Simon E. Kenny

Characterisation and transplantation of enteric nervous system progenitor cells

Aims: Enteric nervous system (ENS) progenitor cells have been postulated to be an appropriate source of cells for the treatment of Hirschsprung’s disease. In order for this to be successful, the techniques previously used for the isolation of rodent ENS progenitor cells need to be adapted for postnatal human tissue. In this paper, we describe a method suitable for the preparation of both mouse and human postnatal ENS progenitor cells and assess their transplantation potential. Method: Single cell suspensions were isolated from 11.5 days post-coitum embryonic mouse caecum and postnatal human myenteric plexus. These cells were cultured under non-adherent conditions to generate neurospheres which were implanted into aganglionic embryonic mouse hindgut explants. Cell proliferation, migration and differentiation were observed using immunofluorescence microscopy. Results: Neurospheres generated from both mouse and human tissues contained proliferating neural crest-derived cells that could be expanded in tissue culture to generate both glial cells and neurons. When implanted into aganglionic murine gut, cells migrated from the neurospheres using pathways appropriate for cells derived from the neural crest, and differentiated to become glia and neurons expressing neuronal phenotypic markers characteristic of the ENS including nitric oxide synthase and vasoactive intestinal polypeptide. Conclusion: We have developed a technique for the isolation and expansion of ENS progenitor cells from human neonates. These cells have the ability to differentiate into neurons and glia when transplanted into aganglionic gut, this demonstration being a necessary first step for their autologous transplantation in the treatment of Hirschsprung’s disease.

Human and Mouse Enteric Nervous System Neurosphere Transplants Regulate the Function of Aganglionic Embryonic Distal Colon

BACKGROUND & AIMS Recent advances have raised the possibility of treating enteric nervous system (ENS) disorders with transplanted progenitor cells (ENSPC). Although these cells have been shown to migrate and differentiate after transplantation, no functional effects have been demonstrated. We therefore aimed to investigate whether embryonic mouse and neonatal human ENSPC can regulate the contractility of aganglionic bowel. METHODS Embryonic mouse and neonatal human ENSPC were grown as neurospheres before transplantation into aganglionic embryonic mouse hindgut explants and culture for 8-12 days. Engraftment and neural differentiation were confirmed using immunofluorescence and transmission electron microscopy. The contraction frequency of transplanted bowel was measured and compared with that of embryonic day 11.5 embryonic ganglionic and aganglionic bowel cultured for the same period. Calcium movement was measured at spatially defined points in bowel wall smooth muscle. Neural modulation of bowel contractility was assessed using tetrodotoxin. RESULTS Both mouse and human ENSPC migrated and differentiated after neurosphere transplantation. Transmission electron microscopy demonstrated the existence of synapses. Transplantation restored the high contraction frequency of aganglionic bowel to the lower rate of ganglionic bowel. Calcium imaging demonstrated that neurosphere transplantation coordinates intracellular free calcium levels. Both these effects were reversed by the addition of tetrodotoxin, indicating the functional effect of neurosphere-derived neurons. CONCLUSIONS Neonatal human gut is a source of ENSPC that can be transplanted to restore the contractile properties of aganglionic bowel by a neurally mediated mechanism. This may aid development of a stem cell-based treatment for Hirschsprungs disease.

Expression of endothelin 3 by mesenchymal cells of embryonic mouse caecum

Background Mutations in endothelin 3 (EDN3) and endothelin B receptor (EDNRB) genes cause terminal colonic aganglionosis in mice, and mutations in these genes have also been linked to the terminal aganglionosis seen in human Hirschsprung’s disease. However, details of EDN3 expression during embryogenesis are lacking, and consequently the cellular mechanism by which EDN3 regulates innervation of the terminal gut is unclear. Aims To localise the expression of EDN3 and EDNRB in the embryonic mouse gut. Methods Expression of EDN3 and EDNRB mRNA was analysed by reverse transcription polymerase chain reaction and in situ hybridisation. Results High levels of EDN3 mRNA expression were restricted to mesenchymal cells of the caecum before and after the arrival of neural crest cells. In contrast, EDNRB expression along the gut displayed a time dependent pattern similar to those of the protein tyrosine kinase ret and the neural crest cell marker PGP9.5. Conclusions Mesenchymal cells of the caecum express high levels of EDN3 mRNA during embryogenesis and hence the production of EDN3 at the caecum is likely to act on neural crest cells as a paracrine factor necessary for subsequent innervation of the terminal gut.

Hirschsprung's disease

Hirschsprungs disease (HSCR) is characterized by absence of the enteric nervous system in a variable portion of the distal gut. Affected infants usually present in the days after birth with bowel obstruction. Despite surgical advances, long-term outcomes remain variable. In the last 2 decades, great advances have been made in understanding the genes and molecular biological mechanisms that underlie the disease. In addition, our understanding of normal enteric nervous system development and how motility develops in the developing fetus and infant has also increased. This review aims to draw these strands together to explain the developmental and biological basis of HSCR, and how this knowledge may be used in the future to aid children with HSCR.

Trends in paediatric circumcision and its complications in England between 1997 and 2003

It has been suggested that too many English boys undergo circumcision. This report describes how circumcision rates have changed in England between 1997 and 2003, including data on complication rates and on how age, medical indication and surgical specialty affect postoperative haemorrhage rates.

Evidence-based surgery: interventions in a regional paediatric surgical unit

OBJECTIVES To determine the proportion of paediatric surgical interventions that are evidence-based and to identify areas where randomised controlled trials (RCTs) or further research are required. DESIGN Prospective review of paediatric general surgical inpatients. SETTING A regional paediatric surgical unit. SUBJECTS All consecutive paediatric general surgical patients admitted in November, 1995. MAIN OUTCOME MEASURES Each patient on whom a diagnosis had been made was allocated a primary diagnosis and primary intervention (n=281). On the basis of expert knowledge, Plusnet Medline, and ISI Science Citation database searches, each intervention was categorised according to the level of supporting evidence: category 1, intervention based on RCT evidence; category 2, intervention with convincing non-experimental evidence such that an RCT would be unethical and unjustified; category 3, intervention without substantial supportive evidence. RESULTS Of 281 patient interventions, 31 (11%) were based on controlled trials and 185 (66%) on convincing non-experimental evidence. Only 23% of interventions were category 3. CONCLUSIONS In common with other medical specialties, the majority of paediatric surgical interventions are based on sound evidence. However, only 11% of interventions are based on RCT data, perhaps reflecting the nature of surgical practice. Further RCTs or research is indicated in a proportion of category 3 interventions.

Evolving experience in the management of empyema thoracis

The optimal management of paediatric empyema thoracis remains controversial. The objective of the study was to analyse evolving experience in clinical presentation, management, outcome and factors contributing to adverse morbidity in thoracic empyema. Forty‐seven patients presenting to a paediatric surgical centre were studied in three consecutive 6‐y periods during 1980‐97 to compare any change in the pattern of disease influencing diagnosis and management. Patients were categorized into two treatment groups: (i) conservative management (antibiotics and/or tube thoracostomy), (ii) thoracotomy. The median duration of illness prior to hospital admission was 10 d (range 1‐42 d). Ultrasound was increasingly utilized in the diagnosis and staging of empyema and played an important role in directing definitive management. The presence of loculated pleural fluid determined the need for thoracotomy. Sixteen of 20 patients (80%) who were initially treated with thoracocentesis or tube thoracostomy eventually needed thoracotomy. There was a positive shift in management towards early thoracotomy resulting in prompt symptomatic recovery. Significant complications were noted in seven children who had delayed thoracotomy. These included recurrent empyema with lung abscess (n= 2), scoliosis (n= 2), restrictive lung disease (n= 1), bronchopleural fistula (n= 1) and sympathetic pericardial effusion (n= 1). An unfavourable experience with delayed thoracotomy during the study period has led us to adopt a more aggressive early operative approach to empyema thoracis. The decision to undertake thoracotomy has been influenced by the ultrasound findings of organized loculated pleural fluid. Delayed surgery was associated with adverse outcome.

Time-dependent effects of endothelin-3 on enteric nervous system development in an organ culture model of Hirschsprung's disease.

BACKGROUND/PURPOSE Terminal colonic aganglionosis (Hirschsprung disease) results from incomplete rostrocaudal colonisation of the embryonic gut by neural crest cells (NCC). Mutations in the genes encoding endothelin-3 (EDN3) or its receptor (EDNRB) have been shown to result in a similar aganglionosis. This article describes the development of an organ culture model using embryonic murine gut to determine how endothelin-3 regulates development of the enteric nervous system. METHODS Gut explants from mice of different gestational ages were cultured for up to 3 days in the presence or absence of 5 micromol/L of the specific endothelin-B receptor antagonist BQ788. EDN3 and EDNRB mRNA expression were analysed by reverse-transcription polymerase chain reaction (RT-PCR) and whole-mount in situ hybridisation. NCC were localised using immunoreactivity for PGP 9.5, a specific neuronal marker. RESULTS EDN3 mRNA continued to be expressed by caecal mesenchymal cells and EDNRB mRNA by the migrating NCC in culture. Embryonic day (E)11.5 explants were already colonised by NCC up to the terminal ileum. Complete colonisation occurred in organ culture over the next 72 hours (equivalent to E 14.5). Explants of E 12.5 and E 13.5 showed complete colonisation after 48 and 24 hours culture, respectively. Terminal aganglionosis resulted from treatment of E 11.5 and E 12.5 gut explants with 5 micromol/L BQ788, whereas there was no inhibitory effect on E 13.5 explants. CONCLUSIONS An organ culture model has been developed in which NCC colonisation of embryonic gut mirrors that described in vivo. Blockade of the EDN3/EDNRB receptor pathway shows that the interaction of endothelin-3 with its receptor is only necessary for NCC colonisation at early time-points, despite the continued expression of endothelin-3 mRNA in the gut.

Assessment of protein gene product 9.5 as a marker of neural crest-derived precursor cells in the developing enteric nervous system.

Abstract The neurons and glial cells of the enteric nervous system (ENS) are derived from the neural crest. To study the developmental events involved in congenital abnormalities of the ENS, it is essential to identify all neural-crest cells (NCC) in the prenatal gut. The low-affinity neurotrophin receptor p75 is currently considered to be a gold-standard marker, but because it is a membrane protein, it is lost during procedures that permeabilise cells that are necessary to identify intracellular components and in apoptosis and cell-proliferation assays. We have therefore assessed the potential of the intracellular neuronal marker protein gene product (PGP) 9.5 as a label for neural-crest-derived precursor cells during gut development. Gut was taken from mouse embryos at 11.5 days post-coitum, at which time NCC had reached the proximal colon. Cellular p75 and PGP9.5 expression was determined by double-labelling immunofluorescence. The leading edge of neural-crest migration was defined as the 10 most distal p75-labelled cells. The neuronal marker PGP9.5 labelled NCC as they migrated along the gut at day 11.5. At the leading edge of migration, over 95% of p75-positive cells also expressed PGP9.5, and all PGP9.5-positive cells were also labelled for p75. PGP9.5 is expressed by at least 95% of neural-crest-derived precursor cells at the leading edge of migration along the gut. Thus, it can be used as a robust marker for developing NCC in the gut.

Differentiation of podocyte and proximal tubule-like cells from a mouse kidney-derived stem cell line.

In this study we have shown that the papilla of the mouse kidney contains a population of Pax2+ cells that are detectable from the early postnatal period through to adulthood. Lineage analysis suggests that some of these Pax2+ cells are derived from the metanephric mesenchyme, a population of progenitor cells that gives rise to the nephrons during kidney organogenesis. Here we describe a method for isolating and culturing the Pax2+ population, and demonstrate that some cells within this population are multipotent stem cells, as they are clonogenic and appear to undergo unlimited self-renewal. Further, under appropriate culture conditions, these stem cells can differentiate to generate renal cell types, such as podocyte- and proximal tubule-like cells, and are also able to generate nonrenal cell types, such as adipocytes and osteocytes. The availability of a kidney-derived multipotent stem cell line with the potential to generate podocytes and proximal tubule cells in culture will expedite progress in understanding the biology of these important renal cell types, and will be a useful tool in toxicological studies and drug discovery.