Decellularized porcine aortic intima-media as a potential cardiovascular biomaterial.

OBJECTIVES: The aim of this research is to investigate the histological and mechanical properties of decellularized aortic intima-media, a promising cardiovascular biomaterial. METHODS: Porcine aortic intima-media was decellularized using two methods: high hydrostatic pressurization (HHP) and sodium dodecyl sulphate (SDS). The histological properties were characterized using haematoxylin and eosin staining and Elastica van Gieson staining. The mechanical properties were evaluated using a tensile strength test. RESULTS: The structure of the HHP-treated samples was unchanged histologically, whereas that of the SDS-treated samples appeared structurally loose. Consequently, with regard to the mechanical properties of SDS-decellularized intima-media, elastic modulus and tensile strength were significantly decreased. CONCLUSIONS: The decellularization method affected the structure and the mechanical properties of the biomaterial. The HHP-treated sample was structurally and mechanically similar to the untreated control. Its mechanical properties were similar to those of human heart valves and the iliac artery and vein. Our results imply that porcine aortic intima-media that is decellularized with HHP is a potential cardiovascular biomaterial.

The "no-touch" harvesting technique for vein grafts in coronary artery bypass surgery preserves an intact vasa vasorum.

OBJECTIVES: Our objective was to evaluate the impact of vein graft harvesting technique on structure and function of vasa vasorum. METHODS: Paired segments of great saphenous veins harvested either with conventional harvesting technique or no-touch technique were obtained from 9 consecutive patients undergoing coronary artery bypass grafting. Quantitative measurements, using immunohistochemistry and morphometry, were performed. Ultrastructural analyses of vasa vasorum were performed with electron microscopy. Video footage of superficial vasa vasorum in an implanted saphenous vein graft harvested with the no-touch technique was captured during a coronary bypass operation and is presented for online viewing. RESULTS: The total area of vasa vasorum in vein grafts harvested with the conventional technique was significantly reduced both in the media (P = .007) and in the adventitia (P = .014) compared with vein grafts harvested with the no-touch technique. Ultrastructural findings indicated that the no-touch technique preserved an intact vasa vasorum whereas the conventional technique did not. Video footage showed retrograde flow in the vasa vasorum in vein graft harvested with the no-touch technique. CONCLUSIONS: These findings show that the no-touch technique for saphenous vein graft harvesting for coronary bypass grafting preserves an intact vasa vasorum. This could represent one of the mechanisms underlying the improved patency of saphenous vein grafts harvested with this technique.

Dynamics of medial smooth muscle changes after carotid artery transplantation in transgenic mice expressing green fluorescent protein.

BACKGROUND: Recent observations have demonstrated the importance of host cells in neointima formation after transplantation. Because little is known regarding the dynamics of host-derived cells in the graft media, we investigated this question in a mouse carotid artery transplantation model. METHODS: C57BL/6 carotid arteries were orthotopically transplanted into BALB/c mice ubiquitously expressing enhanced green fluorescent protein. Grafts were harvested at 1, 2, 4, and 8 weeks after transplantation for histologic examination. No immunosuppression was used. RESULTS: Immunostaining and semiquantitative analysis of cross sections showed that donor medial smooth muscle cells decreased over time in the graft media, whereas green fluorescent protein-positive/smooth muscle alpha-actin-positive cells (i.e., cells of host origin) increased over time. Interestingly, host cells were located only in the inner media and the neointima at 2 weeks and thereafter also in the outer media, indicating that the host-derived cells entered the media from the luminal side rather than from the adventitia. In longitudinal sections, there were no differences in the accumulation of donor- and host-derived cells between the end and middle regions of the graft media at 8 weeks. CONCLUSIONS: After transplantation, medial cells were replaced by alpha-actin-expressing host cells that were probably derived from circulating precursor cells. Our observations differ from the traditional view of a major contribution of donor medial smooth muscle cells to the neointima formation. Thus, circulating progenitor cells may be important for graft vessel disease.

Inhibition of intimal hyperplasia in rat aortic allografts with cyclosporine.

The rat aortic transplant model of chronic rejection was used to study the effect of cyclosporine (CsA) on the development of intimal hyperplasia. ACI and Lewis rat strains were used to create isograft and allograft CsA nontreated and treated groups. After orthotopic abdominal aortic transplantation, recipients received either no treatment, CsA 2.5 mg/kg/day, CsA 5 mg/kg/day, or CsA 10 mg/kg/day by gavage. Treated grafts were harvested at 3 and 6 months after transplantation, and computer image digital analysis was used to measure intimal and medial areas of graft cross-sections. At 3 months, the reduction in percent intima was 62% (P = 0.005), 74% (P = 0.002), and 97% (P < 0.0001) for the 2.5-, 5-, and 10-mg/kg allograft groups, respectively. There was a 93% (P < 0.0001) reduction in percent intima at 6 months in the 10-mg/kg allograft group. CsA treatment also preserved the aortic media. In comparison to nontreated isografts, medial area in nontreated allografts was decreased by 37% at 3 months after transplantation. In contrast, medial area was not significantly changed in CsA-treated recipients (10 mg/kg/day) in comparison to nontreated isografts. More importantly, medial nuclear density was preserved in the CsA-treated recipients in comparison to nontreated allografts and was similar to treated or nontreated isografts. In conclusion, daily high dose CsA treatment was found to markedly inhibit intimal hyperplasia in rat aortic allografts up to 6 months after transplantation, which suggests that CsA at an adequate dosage can suppress chronic rejection.

Enhancement of transplantation-associated atherosclerosis by CMV, which can be prevented by antiviral therapy in the form of HPMPC.

Effects of acute cytomegalovirus (CMV) infections on transplantation-associated atherosclerosis (TxAA) were studied in a rat model for chronic vascular rejection. Rats underwent orthotopic abdominal allogeneic aorta transplantation. Neo-intima formation and media thinning was quantitated by measurement of cross-sectional surface areas (CSA) at day 50 post transplantation (Tx). Acute rat cytomegalovirus (RCMV) infection, established at the moment of maximum intimal proliferation and influx of inflammatory cells in the adventitia, resulted in enhanced neo-intima formation, accompanied by increased influx and proliferation of smooth muscle cells (smc) in the intima. This effect was completely inhibited by HPMPC, a very potent and selective inhibitor of CMV replication, indicating the virus specificity of the measured effects. Despite increased neointima formation, media thinning ("necrosis") was not affected by RCMV infection.

Effect of 15-deoxyspergualin on allograft arterio-sclerosis and growth factor synthesis in the rat.

Chronic rejection is a major cause for late graft loss. Typical vascular changes in the grafts are adventitial inflammation, disappearance of myocytes in the media and thickening of the intimal layer. We investigated the effect of a new immunosuppressive drug, 15-deoxyspergualin (DSG), on chronic rejection using our rat aortic allograft model. At the dose of 1.0 mg/kg per day, DSG significantly reduced all histopathological parameters of chronic rejection, thus, inhibiting the generation of allograft arteriosclerosis. Growth factor synthesis in the grafts was determined by reverse transcription reaction with oligo dT primers and semiquantitated by polymerase chain reaction. The expression of several growth factors, PDGF-BB, IGF-1, EGF an TGF-beta, was suppressed to 16-60% of the non-treated allograft level. This indicated that DSG may work via suppression of growth factor synthesis and, thus, inhibits the generation of chronic rejection.