PATHOLOGICAL ENGINEERING ANALYSIS OF HUMAN UNRUPTURED CEREBRAL ANEURYSMS FOR INVESTIGATION OF RELATIONSHIP BETWEEN HEMODYNAMIC STRESS AND SMOOTH MUSCLE CELLS
Yasutaka Tobe1, Kenta Suto1, Takanobu Yagi1,2, Koichi Kawamura1, Mitsuo Umezu1, Hirotaka Yoshida3, Yoshifumi Hayashi3, Kazutoshi Nishitani3, Yoshifumi Okada3, Shigemi Kitahara3
1Waseda University, Japan;
2EBM Corporation, Japan;
3Kitahara Neurosurgical Institute, Japan
Cerebral aneurysm diagnostics currently do not reflect any pathological information because the causality of hemodynamics and growths are not elucidated. Recent studies of hemodynamics and pathology comparison studies reported that the impingement flow are located at the blood blister-like lesion with removal of endothelial cells. Therefore, this study investigated the effect of impingement flow on the smooth muscle cells (SMC) of aneurysm wall in an effort to elucidate the thinning mechanism of aneurysm.
21 aneurysms from 20 cases, average age of 63, were harvested by surgeons after clipping surgery. All samples were divided into blood blister-like (thickness less than 80 μm), transition (thickness between 80 to 100 μm), and hypertrophic (thickness greater than 100 μm). SMC densities were determined by counting the cell cores of every 200 μm segments. SMC properties were determined by observing the ultrastructure of core and cell surface. Hemodynamics of each case was analyzed by hemoscope (EBM Corp.).
The SMC densities of blood blister-like, transition, and hypertrophic lesions were 643±192 cells/mm2, 795±348 cells/mm2, 1103±317 cells/mm2, respectively. The SMC density of blood blister-like lesion was significantly less than the hypertrophic lesion (Tukeykramer, p<0.05). The SMC property analysis showed that synthetic type, damaged, contracted, and necrotic SMCs were present in all lesions. The damage levels of SMCs showed strong correlation with the depths of the wall from the inner surface (r=0.738), but did not show any correlation with the thickness. The hemodynamic analysis showed that the blood blisterlike, transition, and hypertrophic lesions had 76% impingement, 100% parallel, and 94% parallel types of flow, respectively.
The study suggested that the impingement type of flow interrupts/disables the survival and proliferation of SMCs to delay/stop the thickening process of aneurysm wall and parallel type of flow allows the survival/proliferation of SMCs to progress the thickening of aneurysm wall.