Effects of a single heparin bolus on neointimal growth after arterial injury in intact rabbits

Heparin coating of small-caliber decellularized xenografts reduces macrophage infiltration and intimal hyperplasia

Small-caliber decellularized xenografts with surface heparin coating are known to reduce in vivo thrombogenicity. This study was performed to examine whether heparin coating on the small-caliber decellularized xenografts would reduce macrophage infiltration and intimal hyperplasia. In a rabbit model of bilateral carotid implantation, each of the animals (n = 18) received a heparin-coated decellularized xenograft from a canine carotid artery on one side and a nonheparin-coated one on the other side. These experiments were terminated respectively at 1 week (n = 6), 3 weeks (n = 6), and 12 weeks (n = 6). Results showed that, compared with the nonheparin-coated grafts, the heparin-coated grafts had significantly less macrophage infiltration 1 week after implantation, identified by the mouse antirabbit macrophage antibody (RAM11)-positive cells on the vascular wall, covering all the proximal, middle, and distal parts of the grafts (P < 0.01). Moreover, the heparin-coated grafts also showed less deposition of proliferation cell nuclear antigen (PCNA)-positive cells on the vascular wall, indicating less cell proliferation, which was significant not only at 1 week (P < 0.01) but also at 12 weeks (P < 0.01). Intimal hyperplasia, measured by the intimal : media (I : M) ratio, was found similar in both groups at 1 and 3 weeks. However, the I : M ratio was significantly lower in the heparin-coated group than in the nonheparin-coated group at 12 weeks, especially in the proximal anastomosis area (0.76 +/- 0.12 vs. 0.345 +/- 0.06, P < 0.01). Heparin coating of small-caliber decellularized xenografts is associated with an early reduction of macrophage infiltration and intimal hyperplasia in a rabbit model of bilateral carotid artery implantation for 12 weeks. Thus, heparin coating appears to deliver not only the antithrombogeneity but also the antiproliferative property for small-caliber decellularized xenografts.

INVESTIGAÇÃO DO USO DE HEPARINIZAÇÃO REGIONAL DURANTE ISQUEMIA ARTERIAL TEMPORÁRIA EM COELHOS

O objetivo deste trabalho foi avaliar o efeito da heparinização regional durante a isquemia arterial temporária em coelhos. Os parâmetros avaliados foram a medida do tempo de tromboplastina parcial ativada (TTPa) e a presença ou ausência de trombos ou edema endotelial nos vasos estudados. Foram utilizados 40 coelhos Nova Zelândia, distribuídos em dois grupos de 20 animais. Após dissecção e reparo da artéria ilíaca esquerda, realizou uma arteriotomia e introduziu-se um cateter de polietileno para injeção de solução de heparina no grupo experimento ou de soro fisiológico no grupo controle. O TTPa foi medido no início do experimento e após 90 minutos de isquemia, não sendo encontrado diferenças significantes entre os valores iniciais e ao final do experimento. Na avaliação microscópica não foi encontrada a presença de trombos nos vasos dos animais de ambos os grupos. Em apenas um animal do grupo controle houve a ocorrência de espessamento intimal e desarranjo da camada média, interpretado como edema endotelial, porém este dado não foi significante. Concluiu-se que a injeção intra-arterial de heparina na dose de 60 UI/kg peso não provocou alterações significantes na coagulação sistêmica do coelho, e que na ausência de lesão endotelial não ocorreu trombose dos vasos estudados, com ou sem a utilização de heparina.

Heparin proteoglycans released from rat serosal mast cells inhibit proliferation of rat aortic smooth muscle cells in culture

-Mast cells are present in the human arterial intima. To study whether mast-cell degranulation influences the rate of proliferation of smooth muscle cells, we cocultured sensitized (IgE-bearing) rat serosal mast cells and rat aortic smooth muscle cells (SMCs). When sensitized mast cells were stimulated to degranulate with antigen, the rate of proliferation of the cocultured SMCs decreased sharply. This inhibitory effect was found to be due mainly to the very high molecular weight (Mr) heparin proteoglycans (average Mr 750 000) released from the stimulated mast cells. When the heparin proteoglycans were purified from mast-cell granule remnants and added to the SMC culture, they were found to block the cell cycle at the G0-->S transition and the exit from the G2/M phase, their inhibitory effect resembling that of commercial heparin. However, in contrast to the reported dependence of the inhibitory effect of commercial heparin on the release of transforming growth factor-beta from serum, the inhibitory effect of the mast cell-derived heparin proteoglycans in the presence of serum was not transforming growth factor-beta dependent. Moreover, the effect of the mast cell-derived heparin proteoglycans was more efficient than that of commercial heparins of high (average Mr 15 000) and low (average Mr 5000) molecular weight. We also purified heparin glycosaminoglycans (average Mr 75 000) from the mast cell-derived heparin proteoglycans and found that they also inhibited SMC growth efficiently, although less strongly than their parent heparin proteoglycans. These results reveal, for the first time, that mast cells are able to regulate SMC growth. Thus, activated mast cells, by releasing heparin proteoglycans, possibly participate in the regulation of SMC growth in the human arterial intima, the site of atherogenesis.

Materials and biomaterials for interventional radiology

Devices used in interventional radiology have significantly developed in the past few years. In order to understand the trends of this development, we analyzed how new interventional devices are progressively incorporating materials having original physical properties, and how developers are today progressively turning towards biomaterials, with respect to the new regulatory environment, and the requirements of biocompatibility.