Production and analysis of transgenic mice exhibiting concentric hypertrophy in a heart using Cre-loxP system

白细胞介素-1（Interleukin-1，IL-1）是由多种细胞包括负责控制免疫的细胞产生和分泌的生理活性因子，在免疫反应中起重要作用。已知IL-1抑制分离的心脏和肌细胞的收缩性，并且还引起培养的肌细胞的肥大。所有这些发现都来自体外事件，因此需要使用转基因（Tg）小鼠进行体内实验。在过去的几年中，我们在CMV增强子/鸡β-肌动蛋白启动子（CAG）系统的控制下产生了两个过表达人IL-1α（hIL-1α）的品系，并发现两个品系中的一个表现出同心性肥大伴心肌细胞肥大，并在性成熟前死亡（Isoda et al.，J. Cardiac Failure 7，355-364，2001）。对这条线的几项分析表明，心脏是由像增殖的胎儿肌细胞一样的细胞组成的。这一发现表明，心脏中IL-1α水平的组成性升高可能使心肌细胞处于一种应激状态， ...更多信息 甚至在出生后也是如此。为了进一步研究，需要维持表达hIL-1α的Tg小鼠作为能够产生后代的小鼠。为此，我们采用Cre-loxP系统。我们产生了携带CELIZ转基因的Tg小鼠，所述CELIZ转基因包括CAG启动子、loxP-floxed EGFP/CAT、hIL-1α cDNA、IRES和lacZ基因。我们获得了两条线，所有这些似乎表达EGFP相对较强，在紫外线照射下的EGFP荧光强度的评价。当这些Tg小鼠与MNCE Tg小鼠交配时（Sato等人，Mol Reprod Dev 60，446-456，2001），所得到的双Tg小鼠（8-10周龄）在包括心脏在内的各种组织中表现出hIL-1α和lacZ基因的表达，但在它们的心脏中没有向心性肥大。这可能是由于这些双Tg小鼠产生的hIL-1α水平极低，因为北方印迹分析未能检测到hIL-1α mRNA的明显条带。进一步提高hIL-1α水平是小鼠心脏向心性肥大的表现。少

Interleukin-1 (IL-1) is a physiologically active factor produced and secreted by a variety of cells including those responsible for controlling immunity, and it plays an important role in immunity reactions. IL-1 is known to inhibit contractility in isolated heart and myocytes, and also cause hypertrophy in cultured myocytes. All these findings came from the in vitro events, and therefore in vivo experiments using transgenic (Tg) mice are required In the past few years, we generated two lines overexpressing human IL-1α (hIL-1α) under control of CMV enhancer/chicken β-actin promoter (CAG) system, and found that of two lines one exhibited concentric hypertrophy with cardiomyocyte hypertrophy and died before sexual maturation (Isoda et al., J. Cardiac Failure 7, 355-364, 2001). Several analyses of this line revealed that the heart was composed by cells like proliferative fetal myocytes. This finding suggests that constitutively elevated levels of IL-1α in a heart may keep myocytes in a ju … More venile state even after birth. For further study, it was required for maintaining Tg mice expressing hIL-1α as those capable of producing offspring. For this purpose, we employed Cre-loxP system. We produced Tg mice carrying a CELIZ transgene comprising CAG promoter, loxP-floxed EGFP/CAT, hIL-1α cDNA, IRES and lacZ gene. We obtained two lines all of which appeared to express EGFP relatively strongly, as evaluated for the strength of EGFP fluorescence under UV illumination. When these Tg mice were mated to MNCE Tg mice (Sato et al., Mol Reprod Dev 60, 446-456, 2001) which expressed Cre gene ubiquitously, the resulting double Tg mice (aged 8-10 weeks) exhibited expression of hIL-1α and lacZ gene in various tissues including heart, but did not concentric hypertrophy in their hearts. This is probably due to extremely low level of hIL-1α produced in these double Tg mice, since Northern blot analysis failed to detect distinct band for hIL-1α mRNA. Further attempt to increase the level of hIL-1α is strictly required for manifestation of concentric hypertrophy in murine heart. Less