Kengo Nishimura

Effects of different types of fluid shear stress on endothelial cell proliferation and survival.

We attempted to clarify the effect of different types of shear stress on endothelial cell (EC) proliferation and survival. Bovine aortic ECs were subjected to either steady laminar, 1 Hz pulsatile, or 1 Hz to and fro shear at 14 dyne/cm2. % of BrdU positive EC was 14.3 ± 1.6% in steady, 21.5 ± 3.2% in pulsatile, and 11.4 ± 2.4% in to and fro after 4 h, respectively (P < 0.05). Pulsatile shear compared with static control. Rapamycin reduced BrdU incorporation in all shear regimens (P < 0.001). However, it was still higher in EC exposed to pulsatile shear than the other regimens (P < 0.005). PD98059 completely abolished the increased BrdU incorporation in all shear regimens, including pulsatile shear. Pulsatile shear had significantly elevated ERK1/2 phosphorylation at 5 min compared with steady (P < 0.05) and to and fro shear (P < 0.01) while there was no significant difference in pp70S6k phosphorylation between any shear regimen. The ratio of apoptotic cells in serum deprived EC in the presence of steady laminar, pulsatile and to and fro shear for 4 h were 2.7 ± 0.78%, 2.7 ± 0.42%, and 2.9 ± 0.62%, respectively while after the addition of serum for 4 h, it was 4.3 ± 0.73%. All shear regimens phosphorylated AKT in a time‐dependent manner with no significant difference between regimens. Our results demonstrate that different types of shear stress regimens have different effects on EC and may account for the variable response of EC to hemodynamics in the circulation. J. Cell. Physiol. 212: 244–251, 2007.

Effect of different frequencies of tensile strain on human dermal fibroblast proliferation and survival

The aim of this study is to compare the effect of a high‐frequency repetitive (HF) stretch or an intermittent (I) stretch on the cell proliferation and survival of human dermal fibroblasts and to determine the activation of any relevant signal pathways. Cultured human dermal fibroblasts were exposed to either HF or I stretch. Cell number was measured by counting, while DNA synthesis was assessed by 5‐bromo‐2′‐deoxyuridine (BrdU) staining and apoptosis by terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling staining. To investigate the potential mechanisms of repetitive strain on the proliferation and survival of fibroblasts, the activation of relevant transduction pathways, such as p38 mitogen‐activated protein kinase (MAPK), extracellular signal‐regulated kinase (ERK)1/2, AKT, and BAD, was assessed by Western blot. In addition, the effect of inhibition of these pathways on the fibroblast response was also studied. After either HF or I stretch for 7 days, fibroblast number was significantly decreased and there were less BrdU‐positive cells. The numbers of apoptotic and/or necrotic fibroblasts were not affected. p38 MAPK and ERK1/2 were significantly activated after HF stretch, but AKT and BAD were significantly activated after I stretch. The inhibitors of p38 MAPK and MAPK/ERK kinase as well as dominant‐negative AKT reduced cell number after both HF and I stretch but these pathways were not critical for the stretch‐induced decrease in cell number.

p38 Mitogen-Activated Protein Kinase Activation in Endothelial Cell Is Implicated in Cell Alignment and Elongation Induced by Fluid Shear Stress

Fluid shear stress is thought to be important in maintaining the phenotype of endothelial cells (ECs) in vivo. The purpose of the study was to determine the effect of varying levels of laminar shear stress on EC elongation and alignment and the role of p38 mitogen-activated protein kinase (MAPK) on the morphologic change induced by shear stress. Cultured bovine aortic ECs were subjected to 1, 4, 7, 14, or 20 dyne/cm(2) laminar steady shear stress. On morphometric analysis of static ECs, the average orientation angle was 41 degrees , whereas after 24 h shear stress at 1, 4, 7, 14, and 20 dyne/cm(2) the angles were 34 degrees, 33 degrees, 16 degrees, 11 degrees, and 10 degrees, respectively. The shape index of static ECs was 0.76, whereas the indexes of ECs exposed to shear stress were 0.72, 0.72, 0.65, 0.50, and 0.47, respectively. The time and the magnitude of activation of p38 MAPK were dependent on the level of shear stress. The results indicate that a minimum shear stress of 7 to 14 dynes/cm(2) is necessary for cell alignment and elongation and this correlates with activity of p38 MAPK. ECs exposed to shear stress in the presence of the p38 MAPK inhibitor SB-203580 did not orient in any manner and the shape index was similar to the static cells.

The Effect of Different Frequencies of Stretch on Human Dermal Keratinocyte Proliferation and Survival

The effects of cyclic stretch on mitogen-activated protein kinase (MAPK) and apoptosis in keratinocytes are not well understood. The aim of this study is to compare the effect of high frequency repetitive (HF) stretch to intermittent (I) stretch on human dermal keratinocytes proliferation and survival. Cultured human dermal keratinocytes were exposed to either repetitive HF or I stretch. Cell number was measured by coulter counter, DNA synthesis was assessed by BrdU staining, and apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. The activation of p38 MAPK, ERK 1/2, and AKT was assessed by immunoblotting. p38 MAPK, ERK 1/2, and AKT exhibited no change after HF stretch, while AKT and Homo sapiens BCL-2-antagonist of cell death (BAD) were significantly activated after I stretch. After experiencing I stretch for 2 d, keratinocyte proliferation rates were significantly decreased. This decrease was most likely not due to apoptosis as TUNEL-positive cells only increased for cells treated with an AKT inhibitor.

Phosphatase PTEN is inactivated in bovine aortic endothelial cells exposed to cyclic strain

Hemodynamic forces, including cyclic strain (CS) and shear stress (SS), have been recognized as important modulators of vascular cell morphology and function. PTEN (also known as MMAC1/TEP1) is a lipid phosphatase that leads to a decrease in intracellular phosphatidylinositol 3,4,5 trisphosphate (PIP3) and therefore can modulate the stimulating effect of phosphatidylinositol 3‐kinase (PI3K). In this study, we focused on the upstream regulators of the PI3K‐Akt pathway by assessing Akt, PTEN, casein kinase 2 (CK2) (a kinase that catalyzes phosphorylation of PTEN), and PI3K activity in endothelial cells (EC) exposed to CS. The activity of phospho‐PTEN (n = 4) and phospho‐CK2 (n = 4) increased in a time‐dependent fashion, reaching maximal activity by 10 min of CS stimulation. The peak of phospho‐Akt activity (n = 4) occurred later, at 60 min. Akt activity was altered by transfection of EC with dominant negative PTEN plasmids. Furthermore, CS increased PIP3 immunoreactivity in a time‐dependent manner, reaching maximal activity after 60 min of CS stimulation, and these effects were affected by transfection of EC with dominant negative PTEN plasmids. Inhibition of PTEN activity had no effect on CS‐mediated cell proliferation but inhibited CS‐mediated suppression of apoptosis. J. Cell. Biochem. 100: 515–526, 2007.

Elective Treatment of Middle Colic Artery Aneurysm

Middle colic artery aneurysms are rare and most have been reported with rupture or symptom. We report the successful elective treatment of a middle colic artery aneurysm without symptom, which is very rare. It failed to perform transcatheter arterial embolization for anatomical reasons, and, thus, the patient, a 77-year-old man, underwent surgical resection in spite of a history of laparotomy. Although a common cause of middle colic artery aneurysms is segmental arterial mediolysis, the present pathological findings indicated that fragmented or degenerated elastic fibers may also play an important role like aortic aneurysms.

Endovascular Treatment of Left Subclavian Artery Pseudoaneurysm after Clavicle Fracture in an Elderly Adult with a 40-Year History of Behçet’s Disease

Behçets disease (BD) is a rare chronic systemic vasculitis of unknown etiology that presents in young adults. We report a very rare case of a left subclavian artery pseudoaneurysm identified after a left clavicle fracture in a 70-year-old man with a 40-year history of intestinal BD. The patient received fixation by banding to treat a fracture after falling from a bed about 5 months previously, and he was referred to our hospital due to the finding of a left subclavian pulsatile mass. As enhanced computed tomography showed a left subclavian artery pseudoaneurysm, it was repaired using an endovascular stent graft.

A case of acute arterial thrombosis caused by nephrotic syndrome.

Venous thromboembolic complications are frequently caused by nephrotic syndrome, while arterial thrombosis has rarely been reported. We report the successful treatment of a 53-year-old man who suffered from sudden severe pain of the left lower limb and facial edema. Abdominal computed tomography showed that the left common iliac artery was occluded from its origin. Although he had left peroneal nerve paralysis, thrombectomy and fasciotomy were performed for limb salvage. Renal biopsy revealed minimal change nephrotic syndrome after the operation. No recurrence has been observed. Nephrotic syndrome might be considered as a cause of acute arterial thrombosis.

A Case of True Brachial Artery Aneurysm with Severe Left Upper Limb Ischemia

Brachial artery (BA) aneurysms are rare, and most are false aneurysms. Although true BA aneurysms have been reported, most have been reported without symptoms. A 65-year-old man was referred due to a left upper limb mass with rest pain and slight ulceration of the left second and third fingers. As enhanced computed tomography revealed the patency of only the left proximal and distal BA as well as the thrombosed mass, excision of the aneurysm and BA replacement were performed with a great saphenous vein graft. The postoperative course was uneventful, and the rest pain and ulceration were resolved.

Revascularization for acute blunt popliteal artery injury

A 45‐year‐old man was brought to our hospital in pre‐shock after falling from a motorcycle. As we diagnosed him with open fracture of the right femur with leg ischemia, we performed revascularization of injured popliteal artery and treated the leg. The pathological findings showed fragmentation and decrease of elastic fibers and fragmentation of collagen fibers, but no inflammatory cells or intimal hyperplasia, and no dissection.