Fifty years of Weibel-Palade bodies: the discovery and early history of an enigmatic organelle of endothelial cells.

In 1962, a rod-shaped cytoplasmic organelle of endothelial cells, later called the Weibel-Palade body, was serendipitously discovered by electron microscopy. It contains a set of parallel tubules and is wrapped in a membrane. Subsequent studies in the following decades established the unique localization of this organelle in endothelial cells of all vertebrates studied, meaning that it could serve as a marker of endothelial cells in tissue cultures. However, these studies did not reveal its functional significance, except for an indication that it could be related to an undefined thromboplastic substance. Twenty years after its discovery as a structural entity, it was shown by others that it houses von Willebrand factor and is thus clearly related to the coagulation system. In this review, I provide a personal historical account of the discovery and the subsequent limited work that I carried out on the organelle, putting it in the perspective of the current state of knowledge after half a century of research by many scientists.