Histological Characterizations of the Brain Vascular Hyalinosis in Patients with Systemic Hypertension‐Induced Ischemic Stroke

Background Ischemic stroke is a major cause of death among patients with systemic hypertension. The narrowing of the brain vascular lumen increases the incidence of stroke and the formation of hyalinosis lesion is an irreversible process that occurs in the late stage of the disease and contributes to the vascular narrowing and stroke. Understanding pathologic mechanisms of brain vascular hyalinosis, thus, should contribute to the development of new therapeutic agents that inhibits and/or reverse the formation of hyalinosis, thereby reducing the incidence of ischemic stroke. Despite the clinical importance of this lesion, properties of brain vascular hyalinosis have not been well investigated. Thus, the present study performed detailed histological examinations of the hyalinosis lesions of postmortem brain vascular tissues of human patients who died of ischemic stroke due to systemic hypertension. Methods & Results Hematoxylin and eosin staining, as well as periodic acid‐Schiff staining, showed the presence of vascular hyalinosis in patient brain tissues. In these lesions, the protein organization of the extracellular matrix was changed, the number and size of smooth muscle cells were altered, and plasma proteins, such as apolipoprotein E and fibrin, infiltrated into the vessel wall. Signs of oxidative stress and lipid peroxidation were also found. These changes are pronounced at the loci of the infiltration of the vessel walls by ApoE. We found increased number of vasa vasorum in adventitia of the small arteries. The formation and deposition of hyaline occur both from the side of the lumen of the artery and from the side of the vase vasorum. Transmission electron microscopy showed that with the development of hyalinosis, the number of smooth muscle cells that undergo atrophy. The deposition of proteins in the arterial wall is also associated with the degree of damage to endothelial cells in the lumen of the vessel and in the vasa vasorum. Conclusions These results demonstrate that, at the beginning of the development of hyalinosis, smooth muscle cells and vasa vasorum are increased. This process seem to involve oxidative stress, which damages endothelial cells both in the lumen of the arteries and in the vasorum vase and contributes to the infiltration of blood plasma proteins into the vascular wall. The resulting hyalinosis decreases the lumen of the arteries and increases the incidence of stroke. Support or Funding Information Supported by NIH