Makoto Sumi

Long-term patency of small-diameter vascular graft made from fibroin, a silk-based biodegradable material

OBJECTIVE There is an increasing need for vascular grafts in the field of surgical revascularization. However, smaller vascular grafts made from synthetic biomaterials, particularly those <5 mm in diameter, are associated with a high incidence of thrombosis. Fibroin is a biodegradable protein derived from silk. Silk fibroin from Bombyx mori provides an antithrombotic surface and serves as a scaffold for various cell types in tissue engineering. We evaluated the potential of fibroin to generate a vascular prosthesis for small arteries. METHODS A small vessel with three layers was woven from silk fibroin thread. These fibroin-based grafts (1.5 mm diameter, 10 mm length) were implanted into the abdominal aorta of 10- to 14-week-old male Sprague-Dawley rats by end-to-end anastomosis. Polytetrafluoroethylene (PTFE)-based grafts were used as the control. To investigate the origin of the cells in the neointima and media, bone marrow transplantation was performed from green fluorescent protein (GFP) rats to wild-type rats. RESULTS The patency of fibroin grafts at 1 year after implantation was significantly higher than that of PTFE grafts (85.1% vs 30%, P < .01). Endothelial cells and smooth muscle cells (SMCs) migrated into the fibroin graft early after implantation and became organized into endothelial and medial layers, as determined by anti-CD31 and anti-alpha-smooth muscle actin immunostaining. The total number of SMCs increased 1.6-fold from 1 month to 3 months. Vasa vasorum also formed in the adventitia. Sirius red staining of the fibroin grafts revealed that the content of collagen significantly increased at 1 year after implantation, with a decrease in fibroin content. GFP-positive cells contributed to organization of a smooth muscle layer. CONCLUSIONS Small-diameter fibroin-based vascular grafts have excellent long-term patency. Bone marrow-derived cells contribute to vascular remodeling after graft implantation. Fibroin might be a promising material to engineer vascular prostheses for small arteries.

Reconstituted High-Density Lipoprotein Stimulates Differentiation of Endothelial Progenitor Cells and Enhances Ischemia-Induced Angiogenesis

Background—Plasma high-density lipoprotein (HDL) levels have an inverse correlation with incidence of ischemic heart disease as well as other atherosclerosis-related ischemic conditions. However, the molecular mechanism by which HDL prevents ischemic disease is not fully understood. Here, we investigated the effect of HDL on differentiation of endothelial progenitor cells and angiogenesis in murine ischemic hindlimb model. Methods and Results—Intravenous injection of reconstituted HDL (rHDL) significantly augmented blood flow recovery and increased capillary density in the ischemic leg. rHDL increased the number of bone marrow–derived cells incorporated into the newly formed capillaries in ischemic muscle. rHDL induced phosphorylation of Akt in human peripheral mononuclear cells. rHDL (50 to 100 &mgr;g apolipoprotein A-I/mL) promoted differentiation of peripheral mononuclear cells to endothelial progenitor cells in a dose-dependent manner. The effect of rHDL on endothelial progenitor cells differentiation was abrogated by coadministration of LY294002, an inhibitor of phosphatidylinositol 3-kinase. rHDL failed to promote angiogenesis in endothelial NO–deficient mice. Conclusions—rHDL directly stimulates endothelial progenitor cell differentiation via phosphatidylinositol 3-kinase/Akt pathway and enhances ischemia-induced angiogenesis. rHDL may be useful in the treatment of patients with ischemic cardiovascular diseases.

Local delivery of synthetic prostacycline agonist augments collateral growth and improves cardiac function in a swine chronic cardiac ischemia model.

AIMS It was reported that administration of angiogenic growth factors can augment collateral growth in ischemic tissues. It is assumed that angiogenic effects of cell transplantation may be mainly mediated by secretion of angiogenic cytokines. We tested feasibility of clinical use of ONO-1301, a synthetic small molecule that stimulates secretion of growth factors from various cell types, to treat patients with chronic myocardial ischemia. MAIN METHODS Effects of ONO-1301 on fibroblasts and endothelial cells were evaluated in vitro. We examined the efficacy of local delivery of ONO-1301 in models of rat hindlimb ischemia and swine chronic ischemic myocardium. KEY FINDINGS ONO-1301 stimulated hepatocyte growth factor secretion from human fibroblasts. ONO-1301 promoted vascular-like tube formation by endothelial cells in vitro. Direct injection of a slow-release form of ONO-1301 (SR-ONO) to rat hindlimb ischemic muscle enhanced perfusion recovery. In a swine cardiac ischemia model, direct injection of SR-ONO into the ischemic myocardium significantly augmented collateral formation (SR-ONO vs. control; 1.7+/-0.2 vs. 1.0+/-0.2 Rentrop score), with improved local ventricular wall motion, reduced enlargement of left ventricular diastolic volume (49.5+/-1.9 mL vs. 59.7+/-4.2 mL) and increased cardiac index (4.2+/-0.1 vs. 3.4+/-0.2 L/min/m(2)). Histological analysis revealed that SR-ONO suppressed fibrosis in ischemic tissue (collagen volume fraction; 7.5+/-1.1% vs. 12.8+/-2.2%) and enhanced neovascularization (capillary density, 275.6 vs. 159.3/mm(2); arterioles 36.6 vs. 25.5 /mm(2)). SIGNIFICANCE Local delivery of SR-ONO might be effective for therapeutic angiogenesis and propose that local administration of slow-release of synthetic small molecules represents new strategy for therapeutic angiogenesis.

Quercetin glucosides promote ischemia-induced angiogenesis, but do not promote tumor growth.

AIMS Dietary flavonoid intake shows a significant inverse association with mortality from coronary heart disease, incidence of myocardial infarction and stroke. Quercetin is one of the most common flavonoids in our diet and has several favorable biological activities. Quercetin glucosides, which are enzymatically trans-glycosylated isoquercitrin, have high water-solubility and bioavailability compared with quercetin. Here, we investigated the effects of quercetin glucosides on collateral development in a murine hindlimb ischemia model. MAIN METHODS We induced hindlimb ischemia in 24- to 32-week-old male C3H/HeJ mice by resecting the right femoral artery. Then, 0.5% carboxymethyl cellulose (control) or quercetin glucosides (100mg/kg/day) were administered daily by gavage. Blood flow was monitored weekly by laser Doppler imaging. KEY FINDINGS Recovery of blood flow to the ischemic leg was significantly enhanced by quercetin glucosides (blood flow ratio at 4 weeks: control, 0.57 ± 0.11; quercetin glucosides, 0.95 ± 0.10, p<0.05). Furthermore, anti-CD31 immunostaining revealed that quercetin glucosides increased capillary density in the ischemic muscle (control, 200 ± 24/mm(2); quercetin glucosides, 364 ± 41/mm(2), p<0.01). Quercetin glucosides did not promote tumor growth. The beneficial effect of quercetin glucosides was abrogated in eNOS-deficient mice. SIGNIFICANCE These results suggest that quercetin glucosides may have therapeutic potential to promote angiogenesis in ischemic tissue.

Perigraft Seroma after Endovascular Repair of the Abdominal Aortic Aneurysm

症例は75歳,男性.腹部大動脈瘤の診断で1997年にステントグラフト(SG)手術(大動脈-片側大腿動脈型SG+大腿-大腿動脈交叉バイパス)を施行した.術後は順調でendoleakも認めなかった.2001年6月に腹部膨満感を認めたため当科を受診した.CT検査で,空置した瘤径が13cmと増大していた.画像上明らかなendoleakは認めなかったが,切迫破裂の状態と判断して再手術を行った.手術所見では,空置瘤内に血流を認めず白色のゼリー状の物質が充満していた.PTFEグラフトによるseromaと判断し,グラフト部を可及的に摘出してDacronグラフトで置換した.その後の経過は良好であった.瘤内の病理所見では,血球成分や血小板の関与がないことから,浸出物により構成されたperigraft seromaとして矛盾ない所見であった.