Modelos experimentais de hiperplasia intimal: efeitos da radiação ionizante

Abstract

A hiperplasia intimal ocorre em resposta à lesão vascular, pode complicar significantemente os procedimentos vasculares abertos e endovasculares, levando a diferentes graus de estenose do lume vascular e isquemia. De certo modo, a hiperplasia intimal está presente em todos os tipos de reconstruções vasculares, incluindo enxertos autólogos, homólogos e sintéticos, após angioplastias com ou sem colocação de stent e em órgãos transplantados. Um dos maiores desenvolvimentos experimentais nos últimos anos, para prevenção da hiperplasia intimal, é a utilização da radiação ionizante. A radiação ionizante inibe a proliferação de muitos tipos celulares, incluindo fibroblastos e células musculares lisas in vitro e a síntese de colágeno em culturas de fibroblastos. Modelos animais de experimentação têm sido utilizados para o desenvolvimento de novas estratégias de tratamento e entendimento dos mecanismos fisiopatológicos básicos da hiperplasia intimal. Assim, o objetivo desta revisão e atualização da literatura é o de expor os diferentes modelos de animais de experimentação para o desenvolvimento de hiperplasia intimal, o tipo de lesão empregada, as artérias mais utilizadas e os efeitos encontrados com o uso de diferentes tipos de fontes de radiação ionizante.<br>Most complications that may occur in response to vascular injury of endovascular and open vascular procedures are due to intimal hyperplasia. To a certain extent, intimal hyperplasia is present in all types of vascular reconstruction, including autologous grafts, allografts, and prosthetic grafts found in solid organs transplanted, having a substantial role in chronic rejection and following angioplasty with or without stenting. One of the greatest developments in recent years towards prevention of intimal hyperplasia is the use of ionizing radiation. Ionizing radiation inhibits proliferation of many cell types including fibroblasts and smooth muscle cells in vitro, and also suppresses the synthesis of collagen by cultured fibroblasts. Animal models have been a cornerstone to develop strategies aimed at understanding the basic physiopathologic mechanisms of intimal hyperplasia and at evaluating novel treatment strategies for clinical conditions. So, the aim of this study was to analyze animals models of intimal hyperplasia, type of injury, artery segments most used, as to the effects of different kinds and sources of ionizing radiation

Morphometric analysis of the intimal reaction after stent implantation in iliac arteries submitted to angioplasty in pigs

“…Schwartz 14,15 states that the phases of neointimal formation may be similar to humans in the pig model. These considerations agree with Costa et al 16 , which emphasises the similarities between pigs and humans as regards to the cardiovascular anatomy, physiology and coagulation system. The major limitation of the animal models is the lack of pre-existing disease of the vascular wall, like arteriosclerosis in humans 8 .…”

“…The reaction to a lesion in the pig experimental model led to the formation of neointimal hyperplasia in one or two weeks, and the process is complete in twenty-eight days. In terms of histology, size and cellular density this is similar to what happens in humans 13,16 . Verheye et al 20 , after implanting stents in the iliac and carotid arteries of pigs, conducted histological studies of one to six months, stating that within one month the vascular wall was completely covered by endothelial-type cells.…”

Computational Analysis of Anastomotic Angles by Blood Flow Conditions in Side-to-End Radio-Cephalic Fistulae Used in Hemodialysis

“…where u is the velocity vector, p is the hydrostatic pressure, τ is the deviatoric part of the stress tensor, ρ is the blood density (here set as 1045 kg/m 3 ), µ is the blood viscosity (considered 4.0 mPa.s), div is the divergence operator, ∇ is the gradient operator and n is the unit outward normal vector. Equations (4) and (5) represent nonslip and developed flow boundary conditions, and Equation 6accommodates a pulsating function at the inlet of the artery, with pulse period 1.0 s T = with data taken from [2] which have been fitted here by Equation 7and illustrated in Figure 2. This inlet pulsating velocity was prescribed for each anastomotic angle case as being a plug profile, according to the boundary condition Equation 6, which means a zero injection angle relative to the longitudinal axis of the artery, at a sufficient distance from the fistula (half of the artery length) to ensure fully developed flow before approaching the fistula.…”

“…Intimal hyperplasia is a process in which cells proliferate on the vessel walls in response to injury. This can reduce the diameter of the vessels, obstructing the passage of blood, and can lead to blood clotting [4] [5] forming stenoses. The main region of stenosis formation generated by hyperplasia is near the junction of the vein or graft and the main vessel, generally an artery, causing failure in the maturation of vascular grafts for hemodialysis [6].…”

Light-emitting diode stimulates radiodermatitis recovery

“…Signs and symptoms range from mild local burning sensitivity to skin ulcerations in the irradiated area. Radiodermatitis can also be classified according to the time of onset for the appearance of symptoms in acute (in the first 90 days after irradiation) or chronic (months and years after irradiation) 1 , 5 , 6 .…”