All endothelial cells are involved in the production of thrombomodulin EXCEPT those found in:

Endothelium of the blood vessels plays an active role in preventing the extension of clots into blood vessels. All endothelial cells except those in the cerebral circulation produce thrombomodulin. Ref: Review of Medical Physiology By Ganong, 22nd Edition, Page 543; Robbins Pathologic Basis of Disease, 6th Edition, Page 120