Increased fibronectin expression in developing embryos is associated with abnormal notochord in the Adriamycin rat model

Background The VACTERL association is a spectrum of clinical conditions, including esophageal atresia (EA) and tracheoesophageal fistula (TEF), which affects approximately 1 in 5,000 live human births. The administration of intraperitoneal Adriamycin to pregnant rats reliably induces anomalies, such as EA and TEF, in their offspring, in what is known as the Adriamycin rat model (ARM). In affected embryos the presence of gross notochord abnormalities is commonly found, with typical features being ectopic ventral branches and adherence of the notochord to the foregut. Fibronectin (FN) is an extracellular matrix (ECM) glycoprotein present on most cell surfaces, in extracellular fluids and in plasma. FN is involved in various functions, including cell adhesion, cell motility and wound healing. Previous studies in rats have shown that a single dose of Adriamycin can produce an appreciable rise in FN levels in various organs such as kidney and heart. We hypothesised that Adriamycin administration could promote upregulation of FN expression contributing to increased gut–notochord adherence and the development of abnormal ventral notochordal branching in the ARM. This study was designed to investigate FN expression in ARM embryos.Methods Adriamycin (1.75 mg/kg) was administered intraperitoneally to pregnant rats on days 7,8 and 9 of gestation (E7, E8 and E9 respectively). Control animals were given saline. Embryos recovered on E10–E14 were fixed, embedded in paraffin and sectioned. Immunohistochemistry using an anti-FN rabbit polyclonal antibody was performed.Results FN expression in both Adriamycin and control embryos on E10, E11 and E12 was comparable. However, the levels of FN expression in Adriamycin embryos on E13 and E14 were significantly greater in embryos with abnormal notochords than in equivalent control embryos.Conclusion Adriamycin-induced increased expression of FN, in the ARM, may contribute to abnormal notochord development leading to the VACTERL association.     

Demonstration of abnormal notochord development by three-dimensional reconstructive imaging in the rat model of esophageal atresia

 The notochord (Nt) is believed to have a role in the development of axial organs. This study was undertaken to reconstruct in three dimensions (3D) the relationship of the Nt to abnormal development of the foregut (Fg) in the adriamycin-induced rat model of esophageal atresia (EA). Pregnant Sprague-Dawley rats were given 1.75 mg/kg adriamycin intraperitoneally on gestational days 6–9 inclusive; control rats received i.p. saline of equal volume, or no injection. Rats were killed between days 11 and 14 and their embryos harvested, histologically sectioned serially, and stained with hematoxylin and eosin. Digitized photographs were taken of serial transverse sections; these photos were traced and used as the basis for 3D reconstruction. From day 11 the normal Nt is no longer in contact with the respiratory or Fg mesenchyme. In adriamycin-treated embryos the Nt branches abnormally as it enters the Fg mesenchyme. Adherence of the Nt to the mesenchyme of the Fg exerts mechanical traction pulling the upper Fg dorsally. The severity of the Fg abnormalities correlates with the length of the ventral extension of the Nt within the Fg mesenchyme: the embryo develops atresia of the esophagus or trachea when the Nt is grossly abnormal. The Nt undergoes reactive thickening in the absence of Fg structures ventral to it. Thus, structural lesions of the Fg (e.g., atresias) are associated with abnormalities of the Nt. The relationship of the Nt to the Fg mesenchyme determines the severity of the abnormality induced by adriamycin: extensive adherence produces tracheal agenesis and EA. Accepted: 13 January 2000     

Adriamycin produces a reproducible teratogenic model of gastrointestinal atresia in the mouse

Gastrointestinal atresia is a major cause of bowel obstruction in the newborn. Experimental models and clinical observations have demonstrated the heterogeneous nature of its pathogenesis. A proportion is due to late intra-uterine vascular insults and some are genetic in nature. Epidemiological studies have found gastrointestinal atresia to occur with other birth defects, in particular VACTERL anomalies, suggesting that a subset of cases may result from an early disturbance to intestinal morphogenesis. Adriamycin is teratogenic in rats, producing gastrointestinal atresia and VACTERL anomalies. The mouse is the foremost mammal studied by developmental biologists, offering an expanding wealth of knowledge and scientific research techniques. The aim of this study was to create an Adriamycin mouse model for investigating the development of gastrointestinal atresia. CBA/Ca mice were accurately time-mated (n = 30). Four different doses of Adriamycin (0-saline control, 4, 5 and 6 mg/kg) at three different timings of injections were compared (12 groups). Dams received two intraperitoneal injections, 24 h apart, commencing on day 7, 7.5 or 8. Foetuses were harvested on day 18. Gastrointestinal atresia and VACTERL anomalies were examined using a dissecting microscope. Adriamycin produced type IIIa gastrointestinal atresia in six treatment groups. The effect of Adriamycin depended on the timing and dose of the injections. VACTERL anomalies were only found in four treatment groups, proposing overlapping critical embryological windows for these malformations. Gastrointestinal atresia can be induced by the teratogen Adriamycin, occurring with and without VACTERL anomalies. This produces a reproducible mouse model in which the molecular pathogenesis of gastrointestinal atresia may be studied.     

Adriamycin mouse model: a variable but reproducible model of tracheo-oesophageal malformations

A spectrum of tracheo-oesophageal malformations is seen in humans: oesophageal atresia, tracheal agenesis and laryngotracheo-oesophageal clefts. They are thought to share a common but unknown aetiology. These birth defects are frequently associated with other VACTERL anomalies. The adriamycin rat model (ARM) has proved to be a valuable model of the VACTERL anomalies, illustrating the dysmorphogenesis of oesophageal atresia and tracheal agenesis. As organogenesis relies on temporaspatially co-ordinated signalling systems, the next step would be to study the molecular pathogenesis of tracheo-oesophageal malformations. However, the mouse is the foremost mammal studied by developmental biologists, offering an expanding wealth of knowledge and scientific research techniques with which to investigate these anomalies. A limited dose response analysis of the teratogenicity of adriamycin in the mouse has identified a dose and timing of injections that produced tracheo-oesophageal malformations and other VACTERL anomalies. A clear account of the types and variability of the tracheo-oesophageal malformations produced by this dose is essential in order to be able to plan and interpret any future investigations of early gestation fetuses. CBA/Ca mice were accurately time-mated (n = 10). Nine dams received intraperitoneal injections of adriamycin (6 mg/kg) and one control dam received saline injections, on days 7 and 8. Fetuses were harvested on day 18, near term. Tracheo-oesophageal malformations were examined by dissecting microscope and serial transverse sections. Results are reported in the standard teratological manner as mean percentage per litter (±SEM). The resorption rate of the adriamycin treated fetuses was 50.4%. There were 29 adriamycin treated fetuses for inspection. Tracheo-oesophageal malformations were found in 29.2% (±10.3), affecting five out of nine litters. Oesophageal atresia occurred in 15.6% (±8.1), laryngotracheo-oesophageal cleft in 10.4% (±7) and tracheal agenesis in 3.1% (±3.1). All of these malformations occurred with a tracheo-oesophageal fistula. Unlike the ARM, the AMM can produce fetuses with complete laryngotracheo-oesophageal cleft as well as oesophageal atresia or tracheal agenesis. Their occurrence was found to be reproducible but variable. These are important considerations when planning and interpreting experiments using this model.     

The Adriamycin rat/mouse model and its importance to the paediatric surgeon

The teratogenic effect of Adriamycin (doxorubicin) in the rat model, and more recently in the mouse, has provided paediatric surgeons with a reliable, easily reproducible method of studying the embryology and molecular biology for a range of complex congenital anomalies. Concomitantly these animal models have stimulated interest among embryologists for the effect on the notochord, shedding more light on the important organizational role of this structure in the developing embryo. Finally, as more is learnt of the pathogenesis of the various malformations induced by Adriamycin, future therapeutic interventions involving gene therapy, drugs or surgery may arise. This article reviews the establishment of the Adriamycin rat and mouse models, examines their impact on various congenital malformations, and suggests targets for further research.     

Bilateral megaureters in the Adriamycin rat model

Congenital obstructive uropathy is associated with significant morbidity and mortality in the human neonate. The pathophysiology of congenital obstructive uropathy is poorly understood. There are very few experimental models of prenatal obstruction of the urinary tract, except in the fetal lamb or inbred rats. Prenatal exposure to Adriamycin in a rat model leads to a spectrum of malformations including urinary tract anomalies. We hypothesized that Adriamycin administration during a particular time frame could yield a high incidence of urinary tract anomalies and therefore designed this study to investigate the rates of urinary tract anomalies at different windows of Adriamycin injection in rat embryos. Adriamycin (1.75 mg/kg) was administered intraperitoneally to pregnant rats at different times from days 6 to 10 of gestation. Control animals were given saline. Embryos recovered on gestational day 21 by cesarean section were examined for urinary tract anomalies, and malformations were noted. Sections were then processed for paraffin embedding, sectioned at 5 m, and stained with hematoxylin and eosin for histological examination. Anomalies of the urinary tract occurred maximally following Adriamycin administration on days 7, 8, and 9 of gestation (91.6%) compared with 16% of controls. The most common urinary tract anomaly in the Adriamycin group was bilateral megaureters with a hypoplastic bladder (81%). Other anomalies included unilateral or bilateral ureterohydronephrosis with a normal-sized bladder, duplex kidney, and unilateral or bilateral renal agenesis. In conclusion, the critical embryologic window for the development of bilateral megaureters with a small bladder in the Adriamycin rat model occurs following Adriamycin administration on gestational days 7–9. This simple experimental model of bilateral megaureter may allow further research into the pathophysiology of this condition.     

Altered Tbx1 gene expression is associated with abnormal oesophageal development in the adriamycin mouse model of oesophageal atresia/tracheo-oesophageal fistula

Introduction

Oesophageal atresia/tracheo-oesophageal atresia (OA/TOF) frequently arises with associated anomalies and has been clinically linked with 22q11 deletion syndromes, a group of conditions due to Tbx1 gene mutation which include Di George syndrome. Tbx1 and Tbx2 genes modulate pharyngeal and cardiac development, but are also expressed in the developing foregut and are known to interact with key signalling pathways described in oesophageal formation including bone morphogenic proteins. The adriamycin mouse model (AMM) reliably displays OA/TOF-like foregut malformations providing a powerful system for investigating the disturbances in gene regulation and morphology involved in tracheo-oesophageal malformations. We hypothesised that foregut abnormalities observed in the AMM are associated with altered Tbx1 and Tbx2 gene expression.

Methods

Time-mated CBA/Ca mice received intra-peritoneal injection of adriamycin (for treated) or saline (for controls) on embryonic days (E)7 and 8. Untreated Cd1 embryos were used to establish normal expression patterns. Embryos harvested on E9–E11 underwent whole-mount in situ hybridization with labelled RNA probes for Tbx1 and Tbx2. Optical projection tomography was used to visualise expression in whole embryos by 3D imaging.

Results

Tbx1 expression was visualised in a highly specific pattern in the proximal oesophageal endoderm in normal and control embryos. In the AMM, extensive ectopic expression of Tbx1 was detected in the dorsal foregut and adjacent to the TOF. The focally restricted oesophageal expression pattern persisted in the AMM, but was posteriorly displaced in relation to the tracheal bifurcation. Tbx2 was widely expressed in the ventral foregut mesoderm of controls, lacking specific endoderm localisation. In the AMM, altered Tbx2 expression in the foregut was only seen in severely affected embryos.

Conclusion

Highly specific Tbx1 expression in the proximal oesophageal endoderm suggests that Tbx1 may be an important regulator of normal oesophageal development. Altered Tbx1 expression in dorsal foregut and adjacent to the TOF in the AMM suggests that Tbx1 gene disruption may contribute to the pathogenesis of tracheo-oesophageal malformations.     

Embryology of the hindgut

Normal and abnormal development of the hindgut is still in debate. Normal development of the hindgut critically depends on the cloacal membrane. In this study, scanning electron microscopy of staged rat embryos between the gestational days 10-15 was performed to show the normal development of the hindgut and the abnormal development in Danforth's short tail (SD) mice. Our studies in normal and abnormal development indicate that the embryonic cloaca never passes through a stage that is similar to any form of anorectal malformation in neonates, including the so-called "cloacas" in females. To explain the abnormal development in anorectal malformations, further studies are mandatory.     

dhfr基因过表达对乙醇致斑马鱼胚胎心血管发育异常的效应研究

目的 观察二氢叶酸还原酶基因（dhfr）过表达对乙醇致斑马鱼胚胎心脏和血管发育异常的作用,并初步探讨其机制。方法 体外转录dhfr mRNA并将其显微注射入斑马鱼受精卵内使dhfr基因过表达,并进行过表达的效率验证。将野生型斑马鱼分为正常对照组、乙醇处理组（400?mmol/L乙醇溶液）、乙醇+dhfr mRNA组（显微注射6?nL dhfr mRNA）,观察各组胚胎的整体发育情况。按照上述分组,利用红色荧光蛋白标记心脏的转基因斑马鱼系Tg（cmlc2：mcherry）观察胚胎心房和心室的发育状况;利用荧光显微造影观察野生型斑马鱼胚胎心脏流出道及血管发育情况;通过心率和心室收缩指数评估心功能情况。构建基因探针并通过胚胎整体原位杂交及Real-time PCR法,检测胚胎nkx2.5、tbx1、flk-1的基因表达情况。结果 与乙醇处理组相比,乙醇+dhfr mRNA组斑马鱼胚胎发育异常百分率明显下降,存活百分率显著上升（P < 0.05）;心房、心室、心脏流出道和血管发育的异常表型及心功能情况明显改善。乙醇处理组nkx2.5、tbx1、flk-1 mRNA的表达较对照组下降（P < 0.05）;乙醇+dhfr mRNA组nkx2.5、tbx1、flk-1 mRNA的表达较乙醇处理组上调,但仍未达到正常对照组水平（P < 0.05）。结论 dhfr基因过表达可部分挽救乙醇所致胚胎心脏和血管发育异常,其机制可能与dhfr基因过表达后上调乙醇导致的nkx2.5、tbx1、flk-1水平降低有关。     

Artificial rearing of mouse pups: development of a mouse pup in a cup model

Artificial rearing of rat pups has been used in the investigation of the neonatal gut. We propose to adapt the model of artificially rearing rat pups for use in mouse pups, thereby allowing the use of transgenic animals for our research. We hypothesized that gastrostomy catheters may be placed successfully into neonatal mouse pups and that the pups may be artificially reared without significant alterations in their growth or intestinal development. Gastrostomy tubes are placed into 5-d-old mouse pups [artificially reared (AR); n = 32], and the mice are fed rodent milk substitute. Littermate pups [maternally reared (MR); n = 22] are used as controls. After 5 d, pups are killed and their organs are harvested. Intestinal villus measurements, protein content, and DNA content are determined. Data are reported as mean +/- SEM, compared with appropriate statistical methods, and significance is determined at P < 0.05. Initial weights and lengths are not different between the two groups, but after 5 d, MR pups weigh more than their AR counterparts (5.0 +/- 0.13 versus 4.1 +/- 0.14 g, MR versus AR; P < 0.01). However, the pups' length and the intestinal villus height-to-width ratios, protein, and DNA content are not different between the MR and AR pups. To our knowledge, this is the first report of artificially rearing mouse pups. Development of this technique will permit nutritional manipulation in neonatal mice, a mammalian model wherein the genome is sequenced and transgenic mutants are available.     

复方丹参对阿霉素致大鼠支气管损伤的保护作用

目的探讨复方丹参注射液对阿霉素致大鼠支气管损伤的保护作用。方法静脉注射阿霉素7.5mg/kg,制备大鼠支气管损伤模型。丹参组造模前1d,经腹腔注射复方丹参注射液1.6g/kg,连续14d。观察复方丹参注射液对其血清超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量及支气管组织病理学的影响。结果与对照组比较,模型组大鼠血清SOD活性降低(t=3.7162P<0.01),MDA含量升高(t=6.7688P<0.001)。模型组各级支气管黏膜上皮细胞变性、坏死,部分黏膜上皮成片状脱落;管壁充血,水肿,有淋巴细胞和单核细胞浸润;支气管管腔内见大量伊红淡染的蛋白样渗出物、脱落的上皮细胞、红细胞、淋巴细胞、中性粒细胞和单核细胞。丹参组血清SOD活性增高[(37.85±9.96)U/mL],MDA含量降低[(1.55±0.27)nmol/L],与模型组比较有显著差异(t=2.5463P<0.05;t=5.1937P<0.001),其支气管病理损伤程度明显轻于模型组。结论复方丹参注射液对阿霉素所致大鼠支气管损伤具有保护作用,其机制与提高机体抗氧化能力,抑制脂质过氧化反应有关。     

白细胞介素18结合蛋白对多柔比星肾病模型小鼠的疗效

目的 探讨IL-18结合蛋白(IL-18BP)通过结合内源性IL-18抑制下游致炎因子释放,对多柔比星(ADR)微小病变型肾病模型小鼠的治疗作用.方法 雄性昆明种小鼠,一次性尾静脉注射ADR 7.5 mg·kg-1进行造模,正常对照组注射同等量的9 g·L-1盐水.于ADR造模后第5、7、12、21天分别注射鼠源性IL-18BP 0.5 mg·kg-1(IL-18BP治疗组)或等量PBS(非治疗组).隔周检测尿蛋白1次,观察并记录其体征.42 d后心脏采血处死小鼠,分离血清检测相关细胞因子和生化指标,并在电镜下对肾脏组织病理改变进行观察.结果 1.注射ADR造模后小鼠均出现肾病综合征表现,以大量蛋白尿、低蛋白血症、高胆固醇血症为特征.2.动态24 h尿蛋白定量:非治疗组与正常对照组及IL-18BP治疗组比较明显升高,差异具有统计学意义(Pa<0.01).3.血液生化:非治疗组血清中三酰甘油(TG)、胆固醇(CH)明显高于正常对照组、IL-18BP治疗组(Pa<0.01),总蛋白(TP)、清蛋白(ALB)明显低于后两组(Pa<0.01);BUN、血肌酐(SCr)水平各组间差异无统计学意义(Pa>0.05).4.细胞因子检测:IL-18BP治疗组与非治疗组比较IL-18及下游细胞因子IFN-γ、TNF-α水平均明显降低(Pa<0.05),IL-4水平有所回升(P<0.01).5.病理观察:电镜下非治疗组小鼠肾脏足突细胞完全融合或消失,IL-18BP治疗组小鼠肾脏组织学改变显著减轻,足突细胞仅部分融合.结论 内源性IL-18作为Th1型上游细胞因子在ADR肾病的形成中发挥重要作用,有可能作为关键致病因子影响病情的发展与转归.IL-18BP可通过特异性结合内源性IL-18,抑制Th1细胞介导的免疫反应,对ADR肾病发挥治疗作用,从而调节免疫平衡,改善肾脏功能.     

Gli2基因在胎鼠后肠发育后期的表达

目的探讨胎鼠后肠发育与sonichedgehog(Shh)基因转录因子Gli2基因表达水平的关系。方法48只妊娠Wistar大鼠随机分成2组,实验组(n=24)在孕11d按125mg/kg胃管注入1%乙烯硫脲(ethylenethiourea,ETU),对照组(n=24)给予等量蒸馏水。两组分别于孕12d、14d和16d各处死8只母鼠,每只母鼠取4只体重相似的胎鼠,取其直肠1cm提取RNA,采用半定量RT_PCR法检测Gli2基因表达。结果实验组胎鼠直肠Gli2基因表达水平明显低于对照组(P<0.05),实验组Gli2基因表达呈一低水平线,而对照组随妊娠时间呈一下降的曲线。结论Gli2基因表达水平在胎鼠后肠发育中具有重要的作用。     

Adriamycin effects on the chick embryo

Adriamycin is an anthracycline, anti-neoplastic drug with known teratogenic effects on foetal rats in what is known as the Adriamycin rat model (ARM). This includes conditions similar to those in newborn humans, known collectively as the VACTERL association. This comprises vertebral (V), anorectal (A), cardiac (C), tracheoesophageal (TE), renal (R) and limb (L) anomalies. We designed this study to test the hypothesis that the administration of Adriamycin to chick embryos would cause similar anomalies to those in the VACTERL association seen in the ARM. Fertilized Ross eggs received Adriamycin doses from 2–50 g into the air sac and from 0.9–6 g into the albumin. Administration varied from day 0–3 (D_0–3) with D₀ being the first day of incubation. Control eggs received saline. Embryos were incubated at 38°C and a relative humidity of 70%. Embryos were recovered on D₁₄, paraffin-embedded and transverse sections studied for morphological abnormalities. In the air sac group (n=142), 71% of Adriamycin embryos survived versus 86% of controls (n=29). In the albumin group (n=121), 42% of Adriamycin embryos survived versus 55% of controls (n=69). No embryos demonstrated anomalies consistent with the VACTERL association. Ventral defects affected 1% of surviving Adriamycin embryos versus 4% of controls in the air sac group. In the albumin group, 19.8% of surviving Adriamycin embryos had ventral defects compared to 15.7% of surviving controls. Anophthalmia affected 1% of the surviving embryos in the Adriamycin air sac group and 2% of the Adriamycin albumin group. No controls developed anophthalmia. Exencephaly affected 2% of the survivors in the Adriamycin air sac group but none of the albumin group or controls. The administration of Adriamycin to chick embryos in comparable doses and times to those used in the ARM does not appear to produce comparable effects in relation to developmental anomalies, such as the VACTERL association. Despite examining different administration routes and mimicking the ARM, by giving Adriamycin to embryos at gastrulation, we were unable to re-create the anomalies seen in the ARM.     

Cell death in normal and abnormal development

Research over the past 50 years has consistently documented that cell death is an integral part of both normal development and the etiology of birth defects; however, the significance of this cell death has been, until recently, unclear. Research published during the past 15 years has now shown that programmed cell death (PCD) and teratogen-induced cell death are genetically controlled processes (apoptosis) that play important roles in both normal and abnormal development. Therefore, the purpose of this review is to highlight what is known about PCD and teratogen-induced cell death and their relationships to the mechanisms of apoptosis and abnormal development.     

Heritability and environment in normal and abnormal development

The environmental influence on human development can be studied by assessing similarities and discrepancies in developmental traits between biological and adopted siblings and twins, reared together and reared apart. Approximately 50% of total variance of general cognitive ability in a given population can be explained by the environment. This influence gradually decreases with age, from infancy to adulthood. Two types of environments can be distinguished: shared and non shared. The former one, acts predominantly in childhood, and the non shared environment becomes more important in adulthood. Paradoxically, quantitative genetics can make a significant contribution to knowledge on the influence of environment on human development.