====== Lymphatic vessels ======

Saccular [[intracranial aneurysm rupture]] leads to [[subarachnoid hemorrhage]] and is preceded by chronic [[inflammation]] and atherosclerotic changes of the Saccular intracranial [[aneurysm wall]]. Increased [[lymphangiogenesis]] has been detected in atherosclerotic extracranial arteries and in [[abdominal aortic aneurysm]]s, but the presence of lymphatic [[vessel]]s in [[saccular intracranial aneurysm]]  (sIAs) has remained unexplored. 
Huuska et al. studied the presence of lymphatic vessels in 36 intraoperatively resected sIAs (16 unruptured and 20 ruptured), using immunohistochemical and [[immunofluorescence]] stainings for [[Lymphatic endothelial cells]] (LEC)[[ marker]]s. Of these LEC-markers, both extracellular and intracellular [[LYVE1]], [[podoplanin]], [[VEGFR-3]], and [[Prox1]]-positive stainings were detected in 83%, 94%, 100%, and 72% of the 36 sIA walls, respectively. Lymphatic vessels were identified as ring-shaped structures positive for one or more of the LEC markers. Of the sIAs, 78% contained lymphatic vessels positive for at least one LEC marker. The presence of LECs and lymphatic vessels were associated with the number of CD68+ and CD163+ cells in the sIA walls, and with the expression of inflammation indicators such as serum amyloid A, myeloperoxidase, and cyclo-oxygenase 2, with the presence of a [[thrombus]], and with the sIA wall rupture. Large areas of VEGFR-3 and α-smooth muscle actin (αSMA) double-positive cells were detected in medial parts of the sIA walls. Also, a few [[podoplanin]] and αSMA double-positive cells were discovered. In addition, LYVE-1 and [[CD68]] double-positive cells were detected in the sIA walls and in the thrombus revealing that certain CD68+ [[macrophage]]s are capable of expressing LEC markers. This study demonstrates for the first time the presence of [[lymphatic vessels]] in human sIA walls. Further studies are needed to understand the role of lymphatic vessels in the [[saccular intracranial aneurysm pathogenesis]] 
((Huuska N, Netti E, Lehti S, Kovanen PT, Niemelä M, Tulamo R. [[Lymphatic vessels]] are present in human [[saccular intracranial aneurysm]]s. Acta Neuropathol Commun. 2022 Sep 5;10(1):130. doi: 10.1186/s40478-022-01430-8. PMID: 36064651.)).