Whiteley L O, Hudson L, Pretlow T P
Procter & Gamble, Cincinnati, Ohio 45253, USA.
Toxicol Pathol. 1996 Nov-Dec;24(6):681-9. doi: 10.1177/019262339602400602.
Aberrant crypt foci (ACFs) are putative preneoplastic lesions in the colonic mucosa identified by examining methylene blue-stained whole mounts of colon. ACFs have been previously described in rats treated with genotoxic colon carcinogens. This study determined whether or not a nongenotoxic colon carcinogen could induce ACFs and compared the morphology of these ACFs with those induced by a genotoxic colon carcinogen. Six-wk-old Fischer-344 rats were administered dextran sulfate (DSS, nongenotoxin) in the drinking water or azoxymethane (AOM, genotoxin) by single subcutaneous injection. Rats were sacrificed at 9 and 14 wk after study initiation. Colons were fixed and stained with methylene blue, and the mucosal surface of transilluminated whole mounts was examined with a microscope. The number of ACFs and number of crypts per focus (multiplicity) were recorded. Representative ACFs were processed into glycol methacrylate for hexosaminidase enzyme histochemistry and sections of the remaining colon containing ACFs were embedded in paraffin for morphologic evaluation. In whole mounts, ACFs from AOM- and DSS-treated rats had elongated slit-to-oval-shaped lumens surrounded by a thickened and intensely stained epithelium. DSS-induced aberrant crypts differed from those induced by AOM in that they were frequently larger, tended not to form discrete foci circumscribed by normal crypts, and were located adjacent to ulcers. Total ACFs and large foci (4 or more crypts/focus) were significantly more numerous in AOM-treated rats at both time points. Histologically, DSS-induced ACFs had segmental to diffuse loss of hexosaminidase activity, mucin depletion to increased prominence of goblet cells, and marked distortion of crypt architecture. AOM-induced ACFs had diffuse loss of hexosaminidase activity, variable depletion of mucin, and less distortion of crypt architecture. Variable degrees of epithelial dysplasia were seen in ACFs with both carcinogens, but dysplasia was more severe in DSS-induced ACFs. Colonic mucosal neoplasms were induced by both carcinogens. In subchronic studies, the ACF assay may be a useful method to improve the identification and characterization of xenobiotic-induced changes in colonic mucosal crypts.
异常隐窝灶（ACFs）是结肠黏膜中假定的癌前病变，通过检查亚甲蓝染色的全层结肠标本得以识别。ACFs此前已在经基因毒性结肠致癌物处理的大鼠中被描述过。本研究确定了一种非基因毒性结肠致癌物是否能诱导ACFs，并将这些ACFs的形态与由基因毒性结肠致癌物诱导的ACFs的形态进行比较。六周龄的Fischer-344大鼠通过在饮用水中给予硫酸葡聚糖（DSS，非基因毒素）或通过单次皮下注射给予氧化偶氮甲烷（AOM，基因毒素）进行处理。在研究开始后的第9周和第14周处死大鼠。将结肠固定并用亚甲蓝染色，然后用显微镜检查透照全层标本的黏膜表面。记录ACFs的数量和每个病灶的隐窝数量（多灶性）。选取代表性的ACFs用甲基丙烯酸乙二醇酯处理用于己糖胺酶组织化学分析，将剩余含有ACFs的结肠部分切片用石蜡包埋用于形态学评估。在全层标本中，AOM处理组和DSS处理组大鼠的ACFs都有细长的裂隙状至椭圆形管腔，周围是增厚且染色强烈的上皮。DSS诱导的异常隐窝与AOM诱导的不同，在于它们通常更大，往往不形成由正常隐窝界定的离散病灶，且位于溃疡附近。在两个时间点，AOM处理组大鼠的总ACFs和大病灶（每个病灶4个或更多隐窝）数量明显更多。组织学上，DSS诱导的ACFs有节段性至弥漫性的己糖胺酶活性丧失黏液耗尽至杯状细胞突出增加，以及隐窝结构明显扭曲。AOM诱导的ACFs有弥漫性的己糖胺酶活性丧失、黏液可变程度的耗尽以及隐窝结构较少的扭曲。两种致癌物诱导的ACFs中均可见不同程度的上皮发育异常，但DSS诱导的ACFs中发育异常更严重。两种致癌物均可诱导结肠黏膜肿瘤。在亚慢性研究中，ACF检测可能是一种有用的方法，可用于改进对外源性物质诱导的结肠黏膜隐窝变化的识别和表征。
