Lee B, Dennis J A, Healy P J, Mull B, Pastore L, Yu H, Aguilar-Cordova E, O'Brien W, Reeds P, Beaudet A L
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.
Proc Natl Acad Sci U S A. 1999 Mar 30;96(7):3981-6. doi: 10.1073/pnas.96.7.3981.
The development of gene-replacement therapy for inborn errors of metabolism has been hindered by the limited number of suitable large-animal models of these diseases and by inadequate methods of assessing the efficacy of treatment. Such methods should provide sensitive detection of expression in vivo and should be unaffected by concurrent pharmacologic and dietary regimens. We present the results of studies in a neonatal bovine model of citrullinemia, an inborn error of urea-cycle metabolism characterized by deficiency of argininosuccinate synthetase and consequent life-threatening hyperammonemia. Measurements of the flux of nitrogen from orally administered 15NH4 to [15N]urea were used to determine urea-cycle activity in vivo. In control animals, these isotopic measurements proved to be unaffected by pharmacologic treatments. Systemic administration of a first-generation E1-deleted adenoviral vector expressing human argininosuccinate synthetase resulted in transduction of hepatocytes and partial correction of the enzyme defect. The isotopic method showed significant restoration of urea synthesis. Moreover, the calves showed clinical improvement and normalization of plasma glutamine levels after treatment. The results show the clinical efficacy of treating a large-animal model of an inborn error of hepatocyte metabolism in conjunction with a method for sensitively measuring correction in vivo. These studies will be applicable to human trials of the treatment of this disorder and other related urea-cycle disorders.
代谢性先天性疾病基因替代疗法的发展受到这些疾病合适的大型动物模型数量有限以及治疗效果评估方法不足的阻碍。此类方法应能在体内灵敏地检测到表达情况，且不受同时进行的药物和饮食方案的影响。我们展示了在瓜氨酸血症新生牛模型中的研究结果，瓜氨酸血症是一种尿素循环代谢的先天性疾病，其特征是精氨琥珀酸合成酶缺乏，继而导致危及生命的高氨血症。通过测量口服15NH4到[15N]尿素的氮通量来测定体内尿素循环活性。在对照动物中，这些同位素测量结果证明不受药物治疗的影响。全身给予表达人精氨琥珀酸合成酶的第一代E1缺失腺病毒载体导致肝细胞转导，并部分纠正了酶缺陷。同位素方法显示尿素合成有显著恢复。此外，小牛在治疗后临床症状改善，血浆谷氨酰胺水平恢复正常。结果表明，结合一种在体内灵敏测量纠正情况的方法，治疗肝细胞代谢先天性疾病大型动物模型具有临床疗效。这些研究将适用于该疾病及其他相关尿素循环障碍的人体治疗试验。
