Effects of BSA and fetal bovine serum in culture medium on development of rat embryos

Media optimization to promote rat embryonic development to the blastocyst stage in vitro

Efficient model production in rats that incorporates newly developed genetic editing and embryo transfer tools, such as CRISPR/Cas9 technology and non-surgical embryo transfer, requires availability of an optimal embryo culture system. However, current technologies for in vitro manipulation of rat gametes, including embryo culture techniques, are less advanced compared to those in mice. In this study, we (1) identified a culture medium that was able to support optimal rat embryonic development by comparing two rat culture media: mR1ECM (modified rat 1-cell embryo culture medium) and KSOM-R (modified potassium simplex optimized medium for rats), and (2) evaluated the effect of glutamine dipeptides: alanyl-l-glutamine and glycyl-l-glutamine, on rat embryonic development. We also investigated the possibility of simplifying the KSOM-R culture procedure by increasing the volume of culture medium, reducing the need for daily medium changes. The results showed that rat embryos cultured in KSOM-R developed faster than those cultured in mR1ECM. Both alanyl-l-glutamine and glycyl-l-glutamine showed detrimental effects on rat embryonic development when supplemented in KSOM-R at the same concentration as glutamine. By increasing the volume of KSOM-R, rat zygotes were able to develop without daily medium refreshment at a similar rate and developmental competence as those in smaller volumes with daily medium changes. These results represent important improvements to rat embryo culture methods and will assist in more efficient production of rat models.

Fetal bovine serum promotes the development of in vitro porcine blastocysts by activating the Rho-associated kinase signalling pathway

Fetal bovine serum (FBS) supplementation has beneficial effects on invitro porcine embryonic development, but the underlying mechanisms are unclear. In the present study we found that the addition of FBS to PZM-3 increased the number of cells in porcine blastocysts and hatching rate invitro primarily by promoting proliferation of the inner cell mass and further differentiation. Moreover, based on the following results, we surmise that FBS benefits blastocyst development by activating Rho-associated kinase (ROCK) signalling: (1) the ROCK signalling inhibitor Y-27632 decreased the blastocyst rate and the number of cells in blastocysts, whereas FBS rescued the developmental failure induced by Y-27632; (2) the mRNA levels of two ROCK isoforms, ROCK1 and ROCK2, were significantly increased in blastocysts derived from medium containing FBS; and (3) FBS increased RhoA/Rho-kinase expression in the nucleus of embryonic cells. These results indicate that FBS promotes the invitro development of porcine embryos by activating ROCK signalling in a chemically defined medium.

Effect of Knockout Serum Replacement During Postwarming Recovery Culture on the Development and Quality of Vitrified Parthenogenetic Porcine Blastocysts

The postwarming recovery culture, as one of the steps in cryopreservation process, is directly correlated with the survival and quality of embryos. Generally, recovery medium includes undefined serum or serum components that may cause the instability of results and other problems. The objective of this study was to evaluate the effect of knockout serum replacement (KSR) as a substitute for serum during recovery culture on the development and quality of vitrified parthenogenetic porcine blastocysts. Fetal bovine serum (FBS) was used as a positive control. The expanded blastocysts on day 5 were vitrified by the Cryotop method, and recovered with 10% (v/v) KSR or 10% (v/v) FBS for 48 hours after warming. Survival and hatching rates of vitrified blastocysts were significantly increased by KSR or FBS supplementation. The vitrified blastocysts recovered in KSR or FBS exhibited significantly decreased percentages of membrane damage and apoptosis, and increased total cells. Addition of KSR or FBS during recovery culture significantly reduced reactive oxygen species levels, and improved mitochondrial activity and adenosine triphosphates content in the vitrified blastocysts. Vitrification did not affect the gene expression of PCNA, CDX2, and CPT1, but significantly increased mRNA levels of POU5F1 and uPA. KSR added to the recovery medium significantly upregulated mRNA levels of PCNA and CPT1, and downregulated POU5F1 mRNA levels. The expression levels of PCNA, CDX2, CPT1, and uPA in vitrified blastocysts were significantly upregulated by addition of FBS to recovery medium. Moreover, the BAX: BCL2L1 ratio was similar between fresh and vitrified blastocysts, and KSR or FBS supplementation had no effect on the value. In conclusion, our data showed that KSR supplementation during recovery culture can improve the development and quality of vitrified parthenogenetic porcine blastocysts. These findings provide a useful reference that KSR could be used to replace FBS as a defined serum supplement for recovery culture of vitrified blastocysts.

In Vitro Culture of Rat Preimplantation Embryos

The rat is one the most widely used laboratory animal species in many aspects of biomedical research, including the production of genetically engineered animal models to study human diseases and conditions. In addition to in vitro fertilization (IVF), the ability to grow IVF-derived or in vivo-collected zygotes to a desired preimplantation stage (zygote to blastocyst) entirely in vitro has a great importance for studies of developmental biology and genetic modification of laboratory rats for biomedical research. Although embryo biotechnologies are required to study or manipulate the genome effectively, such technologies for rat preimplantation embryos are not currently as successful as they are in the mouse. Here we provide a brief history of the development of rat in vitro culture systems and a step-by-step protocol to produce rat blastocyst stage embryos from zygotes under in vitro conditions from commonly used laboratory rat strains in biomedical research.

Dual effect of fetal bovine serum on early development depends on stage-specific reactive oxygen species demands in pigs

Despite the application of numerous supplements to improve in vitro culture (IVC) conditions of mammalian cells, studies regarding the effect of fetal bovine serum (FBS) on mammalian early embryogenesis, particularly in relation to redox homeostasis, are lacking. Herein, we demonstrated that early development of in vitro-produced (IVP) porcine embryos highly depends on the combination of FBS supplementation timing and embryonic reactive oxygen species (ROS) requirements. Interestingly, FBS significantly reduced intracellular ROS levels in parthenogenetically activated (PA) embryos regardless of the developmental stage. However, the beneficial effect of FBS on early embryogenesis was found only during the late phase (IVC 4-6 days) treatment group. In particular, developmental competence parameters, such as blastocyst formation rate, cellular survival, total cell number and trophectoderm proportion, were markedly increased by FBS supplementation during the late IVC phase. In addition, treatment with FBS elevated antioxidant transcript levels during the late IVC phase. In contrast, supplementation with FBS during the entire period (1-6 days) or during the early IVC phase (1-2 days) greatly impaired the developmental parameters. Consistent with the results from PA embryos, the developmental competence of in vitro fertilization (IVF) or somatic cell nuclear transfer (SCNT) embryos were markedly improved by treatment with FBS during the late IVC phase. Moreover, the embryonic stage-specific effects of FBS were reversed by the addition of an oxidant and were mimicked by treatment with an antioxidant. These findings may increase our understanding of redox-dependent early embryogenesis and contribute to the large-scale production of high-quality IVP embryos.

Improved Murine Blastocyst Quality and Development in a Single Culture Medium Compared to Sequential Culture Media

OBJECTIVE

Validate single versus sequential culture media for murine embryo development.

DESIGN

Prospective laboratory experiment.

SETTING

Assisted Reproduction Laboratory.

ANIMALS

Murine embryos.

INTERVENTIONS

Thawed murine zygotes cultured for 3 or 5 days (d3 or d5) in single or sequential embryo culture media developed for human in vitro fertilization.

MAIN OUTCOME MEASURES

On d3, zygotes developing to the 8 cell (8C) stage or greater were quantified using 4',6-diamidino-2-phenylindole (DAPI), and quality was assessed by morphological analysis. On d5, the number of embryos reaching the blastocyst stage was counted. DAPI was used to quantify total nuclei and inner cell mass nuclei. Localization of ubiquitin C-terminal hydrolase L1 (UCHL1) and ubiquitin C-terminal hydrolase L3 (UCHL3) was reference points for evaluating cell quality.

RESULTS

Comparing outcomes in single versus to sequential media, the odds of embryos developing to the 8C stage on d3 were 2.34 time greater (P = .06). On d5, more embryos reached the blastocyst stage (P = <.0001), hatched, and had significantly more trophoblast cells (P = .005) contributing to the increased total cell number. Also at d5, localization of distinct cytoplasmic UCHL1 and nuclear UCHL3 was found in high-quality hatching blastocysts. Localization of UCHL1 and UCHL3 was diffuse and inappropriately dispersed throughout the cytoplasm in low-quality nonhatching blastocysts.

CONCLUSIONS

Single medium yields greater cell numbers, an increased growth rate, and more hatching of murine embryos. Cytoplasmic UCHL1 and nuclear UHCL3 localization patterns were indicative of embryo quality. Our conclusions are limited to murine embryos but one might speculate that single medium may also be more beneficial for human embryo culture. Human embryo studies are needed.

Enhancing effects of serum-rich and cytokine-supplemented culture conditions on developing blastocysts and deriving porcine parthenogenetic embryonic stem cells

The present study was conducted to develop an effective method for establishment of porcine parthenogenetic embryonic stem cells (ppESCs) from parthenogenetically activated oocyte-derived blastocysts. The addition of 10% fetal bovine serum (FBS) to the medium on the 3rd day of oocyte culturing improved the development of blastocysts, attachment of inner cell masses (ICMs) onto feeder cells, and formation of primitive ppESC colonies. ICM attachment was further enhanced by basic fibroblast growth factor, stem cell factor, and leukemia inhibitory factor. From these attached ICMs, seven ppESC lines were established. ppESC pluripotency was verified by strong enzymatic alkaline phosphatase activity and the expression of pluripotent markers OCT3/4, Nanog, and SSEA4. Moreover, the ppESCs were induced to form an embryoid body and teratoma. Differentiation into three germ layers (ectoderm, mesoderm, and endoderm) was confirmed by the expression of specific markers for the layers and histological analysis. In conclusion, data from the present study suggested that our modified culture conditions using FBS and cytokines are highly useful for improving the generation of pluripotent ppESCs.

Production of cloned sei whale (Balaenoptera borealis) embryos by interspecies somatic cell nuclear transfer using enucleated pig oocytes

In this study, we examined the feasibility of using subzonal cell injection with electrofusion for interspecies somatic cell nuclear transfer (iSCNT) to produce sei whale embryos and to improve their developmental capacity by investigating the effect of osmolarity and macromolecules in the culture medium on the in vitro developmental capacity. Hybrid embryos produced by the electrofusion of fetal whale fibroblasts with enucleated porcine oocytes were cultured in modified porcine zygote medium-3 to examine the effects of osmolarity and fetal serum on their in vitro developmental capacity. More than 66% of the whale somatic cells successfully fused with the porcine oocytes following electrofusion. A portion (60~81%) of the iSCNT whale embryos developed to the two- to four-cell stages, but no embryos were able to reach the blastocyst stage. This developmental arrest was not overcome by increasing the osmolarity of the medium to 360 mOsm or by the addition of fetal bovine or fetal whale serum. Our results demonstrate that sei whale-porcine hybrid embryos may be produced by SCNT using subzonal injection and electrofusion. The pig oocytes partly supported the remodeling and reprogramming of the sei whale somatic cell nuclei, but they were unable to support the development of iSCNT whale embryos to the blastocyst stage.

Effects of different concentrations of bovine follicular fluid and estrous cow serum on development of murine 2-cell embryos

Murine 2-cells embryos were isolated from murine oviducts at laboratory and transferred into Ham's F-10 medium containing 0.1 mg mL(-1) streptomycin and 100 IU mL(-1) penicillin G and supplemented with 3 mg mL(-1) bovine serum albumin (BSA) or different concentrations of bovine follicular fluid (bFF) and estrous cow serum (ECS). Significantly higher (p<0.05) > or =4-cell embryos were developed when embryos were cultured 20% bFF (84.33%) comparing to 10 and 15% bFF (48.33 and 69.33%) as well as 3 mg mL(-1) BSA (65.66%). Morula rates were also lower in 10% bFF (22.33%) comparing to the other groups and were similar in 15 and 20% bFF (62.66 and 72.33% morula rates) as well as BSA containing media (55.33%). The highest (p<0.05) blastocyst rates were obtained in medium containing 20% bFF (64.33%) and the lowest belonged to 10% bFF (15%) comparing to 15% bFF (33.66%) or 3 mg mL(-1) BSA. When embryos were cultured in ECS, no significant different was observed in different culture media (76.66, 72.33, 82.5 and 65.66% > or =4-cell embryos in 10, 15 and 20% bFF and 3 mg mL(-1) BSA, respectively). Morula and blastocyst rates were also similar in all groups (32.33, 41.66 and 66.25 and 55.33% morula rates and 15.33, 27, 44.50 and 29.66% blastocyst rates for 10, 15 and 20% bFF and 3 mg mL(-1) BSA, respectively). The results of the present study demonstrated that 20% bFF could be substituted for BSA when in vitro culture of murine embryos is carried.

Serum replacement with a growth factor-free synthetic substance in culture medium contributes to effective establishment of mouse embryonic stem cells of various origins

OBJECTIVE

To evaluate whether serum replacement with growth factor-free synthetic substances contributed to the effective establishment of embryonic stem (ES) cells.

DESIGN

Randomized, prospective model study.

SETTING

Gamete and stem cell biotechnology laboratory at Seoul National University in Korea.

ANIMAL(S)

F1 (C57BL6 x DBA2) mice.

INTERVENTION(S)

Blastocysts of different origins were cultured in serum-replaced media.

MAIN OUTCOME MEASURE(S)

Embryonic stem cell establishment.

RESULT(S)

Eight batches of ES cells were established from colony-forming inner cell mass cells after the replacement of fetal bovine serum (FBS) with synthetic knockout serum replacement (KSR) in mkDMEM. The established cells were positive for ES cell markers and formed both embryoid bodies in vitro and teratomas in vivo, but the established cell batches and control (transformed) ES cells responded differently to the culture media. Higher levels of cell viability were detected after the replacement with the 75:25 FBS-KSR mixture than with any other mixtures, and a gradual decrease in viability was detected as the KSR volume ratio was increased. The 75:25 FBS-KSR mixture-containing medium supported ES cell establishment of outbred ICR, F1, and F2 of C57BL6/DBA2; F1 parthenogenetic and ES cell-complemented tetraploid blastocysts; and single ES-cell cultures.

CONCLUSION(S)

A serum-replaced medium could be used for effective ES-cell establishment of various origins.

Factors required during preculture of rat oocytes soon after sperm penetration for promoting their further development in a chemically defined medium

Blastocyst formation in a chemically defined medium (mR1ECM) of rat oocytes soon after sperm penetration is less frequent than in those undergoing male pronuclear formation. This inhibition is released by preculturing the oocytes for a few hours in modified Krebs-Ringer bicarbonate solution (mKRB). The present study examined the effects of phosphate (Pi), bovine serum albumin (BSA) and osmolarity during preculture of sperm penetrated rat oocytes on their development to blastocysts in mR1ECM in vitro. These are the major factors that differ between mR1ECM and mKRB. When oocytes collected at 0730-0800 h on the day following mating and freed from cumulus cells were precultured for 5 h in mKRB or Pi-free mKRB and then cultured for 127 h in mR1ECM, about 73-74% of oocytes developed to blastocysts. In both media, replacement of BSA with polyvinylalcohol (PVA) or osmolarity of 246 mOsM reduced blastocyst formation compared with media containing BSA or with osmolarity of 304 mOsM; blastocyst formation was greatly inhibited when oocytes were precultured in media with PVA and osmolarity of 246 mOsM. On the other hand, when precultured in mR1ECM or mR1ECM with osmolarity of 304 mOsM or BSA instead of PVA, fewer oocytes developed to blastocysts than those precultured in Pi-free mKRB and mR1ECM with osmolarity of 304 mOsM and BSA. These results indicate that both BSA and osmolarity, but not Pi, are essential factors during preculture of rat oocytes soon after sperm penetration for promoting their further development to blastocysts in a chemically defined medium.

Donor and recipient rat strains affect full-term development of one-cell zygotes cultured to morulae/blastocysts

The present study was conducted to examine the developmental potential to offspring of rat embryos cultured from 1-cell to morula/blastocyst stage. Pronuclear zygotes from Wistar x Wistar or (SD x DA) x Wistar strains were cultured in modified rat 1-cell embryo culture medium (mR1ECM) for 96 h in 5% CO(2) in air at 37 C. The proportion of the 3-way cross hybrid zygotes developing into morula/blastocyst stage (74%) was higher than that of the Wistar zygotes (66%). Day-5 morulae/blastocysts developed in vitro were transferred into Day-3 or -4 pseudopregnant recipients of Wistar or SD x DA strain. The transfer of cultured embryos resulted in the birth of offspring at 13-59%, while that of non-cultured control blastocysts showed birth rates of 35-65%. The best offspring rate of cultured embryos (59%) was obtained when the hybrid 1-cell zygotes were cultured in mR1ECM medium and transferred into the 2-days earlier uteri of SD x DA recipients. These results suggest that genetic background of recipients as well as donors is a possible factor affecting full-term development of rat morulae/blastocysts derived from 1-cell stage zygotes cultured in vitro.