ICAM1 and hypervitaminosis A: Here we found enlarged blood vessels in the well perfused dura mater membrane covering the endocranial bone surface in hypervitaminosis A. In addition, we observed increased staining of Icam1, a key endothelial molecule involved in active recruitment of osteoclast precursors [25], in the dura mater close to the endocranial osteoclasts found in hypervitaminosis A animals.