Rubin P, Williams J P, Riggs P N, Bartos S, Sarac T, Pomerantz R, Castano J, Schell M, Green R M
Department of Radiation Oncology, University of Rochester Medical Center, NY, USA.
Int J Radiat Oncol Biol Phys. 1998 Mar 1;40(4):929-41. doi: 10.1016/s0360-3016(97)00937-1.
The major radiobiological issue in determining the rationale for the use of radiation to inhibit vascular restenosis is the identification of the target cell(s) and/or cytokine(s) responsible for neointimal hyperplasia and vascular remodeling. The central hypothesis of this report is that the macrophage/monocyte and PDGF are key elements in the process of neointimal hyperplasia seen following angioplasty, similar to their role in lesion formation and progression found in atherosclerotic thickening. Specific immunohistochemical and cytochemical stains were applied to a rat carotid model in a temporal series after balloon angioplasty to determine macrophage activity vs. smooth muscle cell proliferation, the latter being classically thought to be the cell responsible for restenosis.
Neointimal hyperplasia was created in an established rat carotid artery model by a balloon catheter technique. Immediately following injury, treatment groups received irradiation via high dose rate (HDR) brachytherapy, the 192Ir source being placed externally to the vessel. Radiation was delivered to a length of 2 cm of the injured vessel at doses of 5, 10, and 15 Gy, and the animals were sacrificed at various time points following treatment (24 h to 6 months). Serial sections of tissue were stained immunohistochemically with the primary antibodies CD11b, mac-1, anti-PDGF, and alpha-smooth muscle actin.
Immediately (24 h) postinjury, there is an apparent migration of macrophages seen in the adventitia; after 1 week, proliferation and migration of macrophages could be seen clearly within all the vessel layers, especially in the intima; by 3 weeks, when there was evidence of neointimal hyperplasia, macrophages could still be seen, mainly in the intima scattered among the smooth muscle cells and myofibroblasts, and to a lesser degree at 6 months. There was corresponding expression of PDGF, whenever and wherever there were zones of activation/neointimal hyperplasia. Alpha-smooth muscle actin staining identified the smooth muscle cells distinct from the macrophages, and these SMCs exhibited activation in the neointimal hyperplasia zones at all later time points. Furthermore, we showed that radiation significantly reduced the macrophage population, while the onset of neointimal hyperplasia was accompanied by a return of the macrophage population.
Our results suggest that the activated adventitial macrophage/monocyte are the key cells responsible for initiating the arterial neointimal hyperplasia and vascular remodeling developing postangioplasty as they are in the initiation and perpetuation of atheromatous thickening. Irradiation delivered immediately postinjury is, therefore, highly effective, because the macrophage population is exquisitely radiosensitive.
确定使用辐射抑制血管再狭窄的基本原理时，主要的放射生物学问题是识别导致内膜增生和血管重塑的靶细胞和/或细胞因子。本报告的核心假说是，巨噬细胞/单核细胞和血小板衍生生长因子（PDGF）是血管成形术后内膜增生过程中的关键因素，类似于它们在动脉粥样硬化增厚的病变形成和进展中所起的作用。在球囊血管成形术后的不同时间点，对大鼠颈动脉模型进行特定的免疫组织化学和细胞化学染色，以确定巨噬细胞活性与平滑肌细胞增殖情况，传统观点认为平滑肌细胞是导致再狭窄的细胞。
采用球囊导管技术在已建立的大鼠颈动脉模型中造成内膜增生。损伤后立即对治疗组进行高剂量率（HDR）近距离放射治疗，将铱-192源置于血管外部。以5、10和15 Gy的剂量对损伤血管2 cm的长度进行照射，并在治疗后的不同时间点（24小时至6个月）处死动物。组织连续切片用抗CD11b、巨噬细胞抗原-1（mac-1）、抗血小板衍生生长因子（PDGF）和α-平滑肌肌动蛋白的一抗进行免疫组织化学染色。
损伤后立即（24小时），在外膜可见巨噬细胞明显迁移；1周后，在所有血管层中均可清晰看到巨噬细胞的增殖和迁移，尤其是在内膜；到3周时，有内膜增生的证据，巨噬细胞仍可见，主要在内膜中散在于平滑肌细胞和成肌纤维细胞之间，6个月时程度较轻。只要有激活/内膜增生区域，就有血小板衍生生长因子的相应表达。α-平滑肌肌动蛋白染色可识别出与巨噬细胞不同的平滑肌细胞，这些平滑肌细胞在所有后期时间点的内膜增生区域均表现出激活状态。此外，我们还表明，辐射显著减少了巨噬细胞数量，而内膜增生的开始伴随着巨噬细胞数量的回升。
我们的结果表明，激活的外膜巨噬细胞/单核细胞是血管成形术后引发动脉内膜增生和血管重塑的关键细胞，就如同它们在动脉粥样硬化增厚的起始和持续过程中所起的作用一样。因此，损伤后立即进行照射非常有效，因为巨噬细胞群体对辐射极为敏感。
