Lymphatic vessels accompanying dorsal and basal dural sinuses in the human brain

Abstract

Recent investigations showed the presence of meningeal lymphatic vessels (mLVs) along the superior sagittal and transverse dural sinuses which drain both fluid and immune cells from the cerebrospinal fluid (CSF) to the deep cervical lymph nodes. This study uses immunohistochemistry (IHC) and the Western Blot technique to show the presence of mLV accompanying the dorsal (superior sagittal, inferior sagittal, transverse, sigmoid, and straight) and basal (cavernous, sphenoparietal, superior, and inferior petrosal) dural sinuses in the human brain. Samples for IHC were obtained from dorsal and basal meningeal dural sinuses of 3 human cadavers and 3 autopsies. Routine histological techniques were carried out for the specimens. Podoplanin (PDPN, lymphatic vessel endothelial cell marker) and CD31 (vascular endothelial cell marker) IHC staining were applied to the 5 µm thick paraffin sections. Furthermore, PDPN and CD31 protein expressions were evaluated using Western Blot to the tissue samples from the same regions of 4 autopsies. Two consecutive sections from each sinus were PDPN, and CD31 was stained to differentiate blood vessels (BV) from mLV. The IHC staining showed the presence of mLVs accompanying both dorsal and basal dural sinuses. The mLVs accompanying the dorsal dural sinuses had a larger dimensions range compared to the basal dural sinuses. However, the number of mLVs along the basal dural sinuses was more than the mLVs along the dorsal ones. Further, fluid channels were closely localized to the mLV, with varying diameters and densities. Western Blotting technique showed the presence of PDPN expression in both dorsal and basal dural sinus samples. The knowledge of the presence of mLV along both dorsal and basal dural sinuses in humans can increase the understanding of how mLV contributes to the brain lymphatic circulation and may help understand the neuropathophysiological processes of various neurological diseases.