Germfree status of mice obtained by embryo transfer in an isolator environment

Abstract

The technique of embryo transfer has been evaluated for the purpose of changing the mouse stocks to a germfree (GF) status. Our results show reproducible and quality-assured conversion of animals to those which are negative for the presence of microorganisms. Rapid and easy access to GF mice is advantageous for studies of selected microflora and their cross-talks with the host, when applying, e.g. genomic, proteomic and metabolic methodology. The study involved embryo transfer in an isolator environment, thereby allowing implantation of cleansed embryos into GF recipients under well-controlled conditions. The recipient females gave birth normally and took care of the offspring as if they were their own pups, thus enhancing the survival rate. Access to full technical resources required to maintain GF isolators are, however, a prerequisite. In this study, we used stainless steel isolators designed by Gustafsson (1959), on which a stereomicroscope was mounted to facilitate embryo transfer inside the isolator. The use of embryo transfer and isolator techniques will facilitate the availability of various mouse mutant models under different gnotobiotic conditions, GF, monoxenic or polyxenic animals, to enable comparison with conventional animals for physiological and pathophysiological studies.

Colonization of the upper genital tract by vaginal bacterial species in nonpregnant women

“…37 This finding raises the possibility that the presence of intrauterine commensal bacteria may have a similar role in the selection of uterine T-regulatory cells as commensal gut microbiota do for colonic T-regulatory cells. While many other factors contribute to a successful pregnancy, it is worth noting that germ-free mice raised in sterile conditions have lower rates of reproductive success after embryo transfer than conventional animals, 38 suggesting a potential role for intrauterine bacteria in successful pregnancy. This potentially critical issue is largely unexplored.…”

Current insights into neutrophil homeostasis

“…To establish the role of commensal germs in neutrophil homeostasis, we took advantage of germ‐free mice 12 . These mice are maintained in special isolators and in an environment devoid of microorganisms or viruses 52 . The peripheral blood of germ‐free mice was found to contain less than 10% of normal neutrophil levels, and plasma G‐CSF was low 12 .…”

Gnotobiotics and the Microbiome

“…Although embryo transplantation technology (Smithies, 2007) is used by some commercial suppliers and others (Inzunza et al, 2005) to quickly derive new strains of GF rodents or those that have been genetically manipulated, the primary method of deriving GF rats for noncommercial operations is through surgical intervention of pregnancy at term. Another technique has been reported whereby the gut tract has been rendered sterile through the successive use of a variety of broadspectrum antibiotics.…”

“…In spite of the previously mentioned success using embryo transfer to obtain GF mouse lines (Inzunza et al, 2005), those researchers found the traditional cesarean delivery, the classic method of deriving axenic animals, to be preferred (Norin, 2019). Since this approach is still widely used in research institutions (Carter, 1976), academic or private, and by small and large commercial lab animal suppliers, it is described in detail below.…”