Improving diagnosis and outcome prediction of gastric cancer via multimodal learning using whole slide pathological images and gene expression

For the diagnosis and outcome prediction of gastric cancer (GC), machine learning methods based on whole slide pathological images (WSIs) have shown promising performance and reduced the cost of manual analysis. Nevertheless, accurate prediction of GC outcome may rely on multiple modalities with complementary information, particularly gene expression data. Thus, there is a need to develop multimodal learning methods to enhance prediction performance. In this paper, we collect a dataset from Ruijin Hospital and propose a multimodal learning method for GC diagnosis and outcome prediction, called GaCaMML, which is featured by a cross-modal attention mechanism and Per-Slide training scheme. Additionally, we perform feature attribution analysis via integrated gradient (IG) to identify important input features. The proposed method improves prediction accuracy over the single-modal learning method on three tasks, i.e., survival prediction (by 4.9% on C-index), pathological stage classification (by 11.6% on accuracy), and lymph node classification (by 12.0% on accuracy). Especially, the Per-Slide strategy addresses the issue of a high WSI-to-patient ratio and leads to much better results compared with the Per-Person training scheme. For the interpretable analysis, we find that although WSIs dominate the prediction for most samples, there is still a substantial portion of samples whose prediction highly relies on gene expression information. This study demonstrates the great potential of multimodal learning in GC-related prediction tasks and investigates the contribution of WSIs and gene expression, respectively, which not only shows how the model makes a decision but also provides insights into the association between macroscopic pathological phenotypes and microscopic molecular features.

Characterization of alternative splicing events and prognostic signatures in gastric cancer

BACKGROUND

Accumulating evidences indicate that the specific alternative splicing (AS) events are linked to the occurrence and prognosis of gastric cancer (GC). Nevertheless, the impact of AS is still unclear and needed to further elucidation.

METHODS

The expression profile of GC and normal samples were downloaded from TCGA. AS events were achieved from SpliceSeq database. Cox regression together with LASSO analysis were employed to identify survival-associated AS events (SASEs) and calculate risk scores. PPI and pathway enrichment analysis were implemented to determine the function and pathways of these genes. Kaplan-Meier (K-M) analysis and Receiver Operating Characteristic Curves were used to evaluate the clinical significance of genes of SASEs. Q-PCR were applied to validate the hub genes on the survival prognosis in 47 GC samples. Drug sensitivity and immune cell infiltration analysis were conducted.

RESULTS

In total, 48 140 AS events in 10 610 genes from 361 GC and 31 normal samples were analyzed. Through univariate Cox regression, 855 SASEs in 763 genes were screened out. Further, these SASEs were analyzed by PPI and 17 hub genes were identified. Meanwhile, using Lasso and multivariate Cox regression analysis, 135 SASEs in 132 genes related to 7 AS forms were further screened and a GC prognostic model was constructed. K-M curves indicates that high-risk group has poorer prognosis. And the nomogram analysis on the basis of the multivariate Cox analysis was disclosed the interrelationships between 7 AS forms and clinical parameters in the model. Five key genes were then screened out by PPI analysis and Differential Expression Gene analysis based on TCGA and Combined-dataset, namely STAT3, RAD51B, SOCS2, POLE2 and TSR1. The expression levels of AS in STAT3, RAD51B, SOCS2, POLE2 and TSR1 were all significantly correlated with survival by qPCR verification. Nineteen drugs were sensitized to high-risk patients and eight immune cells showed significantly different infiltration between the STAD and normal groups.

CONCLUSIONS

In this research, the prognostic model constructed by SASEs can be applied to predict the prognosis of GC patients and the selected key genes are expected to become new biomarkers and therapeutical targets for GC treatment.

[Comparison of surgical outcomes between Kahook Dual Blade goniotomy and Trabectome surgery in patients with open-angle glaucoma]

Objective: To compare the medium-term therapeutic effects of Kahook Dual Blade (KDB) goniotomy and Trabectome surgery in the treatment of patients with primary open-angle glaucoma (POAG). Methods: This study was a non-randomized prospective interventional controlled clinical study. POAG patients who underwent KDB goniotomy or Trabectome surgery at Beijing Tongren Hospital from May 2017 to April 2022 were enrolled. The definition of successful surgery was postoperative average intraocular pressure (IOP)≤21 mmHg (1 mmHg=0.133 kPa) and IOP decrease≥20%. Follow-up visits were conducted on the 1st day, 1st week, 1st, 3rd and 6th month after surgery. The IOP value, the number of IOP-lowering medications, the proportion of surgical success (average IOP≤21 mmHg at 6 months), and complications were evaluated. Statistical methods included independent sample t-test, Mann-Whitney rank sum test, χ2 test, repeated measures two-factor analysis of variance, Bonferroni, Friedman M test, Wilcoxon, and Log-rank. The Kaplan-Meier method was used to calculate the cumulative success rate of each group. Results: Seventeen male patients (17 eyes) and 10 female patients (10 eyes) were included. The mean age was (39.9±17.7) years old. There were 11 patients in the KDB group and 16 patients in the Trabectome group. There was no significant difference in clinical baseline conditions between the two groups (P>0.05). The IOPs in the KDB and Trabectome groups at postoperative 1 week [(16.6±6.3) and (16.4±4.1) mmHg) and 6 months [(17.8±5.3) and (19.9±4.4) mmHg) were lower than those before surgery [(25.1±9.3) and (27.4±9.1) mmHg) (all P<0.05). There was no significant difference in the overall IOP between groups (P>0.05). The IOP reduction rates in the KDB and Trabectome groups were 23.4% and 19.0%, with no significant difference (P=0.674). The numbers of IOP-lowering medications used in the KDB and Trabectome groups at 3 months [2.0 (1.0, 4.0) and 2.0 (1.0, 2.3)] and 6 months [2.0 (0.0, 4.0) and 2.0 (1.0, 3.0)] after surgery were not significantly different from those before surgery [4.0 (2.0, 4.0) and 3.0 (2.0, 4.0)] (both P>0.05). There was no statistical significance in the overall number of IOP-lowering medications used between the two groups (P>0.05). There was also no statistically significant difference in the proportion of patients with an IOP decrease of≥20% and the proportion of patients whose mean postoperative IOP was≤21 mmHg (all P>0.05). The proportions of IOP≤21 mmHg in the KDB group and the Trabectome group at 6 months after surgery were 81.8% and 68.8% (P>0.05). Serious intraoperative or postoperative complications occurred in neither group. Conclusions: Both KDB trabeculotomy and Trabectome surgery can effectively reduce IOP and have a good safety profile in treating POAG, with the same number of IOP-lowering medications.

BPTF Drives Gastric Cancer Resistance to EGFR Inhibitor by Epigenetically Regulating the C-MYC/PLCG1/Perk Axis

Erlotinib, an EGFR tyrosine kinase inhibitor, is used for treating patients with cancer exhibiting EGFR overexpression or mutation. However, the response rate of erlotinib is low among patients with gastric cancer (GC). The findings of this study illustrated that the overexpression of bromodomain PHD finger transcription factor (BPTF) is partially responsible for erlotinib resistance in GC, and the combination of the BPTF inhibitor AU-1 with erlotinib synergistically inhibited tumor growth both in vivo and in vitro. AU-1 inhibited the epigenetic function of BPTF and decreased the transcriptional activity of c-MYC on PLCG1 by attenuating chromosome accessibility of the PLCG1 promoter region, thus decreasing the expression of p-PLCG1 and p-Erk and eventually improving the sensitivity of GC cells to erlotinib. In patient-derived xenograft (PDX) models, AU-1 monotherapy exhibited remarkable tumor-inhibiting activity and is synergistic anti-tumor effects when combined with erlotinib. Altogether, the findings illustrate that BPTF affects the responsiveness of GC to erlotinib by epigenetically regulating the c-MYC/PLCG1/pErk axis, and the combination of BPTF inhibitors and erlotinib is a viable therapeutic approach for GC.

Androgen receptor promotes cell stemness via interacting with co-factor YAP1 in gastric cancer

Cancer stem cells (CSCs) have been proposed to explain tumor relapse and chemoresistance in various types of cancers, and androgen receptor (AR) has been emerged as a potential regulator of stemness in cancers. However, the underlying mechanism of AR-regulated CSCs properties and chemoresistance in gastric cancer (GC) remains unknown. Here, we shown that AR is upregulated in GC tissues and correlates with poor survival rate and CSCs phenotypes of GC patients. According to our experimental data, overexpression of AR upregulated the expression of CSCs markers and this was consistent with the result concluded from data analysis that the expression of AR was positively correlated with CD44 in GC patients. In addition, AR overexpression obviously enhanced the tumor sphere formation ability and chemoresistance of GC cells in vitro. Whereas these effects were attenuated by inhibition of AR. These results were further validated in vivo that MGC-803 cells overexpressing AR had stronger properties to initiate gastric tumorigenesis than the control cells, and inhibition of AR increased the chemosensitivity of GC cells. Mechanically, AR upregulated CD44 expression by directly binding to its promoter region and Yes-associated protein 1 (YAP1) served as the co-factor of AR, which was demonstrated by the fact that the promoting effects of AR on GC cells stemness were partially counteracted by YAP1 knockdown. Thus, this study revealed that AR facilitates CSCs properties and chemoresistance of GC cells via forming complex with YAP1and indicates a potential therapeutic approach to GC patients.

[A preliminary study on the efficacy and safety of a new type of trabeculotome tunnelling trabeculoplasty for open-angle glaucoma]

Objective: To compare the efficacy and safety of trabeculotome tunnelling trabeculoplasty and gonioscopy-assisted transluminal trabeculotomy (GATT) in the treatment of open-angle glaucoma. Methods: A prospective randomized controlled study. The patients with open-angle glaucoma diagnosed in the ophthalmology center of Beijing Tongren Hospital affiliated to Capital Medical University from January to July 2022 were collected and divided into GATT group (undergoing GATT) and 3T group (undergoing 3T operation) using a random number table. Intraocular pressure (IOP) was recorded for both groups at 1 day, 1 week, 1 month, and 3 months after the operation, and the types and quantities of anti-glaucoma drugs used, postoperative complications, and surgical success rate were compared. Normal distribution measurement data were analyzed using independent sample t-tests, non-normal distribution measurement data were analyzed using non-parametric tests, and counting data were analyzed using chi-square tests. Results: This study included 35 patients (43 eyes), consisting of 27 males and 8 females, with an average age of (43.0±14.3) years. There were 21 patients (23 eyes) in the GATT group and 19 patients (20 eyes) in the 3T group. The maximum IOP without anti-glaucoma drugs before surgery, the highest IOP with the maximum number of anti-glaucoma drugs, and the IOP at 3 months after surgery in the GATT group were (33.5±9.1), (22.2±6.1), and (16.0±3.1) mmHg (1 mmHg=0.133 kPa), respectively. The corresponding values for the 3T group were (35.2±7.8), (21.5±6.8), and (16.1±2.0) mmHg. After surgery, the IOP in both groups was lower than before surgery, with a statistically significant difference (P<0.05) and no significant difference between the two groups (P>0.05). In the 3 months following surgery, 13 eyes in the GATT group and 11 eyes in the 3T group received more than two types of anti-glaucoma drugs, with no significant difference between the two groups (P>0.05). Three months after surgery, the complete and conditional success rates of the GATT group were 14/18 and 16/18, respectively, and those of the 3T group were 12/15 and 13/15, respectively, with no significant difference between the two groups (P>0.05). The incidence of hyphema, ciliary detachment, and shallow anterior chamber 1 day after surgery was 91%(21/23), 35%(8/23), and 30%(7/23), respectively, in the GATT group and 55%(11/20), 5%(1/20), and 0 in the 3T group, with a statistically significant difference between the two groups (P<0.05). Conclusion: 3T and GATT have similar success rates in the treatment of open-angle glaucoma. However, compared with GATT, 3T has fewer complications and is considered to be safer. (This article was published ahead of print on the Online-First Publishing Platform for Excellent Scientific Researches of Chinese Medical Association Publishing House on February 28, 2023).

VPS35 promotes cell proliferation via EGFR recycling and enhances EGFR inhibitors response in gastric cancer

BACKGROUND

Vacuolar protein sorting-associated protein 35 (VPS35) is a core component of the retromer complex which mediates intracellular protein transport. It is well known that dysfunctional VPS35 functions in the accumulation of pathogenic proteins. In our previous study, VPS35 was found to be a potential gene related to poor prognosis in gastric cancer. However, the biological functions of VPS35 in gastric cancer remain unclear.

METHODS

Cell viability assays were performed to examine whether VPS35 affected cell proliferation. Immunoprecipitation and biotin assays showed that VPS35 bound to epidermal growth factor receptor (EGFR) in the cytoplasm and recycled it to the cell surface. Patient-derived xenografts and organoids were used to evaluate the effect of VPS35 on the response of gastric cancer to EGFR inhibitors.

FINDINGS

VPS35 expression levels were upregulated in tumour tissues and correlated with local tumour invasion and poor survival in patients with gastric cancer. VPS35 promoted cell proliferation and increased tumour growth. Mechanistically, VPS35 selectively bound to endocytosed EGFR in early endosomes and recycled it back to the cell surface, leading to the downstream activation of the ERK1/2 pathway. We also found that high VPS35 expression levels increased the sensitivity of the xenograft and organoid models to EGFR inhibitors.

INTERPRETATION

VPS35 promotes cell proliferation by recycling EGFR to the cell surface, amplifying the network of receptor trafficking. VPS35 expression levels are positively correlated with gastric cancer sensitivity to EGFR inhibitors, which offers a potential method to stratify patients for EGFR inhibitor utilisation.

FUNDING

National Natural Science Foundation of China.

Identification of prognostic gene expression signatures based on the tumor microenvironment characterization of gastric cancer

Increasing evidence has elucidated that the tumor microenvironment (TME) shows a strong association with tumor progression and therapeutic outcome. We comprehensively estimated the TME infiltration patterns of 111 gastric cancer (GC) and 21 normal stomach mucosa samples based on bulk transcriptomic profiles based on which GC could be clustered as three subtypes, TME-Stromal, TME-Mix, and TME-Immune. The expression data of TME-relevant genes were utilized to build a GC prognostic model—GC_Score. Among the three GC TME subtypes, TME-Stomal displayed the worst prognosis and the highest GC_Score, while TME-Immune had the best prognosis and the lowest GC_Score. Connective tissue growth factor (CTGF), the highest weighted gene in the GC_Score, was found to be overexpressed in GC. In addition, CTGF exhibited a significant correlation with the abundance of fibroblasts. CTGF has the potential to induce transdifferentiation of peritumoral fibroblasts (PTFs) to cancer-associated fibroblasts (CAFs). Beyond characterizing TME subtypes associated with clinical outcomes, we correlated TME infiltration to molecular features and explored their functional relevance, which helps to get a better understanding of carcinogenesis and therapeutic response and provide novel strategies for tumor treatments.

Preliminary Screening of a Familial Tuberous Sclerosis Complex Pathogenic Gene

Purpose

The aim of this study was to screen the possible pathogenic genes of one family with tuberous sclerosis complexes (TSCs).

Patients and Methods

All family members were examined through detailed clinical evaluations, auxiliary examinations and CT. Then, we selected five members from this TSC family as the test samples. They were analysed by a new exon group sequencing method. Single nucleotide polymorphisms (SNPs) were screened by using databases, such as dbSNP and HAPMAP, and then the candidate genes were selected. Genes were analysed, and finally, the most likely mutation sites were screened. The results were examined by Sanger sequencing.

Results

In this TSC family, we identified c.913+2T>G, a splicing site mutation in the 9th intron region of TSC1. Family members without TSC did not have this mutation.

Conclusion

The mutations in the intron regions cannot be ruled out as a pathogenic factor for TSC.

The dynamic alteration of transcriptional regulation by crucial TFs during tumorigenesis of gastric cancer

Background

The mechanisms of Gastric cancer (GC) initiation and progression are complicated, at least partly owing to the dynamic changes of gene regulation during carcinogenesis. Thus, investigations on the changes in regulatory networks can improve the understanding of cancer development and provide novel insights into the molecular mechanisms of cancer.

Methods

Differential co-expression analysis (DCEA), differential gene regulation network (GRN) modeling and differential regulation analysis (DRA) were integrated to detect differential transcriptional regulation events between gastric normal mucosa and cancer samples based on GSE54129 dataset. Cytological experiments and IHC staining assays were used to validate the dynamic changes of CREB1 regulated targets in different stages.

Results

A total of 1955 differentially regulated genes (DRGs) were identified and prioritized in a quantitative way. Among the top 1% DRGs, 14 out of 19 genes have been reported to be GC relevant. The four transcription factors (TFs) among the top 1% DRGs, including CREB1, BPTF, GATA6 and CEBPA, were regarded as crucial TFs relevant to GC progression. The differentially regulated links (DRLs) around the four crucial TFs were then prioritized to generate testable hypotheses on the differential regulation mechanisms of gastric carcinogenesis. To validate the dynamic alterations of gene regulation patterns of crucial TFs during GC progression, we took CREB1 as an example to screen its differentially regulated targets by using cytological and IHC staining assays. Eventually, TCEAL2 and MBNL1 were proved to be differentially regulated by CREB1 during tumorigenesis of gastric cancer.

Conclusions

By combining differential networking information and molecular cell experiments verification, testable hypotheses on the regulation mechanisms of GC around the core TFs and their top ranked DRLs were generated. Since TCEAL2 and MBNL1 have been reported to be potential therapeutic targets in SCLC and breast cancer respectively, their translation values in GC are worthy of further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00468-7.

Identification of ARGLU1 as a potential therapeutic target for gastric cancer based on genome-wide functional screening data

BACKGROUND

Due to the molecular mechanism complexity and heterogeneity of gastric cancer (GC), mechanistically interpretable biomarkers were required for predicting prognosis and discovering therapeutic targets for GC patients.

METHODS

Based on a total of 824 GC-specific fitness genes from the Project Score database, LASSOCox regression was performed in TCGA-STAD cohort to construct a GC Prognostic (GCP) model which was then evaluated on 7 independent GC datasets. Targets prioritization was performed in GC organoids. ARGLU1 was selected to further explore the biological function and molecular mechanism. We evaluated the potential of ARGLU1 serving as a promising therapeutic target for GC using patients derived xenograft (PDX) model.

FINDINGS

The 9-gene GCP model showed a statistically significant prognostic performance for GC patients in 7 validation cohorts. Perturbation of SSX4, DDX24, ARGLU1 and TTF2 inhibited GC organoids tumor growth. The results of tissue microarray indicated lower expression of ARGLU1 was correlated with advanced TNM stage and worse overall survival. Over-expression ARGLU1 significantly inhibited GC cells viability in vitro and in vivo. ARGLU1 could enhance the transcriptional level of mismatch repair genes including MLH3, MSH2, MSH3 and MSH6 by potentiating the recruitment of SP1 and YY1 on their promoters. Moreover, inducing ARGLU1 by LNP-formulated saRNA significantly inhibited tumor growth in PDX model.

INTERPRETATION

Based on genome-wide functional screening data, we constructed a 9-gene GCP model with satisfactory predictive accuracy and mechanistic interpretability. Out of nine prognostic genes, ARGLU1 was verified to be a potential therapeutic target for GC.

FUNDING

National Natural Science Foundation of China.

DysRegSig: an R package for identifying gene dysregulations and building mechanistic signatures in cancer

Summary

Dysfunctional regulations of gene expression programs relevant to fundamental cell processes can drive carcinogenesis. Therefore, systematically identifying dysregulation events is an effective path for understanding carcinogenesis and provides insightful clues to build predictive signatures with mechanistic interpretability for cancer precision medicine. Here, we implemented a machine learning-based gene dysregulation analysis framework in an R package, DysRegSig, which is capable of exploring gene dysregulations from high-dimensional data and building mechanistic signature based on gene dysregulations. DysRegSig can serve as an easy-to-use tool to facilitate gene dysregulation analysis and follow-up analysis.

Availability and implementation

The source code and user’s guide of DysRegSig are freely available at Github: https://github.com/SCBIT-YYLab/DysRegSig.

Supplementary information

Supplementary data are available at Bioinformatics online.

Electrospinning for healthcare: recent advancements

This perspective explores recent developments and innovations in the electrospinning technique and their potential applications in biomedicine.

Gene dysregulation analysis builds a mechanistic signature for prognosis and therapeutic benefit in colorectal cancer

The implementation of cancer precision medicine requires biomarkers or signatures for predicting prognosis and therapeutic benefits. Most of current efforts in this field are paying much more attention to predictive accuracy than to molecular mechanistic interpretability. Mechanism-driven strategy has recently emerged, aiming to build signatures with both predictive power and explanatory power. Driven by this strategy, we developed a robust gene dysregulation analysis framework with machine learning algorithms, which is capable of exploring gene dysregulations underlying carcinogenesis from high-dimensional data with cooperativity and synergy between regulators and several other transcriptional regulation rules taken into consideration. We then applied the framework to a colorectal cancer (CRC) cohort from The Cancer Genome Atlas. The identified CRC-related dysregulations significantly covered known carcinogenic processes and exhibited good prognostic effect. By choosing dysregulations with greedy strategy, we built a four-dysregulation (4-DysReg) signature, which has the capability of predicting prognosis and adjuvant chemotherapy benefit. 4-DysReg has the potential to explain carcinogenesis in terms of dysfunctional transcriptional regulation. These results demonstrate that our gene dysregulation analysis framework could be used to develop predictive signature with mechanistic interpretability for cancer precision medicine, and furthermore, elucidate the mechanisms of carcinogenesis.

Systematical Analysis of the Cancer Genome Atlas Database Reveals EMCN/MUC15 Combination as a Prognostic Signature for Gastric Cancer

Digestive cancers-including gastric cancer (GC), colorectal cancer, hepatocellular carcinoma, esophageal cancer, and pancreatic cancer-accounted for 26% of cancer cases and 35% of cancer deaths worldwide in 2018. It is crucial and urgent to develop biomarkers for the diagnosis, prognosis, and therapeutic benefits of digestive cancers, especially for GC, since the incidence of GC is lower only than lung cancer in China, is hard to detect at an early stage, and is associated with poor prognosis. Mucins, glycoproteins encoded by MUC family genes, act as a part of a physical barrier in the digestive tract and participate in various signaling pathways. Some mucins have been used or proposed as biomarkers for carcinomas, such as MUC16 (CA125) and MUC4. However, there are no systematic investigations on the association of MUC family members with diagnoses and clinical outcomes even though relevant data have been largely accumulated in the past decade. By analyzing transcriptomic and clinical data of digestive cancer samples from TCGA involving colon adenocarcinoma (COAD), esophageal carcinoma (ESCA), liver hepatocellular carcinoma (LIHC), stomach adenocarcinoma (STAD), and pancreatic adenocarcinoma (PAAD), it was found that expressions levels of MUC15, MUC13, and MUC21 were individually associated with survival for digestive cancers, and high expressions of EMCN (MUC14) and MUC15 were correlated with poor survival for STAD. Cox regression analysis indicated the predictive power of an EMCN/MUC15 combination for overall survival (OS) of GC patients, which was validated on an independent dataset from GEO. EMCN/MUC15 correlated genes were identified to be enriched in cancer-related processes, such as vasculature development, mitosis, and immunity. Therefore, we propose that an EMCN/MUC15 combination could be a potential prognostic signature for gastric cancer.

Dual-responsive drug delivery systems prepared by blend electrospinning

To prepare temperature and pH dual-responsive drug delivery systems, the thermosensitive polymer poly(N-isopropylacrylamide) (PNIPAAm) was first synthesized by free-radical polymerization. It was then co-dissolved with the pH-sensitive polymer Eudragit® L100-55 (EL100-55) and processed into fibers using electrospinning. Ketoprofen (KET), a model drug, was also incorporated into the composite fibers, and fibers based on a single polymer additionally prepared. The fibers had smooth cylindrical morphologies, and no obvious phase separation could be seen. Using X-ray diffraction, KET was determined to be present in the amorphous state in the fiber matrix. FTIR spectroscopy also indicated the successful incorporation of amorphous KET in the fibers. In vitro drug release studies in media at different pH (4.5 or 7.4) or temperature (25 and 37 °C) showed that the release of KET from the blend PNIPAAm/EL100-55 fibers was dependent both on environmental temperature and pH, reflecting the dual-responsive properties of the fibers. The MTT assay was used to explore the biocompatibility of the PNIPAAm/EL100-55 composite fibers towards L929 fibroblasts. Viability was always found to be >80%, even at polymer concentrations of 100 mg/L. Therefore, the fibers prepared here could lead to the development of multi-responsive materials for drug delivery and tissue engineering.

Core-shell poly(lactide-co-ε-caprolactone)-gelatin fiber scaffolds as pH-sensitive drug delivery systems

Dual-drug-loaded pH-responsive fiber scaffolds were successfully prepared by coaxial electrospinning. These were designed with the aim of being sutured into the resection site after tumor removal, to aid recovery and prevent cancer recurrence. The shell was made up of a mixture of gelatin and sodium bicarbonate (added to provide pH-sensitivity), and was loaded with the anti-inflammatory drug ciprofloxacin; the core comprised poly(lactide-co-ε-caprolactone) with the chemotherapeutic doxorubicin hydrochloride. Scanning electron microscopy revealed most fibers were smooth and homogeneous. Transmission electron microscopy demonstrated the presence of a clear core/shell structure. The fiber scaffolds were further characterized using infrared spectroscopy and X-ray diffraction, which proved that both drugs were present in the fibers in the amorphous form. The gelatin shells were cross-linked with glutaraldehyde to enhance their stability, and water contact angle measurements used to confirm they remained hydrophilic after this process, with angles between 10 and 35°. This is important for onward applications, since a hydrophilic surface is known to encourage cell proliferation. During in vitro drug release studies, a rapid and acid-responsive release of ciprofloxacin was seen, accompanied by sustained and long-term doxorubicin release. Both the release profiles and the mechanical strength of the fibers can effectively be tuned through the sodium bicarbonate content of the fibers: for instance, the break stress varies from 2.00 MPa to 2.57 MPa with an increase in sodium bicarbonate content. The pH values of aqueous media exposed to the scaffolds decrease only slightly, by less than 0.5 pH units, over the two-month timescale, suggesting that only minimal fiber degradation occurs during this time. The fiber scaffolds also have good biocompatibility, as revealed by in vitro cytotoxicity experiments. Overall, our results demonstrate that the novel scaffolds reported here are promising pH-sensitive drug delivery systems, and may be candidates for use after tumor resection surgery.

Electrospun gelatin/sodium bicarbonate and poly(lactide-co-ε-caprolactone)/sodium bicarbonate nanofibers as drug delivery systems

In this work, we report electrospun nanofibers made of model hydrophobic (poly(lactide-co-ε-caprolactone); PLCL) and hydrophilic (gelatin) polymers. We explored the effect on drug release of the incorporation of sodium bicarbonate (SB) into these fibers, using the potent antibacterial agent ciprofloxacin as a model drug. The fibers prepared are smooth and have relatively uniform diameters lying between ca. 600 and 850nm. The presence of ciprofloxacin in the fibers was confirmed using IR spectroscopy. X-ray diffraction showed the drug to be incorporated into the fibers in the amorphous form. In vitro drug release studies revealed that, as expected, more rapid drug release was seen with gelatin fibers than those made of PLCL, and a greater final release percentage was obtained. The inclusion of SB in the gelatin fibers imparts them with pH sensitivity: gelatin/SB fibers showed faster release at pH5 than pH7.4, while fibers without SB gave the same release profiles at both pHs. The PLCL fibers have no pH sensitivity, even when SB was included, as a result of their hydrophobic structure precluding the ingress of solvent. In vitro cell culture studies showed that all the fibers are able to promote cell proliferation. The ciprofloxacin loaded fibers are effective in inhibiting Escherichia coli and Staphylococcus aureus growth in antibacterial tests. Thus, the gelatin-based fibers can be used as pH-responsive drug delivery systems, with potential applications for instance in the treatment of tumor resection sites. Should these become infected, the pH would drop, resulting in ciprofloxacin being released and the infection halted.

Neural circuits in swallowing and abdominal vagal afferent-mediated lower esophageal sphincter relaxation

The purpose of this review is to identify the medullary subnuclei that house neural circuits for lower esophageal sphincter (LES) relaxation. LES relaxation may occur as a component of primary peristalsis elicited by superior laryngeal nerve (SLN) afferent stimulation, secondary peristalsis elicited by esophageal distention or as a component of belch reflex, and transient LES relaxation elicited by gastric vagal afferent stimulation. In mice, SLN stimulation at 10 Hz elicited complete swallowing reflex, including pharyngeal and esophageal peristalsis, and LES relaxation. SLN stimulation at 5 Hz elicited pharyngeal contractions and isolated LES relaxation, which is not accompanied by esophageal peristalsis. Electric stimulation of afferents in the ventral branch of the subdiaphragmatic vagus (vSDV) at 10 Hz also elicited isolated LES relaxation. Using these defined stimuli, c-fos expression was examined in the entire craniocaudal extent of the medullary nuclei. SLN stimulation at 10 Hz induced c-fos expression in neurons in: (1) interstitial (SolI), intermediate (SolIM), central (SolCe), occasional medial (SolM), and dorsomedial (SolDM) solitary subnuclei; (2) motor neurons in the nucleus ambiguus, including its semicompact (NAsc), loose (NAl), and compact (NAc) formations; and (3) dorsal motor nucleus of vagus, including its rostral (DMVr) and caudal (DMVc) parts. The activated neurons represent neurons involved with afferent SLN-mediated reflexes, including swallowing. SLN stimulation at 5 Hz evoked c-fos expression in neurons in SolI, SolIM, SolM, and SolDM but not in SolCe; and motor neurons in NAsc, NAl, and DMVc but not in NAc or DMVr. Stimulation of vSDV induced c-fos expression in neurons in SolM and SolDM and in motoneurons in DMVc. When considered with published reports in other animal species, these data support the speculation that (1) swallow-evoked primary peristalsis involves the following neural circuits: SolI/SolIM --> NAsc/NAl for pharyngeal and SolCe --> NAc for esophageal (striated muscle) peristalsis, SolM/SolDM --> preganglionic neurons in DMVc and DMVr and nitrergic and cholinergic neurons in myenteric plexus for esophageal (smooth muscle) peristalsis, and SolM/SolDM --> preganglionic neurons in DMVc --> postganglionic nitrergic neurons in the myenteric plexus for LES relaxation; and (2) abdominal vagus-stimulated isolated LES relaxation may involve neurons in SolM and SolDM --> preganglionic motor neurons in DMVc --> postganglionic nitrergic neurons in the myenteric plexus.

Manometric heterogeneity in patients with idiopathic achalasia

BACKGROUND & AIMS

In certain cases of achalasia, particularly those in early stages with minimal endoscopic or radiographic abnormalities, the diagnosis may rely on manometry, which is the most sensitive test for the disease. The aim of this study was to critically evaluate the manometric criteria in a population of patients with idiopathic achalasia.

METHODS

Clinical histories and manometric recordings of 58 patients with idiopathic achalasia and 43 control subjects were analyzed with regard to esophageal body contraction amplitude, peristaltic effectiveness in terms of both completeness and propagation velocity, lower esophageal sphincter (LES) resting pressure, LES relaxation pressure, and intraesophageal-intragastric pressure gradient. Variants of achalasia were defined by finding manometric features that significantly differed from the remainder of achalasia patients, such that the diagnosis might be questioned.

RESULTS

Four manometrically distinct variants were identified. These variants were characterized by (1) the presence of high amplitude esophageal body contractions, (2) a short segment of esophageal body aperistalsis, (3) retained complete deglutitive LES relaxation, and (4) intact transient LES relaxation. In each instance, the most extreme variant is discussed and compared with the remainder of the achalasia population and with controls.

CONCLUSIONS

The significance in defining these variants of achalasia lies in the recognition that these sometimes confusing manometric findings are consistent with achalasia when combined with additional clinical data supportive of the diagnosis. Furthermore, such variants provide important clues into the pathophysiology of this rare disorder.

Swallowing reflex and brain stem neurons activated by superior laryngeal nerve stimulation in the mouse

The purpose of the present study was to identify vagal subnuclei that participate in reflex swallowing in response to electrical stimulation of the left superior laryngeal nerve (SLN). SLN stimulation at 10 Hz evoked primary peristalsis, including oropharyngeal and esophageal peristalsis, and LES relaxation. It also induced c-fos expression in interneurons in the interstitial (SolI), intermediate (SolIM), central (SolCe), dorsomedial (SolDM) and commissural (SolC) solitary subnuclei. Neurons in parvicellular reticular nucleus (PCRt) and area postrema (AP) and motoneurons in the semicompact (NAsc), loose (NAl), and compact (NAc) formations of the nucleus ambiguus and both rostral (DMVr) and caudal (DMVc) parts of the dorsal motor nucleus of vagus were also activated. The activated neurons represent all neurons concerned with afferent SLN-mediated reflexes, including the swallowing-related neurons. SLN stimulation at 5 Hz elicited oropharyngeal and LES but not esophageal responses and evoked c-fos expression in neurons in SolI, SolIM, SolDM, PCRt, AP, NAsc, NAl, and DMVc but not in SolCe, NAc, or DMVr. These data are consistent with the role of SolI, SolIM, SolDM, NAsc, NAl, and DMVc circuit in oropharyngeal peristalsis and LES relaxation and SolCe, NAc, DMVc, and DMVr in esophageal peristalsis and LES responses.

Lower esophageal sphincter relaxation and activation of medullary neurons by subdiaphragmatic vagal stimulation in the mouse

BACKGROUND & AIMS

Isolated lower esophageal sphincter (LES) relaxation associated with belching and vomiting and the transient LES relaxation associated with gastroesophageal reflux are gastric afferent-mediated vagovagal reflexes. We aimed to identify the brain stem vagal subnuclei involved in these reflexes.

METHODS

In anesthetized mice, LES pressures were recorded using a manometric technique and response to electrical stimulation of the ventral trunk of subdiaphragmatic vagus was investigated. Anatomy of the vagal subnuclei was defined, and activated subnuclei with ventral subdiaphragmatic vagus stimulation were detected by c-fos immunohistochemical staining.

RESULTS

Ventral subdiaphragmatic vagal stimulation elicited frequency-dependent LES relaxation without evoking esophageal contractions and induced c-fos expression in interneurons in medial, dorsomedial, and commissural subnuclei along with outer shell of area postrema and motoneurons in the caudal dorsal motor nucleus of vagus. Brain stem subnuclei including interstitial, intermediate, and central subnuclei, and nucleus ambiguous, which have been reported to be involved in the response to swallowing, were not activated.

CONCLUSIONS

Stimulation of the ventral subdiaphragmatic vagus causes isolated LES relaxation and activates neurons in select vagal subnuclei that may represent the brain stem circuit involved in the abdominal vagal-afferent-evoked isolated LES relaxation. These observations suggest that different brain stem circuits are involved in swallow-induced and gastric afferent-mediated isolated LES relaxations.

Innervation of the esophagus in mice that lack MASH1

The striated muscle of the esophagus differs from other striated muscle, because it develops by the transdifferentiation of smooth muscle, and the motor end plates receive a dual innervation from vagal (cholinergic) motor neurons and nitric oxide synthase (NOS)-containing enteric neurons. Mash1-/- mice have no enteric neurons in their esophagus and die within 48 hours of birth without milk in their stomachs (Guillemot et al. [1993] Cell 75:463-476). In this study, the innervation of the esophagus of newborn Mash1-/-, Mash1+/- and wild type mice was examined. There was no difference between Mash1-/-, Mash1+/-, and wild type mice in the transdifferentiation of the muscle and the development of nicotinic receptor clusters. However, there were significantly more cholinergic nerve terminals per motor end plate in Mash1-/- mice than Mash1+/- or wild type mice. Each of the Mash1-/- mice had fewer than 50 NOS neurons per esophagus, compared with approximately 3,000 in wild type mice. Newborn Mash1+/- mice also contained significantly fewer NOS neurons than wild type mice. In Mash1-/- mice, NOS nerve fibers were virtually absent from the external muscle but were present at the myenteric plexus. Unlike that of newborn wild type mice, the lower esophageal sphincter of Mash 1-/- mice lacked NOS nerve fibers; this may explain the absence of milk in the stomach. We conclude that 1) the transdifferentiation of the esophageal muscle and the development of the extrinsic innervation do not require enteric neurons or MASH1, 2) extrinsic NOS neurons only innervate the myenteric plexus.

The origin and development of the vagal and spinal innervation of the external muscle of the mouse esophagus

Retrograde and anterograde tracing and immunohistochemical techniques were used to examine the origin of the extrinsic innervation, and the development of the vagal innervation to the mouse esophagus. Cholinergic nerve terminals were localised using an antiserum to the vesicular acetylcholine transporter and cholinergic cell bodies were localised using an antiserum to choline acetyltransferase. Cholinergic nerve terminals, which also contained calcitonin gene-related peptide, were present at the motor end plates in the external (striated) muscle of the esophagus. Following injection of Fast Blue into subdiaphragmatic or cervical levels of the esophagus, the only retrogradely-labelled cholinergic nerve cell bodies that also contained calcitonin gene-related peptide were found in the nucleus ambiguus. Neurons in the dorsal motor nucleus of the vagus, the nodose ganglia and dorsal root ganglia gave rise to a number of different types of nerve terminals within the myenteric plexus. Retrogradely-labelled neurons in the dorsal motor nucleus of vagus contained cholinergic markers only, nitric oxide synthase only or cholinergic markers plus nitric oxide synthase, retrogradely-labelled neurons in the dorsal root ganglia contained calcitonin gene-related peptide only, and a small number of retrogradely-labelled neurons in the nodose ganglia contained tyrosine hydroxylase. The development of the vagal innervation to the esophagus was examined following application of DiI to the vagus nerve of fixed mouse embryos. Anterogradely-labelled nerve fibres, which arose from both nodose ganglia and the medulla, were already present in the esophagus of embryonic day 12 (E12) mice. Some of the DiI-labelled vagal nerve fibres were present in among the smooth muscle cells of the external muscle layer prior to their transdifferentiation to striated muscle. We conclude that the neurons in the nucleus ambiguus that project to the esophagus differ from other extrinsic neurons in their chemistry as well as their targets within the esophagus. The development of the extrinsic innervation precedes the transdifferentiation of the external muscle to striated muscle, raising the possibility that, during development, smooth muscle of the esophagus is innervated transiently by vagal neurons.

The identification and chemical coding of cholinergic neurons in the small and large intestine of the mouse

BACKGROUND

The recent availability of antisera to the vesicular acetylcholine transporter (VAChT) and choline acetyltransferase (ChAT) that demonstrate peripheral cholinergic neurons has made possible the anatomical identification of cholinergic neurons in the enteric nervous system. In this study, we localised cholinergic neurons in the mouse small and large intestine and identified which substances are found colocalised in the cholinergic neurons.

METHODS

Immunohistochemical single and double staining techniques were used on whole mount preparations and frozen sections to examine the localisation and chemical coding of cholinergic neurons in the small and large intestine of the mouse. Cholinergic neurons were identified using antisera to ChAT or VAChT.

RESULTS

In both the small and large intestine, numerous ChAT-immunoreactive nerve cell bodies were present in the myenteric and submucous ganglia, and ChAT- and VAChT-immunoreactive nerve terminals were abundant in the myenteric and submucous plexuses and the external muscle. Previous studies have identified two major classes of myenteric neurons in the small intestine of the mouse--those containing calretinin plus substance P, and those containing nitric oxide synthase (NOS) plus vasoactive intestinal peptide (VIP). Double-label studies showed that the vast majority of the calretinin/substance P neurons were cholinergic neurons, whereas only a small proportion of the NOS/VIP cells were cholinergic; the noncholinergic NOS/VIP neurons were motor neurons or interneurons, whereas the cholinergic NOS/VIP neurons appeared to be exclusively interneurons. In the small intestine, all of the 5-HT-loaded neurons and a subpopulation of the calbindin neurons were also cholinergic. In the large intestine, there was a pattern of overlaps similar to that found in the small intestine, except that in the large intestine approximately 25% of the calretinin cells were not cholinergic. Only approximately one third of the GABA-loaded neurons in the large intestine were cholinergic.

CONCLUSIONS

Large subpopulations of motor neurons and interneurons in the mouse small intestine are cholinergic neurons.

The identification and chemical coding of cholinergic neurons in the small and large intestine of the mouse

BACKGROUND

The recent availability of antisera to the vesicular acetylcholine transporter (VAChT) and choline acetyltransferase (ChAT) that demonstrate peripheral cholinergic neurons has made possible the anatomical identification of cholinergic neurons in the enteric nervous system. In this study, we localised cholinergic neurons in the mouse small and large intestine and identified which substances are found colocalised in the cholinergic neurons.

METHODS

Immunohistochemical single and double staining techniques were used on whole mount preparations and frozen sections to examine the localisation and chemical coding of cholinergic neurons in the small and large intestine of the mouse. Cholinergic neurons were identified using antisera to ChAT or VAChT.

RESULTS

In both the small and large intestine, numerous ChAT-immunoreactive nerve cell bodies were present in the myenteric and submucous ganglia, and ChAT- and VAChT-immunoreactive nerve terminals were abundant in the myenteric and submucous plexuses and the external muscle. Previous studies have identified two major classes of myenteric neurons in the small intestine of the mouse--those containing calretinin plus substance P, and those containing nitric oxide synthase (NOS) plus vasoactive intestinal peptide (VIP). Double-label studies showed that the vast majority of the calretinin/substance P neurons were cholinergic neurons, whereas only a small proportion of the NOS/VIP cells were cholinergic; the noncholinergic NOS/VIP neurons were motor neurons or interneurons, whereas the cholinergic NOS/VIP neurons appeared to be exclusively interneurons. In the small intestine, all of the 5-HT-loaded neurons and a subpopulation of the calbindin neurons were also cholinergic. In the large intestine, there was a pattern of overlaps similar to that found in the small intestine, except that in the large intestine approximately 25% of the calretinin cells were not cholinergic. Only approximately one third of the GABA-loaded neurons in the large intestine were cholinergic.

CONCLUSIONS

Large subpopulations of motor neurons and interneurons in the mouse small intestine are cholinergic neurons.

Development of nicotinic receptor clusters and innervation accompanying the change in muscle phenotype in the mouse esophagus

During development, the external muscle of the mouse esophagus undergoes a transdifferentiation from smooth to striated muscle (Patapoutian et al. [1995] Science 270:1818-1821). We now report on the development of the innervation accompanying the change in phenotype of the external muscle of the mouse esophagus. The phenotype of the muscle was monitored by using light and electron microscopy. Nicotinic acetylcholine receptors were localised by using a fluorescence conjugate of alpha-bungarotoxin, and neural elements were localised by using antisera to synaptophysin (a synaptic vesicle protein that was used to label all nerve terminals), the vesicular acetylcholine transporter (VAChT), calcitonin gene-related peptide (CGRP), nitric oxide synthase (NOS), and vasoactive intestinal peptide (VIP). CGRP and VAChT were co-localised in the terminals of vagal motoneurons that innervate the external muscle, and NOS and VIP were co-localised in intrinsic (enteric) neurons, which provide some terminals that are associated with motor endplates. Cells exhibiting striations were first observed in the outer layers of the most rostral regions of the esophagus of embryonic day 15 (E15) mice. Clusters of nicotinic acetylcholine receptors were also first observed at the rostral end of the esophagus of E15 mice, and developed in a rostrocaudal progression that coincided with the appearance of striations within the muscle cells. Synaptophysin-, VAChT- and NOS-immunoreactive nerve terminals were present within the external muscle prior to the formation of receptor clusters, and their appearance did not follow any apparent rostrocaudal sequence. Surprisingly, not all of the receptor clusters at E15 had synaptophysin- and VAChT-immunoreactive nerve terminals closely associated with them. However, from E18 on, almost all of the clusters had synaptophysin-immunoreactive nerve terminals in close association. At late embryonic and early postnatal stages, there was a rostrocaudal gradient in the proportion of receptor clusters having VAChT-immunoreactive nerve terminals associated with them. Nerve terminals associated with nicotinic receptor clusters did not show detectable CGRP-immunoreactivity until one to two weeks after the appearance of synaptophysin- and VAChT-immunoreactivity. The NOS-immunoreactive neurons did not show detectable VIP-immunoreactivity until three days after NOS could be detected. These results show that the appearance of clusters of nicotinic receptors in the external muscle of the esophagus coincides with the expression of a striated muscle phenotype, but not with the presence of ingrowing nerve terminals. However, many of the receptor clusters that were observed first were apparently uninnervated.

Projections of chemically identified myenteric neurons of the small and large intestine of the mouse

The projections of different subpopulations of myenteric neurons in the mouse small and large intestine were examined by combining immunohistological techniques with myotomy and myectomy operations. The myotomies were used to examine the polarity of neurons projecting within the myenteric plexus and showed that neurons containing immunoreactivity for nitric oxide synthase (NOS), vasoactive intestinal peptide (VIP), calbindin and 5-HT projected anally, while neurons with substance P (SP)-immunoreactivity projected orally, in both the small and large intestine. Neurons containing neuropeptide Y (NPY)- and calretinin-immunoreactivity projected locally. In the large intestine, GABA-immunoreactive neurons projected both orally and anally, with more axons tending to project anally. Myectomy operations revealed that circular muscle motor neurons containing NOS/VIP/ +/-NPY and calretinin neurons projected anally both in the small and large intestine, while SP-immunoreactive circular muscle motor neurons projected orally. In the large intestine, GABA-IR circular muscle motor neurons projected both orally and anally. This study showed that although some neurons, such as the NOS/VP inhibitory motor neurons and interneurons, SP excitatory motor neurons and 5-HT interneurons had similar projections to those in other species, the projections of other chemical classes of neurons in the mouse intestine differed from those reported in other species.

Chemical coding of neurons in the myenteric plexus and external muscle of the small and large intestine of the mouse

Immunohistochemical techniques were used to examine the presence and co-localisation of a range of putative neurotransmitters and other neuronal markers in the myenteric plexus of the small and large intestine of the mouse. Distinct sub-populations of myenteric neurons were identified, based on the combinations of substances they contained and the distribution of their fibres. In the small intestine, there were two major classes of circular muscle motor neurons; one class was characterised by the presence of nitric oxide synthase, vasoactive intestinal peptide plus neuropeptide Y (NOS/VIP/NPY), and the second class contained calretinin plus substance P (CalR/SP). There were seven classes of neurons that innervated myenteric ganglia; these contained nos, vip, nos/vip, npy, calr/calbindin (calb), sp or 5-ht. In the large intestine, there were five major classes of motor neurons that contained nos, nos/vip, gaba, sp, or calr/sp, and seven major classes of neurons that innervated myenteric ganglia and contained nos, vip, calr/calb, calr, sp, gaba or 5-ht. Although some aspects of the patterns of co-localisation are similar to those in other species, this study re-inforces recent analyses that indicate significant species differences in neurochemical patterns in the enteric neurons of different species.