Strain Differences in Superovulatory Response, Embryo Development and Efficiency of Transgenic Rat Production

Abstract

The differences between rat strains in superovulation response, in vitro and in vivo development of preimplantation embryos and overall transgenic efficiency was studied. The protocols for induction of superovulation using single injections of pregnant mare's serum gonadotropin (PMSG) or minipumps with follicle stimulating hormone (FSH) were compared in Lewis (LEW), Wistar-Kyoto (WKY), and stroke-prone spontaneously hypertensive rats (SHRSP) or Sprague-Dawley (SD) and Wistar rats as representative inbred or outbred strains, respectively. The percentage of mated animals with positive superovulatory response was similar in all strains (60.0-100%). The mean number of ova per donor was not dependent on the kind of hormonal treatment used within each rat strain. In general, females from outbred SD and Wistar rats were more responsive to hormonal treatments than animals from inbred rat strains. In addition, SD female rats produced a significantly higher number of embryos per female in response to PMSG-treatment compared to all other strains. Between the inbred strains, SHRSP was the most effective for superovulation. In vitro development of intact zygotes to the blastocyst stage was not different between SD, Wistar and SHRSP rats. In contrast, in vitro development of WKY zygotes was significantly less efficient than in other strains. However, 2-cell stage embryos in vivo produced from SD, SD x Wistar and WKY animals showed no difference in competence to develop to blastocyst stage in vitro. The proportion of offspring developing after oviduct transfer of intact zygotes was similar in all strains (44.0-56.4%) with the exception of WKY rats (35.9%). We also compared the survival rate after injection, ability of manipulated zygotes to develop to term and overall transgenic efficiency in various rat strains. SD and SHRSP zygotes survived after microinjection better than the WKY and Lewis zygotes. No differences were found in the efficiency of transgene integration per newborn in different strains ranging from 5.7 to 16.7%. The results of this study demonstrate that different rat strains have varying responses to superovulation, sensitivity to microinjection, capability to develop in vitro until blastocyst stage or in vivo to term after transfer to foster mothers. Despite these differences all studied strains can be used for efficient transgenic rat production.

Superovulatory Response, Oocyte Spontaneous Activation, and Embryo Development in WMN/Nrs Inbred Rats

“…Although various superovulatory methods for rats have been described, such as continuous injection of gonadotropin [1] and immunization against inhibin [12], gonadotropin injection used successfully in mice, has also worked well in Wistar rats [21,26,33]. In most outbred and inbred rats, superovulation can be successfully induced using immature females [4,30]. However, some Wistar rats such as Wistar-Imamichi and BrlHan:WIST@Jcl(GALAS) respond to superovulatory treatments independent of age and the estrous cycle [15,21,26,33].…”

“…Among these methods, the PMSG-hCG injection regimen seems to be the most practical and economical method of inducing superovulation and may be applied to a wide range of ages in Wistar rats [15,21,26,30,33]. However, quantitative data on the actual use of this technique in rats is limited to studies of juvenile rats and a few adult strains.…”

“…Data reported for mice and hamsters are controversial, with some studies showing significant differences in quality and other showing no difference [5,6,22,23,32,34,37]. However, in rats the quality of superovulated oocytes or embryos, as indicated by developmental ability to the fetus, has not been directly compared with that obtained by natural ovulation [10,30,33,40], and such information is essential for estimating the efficiency of animal production and the normality of embryos. Thus, obtaining normative information concerning superovulation and the quality of superovulated oocytes or embryos on a strain-by-strain basis, especially for inbred rats, would be quite useful for ARTs of laboratory rats.…”

Developmental Responses of 2-Cell Embryos to Oxygen Tension and Bovine Serum Albumin in Wistar Rats

“…Wistar rats from two breeders, Crlj:WI and Slc:Wistar, were used to examine whether or not their effects are -Note-consistent across colonies since some differences in developmental responses have been observed among rat strains [14], and these particular breeder colonies are likely to have different genetic backgrounds [16].…”

Efecto De La Aplicación De Gonadotropinas Recombinantes Humanas Sobre La Producción Y Calidad De Ovocitos Y Embriones en Coneja

“…Por otra parte, los resultados obtenidos tras la superovulatoria se puede ver afectada por el tipo de animal (raza o línea, individuo, edad, estado nutricional y fisiológico), el tipo de hormona empleado y el protocolo de administración. Por un lado, se ha observado, tanto en conejos como en otras especies, que la línea con la que se trabaja tiene un impacto importante en la respuesta a los tratamientos de superovulación, tanto en términos de tasa de ovulación, como en la capacidad de desarrollo de los embriones obtenidos (Popova et al, 2005;Salvetti et al, 2007b).…”