Makoto Mo

Angiogenic growth factor release system for in vivo tissue engineering: a trial of bone marrow transplantation into ischemic myocardium

For successful in vivo tissue engineering, a growth factor release system will be useful. We adopted autologous bone marrow transplantation as an angiogenic growth factor release system. Bone marrow transplanted into a synthetic vascular prosthesis produced continuous synthesis of angiogenic growth factors, resulting in rapid neointima formation on the prosthesis after implantation. We expected a similar angiogenic phenomenon to occur if bone marrow was transplanted into ischemic myocardium. Bone marrow was transplanted into ischemic myocardium created in dogs. Marrow cells continued synthesis of angiogenic growth factors, which were effective in protecting the capillary network from ischemia, but not myocytes. Autologous bone marrow was injected intramuscularly into ischemic myocardium created in the left ventricular wall of dogs. Control operations were performed without bone marrow. On days 3 and 7, marrow cells survived, and their adjacent cells and the surrounding extracellular matrix were immunohistochemically bFGF reactive. At 3 weeks, no marrow cells were identified. Myocytes disappeared, but the capillary blood vessel networks remained. With some exceptions, these capillaries did not contain blood cell components. In the controls, scar tissue with a very small number of capillaries was formed. In conclusion, marrow cells survived for a short period of time after transplantation, and continued synthesis of angiogenic growth factors, which were effective in protecting endothelial cells from ischemia, but not myocytes. Therefore, the results also suggest that there are limitations in the treatment of ischemic myocardium using angiogenic growth factors alone.For successful in vivo tissue engineering, a growth factor release system will be useful. We adopted autologous bone marrow transplantation as an angiogenic growth factor release system. Bone marrow transplanted into a synthetic vascular prosthesis produced continuous synthesis of angiogenic growth factors, resulting in rapid neointima formation on the prosthesis after implantation. We expected a similar angiogenic phenomenon to occur if bone marrow was transplanted into ischemic myocardium. Bone marrow was transplanted into ischemic myocardium created in dogs. Marrow cells continued synthesis of angiogenic growth factors, which were effective in protecting the capillary network from ischemia, but not myocytes. Autologous bone marrow was injected intramuscularly into ischemic myocardium created in the left ventricular wall of dogs. Control operations were performed without bone marrow. On days 3 and 7, marrow cells survived, and their adjacent cells and the surrounding extracellular matrix were immunohistochemically bFGF reactive. At 3 weeks, no marrow cells were identified. Myocytes disappeared, but the capillary blood vessel networks remained. With some exceptions, these capillaries did not contain blood cell components. In the controls, scar tissue with a very small number of capillaries was formed. In conclusion, marrow cells survived for a short period of time after transplantation, and continued synthesis of angiogenic growth factors, which were effective in protecting endothelial cells from ischemia, but not myocytes. Therefore, the results also suggest that there are limitations in the treatment of ischemic myocardium using angiogenic growth factors alone.

A new antithrombogenic RV-PA valved conduit.

A new antithrombogenic right ventricular (RV)-pulmonary artery (PA) valved conduit was developed using a bovine jugular vein containing a natural valve. To maintain the natural and mechanical properties of the venous tissue, a hydrophilic cross-linking reagent, glycerol polyglycidyl ether polyepoxy compound (PC) was used instead of glutaraldehyde (GA). Moreover, to induce antithrombogenicity, heparin was bonded to the inner surface of the bovine jugular vein cross-linked with PC. Conduits of 18 to 20 mm inner diameter (ID) were implanted between the RV and PA in nine dogs weighing 7-17 kg, with the native main PA being ligated proximally. The handling and suturing of the graft was easy and adaptable, and the anastomosis was completed with excellent coaptation and no blood leakage at the suture lines. All animals were chronic survivors, but one animal died of hematemesis on the 438th postoperative day. Grafts were explanted from 182 to 385 days after implantation. The luminal surface of the conduits were white, glistening, and smooth with good coaptation of the cusps, without calcification or degenerative changes except for one cusp that showed a minimal deformation with a small thrombus. Macroscopic and microscopic observation showed that there were no thrombi at the anastomotic lines, but small thrombi on the luminal surface of the conduits near the cusps and in some cusps. Endothelium-like cells were noticed on the luminal surface of the graft, except in the area near the cusps, and on one cusp at 196 days after surgery. These results indicated that the new RV-PA valved conduit provided adequate antithrombogenicity by temporary slow heparin release, followed later by endothelialization of the graft in a low pressure system at 1 year after implantation.

A New Cardiac Wall Substitute with High Affinity for Fibroblasts that Can Induce an Endothelial Cell Lining

A new cardiac wall substitute (PC graft) was developed using equine pericardium cross-linked with a polyepoxy compound. Compared with glutaraldehyde cross-linked pericardium (GA graft), the PC graft showed an approximately 10 times higher affinity for fibroblasts as measured by our in vitro cell migration and proliferation test. Six PC grafts (5 x 3 cm) were implanted into the right ventricular-pulmonary outflow tract position as a cardiac wall patch. Three GA grafts were used as controls. The PC grafts showed excellent handling during surgery because of their softness and elasticity. These grafts were explanted at 2 and 7-8 weeks after implantation. All PC grafts showed a white and glistening surface without any thrombus formation except in one case where thrombus deposition was observed in the center of the graft. In the GA grafts, thrombus adhered to the luminal surface. Light microscopic observation showed that the PC graft surface was covered with a connective tissue layer and significant fibroblast infiltration. Approximately 60% of the area infiltrated by these fibroblasts was endothelialized, whereas in the GA graft, endothelialization was limited to within 2-5 mm of the suture line. Other areas were covered with a thrombus layer without any endothelial cells or fibroblast infiltration. PC cross-linking can maintain the biologic and mechanical properties of the original materials. The PC graft offered excellent affinity for fibroblast migration and proliferation, which induced an endothelial cell lining on the surface. The results of this experiment indicated that the PC graft, which obtained the natural antithrombogenic property, was superior to a GA graft in terms of safety as well as mechanical, physiologic, and biologic properties as a cardiac wall substitute.

A collagen coated fabric vascular prosthesis as a punctureable A-V shunt.

A fabric vascular prosthesis sealed with succinylated collagen (SC) was developed as an arteriovenous (A-V) shunt graft for hemodialysis. The SC graft was soft, pliable, flexible, and puncturable, with quick hemostasis. A needle puncture made a smaller hole in the SC graft wall than in a control expanded-polytetrafluoroethylene (e-PTFE) graft such as is usually used for an A-V shunt. The SC graft was extremely hydrous, because it is sealed with water, which is absorbed into the intermolecular spaces of negatively charged collagen. The SC suspension was injected with pressure into a knitted fabric vascular prosthesis wall (water permeability, 1,200 ml) so as to become entangled in the Dacron network. The graft then was lyophilized and thermally cross-linked. Water leakage from six holes created by an 18 G needle puncture in vitro under water pressure of 120 mmHg was 34.5 +/- 29.9 ml/min in the SC graft and 169.9 +/- 38.5 ml/min in the control e-PTFE graft. Hemostatic time at six 18G needle puncture sites on grafts implanted in the abdomen of 12 dogs was 4.5 +/- 2.5 mins in the SC graft and 34.2 +/- 11.5 mins in the control graft. After implantation, the luminal surface of the SC grafts had a thinner thrombus layer than did the control grafts. After 1 week, a thin thrombus layer covered the luminal surface of the SC grafts, and puncture sites were recognized as small dots under it, but in the control grafts, the thrombus layer was thick and the puncture sites could not be seen. These results suggest that the SC graft is less thrombogenic and has less blood leakage from the puncture sites than does the control graft.

Clinical Results of Long and Short Saphenous Vein Stripping for Primary Varicose Veins

To review the long term clinical results of long and short saphenous vein stripping (LSS) as radical operation for primary varicose veins.

Sonographic Findings of Preserved Saphenous Veins in Primary Varicose Veins Patients

High ligation of the saphenous vein without stripping (HL) and selective stripping of upper part of the saphenous veins (SS ) have been performed to reduce surgical invasiveness of conventional varicose veins surgery and to preserve possible future graft materials for arterial reconstruction[1,2,3]. Aim of this study is to evaluate morphology and competence of preserved saphenous veins by sonography and Doppler flowmetry or Duplex scanning.

Natural Antithrombogenic Surface Created In Vivo for an Artificial Heart

Thromboses and embolisms arising from the prosthesis surface are among the most significant problems in artificial hearts. Although antithrombogenic polymer materials have been developed to prevent thrombus formation, they have problems in long-term applications. While the natural antithrombogenicity of endothelial cells is reliable, development of the cell lining requires long periods after implantation. To overcome this problem, we developed a method to obtain rapid endothelialization by seeding autologous venous tissue fragments. The rate of endothelialization and the antithrombogenicity were evaluated in a small-diameter vascular graft treated by this method. A canine jugular vein was minced and suspended with heparin. This was sieved through the wall of a fabric prosthesis by pressurized injection, causing tissue fragments to be trapped in the graft wall. Twenty out of 32 grafts were patent up to 400 days, while all 12 control fabric grafts with preclotting were occluded. The luminal surface at 1 h showed no thrombus deposition. At 1 month, complete endothelialization was noted. There were no degenerative changes in any neointimae of the explanted grafts. These results indicated that heparin reduces the thrombogenicity of collagen by electrostatic binding during endothelialization, and that a natural antithrombogenic surface can be obtained by this method within a short period.