic islets isolated from intact fetal sheep, beta cell proliferation in vitro was reduced by T3 in a dose‐dependent manner and increased by insulin at high concentrations only. Leptin induced a bimodal response whereby beta cell proliferation was suppressed at the lowest, and increased at the highest, concentrations. Therefore, proliferation of beta cells isolated from the ovine fetal pancreas is sensitive to physiological concentrations of T3, insulin and leptin. Alterations in these hormones may be responsible for the increased beta cell proliferation and mass observed in the hypothyroid sheep fetus and may have consequences for pancreatic function in later life.

Hyperglycemia impedes definitive endoderm differentiation of human embryonic stem cells by modulating histone methylation patterns.

Exposure to maternal diabetes during fetal growth is a risk factor for the development of type II diabetes (T2D) in later life. Discovery of the mechanisms involved in this association should provide valuable background for therapeutic treatments. Early embryogenesis involves epigenetic changes including histone modifications. The bivalent histone methylation marks H3K4me3 and H3K27me3 are important for regulating key developmental genes during early fetal pancreas specification. We hypothesized that maternal hyperglycemia disrupted early pancreas development through changes in histone bivalency. A human embryonic stem cell line (VAL3) was used as the cell model for studying the effects of hyperglycemia upon differentiation into definitive endoderm (DE), an early stage of the pancreatic lineage. Hyperglycemic conditions significantly down-regulated the expression levels of DE markers SOX17, FOXA2, CXCR4 and EOMES during differentiation. This was associated with retention of the repressive histone methylation mark H3K27me3 on their promoters under hyperglycemic conditions. The disruption of histone methylation patterns was observed as early as the mesendoderm stage, with Wnt/β-catenin signaling being suppressed during hyperglycemia. Treatment with Wnt/β-catenin signaling activator CHIR-99021 restored the expression levels and chromatin methylation status of DE markers, even in a hyperglycemic environment. The disruption of DE development was also found in mouse embryos at day 7.5 post coitum from diabetic mothers. Furthermore, disruption of DE differentiation in VAL3 cells led to subsequent impairment in pancreatic progenitor formation. Thus, early exposure to hyperglycemic conditions hinders DE development with a possible relationship to the later impairment of pancreas specification.

Immunohistochemistry detected and localized cannabinoid receptor type 2 in bovine fetal pancreas at late gestation.

At present, data on the endocannabinoid system expression and distribution in the pancreatic gland appear scarce and controversial as descriptions are limited to humans and laboratory animals. Since the bovine pancreas is very similar to the human in endocrine portion development and control, studies on the fetal gland could prove to be very interesting, as an abnormal maternal condition during late pregnancy may be a predisposing trigger for adult metabolic disorders. The present investigation studied cannabinoid receptor type 2 presence and distribution in the bovine fetal pancreas towards the end of gestation. Histological analyses revealed numerous endocrinal cell clusters or islets which were distributed among exocrine adenomeri in connectival tissue. Immunohistochemistry showed that endocrine-islets contained some CB2-positive cells with a very peculiar localization that is a few primarily localized at the edges of islets and some of them also scattered in the center of the cluster. Characteristically, also the epithelium of the excretory ducts and the smooth muscle layers of the smaller arteries, in the interlobular glandular septa, tested positive for the CB2 endocannabinoid receptor. Consequently, the endocannabinoid system, via the cannabinoid receptor type 2, was hypothesized to play a major role in controlling pancreas function from normal fetal development to correct metabolic functioning in adulthood.

The Vascular Microarchitecture of the Human Fetal Pancreas: A Corrosion Casting and Scanning Electron Microscopy Study.

Detailed knowledge on the development of the pancreas is required to understand the variability in its blood supply. The aim of our study was to use the corrosion casting method combined with scanning electron microscopy to study the organization of the pancreatic microcirculation in human fetuses. The study was conducted on 28 human fetuses aged 18 to 25 gestational weeks. The fetal vasculature was appropriately prepared and then perfused with a low-viscosity Mercox CL-2R resin. The prepared vascular casts of the surface of the fetal pancreas were then examined in scanning electron microscopy and digitally analyzed. The lobular structure of the pancreas has a strong impact on the organization of the microvasculature. The lobular networks were supplied by the interlobular arteries and drained by the interlobular veins. The vascular system of fetal human pancreas has many portal connections, including islet-lobule and islet-duct portal circulations, which likely play a key role in the coordination of both endocrine and exocrine pancreatic functions. The organization of the microvascular network of the human pancreas in fetuses aged 18 to 25 gestational weeks is very similar to that of an adult but with more prominent features suggesting active processes of angiogenesis and vascular remodeling.