ADAMTS18+ villus tip telocytes maintain a polarized VEGFA signaling domain and fenestrations in nutrient-absorbing intestinal blood vessels

The small intestinal villus tip is the first point of contact for lumen-derived substances including nutrients and microbial products. Electron microscopy studies from the early 1970s uncovered unusual spatial organization of small intestinal villus tip blood vessels: their exterior, epithelial-facing side is fenestrated, while the side facing the villus stroma is non-fenestrated, covered by pericytes and harbors endothelial nuclei. Such organization optimizes the absorption process, however the molecular mechanisms maintaining this highly specialized structure remain unclear. Here we report that perivascular LGR5⁺ villus tip telocytes (VTTs) are necessary for maintenance of villus tip endothelial cell polarization and fenestration by sequestering VEGFA signaling. Mechanistically, unique VTT expression of the protease ADAMTS18 is necessary for VEGFA signaling sequestration through limiting fibronectin accumulation. Therefore, we propose a model in which LGR5⁺ ADAMTS18⁺ telocytes are necessary to maintain a “just-right” level and location of VEGFA signaling in intestinal villus blood vasculature to ensure on one hand the presence of sufficient endothelial fenestrae, while avoiding excessive leakiness of the vessels and destabilization of villus tip epithelial structures.

The molecular mechanisms ensuring the specialized structure of small intestinal villus tip blood vessels are incompletely understood. Here the authors show that ADAMTS18⁺ telocytes maintain a “just-right” level and location of VEGFA signaling on intestinal villus blood vessels, thereby ensuring the presence of endothelial fenestrae for nutrient absorption, while avoiding excessive leakiness and destabilization of villus tip epithelial structures.

Apelin-driven endothelial cell migration sustains intestinal progenitor cells and tumor growth

Stem and progenitor cells residing in the intestinal crypts drive the majority of colorectal cancers (CRCs), yet vascular contribution to this niche remains largely unexplored. VEGFA is a key driver of physiological and tumor angiogenesis. Accordingly, current anti-angiogenic cancer therapies target the VEGFA pathway. Here we report that in CRC expansion of the stem/progenitor pool in intestinal crypts requires VEGFA-independent growth and remodeling of blood vessels. Epithelial transformation induced expression of the endothelial peptide apelin, directs migration of distant venous endothelial cells towards progenitor niche vessels ensuring optimal perfusion. In the absence of apelin, loss of injury-inducible PROX1+ epithelial progenitors inhibited both incipient and advanced intestinal tumor growth. Our results establish fundamental principles for the reciprocal communication between vasculature and the intestinal progenitor niche and provide a mechanism for resistance to VEGFA-targeting drugs in CRCs.

Lack of Adipocytes Alters Hematopoiesis in Lipodystrophic Mice

Adult hematopoiesis takes place in the perivascular zone of the bone cavity, where endothelial cells, mesenchymal stromal/stem cells and their derivatives such as osteoblasts are key components of bone marrow (BM) niches. Defining the contribution of BM adipocytes to the hematopoietic stem cell niche remains controversial. While an excess of medullar adiposity is generally considered deleterious for hematopoiesis, an active role for adipocytes in shaping the niche has also been proposed. We thus investigated the consequences of total adipocyte deletion, including in the BM niche, on adult hematopoiesis using mice carrying a constitutive deletion of the gene coding for the nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ). We show that Pparg ^Δ/Δ lipodystrophic mice exhibit severe extramedullary hematopoiesis (EMH), which we found to be non-cell autonomous, as it is reproduced when wild-type donor BM cells are transferred into Pparg ^Δ/Δ recipients. This phenotype is not due to a specific alteration linked to Pparg deletion, such as chronic inflammation, since it is also found in AZIP^tg/+ mice, another lipodystrophic mouse model with normal PPARγ expression, that display only very moderate levels of inflammation. In both models, the lack of adipocytes alters subpopulations of both myeloid and lymphoid cells. The CXCL12/CXCR4 axis in the BM is also dysregulated in an adipocyte deprived environment supporting the hypothesis that adipocytes are required for normal hematopoietic stem cell mobilization or retention. Altogether, these data suggest an important role for adipocytes, and possibly for the molecular interactions they provide within the BM, in maintaining the appropriate microenvironment for hematopoietic homeostasis.

Bird breeder's disease: a rare diagnosis in young children

Bird breeder's lung disease is the most common form of hypersensitivity pneumonitis and is a rare entity in young children. We report three cases of children under 7 years of age in whom this diagnosis was confirmed early in the course of the disease. Three children aged 4.4 to 6.5 years presented with dry cough lasting for more than 1 month, dyspnoea, variable loss of appetite, weight loss, fatigue, fever and mild signs of respiratory distress. Chest X-ray films and CT scans showed a bilateral micronodular infiltrate. All three patients had strongly suggestive bronchoalveolar lavage fluid findings with lymphocytosis; two had elevated cell counts and decreased CD4/CD8 ratios. Lung biopsy confirmed the diagnosis in all children. Contact with allergens was identified in all children: two had spent holidays close to a farm in the previous month and one was living next to a pigeon house. In all children, avian precipitins were positive. The symptoms rapidly resolved after allergen avoidance and treatment with oral prednisone. Corticoid treatment was given between 11 and 15 weeks. One child relapsed and required long-term low-dose corticotherapy for 1 year. Lung function tests were normal in all three patients, 3.9 to 5.7 years after diagnosis.

CONCLUSION

Bird breeder's lung disease is a rare entity but should be considered in young children presenting long lasting cough. While rapid allergen exclusion and start of treatment can avoid the evolution into irreversible lung fibrosis, clinical and biological evolution should be monitored carefully even after stopping corticoid treatment because of the possibility of relapse.

Outbreak of echovirus 30 meningitis in Switzerland

This study includes 80 patients (38 children and 42 adults) who contracted aseptic meningitis in the summer of 1996 in Fribourg, Switzerland. Virological studies revealed an enteroviral infection in 65 out of 70 (93%) investigated patients. In 47 out of the 53 cases (89%) where a precise virus could be identified, the causative agent was an Echovirus 30. More than 50 patients lived in an area within a 5-km radius. The patients presented with the classic symptoms and signs of aseptic meningitis. In contrast, polymorphonuclear leukocytes predominated in the cerebrospinal fluid in the first 24 h and 32% of the cases had a left shift in their peripheral blood smear. The patients' age did not influence white blood cell count, the proportion of polymorphonuclear leukocytes or protein concentration in the cerebrospinal fluid. Thirty-three patients (41%) received antibiotic treatment, and 38 patients (48%) left the hospital within 24 h. Only 2 neuroradiological procedures and 1 electroencephalographic recording were performed. The outcome was favourable in all patients.

Recurrent chemical meningitis due to an intraspinal cystic teratoma: case report

✓ This is the first case report of an intraspinal cystic teratoma that manifested itself in recurrent episodes of chemical meningitis, with no sign of a space-occupying lesion.

[Brain tumors in children in a French Canadian environment]

Between 1964 and 1976, we have seen 197 cases of cerebral tumors in children. We have studied the frequency of each histological group of tumors, their localization, the results of the clinical investigation, their clinical manifestations and the prognosis for each group. This study has confirmed that in children brain tumors are more frequently localized in the posterior fossa (56.4%). As in other series, tumors derived from the glia represent nearly 80% of the total. Clinically, increased intro-cranial pressure is the most frequent manifestation of posterior fossa lesion (75% of cases) while cerebellar involvement was seen in 60% of these children. Brain lesions and supratentorial tumors are more insidious in their presentation and their clinical manifestations more diversified. The EEG appeared useful in the investigation of brain tumors and showed irregularities in 78% of our patients. However, a more specific diagnosis requirelography. As in previous series, the mortality rate remained high in the children we have followed, particularly for some groups of tumors (glioblastoma, medulloblastoma, brain stem lesions). It is to be hoped that with the introduction of the CT Scan, the improvement of neurosurgical techniques and the use of immuno and chemotherapy, the prognosis may be improved.

Complete heart block in a young child presumably due to mycoplasma pneumoniae myocarditis

The case is described of an 18 months old boy with sudden onset complete heart block, heralded by Stokes-Adams attacks. General signs of viral illness preceded and accompanied the syndrome; this, along with angiographic evidence of poorly contracting left ventricle, led to the diagnosis of non bacterial myocarditis. Serologic tests disclosed a significant rise in antibodies against mycoplasma pneumoniae (1/16 to 1/128). The His-bundle electrogram showed a block above the His-bundle, but fairly widespread damage to the conduction system is suspected. The complete heart block proved to be permanent and a fixed rate pacemaker had to be implanted.