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 villus tip telocytes (VTTs) are necessary for maintenance of villus tip endothelial cell polarization and fenestration by sequestering VEGFA signaling. To determine a mechanism promoting VTT-mediated VEGFA sequestration we sought to characterize VTTs at the molecular level and performed scRNAseq on CD45neg EpCAMneg CD31neg PDPN+ intestinal cells from wild-type adult mice, using PDPN as a broad marker of intestinal fibroblasts. These scRNAseq results point to VTTs as a distinct population of subepithelial and perivascular fibroblasts. 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 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 villustip epithelial structures.

Contributed by: Jeremiah Bernier-Latmani, Cristina Mauri, Rachel Marcone, François Renevey, Stephan Durot, Liqun He, Michael Vanlandewijck, Catherine Maclachlan, Suzel Davanture, Nicola Zamboni, Graham W. Knott, Sanjiv A. Luther, Christer Betsholtz, Mauro Delorenzi, Cathrin Brisken, Tatiana V. Petrova