Exomphalos with intestinal fistulation: Case series and systematic review for clinical characterization, management and embryopathogenesis.

INTRODUCTION: Exomphalos with intestinal fistulation (EIF) is a rare variant of exomphalos with intestine opening to the surface of an intact sac, and may result in a diagnostic challenge. We report 3 new cases and conducted a systematic review of the literature, to characterize its association with the type of exomphalos and vitellointestinal duct (VI) as well as to evaluate its management and outcomes. METHODS: A literature search from PubMed using keywords pertaining to exomphalos and fistulation was used to identify all unique cases reported between 1950 and 2020, in addition to the case series reported here, to establish the clinical presentation, histological findings, management and outcomes. RESULTS: We found a total of 28 cases of EIF, of which 25 had been reported in 70 years from 19 reports. There was a male predominance (4-to-1 ratio). The majority presented as an exomphalos minor (n = 23, 82%) with a prolapsing patent VI duct (n = 16, 57%), most had evidence of Meckel's diverticulum (n = 25, 89%). All but one case were managed by fistula excision with or without ileal resection and anastomosis, followed by primary closure of the abdominal wall defect. All patients, except one with Trisomy 13 who received only palliative care, underwent surgery. Post-operative complications occurred in 7 patients (25%). Congenital anomalies were present in 12 (43%) and none had Beckwith-Wiedemann syndrome. Mortality occurred in 4 patients (14%) between 3 and 17 days. One EIF with exomphalos major failed early conservative treatment due to sac disintegration and sepsis, requiring staged closure, but had a good outcome. DISCUSSION: EIF is a rare entity usually associated with exomphalos minor and vitelline duct involvement. EIF presentation is variable but primary surgery is the mainstay of treatment with generally good outcomes. Common features of EIF suggest a different embryopathogenesis to other forms of exomphalos.

Membrane Radiolabelling of Exosomes for Comparative Biodistribution Analysis in Immunocompetent and Immunodeficient Mice - A Novel and Universal Approach.

Extracellular vesicles, in particular exosomes, have recently gained interest as novel drug delivery vectors due to their biological origin and inherent intercellular biomolecule delivery capability. An in-depth knowledge of their in vivo biodistribution is therefore essential. This work aimed to develop a novel, reliable and universal method to radiolabel exosomes to study their in vivo biodistribution. Methods: Melanoma (B16F10) cells were cultured in bioreactor flasks to increase exosome yield. B16F10-derived exosomes (ExoB16) were isolated using ultracentrfugation onto a single sucrose cushion, and were characterised for size, yield, purity, exosomal markers and morphology using Nanoparticle Tracking Analysis (NTA), protein measurements, flow cytometry and electron microscopy. ExoB16 were radiolabelled using 2 different approaches - intraluminal labelling (entrapment of 111Indium via tropolone shuttling); and membrane labelling (chelation of 111Indium via covalently attached bifunctional chelator DTPA-anhydride). Labelling efficiency and stability was assessed using gel filtration and thin layer chromatography. Melanoma-bearing immunocompetent (C57BL/6) and immunodeficient (NSG) mice were injected intravenously with radiolabelled ExoB16 (1x1011 particles/mouse) followed by metabolic cages study, whole body SPECT-CT imaging and ex vivo gamma counting at 1, 4 and 24 h post-injection. Results: Membrane-labelled ExoB16 showed superior radiolabelling efficiency and radiochemical stability (19.2 ± 4.53 % and 80.4 ± 1.6 % respectively) compared to the intraluminal-labelled exosomes (4.73 ± 0.39 % and 14.21 ± 2.76 % respectively). Using the membrane-labelling approach, the in vivo biodistribution of ExoB16 in melanoma-bearing C57Bl/6 mice was carried out, and was found to accumulate primarily in the liver and spleen (~56% and ~38% ID/gT respectively), followed by the kidneys (~3% ID/gT). ExoB16 showed minimal tumour i.e. self-tissue accumulation (~0.7% ID/gT). The membrane-labelling approach was also used to study ExoB16 biodistribution in melanoma-bearing immunocompromised (NSG) mice, to compare with that in the immunocompetent C57Bl/6 mice. Similar biodistribution profile was observed in both C57BL/6 and NSG mice, where prominent accumulation was seen in liver and spleen, apart from the significantly lower tumour accumulation observed in the NSG mice (~0.3% ID/gT). Conclusion: Membrane radiolabelling of exosomes is a reliable approach that allows for accurate live imaging and quantitative biodistribution studies to be performed on potentially all exosome types without engineering parent cells.