Production of transgenic rats for human regulators of complement activation

Beyond the rat models of human neurodegenerative disorders

The rat is a model of choice in biomedical research for over a century. Currently, the rat presents the best "functionally" characterized mammalian model system. Despite this fact, the transgenic rats have lagged behind the transgenic mice as an experimental model of human neurodegenerative disorders. The number of transgenic rat models recapitulating key pathological hallmarks of Alzheimer's disease, Huntington's disease, amyotrophic lateral sclerosis, or human tauopathies is still limited. The reason is that the transgenic rats remain more difficult to produce than transgenic mice. The gene targeting technology is not yet established in rats due to the lack of truly totipotent embryonic stem cells and cloning technology. This extremely powerful technique has given the mouse a clear advantage over the rat in generation of new transgenic models. Despite these limitations, transgenic rats have greatly expanded the range of potential experimental approaches. The large size of rats permits intrathecal administration of drugs, stem cell transplantation, serial sampling of the cerebrospinal fluid, microsurgical techniques, in vivo nerve recordings, and neuroimaging procedures. Moreover, the rat is routinely employed to demonstrate therapeutic efficacy and to assess toxicity of novel therapeutic compounds in drug development. Here we suggest that the rat constitutes a slightly underestimated but perspective animal model well-suited for understanding the mechanisms and pathways underlying the human neurodegenerative disorders.

Efficiency of transgenic rat production is independent of transgene-construct and overnight embryo culture

The aim of the present work was to study factors affecting the efficiency of transgenic technology in rats. We investigated the possible effects of pronuclear microinjection of buffer or different DNA-constructs on survival and development of rat zygotes in vitro and in vivo as well as the influence of overnight culture of these embryos before transfer into pseudopregnant foster mothers. The survival rate of zygotes and their development to the two-cell and morula stage was not affected by pronuclear microinjection with different DNA-constructs or buffer. However, the development to the blastocyst stage was impaired. Nevertheless, there was no difference in blastocyst development between zygotes injected with DNA-constructs or with buffer. Neither was there a difference in cell number in in vitro cultured blastocysts resulting from pronuclear microinjection of a transgene compared with non-injected controls. The survival rate to term was about 30% irrespective of whether microinjected embryos were transferred immediately after microinjection or after overnight culture in vitro. However, a reduction in the survival to term was observed for non-injected zygotes when they were developed in vitro to the two-cell stage before transfer to a pseudopregnant female. The percentage of transgenic rats that resulted from microinjected zygotes was similar in all groups regardless of the DNA-construct used (2.7-10.0%). In conclusion, the main detrimental factor in the microinjection of rat zygotes is the introduction of solution in the pronucleus. Overnight culture of zygotes between microinjection and oviduct transfer does not decrease the efficiency of transgenic rat generation.

A new alternative method for superovulation using passive immunization against inhibin in adult rats

The present study was undertaken to investigate the effects of passive immunoneutralization of endogenous inhibin on ovulation rate and embryo development in vivo and in vitro to establish a new alternative superovulation method in the adult rat. Female adult rats of Wistar strain were superovulated with a single injection of inhibin antiserum (inhibin-AS; 100 or 400 microl) or an injection of 20 IU eCG followed by an injection of 10 IU hCG. Untreated animals served as controls. Embryos were collected from oviducts or uteri on Days 1-5 of pregnancy, and the number of embryos and implantation sites were observed. On Day 1 of pregnancy, the two-cell-stage embryos were cultured and embryos from the 100-microl inhibin-AS group and the control group were transferred to recipient females to determine developmental competence. There were no significant differences between groups in fertilization rate. The numbers of normal embryos in the inhibin-AS-treated groups were significantly higher than the control and the eCG-hCG-treated groups throughout Days 1-4 of pregnancy. The number of implantation sites observed on Day 5 of pregnancy in the inhibin-AS-treated groups was significantly higher than both the control and the eCG-hCG-treated groups. Furthermore, the rate of blastocyst development in vitro in the inhibin-AS-treated groups and posttransfer viability in the 100-microl-inhibin-AS group were comparable with those of the control group. These results indicate that immunoneutralization of endogenous inhibin is a new practical alternative for induction of superovulation as a substitution for eCG-hCG method in the adult rat.