Fig. 3

Histological analysis of vessel morphological changes in the human IA samples. a Schematic representation of experimental design. A human sample was resected after microsurgical clipping from a partially thrombosed aneurysm arising from the bifurcation of the right middle cerebral artery. b Hematoxylin eosin staining of human IA sample obtained after clipping reveals thick, hypocellular wall structure with thrombus on the luminal surface. Increased thickness of the vessel wall and the wall decellularization (loss of mural cells) confirms the findings from the mice MCA aneurysms. Scale bar: 10 mm and 200µ. c Coronal view of the preoperative digital subtraction angiography (on the left) shows the filling lumen of the IA (marked with an arrow), while preoperative T1-w black blood MRI sequence without (in d) and with gadolinium contrast (in e). Wall enhancement observed after gadolinium enhancement is marked with arrow in e. f Hematoxylin eosin staining (0.7× magnification) demonstrates that the thickness of IA wall is largely composed of thrombus lining the luminal surface (marked with T). The border between the actual wall and the thrombus is depicted with an interrupted line. Higher magnification microphotographs from a CD31 immunofluorescence in g and from a CD34 immunofluorescence in (h). g, h with 20× magnification and 40× magnification, respectively. The presence of inflammatory cell infiltration is marked with i and capillaries are marked with c (both presented in g). i Adventitial inflammatory cell infiltration within the wall. The dark rectangle in b corresponds to the wall region from with the higher magnification microphotographs in panel i are taken. Similarly, the rectangle in i correspond to the wall regions from which the higher magnification microphotographs were taken. Scale bars: 500 µm, and 200 µm respectively