Clowes A W, Schwartz S M
Circ Res. 1985 Jan;56(1):139-45. doi: 10.1161/01.res.56.1.139.
Cellular accumulation in the intima of injured artery has generally been attributed to smooth muscle cell proliferation. Since smooth muscle cells in normal artery are found mainly in the media, migration of smooth muscle cells into the intima has been considered a necessary prerequisite for subsequent myointimal thickening. The nondividing medial cells would appear to have no role in the reparative process. We have investigated in the rat ballooned carotid the possibility that nondividing cells might also contribute to injury-induced intimal thickening. All proliferating smooth muscle cells were labeled by 3H-thymidine given by continuous intraperitoneal infusion. The amounts of 3H-thymidine used were not toxic and did not inhibit smooth muscle cell proliferation. Autoradiograms performed on histological cross-sections showed a progressive decrease in the fraction of unlabeled cells at 3, 7, and 14 days after carotid injury. However, the actual number of nondividing cells remained constant. The calculated growth fraction for the 14-day period was 40%. A substantial number of unlabeled cells was observed in the intima. These data have led us to conclude that only a small fraction of smooth muscle cells in an artery proliferate in response to the injury stimulus, and do so shortly after injury, or not at all. Furthermore, nondividing, as well as proliferating smooth muscle cells, can migrate and contribute, in a substantial way, to the increase in intimal smooth muscle cell number.
损伤动脉内膜中的细胞积聚通常被认为是平滑肌细胞增殖所致。由于正常动脉中的平滑肌细胞主要存在于中膜，平滑肌细胞向内膜迁移被视为随后肌内膜增厚的必要前提。不分裂的中膜细胞似乎在修复过程中不起作用。我们在大鼠球囊损伤颈动脉模型中研究了不分裂细胞是否也可能导致损伤诱导的内膜增厚。通过连续腹腔内注射给予³H-胸腺嘧啶核苷标记所有增殖的平滑肌细胞。所用的³H-胸腺嘧啶核苷剂量无毒且不抑制平滑肌细胞增殖。对组织学横断面进行的放射自显影片显示，在颈动脉损伤后3天、7天和14天，未标记细胞的比例逐渐下降。然而，不分裂细胞的实际数量保持不变。计算得出的14天期间的生长分数为40%。在内膜中观察到大量未标记细胞。这些数据使我们得出结论，动脉中只有一小部分平滑肌细胞会对损伤刺激产生增殖反应，且这种反应在损伤后不久发生，或者根本不发生。此外，不分裂的以及增殖的平滑肌细胞都可以迁移，并在很大程度上促使内膜平滑肌细胞数量增加。
