[Clinical features and prognostic analysis of testicular relapse in pediatric acute lymphoblastic leukemia]

Objective: To investigate the clinical features and prognosis of testicular relapse in pediatric acute lymphoblastic leukemia (ALL). Methods: Clinical data including the age, time from initial diagnosis to recurrence, relapse site, and therapeutic effect of 37 pediatric ALL with testicular relapse and treated in Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences between November 2011 and December 2022 were analyzed retrospectively. Patients were grouped according to different clinical data. Kaplan-Meier analysis was used to evaluate the overall survival (OS) rate and event free survival (EFS) rate for univariate analysis, and Cox proportional-hazards regression model was used to evaluate the influencing factors of OS rate and EFS rate for multivariate analysis. Results: The age at initial diagnosis of 37 pediatric testicular relapse patients was (5±3) years and the time from initial diagnosis to testicular recurrence was (37±15) months. The follow-up time was 43 (22, 56) months. Twenty-three patients (62%) were isolated testis relapse. The 5-year OS rate and EFS rate of the 37 relapsed children were (60±9) % and (50±9) % respectively. Univariate analysis showed that the 2-year EFS rate in the group of patients with time from initial diagnosis to testicular recurrence >28 months was significantly higher than those ≤28 months ((69±10)% vs. (11±11)%, P<0.05), 2-year EFS rate of the isolated testicular relapse group was significantly higher than combined relapse group ((66±11)% vs. (20±13) %, P<0.05), 2-year EFS rate of chimeric antigen receptor T (CAR-T) cell treatment after relapse group was significantly higher than without CAR-T cell treatment after relapse group ((78±10)% vs. (15±10)%, P<0.05). ETV6-RUNX1 was the most common genetic aberration in testicular relapsed ALL (38%, 14/37). The 4-year OS and EFS rate of patients with ETV6-RUNX1 positive were (80±13) % and (64±15) %, respectively. Multivariate analysis identified relapse occurred≤28 months after first diagnosis (HR=3.09, 95%CI 1.10-8.72), combined relapse (HR=4.26, 95%CI 1.34-13.52) and CAR-T cell therapy after relapse (HR=0.15,95%CI 0.05-0.51) were independent prognostic factors for 2-year EFS rate (all P<0.05). Conclusions: The outcome of testicular relapse in pediatric ALL was poor. They mainly occurred 3 years after initial diagnosis. ETV6-RUNX1 is the most common abnormal gene.Patients with ETV6-RUNX1 positive often have a favorable outcome. Early relapse and combined relapse indicate unfavorable prognosis, while CAR-T cell therapy could significantly improve the survival rate of children with testicular recurrence.

[Clinical and prognostic characteristics of pediatric acute myeloid leukemia with myelodysplasia-related changes under different diagnostic criteria]

Objective: To evaluate the clinical and prognostic differences in acute myeloid leukemia with myelodysplasia-related changes (AML-MRC) children under different diagnostic criteria (World Health Organization (WHO) 2016 and WHO 2022 criteria). Methods: In this retrospective cohort study, clinical characteristics and prognosis information of 260 acute myeloid leukemia (AML) children admitted to Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences from August 2017 to August 2021 were analyzed retrospectively. According to WHO 2016 and WHO 2022 diagnostic criteria, patients were divided into AML-MRC group and non-AML-MRC group, the prognostic and genetic differences between two groups were compared respectively. Meanwhile, the characteristics of children with 8 MRC-related genes defined in WHO 2022 diagnostic criteria were described. Mann-Whitney U test, chi-square test were used for comparison between groups. Survival curve was plotted by Kaplan-Meier method, and comparison between groups was performed by Log-Rank method. Results: Among the 260 children, there were 148 males and 112 females. The follow-up time was 26 (16, 38) months. A total of 28 children (10.8%) were diagnosed with AML-MRC according to the WHO 2016 diagnostic criteria. Compared with non-AML-MRC children, the frequency of PTPN11, RUNX11, SH2B3, MPL and STAG2 mutations was higher in AML-MRC children (25.0% (7/28) vs. 4.3% (10/232), 14.3% (4/28) vs. 3.9% (9/232), 10.7% (3/28) vs. 2.2% (5/232), 10.7% (3/28) vs. 2.2% (5/232), 10.7% (3/28) vs. 0.9% (2/232), all P<0.05). The 2-year overall survival (OS) and events free survival (EFS) rate of 28 AML-MRC children under WHO 2016 diagnostic criteria were worse than those of 232 non-AML-MRC children ((62.1±10.8)% vs. (94.5±1.6)%, χ2=22.1,P<0.001;(48.0±10.6)% vs. (70.9±3.2)%, χ2=6.33,P=0.012). Twenty-seven children (10.4%) were eventually diagnosed with AML-MRC according to WHO 2022 criteria, their 2-year OS rate were worse than 233 non-AML-MRC children ((60.8±11.1)% vs. (94.5±1.6)%, χ2=24.49,P<0.001), and there was no statistically significant difference in EFS rate between two groups at 2 years ((55.1±10.8)% vs. (70.1±3.2)%, χ2=2.44, P=0.119). Conclusions: Compared with the 2022 WHO diagnostic criteria, the survival rates of children with AML-MRC under the 2016 WHO diagnostic criteria were worse than that of children without MRC.The new version of the AML-MRC diagnostic criteria emphasizes the importance of genes.

[Genomics of next generation sequencing in pediatric B-acute lymphoblastic leukemia and its impact on minimal residual disease]

Objective: To describe the gene mutation profile of newly diagnosed pediatric B-acute lymphoblastic leukemia (B-ALL) and analyze its effect on minimal residual disease (MRD). Methods: A total of 506 newly diagnosed B-ALL children treated in Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences from September 2018 to July 2021 were enrolled in this retrospective cohort study. The enrolled children were divided into MRD ≥1.00% group and <1.00% group according to MRD results on the 19th day since chemotherapy, and MRD ≥0.01% group and <0.01% group according to MRD results on the 46th day. Clinical characteristics and gene mutations of two groups were compared. Comparisons between groups were performed with chi-square test or Fisher's exact test. Independent risk factors of MRD results on the 19th day and the 46th day were analyzed by Logistic regression model. Results: Among all 506 patients, there were 318 males and 188 females. On the 19th day, there were 114 patients in the MRD ≥1.00% group and 392 patients in the MRD <1.00% group. On the 46th day, there were 76 patients in the MRD ≥0.01% group and 430 patients in the MRD <0.01% group. A total of 187 gene mutations were detected in 487 (96.2%) of 506 children. The most common gene mutations were signal transduction-related KRAS gene mutations in 111 cases (22.8%) and NRAS gene mutations in 99 cases (20.3%). Multivariate analysis showed that PTPN11 (OR=1.92, 95%CI 1.00-3.63), KMT2A (OR=3.51, 95%CI 1.07-11.50) gene mutations and TEL-AML1 (OR=0.48, 95%CI 0.27-0.87), BCR-ABL1 (OR=0.27, 95%CI 0.08-0.92) fusion genes and age >10 years (OR=1.91, 95%CI 1.12-3.24) were independent influencing factors for MRD ≥1.00% on the 19th day. BCORL1 (OR=2.96, 95%CI 1.18-7.44), JAK2 (OR=2.99, 95%CI 1.07-8.42) and JAK3 (OR=4.83, 95%CI 1.50-15.60) gene mutations and TEL-AML1 (OR=0.43, 95%CI 0.21-0.87) fusion gene were independent influencing factors for MRD ≥0.01% on the 46th day. Conclusions: Children with B-ALL are prone to genetic mutations, with abnormalities in the RAS signaling pathway being the most common. Signal transduction related PTPN11, JAK2 and JAK3 gene mutations, epigenetic related KMT2A gene mutation and transcription factor related BCORL1 gene mutation are independent risk factors for MRD.

[Heterogeneity and clonal evolution in pediatric ETV6-RUNX1(+) acute lymphoblastic leukemia by quantitative multigene fluorescence in situ hybridization]

目的

研究儿童ETV6-RUNX1阳性急性淋巴细胞白血病（ALL）中肿瘤细胞的异质性及克隆演化情况，探讨克隆演化与预后的相关性。

方法

应用单细胞定量多基因荧光原位杂交（QM-FISH）技术对2006年2月至2011年6月收治的48例ETV6-RUNX1阳性ALL患儿的骨髓标本进行多个基因拷贝数变异的检测，并进行克隆演化分析。将4例复发患儿初诊与复发时的情况进行比较。

结果

在48例行QM-FISH检测的患儿中，初诊时为1个克隆的有34例（70.8%），2个克隆的有9例（18.8%），≥3个克隆的有5例（10.4%）。患儿的肿瘤细胞存在异质性，各亚克隆之间呈线性或树枝状演化。白血病细胞的亚克隆数与患者预后无相关性（5年总生存率：P=0.469；5年无病生存率：P=0.116）。复发克隆可能与初诊时克隆一致，也可能为新出现克隆。复发克隆为新出现克隆的患儿再次缓解时间短，预后更差。

结论

ETV6-RUNX1阳性ALL患儿肿瘤细胞存在异质性及克隆演化情况。QM-FISH有助于研究白血病细胞的克隆演化，复发克隆为新出现克隆的患儿可能预后更差。

The development of the proximal oesophageal pouch in the adriamycin rat model of oesophageal atresia with tracheo-oesophageal fistula

This study examined the morphological development of the proximal oesophagus in the Adriamycin-induced rat model of oesophageal atresia. The proximal oesophageal segment in oesophageal atresia with tracheo-oesophageal fistula (OA\TOF) has been assumed to be of similar embryological origin to the distal oesophagus. However, recent research using the Adriamycin model of OA\TOF has indicated that these structures may have a different origin. Time-mated Sprague-Dawley rats were administered either Adriamycin intraperitoneally or saline of an equivalent volume between days 6-9 of gestation. The rats were sacrificed between days 11-19 of gestation, their embryos removed and histologically sectioned. These sections were analysed to observe the morphological changes occurring in the proximal foregut. The proximal oesophageal pouch first appeared on day 15.25 as a dorsal outpouching of the proximal foregut immediately cranial to an area of apoptosis in the dorsal epithelium of the distal pharynx. It elongated through a process of cellular proliferation until it was clearly formed on day 16. Relatively little growth occurred from days 17-19. In the rat developing oesophageal atresia, the proximal oesophageal pouch has an origin different to that of the distal oesophagus. This study may explain the difference in immunohistological properties and intrinsic nervous supply between the proximal and distal oesophageal segments in oesophageal atresia.

Hedgehog in the human: a possible explanation for the VATER association

Foregut malformations are relatively common anomalies, occurring in 1 in 2000-5000 live births. The adriamycin-induced rat model of the VATER association has provided a means of studying the morphogenesis of a variety of major congenital structural abnormalities similar to those seen in humans with VATER association. The secreted glycoprotein, Sonic hedgehog (Shh), may act as an endodermal signal that controls gut and lung patterning. Mice with targeted deletion of Shh have foregut defects that are consistent with those produced by administration of adriamycin. It is possible that mutations induced by adriamycin may result from the breakdown of the Shh signalling pathway.

Evidence of a common pathogenesis for foregut duplications and esophageal atresia with tracheo-esophageal fistula

The pathogenesis of the alimentary tract duplications, including foregut duplications (FgD) remains speculative. The accidental finding of FgD in fetal rats with esophageal atresia and tracheoesophageal fistula (EA-TEF) induced by Adriamycin provided an animal model to investigate a possible relationship between these two entities. Timed-pregnant rats were intraperitoneally injected with Adriamycin (1.75 mg/kg) on gestational Days 6 to 9. Their embryos were harvested by Caesarean section from gestational Days 14 to 21. Forty-six of embryos were processed and serially sectioned in the transverse or sagittal planes. EA-TEF occurred in 43/46 (93%) embryos of which 11 (24%) were found to have an associated FgD located at the level where the esophagus was absent. Six FgDs communicated with the foregut or the trachea. Five noncommunicating FgDs were located between the foregut and the vertebral column. In the control embryo, the notochord was located in the centre of the vertebral column from Day 11 of the gestation. In Day 14, 15 and 16, however, embryos exposed to Adriamycin, an abnormal notochord or branch frequently was located within the mesenchyme of the maldeveloped foregut or attached to the duplication cyst. In some, it appeared that the notochord was drawing the cyst-like structure away from the foregut. The present study confirms that duplications adjacent to the esophagus arise from the foregut and that failure of the foregut to detach from the notochord at the normal time may contribute to the development of foregut duplications.

Development of the bones and synovial joints in the rat model of the VATER association

The adriamycin-induced rat model of the Vertebral, Anorectal, Tracheo-Esophageal, Radial and Renal (VATER) association produces a variety of vertebral, rib, and limb abnormalities. This study was designed to document accurately the nature of these abnormalities and to determine whether synovial joints are affected. Fetuses from pregnant Sprague Dawley rats that had received intraperitoneal injections of 1.75 mg/kg of adriamycin on days 6-9 or 10-13 of gestation were harvested. Double-stained skeletal preparations and histological sections were examined for vertebral, rib, and limb anomalies. The incidence of anomalies was high in the group treated on gestational days (GD) 6-9, while it was low in the GD 10-13 group. The length and thickness of the long bones were reduced, with bowing and reduction in their endochondral ossification. Sirenomelia occurred in the group treated on GD 6-9, and was often associated with a short tail and anal atresia. The joint cavities, and intra-articular structures such as menisci and the cruciate ligaments developed normally from the mesenchymal interzone. These data indicate that adriamycin inhibits skeletal growth and differentiation without any interference in the differentiation of the mesenchymal interzone, thus producing normal synovial joints.

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.

Abnormalities of the tracheal cartilage in the rat fetus with tracheo-oesophageal fistula or tracheal agenesis

Many infants with oesophageal atresia and tracheo-oesophageal fistula (OA/TOF) have associated tracheomalacia (TM), which is one of the reasons for respiratory complications after surgical correction of the atresia. OA/TOF was induced in the offspring of pregnant rats by intraperitoneal injection of adriamycin. Fetuses were harvested by caesarean section. The trachea, oesophagus, lungs, and stomach were removed en bloc and stained for cartilage using Alcian blue. The tracheas were examined, photographed, and relevant parameters pertaining to the tracheal cartilage were measured. Exposure to adriamycin resulted in a range of anatomical defects including OA/TOF (47%) and tracheal agenesis (TA) (41%). Adriamycin-treated fetuses were smaller (P < 0.01), yet had longer tracheas (P < 0.001) than control fetuses. The OA/TOF fetuses had more tracheal cartilage rings than controls (P < 0.01), whereas TA fetuses had fewer (P < 0.001). Both OA/TOF and TA fetuses had more malformed tracheal cartilage rings than controls (P < 0.001 and P < 0.05, respectively). Cartilage in the proximal part of the trachea was most frequently and severely affected (P < 0.05). These observations clarify the structural abnormalities of tracheal cartilage that occur in rat fetuses with OA/TOF or TA induced by adriamycin, and may explain the functional disturbances of TM seen in OA/TOF.

Clarification of the process of separation of the cloaca into rectum and urogenital sinus in the rat embryo

BACKGROUND/PURPOSE

The normal process of division of the cloaca into a rectum and urogenital tract is still not fully understood. The main controversies relate to how the urorectal septum (URS) divides the cloaca and whether the URS fuses with the cloacal membrane. This study used a 3-dimensional reconstruction technique, combined with histologic correlation, to observe the developmental and septational processes of the cloaca of the normal rat embryo from gestational days 11 to 16.

METHODS

Normal rat embryos from gestational days 11 to 16 were sectioned serially both transversely and sagittally and stained with H&E. 3-dimensional reconstructions were performed on embryos younger than day 13.5. The relevant structures were examined in a temporo-spatial sequence.

RESULTS

The tailgut started to regress by apoptosis on day 12 in a cranio-caudal direction. The URS, first evident in day-12.5 embryos, extended and fused with the cloacal membrane on day 15 of gestation, completing the separation of the cloaca into rectum and bladder. Regression of the tailgut and ventral protrusion of the urogenital sinus markedly changed the configuration of the cloaca. The cloacal membrane did not break down until after it had fused with the URS.

CONCLUSIONS

These findings clarify the relative contributions made by active septation of the cloaca by the URS and configurational changes of the cloaca to produce a rectum and bladder. The URS fuses with the cloacal membrane before the anal and urogenital membranes break down.

Does the urorectal septum fuse with the cloacal membrane?

PURPOSE

Traditional theories of cloacal embryogenesis assume that the urorectal septum fuses with the cloacal membrane before the anal membrane disintegrates. However, recent observations in humans and other species raise doubt about this assumption. We determined whether urorectal septum fusion occurs in rats.

MATERIALS AND METHODS

Rat embryos were harvested at specific times between days 11 and 16 of gestation. We evaluated the morphology, growth and relationship of the urorectal septum to the cloacal membrane on serial histological sections.

RESULTS

The urorectal septum consistently fused with the cloacal membrane on day 15 of gestation before the cloacal membrane began to disintegrate.

CONCLUSIONS

In rats the urorectal septum fuses with the cloacal membrane, after which the urogenital membrane and anal membrane disintegrate by a process of apoptosis.

Temporospatial aberrations of apoptosis in the rat embryo developing esophageal atresia

BACKGROUND/PURPOSE

Recent work has shown that apoptosis is a key component of the normal development of the foregut. This study was designed to compare the patterns of apoptosis in the normal foregut with those in the fetus developing esophageal atresia and tracheoesophageal fistula (EA-TEF) using 3-dimensional reconstructive techniques.

METHODS

Timed pregnant rats that received no treatment (control group) or received Adriamycin intraperitoneally (experimental group) had their embryos removed between days 11 and 14 of gestation. The embryos were sectioned serially and stained with H&E. Three-dimensional reconstructions were made of the foregut and areas of apoptosis were marked on them to facilitate analysis of apoptotic patterns.

RESULTS

Apoptosis was evident in control embryos in the region in which tracheoesophageal separation occurs from days 12 and 12.5. Experimental embryos showed no apoptosis until day 13 when apoptosis was observed immediately posterior to the foregut within the esophageal mesenchyme and in the laryngeal mesenchyme ventral to the foregut.

CONCLUSIONS

The pattern, timing and location of apoptosis in rats developing EA-TEF is abnormal. Our work indicates that it is actually a complete lack of apoptosis at the crucial stage of development that leads to this abnormality rather than an alteration in the patterning of apoptosis at this crucial time. The observation of apoptosis only within the mesenchyme raises the possibility that apoptosis in the foregut developing EA-TEF may be a reaction to that abnormal development rather than its cause.

Apoptosis during regression of the tailgut and septation of the cloaca

PURPOSE

Apoptosis is involved in the embryonic morphogenesis of many organs. The current study was undertaken to ascertain the role of apoptosis during cloacal development in the rat.

METHODS

One hundred five rat embryos, ranging from gestational days 11 to 16, were sectioned serially in the transverse or sagittal planes and stained with H&E. The cloaca, urorectal septum, rectum, urogenital sinus, Wolffian ducts, and tailgut (TG) were examined consecutively in temporospatial sequence.

RESULTS

The tailgut immediately distal to the hindgut starts to regress by apoptosis on day 12 of gestation in a craniocaudal direction and has regressed completely by day 13.5. A large number of apoptotic cells and debris can be identified in the urorectal septum during cloacal septation. Vacuoles are formed by coalescence of apoptotic cells at the tip of urogenital sinus from day 15 to 16, and, at the same time, sporadic apoptotic bodies in the anal membrane contribute to its thinning.

CONCLUSION

Results of the current study confirm that apoptosis occurs in a specific temporo-spatial sequence in the hindgut and cloaca and appears to be an important mechanism in TG regression, uro-rectal separation, urethral opening, and rupture of the anal membrane.

Stages of normal tracheo-bronchial development in rat embryos: resolution of a controversy

The embryonic events surrounding tracheo-esophageal separation remain controversial. The present study was undertaken to clarify early tracheo-bronchial development in the rat embryo at a critical period of organogenesis. Twenty-seven timed-mated Sprague-Dawley rats were divided into nine groups of three rats. Their embryos were harvested on gestational days 11-15 at intervals of 8 h, processed and sectioned transversely. The sections were stained with hematoxylin and eosin and examined serially. The foregut is a single tube on gestational day 11. During the following 16 h, there is localized and rapid growth of the respiratory epithelium and a laterocaudal expansion to form the bronchial buds and a protuberance on the ventral wall of the foregut (future tracheal carina). From gestational days 12-12 + 8, cellular debris and apoptotic epithelial cells are specifically located in the tracheo-esophageal groove, resulting in collapse and fusion of the lateral walls of the foregut, effectively separating the trachea and esophagus. Afterwards, the epithelial proliferation dominates the process of tracheo-esophageal separation until it reaches the caudal end of the laryngeal epithelial lamina on gestational day 15. The present study shows that separation of the trachea from the esophagus involves three consecutive stages: (i) epithelial proliferation resulting in the formation of bronchial buds and the tracheal carina; (ii) epithelial apoptosis leading to separation of the trachea and esophagus; and (iii) epithelial proliferation to complete the separation process.

The contribution of the adriamycin-induced rat model of the VATER association to our understanding of congenital abnormalities and their embryogenesis

The adriamycin-induced rat model of the VATER association has provided a means of studying the morphogenesis of a variety of major congenital structural abnormalities similar to those seen in humans with the VATER association. Most interest has been centered on the foregut, where the model has clarified some aspects of the development of esophageal atresia (EA), tracheal agenesis, and other communicating bronchopulmonary foregut malformations. It has demonstrated aberrations in the nerve supply to the esophagus in EA and allowed the study of tracheomalacia. A relationship between an abnormal notochord, foregut abnormalities, and vertebral defects has been shown, and the model has reignited interest in the role of the notochord as a regional organizer of axial development. The normal temporospatial characteristics of apoptosis during fore- and hindgut development is disturbed in this model, resulting in abnormal morphology. The indications are that this model will continue to clarify the processes that lead to many of the structural congenital abnormalities that are seen in infants born with the VATER association.

Relationship of the notochord to foregut development in the fetal rat model of esophageal atresia

BACKGROUND/PURPOSE

The notochord (Nt) is thought to act as a primary organizer for adjacent axial embryonic organs. The current study used the Adriamycin-induced fetal rat model of esophageal atresia and tracheoesophageal fistula (EA-TEF) to determine whether anomalies of the foregut (FG) were associated with an abnormal Nt.

METHODS

Eight experimental female Sprague-Dawley rats received intraperitoneal injection of Adriamycin (1.75 mg/kg) on gestational days 6 to 9 inclusive, and 4 control rats received saline injection only. Their embryos were harvested on gestational days 11, 12, 13, and 14. Embryos from each age subgroup were serially sectioned and stained with H&E. The FG and Nt were traced from the primitive pharynx to the level of the stomach.

RESULTS

By day 11, the Nt of control embryos had completely separated from the FG and was located immediately ventral to the neural tube. On gestational day 12, the Nt detached from the neural tube, and the trachea and esophagus were separating. On day 11, in the Adriamycin-treated embryos, the Nt was still attached to an FG that was narrowed or occluded. On day 12, the Nt remained adherent to the FG from the primitive pharynx to the level above the primitive respiratory buds, at which point it became thicker and branched sagittally, with the anterior branch contacting or merging with the FG. The FG usually loses its lumen or continuity when in contact with the Nt.

CONCLUSIONS

Exposure of rat embryos to Adriamycin leads to abnormal development of the Nt, including prolonged attachment to or fusion with the FG, and abnormal branching. Traction on the FG by the Nt produces occlusion of its lumen and may result in its complete interruption. Separation of the Nt from the FG would appear to be a prerequisite for the normal development of the FG into its derivatives: the esophagus and trachea.

Pathohistological study of adriamycin-induced tracheal agenesis in the fetal rat

There have been few studies of tracheal agenesis (TA) because it is an extremely rare condition and is invariably fatal. However, it is recognised to be associated with a variety of oesophageal abnormalities, including oesophageal atresia (OA) and communicating bronchopulmonary foregut malformations (CBPFM). Except for some gross pathological reports, there has been no detailed histological investigation of this congenital abnormality. Adriamycin-induced TA in fetal rats provides a means of studying this uncommon condition, including its relationship to oesophageal abnormalities. TA was induced in rat features by intra-peritoneal injection of adriamycin (2 mg/kg) into timed-pregnant rats on days 6-9. Their 33 fetuses were removed by caesarean section, cut transversely, and stained after which the slides were examined. OA developed in 27/33 adriamycin-treated fetuses, TA occurred in 5. Four had type III while the 5th had type II TA. The oesophagus of fetuses with TA acquired tracheal features in the region where both ectopic bronchi originated. Two fetuses with TA also had OA, and 4 had a CBPFM. Other abnormalities detected involved the gastrointestinal, urinary and cardiovascular systems. The association of TA and oesophageal abnormalities suggests that there may be a spectrum of abnormalities comprising a number of variants, which may have a common aetiology. The other abnormalities co-existing in this animal model mirror those found in reported cases of human TA. Ultimately, the rat model of OA and TA may give insight into the embryogenesis of these malformations.

Intrinsic innervation of the oesophagus in fetal rats with oesophageal atresia

Although the aetiology of oesophageal dysmotility after repair of oesophageal atresia and tracheo-oesophageal fistula (OA-TOF) remains controversial, oesophageal dysmotility also is present in isolated TOF or OA before surgery, suggesting a congenital cause. Our previous work with a model of OA-TOF in fetal rats demonstrated an abnormality in the course and branching pattern of the vagus nerve. However, little is known about the intramural nervous components of the atretic oesophagus. The intrinsic innervation of the atretic oesophagus was examined by immunohistological staining to see if there is an abnormality that might account for dysmotility. OA-TOF was induced in fetal rats by injecting adriamycin intraperitoneally into pregnant rats. Forty-eight controls, 40 OA-TOF, and 6 treated fetuses without OA-TOF were recovered. Whole-mount preparations of each oesophagus were stained with fluorescent antibodies against neuron-specific enolase (NSE), vasoactive intestinal peptide (VIP), substance P (SP), and calcitonin gene-related peptide (CGRP). Compared with control fetuses, the density of the nerve plexus, ganglia, and number of cell bodies per ganglion immunostained by NSE, VIP, or SP was significantly reduced in OA-TOF fetuses. CGRP-immunoreactive nerve fibres in the oesophageal wall of both control and OA-TOF animals were found to be connected with extrinsic nerve bundles. No plexus-like nerve fibre network was observed. The results of the present study demonstrated significant abnormalities of the intramural nervous components of the oesophagus in OA-TOF fetal rats, involving both the excitatory (SP-labelled) and inhibitory (VIP-labelled) intramural nerves. These abnormalities may underlie the oesophageal dysmotility seen in OA-TOF patients.

Communicating bronchopulmonary foregut malformations in the adriamycin-induced rat model of oesophageal atresia

BACKGROUND

Communicating bronchopulmonary foregut malformations (CBPFM) are rare abnormalities of the development of the primitive foregut that result in an abnormal communication between the upper gastrointestinal tract and pulmonary tissue. They usually occur in isolation, but sometimes are seen in association with oesophageal atresia (OA).

METHODS

Communicating bronchopulmonary foregut malformations were induced in the offspring of pregnant rats by intraperitoneal injection of Adriamycin (Delta West Pty Ltd, Bentley, Western Australia, Australia). Fetuses harvested by caesarean section were fixed in 10% formalin, transversely sectioned and stained with haematoxylin and eosin. Serial examination of the slides allowed three-dimensional reconstruction of the anatomy of the pulmonary system and the oesophagus.

RESULTS

Communicating bronchopulmonary foregut malformations occurred in nine (30%) of fetuses with OA. Three types of CBPFM were produced: an isolated pulmonary structure (accessory lung) attached to the lower oesophagus via a patent bronchus (6 fetuses); an anomalous bronchus from the lower oesophagus to the lower part of the left lung (two fetuses); and atresia of the trachea (one fetus).

CONCLUSIONS

These observations are consistent with the assertion that CBPFM and OA are variations of a spectrum of abnormalities and may have a similar aetiology. In the rat model it would appear that Adriamycin interferes with the timing and progression of lung bud differentiation at a time when the primitive foregut is developing rapidly. Ultimately, this model may shed light on the embryogenesis of both anomalies.

Preliminary evidence that cell death may contribute to separation of the trachea from the primitive foregut in the rat embryo

BACKGROUND/PURPOSE

The embryogenesis of many congenital tracheoesophageal abnormalities has been elucidated poorly, mainly because of an incomplete understanding of the normal mechanism of separation of the primitive foregut into the trachea and esophagus. There has been controversy about the existence and significance of the so-called tracheoesophageal septum. This study investigates the normal mechanism of tracheoesophageal separation in the rat.

METHODS

Timed-pregnant Sprague-Dawley rats were killed on gestational days 11 to 16, respectively (the day on which the vaginal smear showed sperm was considered day 0 of gestation). Thirty-six embryos (six embryos from each age group) were fixed in 10% formalin. Fixed embryos from gestational day 13, 12, and 11 were sandwiched in melted agar to facilitate proper orientation before being processed. Half of the fetuses from each age group were sectioned serially in a transverse plane and the other half in a sagittal plane. The histological sections were stained with H&E.

RESULTS

On gestational day 11, the foregut appears as a ventrodorsal slit in transverse section. Below the primitive pharynx, the epithelial cells on the ventral part of the foregut are actively proliferating, producing two lateral epithelial bulges (primitive bronchial buds). The epithelial cells of the dorsal aspect of the foregut show no sign of active growth. On day 12, the proximal trachea still shares a common lumen with the foregut. The distal trachea, the tracheal bifurcation, and both primary bronchi are recognized easily. At the point of tracheoesophageal separation, there is obvious debris of dead epithelial cells and condensed nuclei. These appearances were specifically located around the so-called tracheoesophageal septum and nearby grooves, resulting in enfolding cristae. There was no cell proliferation or inflammatory response in this region. On gestational day 13, the separation of the trachea and esophagus was almost complete.

CONCLUSION

The present study demonstrates that a specific and consistent pattern of cell death in the region of the "tracheoesophageal septum" produced enfolding cristae that may be part of the mechanism of separation of the trachea and esophagus.

Use of the appendix to replace the choledochus

Ten cases of choledochal cyst (CC) were treated by biliary-appendicoduodenostomy. The follow-up comprised a patient interview, ultrasonography (US), and single-proton ejected computerized tomography (SPECT) scanning. In all cases an anti-reflux submucosal tunnel was added to the distal appendico-duodenostomy; all showed an uneventful postoperative course. All the dilated intrahepatic bile ducts had normalized on B-US postoperatively. Four children under went SPECT examination; all of them had patent neo-bile ducts. In the authors' opinion: (1) Anastomosing the cecal end of the appendix to the common hepatic duct seemed more favorable than the other way around, because the cecal end could be easily trimmed to the size of the common hepatic duct, which was more or less dilated in the presence of a CC; (2) It is necessary to add a submucosal tunnel to the distal appendicoduodenostomy to achieve a more reliable anti-reflux effect; and (3) Transposing the vascularized appendix through the retro-transverse colon simplified the procedure and might reduce the risk of retroperitoneal complications if bile leakage should occur.

Understanding tracheomalacia

Tracheomalacia is an abnormality of the trachea that probably is present to some degree in all infants and children with oesophageal atresia. It causes the trachea to collapse during breathing, leading to obstruction of the upper airway. Our knowledge of the structural abnormalities underlying tracheomalacia is limited, mainly because patients with oesophageal atresia usually survive. Recently, the Adriamycin-induced rat model of oesophageal atresia and tracheomalacia has clarified some aspects of its pathology and the factors which may influence its development. The rat model suggests that the same detrimental factors that cause oesophageal atresia might also affect the development of the trachea, and that anomalous great vessels may exacerbate the severity of tracheomalacia locally.

Tracheomalacia with esophageal atresia and tracheoesophageal fistula in fetal rats

BACKGROUND

Many patients who have esophageal atresia and tracheoesophageal fistula (EA-TEF) have associated tracheomalacia, which is thought to be one of the reasons for respiratory complications after surgical correction of the abnormality.

METHODS

In this study, tracheas from Adriamycin-induced EA-TEF fetal rats were examined histologically and relevant cross-sectional parameters of the tracheas were measured.

RESULTS

The tracheal lumen in tracheomalacia was small and irregular, losing its normal "D" shape. In most rats, the cartilaginous ring was broken into two to four segments, making the trachea lose its rigid support. The submucosa was thickened with prominent bulging of its membranous part into the tracheal lumen. The ratio of the inner luminal cross-sectional area to the outer tracheal cross-sectional area in EA-TEF rats was 15.7%, compared with a control ratio of 47.2%. In EA-TEF rats, the length of the cartilaginous ring was significantly shortened (P < .001), but not the length of membranous trachea, thus resulting in a cartilaginous/membranous (C/M) ratio of 1.55:1, markedly lower than that of normal rats (4.34:1, P < .001). The reduction of anterior-posterior diameter of the tracheal lumen was more marked than that of the transverse diameter.

CONCLUSIONS

These observations suggest that the trachea in EA-TEF rats has a smaller lumen and is more flaccid than normal, making it prone to airway obstruction. The fact that tracheomalacia developed only in fetuses who had EA-TEF indicates that the factors that result in EA-TEF also cause tracheomalacia.

The vagus and recurrent laryngeal nerves in the rodent experimental model of esophageal atresia

BACKGROUND

After surgical correction of their esophageal atresia and tracheoesophageal fistula (EA-TEF), many patients exhibit evidence of esophageal dysmotility. Controversy exists as to whether the esophageal motility disorders result from denervation caused by surgery or from an inherent abnormal innervation of the esophagus.

METHODS

The present study used an Adriamycin-induced EA-TEF fetal rat model to trace the course and branching of both the vagus and recurrent laryngeal nerves. Abnormalities observed in EA-TEF rat fetuses include: (1) fewer branches from both recurrent laryngeal nerves; (2) deviation of the left vagus from its normal course below the aorta, passing behind the fistula to approach and join with the right vagus to form a single nerve trunk on the right side of the esophagus; (3) relatively few branches from the single vagal nerve trunk (composed of fibers of the left and the right vagus) on the surface of the lower esophagus.

CONCLUSIONS

Fetuses affected by EA-TEF have inherent abnormalities in the course and branching pattern of the vagus nerves as they descend through the thorax, culminating in a deficient extrinsic nerve fiber plexus in the lower esophagus. These observations may account for the esophageal motility disorders seen in patients who have EA-TEF even before surgical intervention.

Timing and embryology of esophageal atresia and tracheo-esophageal fistula

BACKGROUND

The embryology of tracheo-esophageal anomalies is controversial. The development of an adriamycin-treated animal model has enabled improved understanding of the embryogenesis of these anomalies. Using this model, we aimed to describe the events leading to esophageal atresia and tracheo-esophageal fistula.

METHODS

Timed-pregnant Sprague-Dawley rats were injected daily with adriamycin intraperitoneally at a dose of 2 mg/Kg on days 6-9 of gestation. Histological sections were prepared from 96 experimental and 34 control rat embryos at 11-14 days gestation (plug day = day 0).

RESULTS

The tracheal bud failed to develop normally from the foregut, leaving the foregut to give origin to both bronchi and differentiate into the respiratory system, and then continue as a fistula to the lower esophageal segment. Dorsal pouching of the proximal foregut, which is seen clearly on day 13, is responsible for the development of the upper esophageal segment.

CONCLUSIONS

We conclude that failure of the tracheal bud to develop normally from the primitive foregut is the main event which leads to the tracheo-esophageal anomalies. As the proximal part of the primitive foregut develops primarily into a trachea rather than an esophagus, the anomaly of the esophagus could be described as agenesis instead of atresia.

Cardiovascular malformations in rat fetuses with oesophageal atresia and tracheo-oesophageal fistula induced by adriamycin

Associated congenital anomalies have emerged as the most significant prognostic factor in babies born with oesophageal atresia and/or tracheo-oesophageal fistula (OA-TOF). The most frequently encountered groups of anomalies are cardiovascular (CV) and gastrointestinal, the former being more significant from a prognostic point of view. Some, such as a right-sided aortic arch (RAA), vascular ring, or major heart defects, may alter the timing and surgical approach for the repair of OA-TOF or adversely affect the prognosis. The rat fetal OA model induced by adriamycin (Adr) has been described previously. In the present experiments, information was sought regarding the incidence and type of CV abnormalities in fetal rats obtained from Adr-treated dams. OA-TOF was induced in 24 of 36 fetal rats from Adr-treated dams. DV abnormalities were found in 18 (75%) OA-TOF fetuses and 10 (83%) Adr-treated fetuses without OA-TOF. The difference was not significant (P >0.05). The most frequently found anomalies were ventricular and atrial septal defects. A RAA was present in 8/36 fetuses and a double aortic arch in 2/36. A patent ductus arteriosus was present in all treated fetuses compared with two-thirds of controls. The findings in the present study emphasise the importance of CV anomalies in association with OA, and reinforce the value of the Adr-induced rat fetal OA model by adding to our knowledge of the basic embryogenesis of both OA and CV anomalies.