Wise L David, Xue Dahai, Winkelmann Christopher T
Merck Research Laboratories, West Point, Pennsylvania 19486, USA.
Birth Defects Res B Dev Reprod Toxicol. 2010 Oct;89(5):408-17. doi: 10.1002/bdrb.20267.
Our laboratory has been conducting positive control studies to evaluate the utility of micro-computed tomography (micro-CT) for qualitative evaluation of fetal skeletal morphology. All-trans-retinoic acid (atRA) was used to produce a different spectrum of defects compared to our previous studies with boric acid and hydroxyurea.
Groups of five mated Crl:CD(SD) female rats each were administered vehicle or atRA (2.5-50 mg/kg) on GD 10, and groups of four mated Dutch Belted rabbits each were dosed with vehicle or atRA (6.25-25 mg/kg) on GD 9. Cesarean sections were performed on GD 21 and 28, respectively. Following external examination the viscera were removed and fetuses scanned in a micro-CT imaging system. Fetuses were subsequently stained with alizarin red. Skeletal morphology was evaluated by each method without the knowledge of treatment group. Total bone mineral content (BMC) of each fetus was quantitated using the micro-CT images.
In rats there were dose-related increases in the incidence of extra lumbar vertebra and non-dose-related increases in supernumerary ribs at all dose levels. There were decreases in mean number of ossified sacrocaudal vertebra at ≥ 5 mg/kg, and increases in skull bone malformations at ≥ 10 mg/kg. Rabbits were less sensitive on a mg/kg basis since skeletal malformations and a decrease in mean number of ossified sacrocaudal vertebra were observed only in the 25-mg/kg group. Micro-CT evaluation detected essentially the same incidence of skeletal abnormalities as seen in alizarin red-stained rat and rabbit fetuses. BMC analysis showed a trend toward slight decreases in atRA-treated rats, but no notable changes in rabbits.
These results add support to our previous work that demonstrates that micro-CT imaging can effectively assess rat and rabbit fetal skeletal morphology.
我们实验室一直在进行阳性对照研究，以评估微型计算机断层扫描（micro-CT）对胎儿骨骼形态进行定性评估的效用。与我们之前使用硼酸和羟基脲的研究相比，全反式维甲酸（atRA）用于产生不同范围的缺陷。
每组五只交配的Crl:CD(SD)雌性大鼠在妊娠第10天给予赋形剂或atRA（2.5 - 50毫克/千克），每组四只交配的荷兰带兔在妊娠第9天给予赋形剂或atRA（6.25 - 25毫克/千克）。分别在妊娠第21天和28天进行剖宫产。外部检查后，取出内脏，将胎儿在微型CT成像系统中扫描。随后胎儿用茜素红染色。在不知道治疗组的情况下，通过每种方法评估骨骼形态。使用微型CT图像对每个胎儿的总骨矿物质含量（BMC）进行定量。
在大鼠中，所有剂量水平下腰椎额外椎体的发生率呈剂量相关增加，多余肋骨的发生率呈非剂量相关增加。在≥5毫克/千克时，骶尾骨化椎体的平均数量减少，在≥10毫克/千克时，颅骨畸形增加。以毫克/千克为基础，兔子的敏感性较低，因为仅在25毫克/千克组中观察到骨骼畸形和骶尾骨化椎体平均数量减少。微型CT评估检测到的骨骼异常发生率与茜素红染色的大鼠和兔胎儿基本相同。BMC分析显示，atRA处理的大鼠有轻微下降趋势，但兔子没有明显变化。
这些结果为我们之前的工作提供了支持，即表明微型CT成像可以有效地评估大鼠和兔胎儿的骨骼形态。
