An animal model for keratosis

鱼鳞病和银屑病是最常见的皮肤病，具有角化过度或角化病的特征性临床特征。这些疾病没有明确的动物模型。视黄酸或其衍生物类视黄酸是常用的治疗药物，但目前尚无动物模型意义上的药物评价模型。我们的援助是一个组织特异性表达点突变的维甲酸受体的转基因小鼠的构建，该点突变的维甲酸受体对内源性维甲酸受体具有显性负效应。将K14启动子与点突变型维甲酸受体cDNA连接，构建了转基因小鼠，获得了点突变型维甲酸受体表皮特异性表达的转基因小鼠。通过从转基因小鼠和对照小鼠中纯化角蛋白来检查分化标记物，如角蛋白。SDS-PAGE显示，野生型表皮细胞含有K1、K5、K10和K14，而转基因小鼠皮肤则含有K1、K5、K10、K14、K6和K16。角蛋白的这些异常表达与银屑病皮肤相似。用单特异性抗角蛋白抗体免疫荧光法检测角蛋白的表达。在正常小鼠中，K5/K14仅在基底细胞层表达，而K1/K10在基底细胞层以上表达。在转基因小鼠皮肤中，K5/K14表达于基底细胞层和基底细胞层上一层。K5/K14在基底细胞层以上两层表达。这些角蛋白的表达模式与在银屑病中观察到的那些相同。在显微镜检查中，皮肤显示Malpigi层变薄，基底膜区的网脊形成松散。这些微观表型不同于已知的人类皮肤病。

Ichtyosis and psoriasis are the most common skin diseases with charactaristic clinical features of hyperkeratosis or keratosis. There is no define animal models for these diseases. Retinoic acid or its derivative, retinoids, are commonly used as a therapeutic drug, whereas there is no drug estimation model in animals in the meanings of animal model of the diseases. Our aid is a construction of transgenic mice with tissue specific expression of a point mutated retinoic acid receptor which has dominant-negative effect to the endogenous retinoic acid receptors. We constructed the plasmid vector with K14 promoter ligated to point mutated retinoic acid receptor cDNA.The resultant transgenic mice showed a epidermal specific expression of a point mutated retinoic acid receptor. Differentiation markers, such as keratins, are examined by purifying keratins from the transgenic mice and control mice. SDS-PAGE revealed that the wild type epidermis conatins K1, K5, K10 and K14, whereas transgenic mice skin showed K1, K5, K10, K14, K6 and K16. These abnormal expression of keratins mimics psoriasis skin. Expression pattern of keratins were examined by immunofluorescent study by using mono-specific anti-keratin antibody. In normal mice, K5/K14 are expressed only in basal cell layrs and reciprocally, K1/K10 are expessed above the basal cell layr. In the transgenic mice skin, K5/K14 are expressed on basal cell layr and one layr above the basal cell layr. K5/K14 are expressed from two layrs above the basal cell layr. These expression pattern of keratins are same to those observed in psoriasis. In the microscopic examination, the skin revealed the thinning of malpigi layr and the loose of rete ridge formation at the basement mombrane zone. These microscopic phenotype are different from those known human skin diseases.