Wnt5a knock-out mouse as a new model of anorectal malformation.

BACKGROUND: Anorectal malformations (ARM) represent a variety of congenital disorders that involve abnormal termination of the anorectum. Mutations in Shh signaling and Fgf10 produce a variety of ARM phenotypes. Wnt signaling has been shown to be crucial during gastrointestinal development. We therefore hypothesized that Wnt5a may play a role in anorectal development. METHODS: Wild type (WT), Wnt5a(+/-) and Wnt5a(-/-) embryos were harvested from timed pregnant mice from E15.5 to E18.5, and analyzed for anorectal phenotype. Tissues were processed for whole-mount in situ hybridization and histology. RESULTS: Wnt5a is expressed in the embryonic WT colon and rectum. Wnt5a(-/-) mutants exhibit multiple deformities including anorectal malformation. A fistula between the urinary and intestinal tracts can be identified as early as E15.5. By E18.5, the majority of the Wnt5a(-/-) mutants display a blind-ending pouch of the distal gut. CONCLUSIONS: The expression pattern of Wnt5a and the ARM phenotype seen in Wnt5a(-/-) mutants demonstrate the critical role of Wnt5a during anorectal development. This study establishes a new model of ARM involving the Wnt5a pathway.

Induction of fibroblast growth factor 10 (FGF10) in the ileal crypt epithelium after massive small bowel resection suggests a role for FGF10 in gut adaptation.

We have previously reported that fibroblast growth factor 10 (FGF10) is crucial for the survival and proliferation of progenitor cells during embryonic gastrointestinal development. We sought to characterize the potential role of FGF10 signaling in the adaptive response following small bowel resection. Adult wild-type and Fgf10(LacZ) mice underwent 50% small bowel resection (SBR) or sham operation. Tissues were harvested 24 or 48 hr after surgery for histology, immunohistochemistry, and in situ hybridization. After SBR, Fgf10 expression was demonstrated in the epithelium at the base of the crypts. Moreover, there was a statistically significant increase in proliferating cells and goblet cells after SBR. In vitro studies using rat intestinal epithelial crypt (IEC-6) cells exposed to medium with or without recombinant FGF10 showed increased proliferation and phosphorylation of Raf and AKT with the addition of FGF10. Our results suggest that FGF10 may play a therapeutic role in diseases involving intestinal failure.

Abdominal involvement in pediatric heart and lung transplant recipients with posttransplant lymphoproliferative disease increases the risk of mortality.

BACKGROUND: Posttransplant lymphoproliferative disease (PTLD) is a serious complication in transplant recipients. Abdominal PTLD has been reported, but the prognosis remains undefined. The purpose of this study was to identify the incidence, predisposing factors, and outcome of abdominal PTLD in pediatric cardiothoracic transplant patients. METHODS: Retrospective chart review of 134 transplant patients (50 heart, 77 lung, 7 heart/lung) at our institution (1995-2005). RESULTS: Posttransplant lymphoproliferative disease was diagnosed in 14 patients. Most were Epstein-Barr virus naive initially, but all had seroconverted when diagnosed with PTLD. Eight had abdominal involvement; 4 required surgical interventions-1 for intussusception and for bowel perforation, 2 for bowel perforation, and 1 for tumor debulking. All had lifelong follow-up, with an average follow-up of 3 years. Of 8 patients with abdominal PTLD, 4 died of complications related to PTLD, whereas 1 of 6 patients with extraabdominal PTLD died of PTLD. CONCLUSIONS: Epstein-Barr virus infection after transplantation is a major risk factor for PTLD. Pediatric patients with PTLD who present with abdominal involvement are more likely to die of PTLD than those without abdominal disease. Delay in diagnosis may contribute to the high mortality. Therefore, prompt evaluation and surveillance for possible abdominal PTLD may decrease mortality associated with this devastating problem.

Late-stage immature neocortical neurons reconstruct interhemispheric connections and form synaptic contacts with increased efficiency in adult mouse cortex undergoing targeted neurodegeneration.

In the neocortex, the effectiveness of potential cellular repopulation therapies for diseases involving neuronal loss may depend critically on whether newly incorporated cells can differentiate appropriately into precisely the right kind of neuron, re-establish precise long-distance connections, and reconstruct complex functional circuitry. Here, we test the hypothesis that increased efficiency of connectivity could be achieved if precursors could be more fully differentiated toward desired phenotypes. We compared embryonic neuroblasts and immature murine neurons subregionally dissected from either embryonic day 17 (E17) (Shin et al., 2000) or E19 primary somatosensory (S1) cortex and postnatal day 3 (P3) purified callosal projection neurons (CPNs) with regard to neurotransmitter and receptor phenotype and afferent synapse formation after transplantation into adult mouse S1 cortex undergoing targeted apoptotic degeneration of layer II/III and V CPNs. Two weeks after transplantation, neurons from all developmental stages were found dispersed within layers II/III and V, many with morphological features typical of large pyramidal neurons. Retrograde labeling with FluoroGold revealed that 42 +/- 2% of transplanted E19 immature S1 neurons formed connections with the contralateral S1 cortex by 12 weeks after transplantation, compared with 23 +/- 7% of E17 neurons. A greater percentage of E19-derived neurons received synapses (77 +/- 1%) compared with E17-derived neurons (67 +/- 2%). Similar percentages of both E17 and E19 donor-derived neurons expressed neurotransmitters and receptors [glutamate, aspartate, GABA, GABA receptor (GABA-R), NMDA-R, AMPA-R, and kainate-R] appropriate for endogenous adult CPNs progressively over a period of 2-12 weeks after transplantation. Although P3 fluorescence-activated cell sorting-purified neurons also expressed these mature phenotypic markers after transplantation, their survival in vivo was poor. We conclude that later-stage and region-specific immature neurons develop a mature CPN phenotype and make appropriate connections with recipient circuitry with increased efficiency. However, at postnatal stages of development, limitations in survival outweigh this increased efficiency. These results suggest that efforts to direct the differentiation of earlier precursors precisely along specific desired neuronal lineages could potentially make possible the highly efficient reconstruction of complex neocortical and other CNS circuitry.