A comparison of the fine structure of late mouse blastocysts developed in vivo and in vitro

Abstract

The ultrastructure of the in uiuo developed late preimplantation mouse blastocyst has been compared with the fine structure of mouse blastocysts developed in uitro for 72 and 92 hours from the late two-cell stage, as well as those grown in uztro for 26 hours from the late morula or early blastocyst stage. Very little difference was observed between the in uiuo developed blastocysts and those cultured 26 hours in uitro. The differences between 72 and 92 hour-embryos and the in uiuo grown ones were significant. The in uiuo specimen and those grown 26 hours in uitro had differentiated a layer of endoderm cells while the ones cultured in uitro from the two-cell stage did not. Nuclear and cytoplasmic structures in the in uiuo developed blastocysts are well-differentiated while those of the embryos grown in uitro from the two-cell stage were less advanced. Possible reasons for the apparently less differentiated stage of blastocysts developed in uitro from the two-cell stage are discussed.Study of mammalian preimplantation development in vitro has been greatly advanced by Brinster's ('63) formulation of a method which allows two-cell mouse ova to grow to the blastocyst stage in a simple, chemically defined culture medium. Searching for a single source of energy, Brinster ('65) found that pyruvate will support the in vitro development of the largest number of embryos. As a matter of fact, their development (as observed by the light microscope) appears to advance at the same rate in vitro as in vivo (Brinster, '63).Although ultrastructural studies have been completed on in vivo developed preimplantation blastocysts of several species (Enders and Schlafke, '65), and on mouse embryos developed to the morula stage in vitro (Hillman and Tasca, '69) and to the early blastocyst stage in uivo (Calarco and Brown, '69), to our knowledge this is the first study which compares the in vitro developed "late" mouse blastocyst with those grown entirely within the maternal environment. Therefore, the purpose of this investigation was (1) to study in detail the fine structure of "late" preimplantation mouse blastocysts developed in vivo J. EXP. ZOOL., 182: 95-118.for 100 to 108 hours after ovulation, and (2) to compare them with mouse blastocysts of the same post-ovulatory age which had been developed in vitro for 72 hours from the late two-cell stage in Brinster's simple culture medium. MATERIALS AND METHODSSexually mature, random-bred SwissWebster female mice were superovulated with pregnant mare serum (PMS, Gestyl) and human chorionic gonadotropin (HCG, Pregnyl), then mated according to the method of Brinster ('63). Since ovulation in the laboratory mouse occurs 11 to 14 hours after the injection of HCG (Edwards and Gates, '59), the embryonic age of the preimplantation embryos used in this investigation was calculated by estimating the total time which had elapsed since ovulation. At the desired stage of development the specimens were collected and were either (1) fixed immediately or (2) cultured in vitro.In vivo developed lat...

Comparative ultrastructure of hatched human, mouse and bovine blastocysts

“…The mouse and bovine blastocysts were cultured for 24 h to facilitate the recovery of just hatched blastocysts. This would not be expected to alter their ultrastructure as mouse embryos cultured for 26 h do not differ from embryos recovered at the same stage of development in vivo (McReynolds & Hadek, 1972). The culture of embryos in vitro is known to alter embryo metabolism (Ozias & Stern, 1973), and to diminish embryo viability, as assessed by implantation after transfer, as the period in culture is increased (Tervit & Rowson, 1974).…”

“…When mouse embryos are cultured for 96 h in vitro they form expanded blastocysts which appear, at low magnification, similar to blastocysts of the same age grown in vivo. although endoderm is observed in embryos grown in vivo (McReynolds & Hadek, 1972). Because of the difficulties of obtaining human blastocysts fertilized and grown in vivo, human blastocysts resulting from in-vitro fertilization and culture can only be compared to blastocysts of other species.…”

Gene Expression During Oogenesis and Oocyte Development in Mammals

“…They accumulate during oocyte growth (Wassarman and Josefowicz, 1978) and occupy 25-30% of the volume of full-grown oocytes or eggs (Dvorak et al, 1977;Garcia et al, 1979). During cleavage and blastocyst formation they decrease steadily (Dvorak et al, 1977), disappearing around the time of implantation (Enders, 1971;McReynolds and Hadek, 1972). This sequence clearly suggests they are stored for some function during embryogenesis.…”

Preimplantation development of the mammalian embryo and its regulation by growth factors

“…Embryos cultured in these media exhibited a variety of defects, such as failure to develop beyond the two-cell stage, a reduction in cleavage rate resulting in embryos having a reduced cell number compared to those developing in vivo, and a failure to hatch from the zona [Bowman and McLaren, 1970;McReynolds and Hadek, 1972]. More recent formulations, particularly those containing amino acids, have resulted in rates of development that approximate those occurring in vivo, with nearly 100% of embryos forming blastocysts [Biggers et al, 1997;Summers et al, 1995].…”