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Cerebral cavernous malformation (CCM) is a rare neurovascular disease that is characterized by enlarged and irregular blood vessels that often lead to cerebral hemorrhage. Loss-of-function mutations to any of three genes results in CCM lesion formation; namely, KRIT1, CCM2, and PDCD10 (CCM3). Here, we report for the first time in-depth single-cell RNA sequencing, combined with spatial transcriptomics and immunohistochemistry, to comprehensively characterize subclasses of brain endothelial cells (ECs) under both normal conditions and after deletion of Pdcd10 (Ccm3) in a mouse model of CCM. Integrated single-cell analysis identifies arterial ECs as refractory to CCM transformation. Conversely, a subset of angiogenic venous capillary ECs and respective resident endothelial progenitors appear to be at the origin of CCM lesions. These data are relevant for the understanding of the plasticity of the brain vascular system and provide novel insights into the molecular basis of CCM disease at the single cell level.

Background Mesenchymal stromal cells (MSC) have been under investigation for a number of therapies and have lately been in focus as immunosuppressive actors in the field of transplantation. Herein we have extended our previously published in vitro model of MSC-islets in an experimental setting of islet transplantation to the abdominal muscle. Human islets coated with luciferase-GFP transduced human MSC were transplanted to the abdomen muscle tissue of NOD-scid ILR2γnull mice and cellular interactions were investigated by confocal microscopy. Results The MSC reduced fibrotic encapsulation and facilitated endothelial cell interactions. In particular, we show a decreased fraction of αSMA expressing fibrotic tissue surrounding the graft in presence of MSC-islets compared to islets solely distributed into the muscle tissue. Also, in the presence of MSC, human islet endothelial cells migrated from the center of the graft out into the surrounding tissue forming chimeric blood vessels with recipient endothelial cells. Further, in the graft periphery, MSC were seen interacting with infiltrating macrophages. Conclusions Here, in our experimental in vivo model of composite human islets and luciferase-GFP-transduced human MSC, we enable the visualization of close interactions between the MSC and the surrounding tissue. In this model of transplantation the MSC contribute to reduced fibrosis and increased islet endothelial cell migration. Furthermore, the MSC interact with the recipient vasculature and infiltrating macrophages. Electronic supplementary material The online version of this article (doi:10.1186/s40340-015-0010-9) contains supplementary material, which is available to authorized users.

SummaryIschaemia-reperfusion injury (IRI) poses a major challenge in many thrombotic conditions and in whole organ transplantation. Activation of the endothelial cells and shedding of the protective vascular glycocalyx during IRI increase the risk of innate immune activation, cell infiltration and severe thrombus formation, promoting damage to the tissue. Here, we present a novel one-step strategy to protect the vasculature by immobilisation of a unique multi-arm heparin conjugate to the endothelium. Applying a new in vitro blood endothelial cell chamber model, the heparin conjugate was found to bind not only to primary human endothelial cells but also directly to the collagen to which the cells adhered. Incubation of hypoxic endothelial cells with freshly drawn human blood in the blood chambers elicited coagulation activation reflected by thrombin anti-thrombin formation and binding of platelets and neutrophils. Immobilisation of the heparin conjugate to the hypoxic endothelial cells created a protective coating, leading to a significant reduction of the recruitment of blood cells and coagulation activation compared to untreated hypoxic endothelial cells. This novel approach of immobilising multi-arm heparin conjugates on the endothelial cells and collagen of the basement membrane ensures to protect the endothelium against IRI in thrombotic disorders and in transplantation.

Long-term survival of implanted cells requires oxygen and nutrients, the need for which is met by vascularization of the implant. The use of scaffolds with surface-attached heparin as anchoring points for angiogenic growth factors has been reported to improve this process. We examined the potential role of surface modification of gelatin scaffolds in promoting endothelial cell infiltration by using a unique macromolecular conjugate of heparin as a coating. Compared to other heparin coatings, this surface modification provides flexible heparin chains, representing a new concept in heparin conjugation. In vitro cell infiltration of scaffolds was assessed using a three-dimensional model in which the novel heparin surface, without growth factors, showed a 2.5-fold increase in the number of infiltrating endothelial cells when compared to control scaffolds. No additional improvement was achieved by adding growth factors (vascular endothelial growth factor and/or fibroblast growth factor-2) to the scaffold. In vivo experiments confirmed these results and also showed that the addition of angiogenic growth factors did not significantly increase the endothelial cell infiltration but increased the number of inflammatory cells in the implanted scaffolds. The endothelial cell-stimulating ability of the heparin surface alone, combined with its growth factor-binding capacity, renders it an interesting candidate surface treatment to create a prevascularized site prepared for implantation of cells and tissues, in particular those sensitive to inflammation but in need of supportive revascularization, such as pancreatic islets of Langerhans.