Mosaic TP53 Mutation on Tumour Development in Pigs: A Case Study

Pigs rarely develop cancer; however, tumour protein p53 (TP53)-modified pigs may have an increased incidence of cancer. In this study, two pigs with mosaic mutations induced by gene editing were compared to determine the role of the wild-type TP53 sequence in tumorigenesis and to speculate how amino acid changes in TP53 sequences are related to tumorigenesis. The pig without tumours had a wild-type TP53 sequence and a 1-bp deletion in the TP53 sequence that resulted in a premature stop codon. In contrast, the pig with nephroblastoma had 6- and 7-bp deletions in the TP53 sequence, resulting in the absence of two amino acids and a premature stop codon, respectively. Our results indicated that TP53 mutations with truncated amino acids may be related to tumour formation.

Generation of mutant pigs by lipofection-mediated genome editing in embryos

The specificity and efficiency of CRISPR/Cas9 gene-editing systems are determined by several factors, including the mode of delivery, when applied to mammalian embryos. Given the limited time window for delivery, faster and more reliable methods to introduce Cas9-gRNA ribonucleoprotein complexes (RNPs) into target embryos are needed. In pigs, somatic cell nuclear transfer using gene-modified somatic cells and the direct introduction of gene editors into the cytoplasm of zygotes/embryos by microinjection or electroporation have been used to generate gene-edited embryos; however, these strategies require expensive equipment and sophisticated techniques. In this study, we developed a novel lipofection-mediated RNP transfection technique that does not require specialized equipment for the generation of gene-edited pigs and produced no detectable off-target events. In particular, we determined the concentration of lipofection reagent for efficient RNP delivery into embryos and successfully generated MSTN gene-edited pigs (with mutations in 7 of 9 piglets) after blastocyst transfer to a recipient gilt. This newly established lipofection-based technique is still in its early stages and requires improvements, particularly in terms of editing efficiency. Nonetheless, this practical method for rapid and large-scale lipofection-mediated gene editing in pigs has important agricultural and biomedical applications.

Effects of individual or in-combination antioxidant supplementation during in vitro maturation culture on the developmental competence and quality of porcine embryos

The oocyte maturation process requires a high supply of energy, which generates reactive oxygen species (ROS), adversely affecting oocyte and embryo development. Balancing ROS by antioxidant supplementation is essential for maintaining oocyte maturation and embryonic quality in vitro. This study aimed to evaluate the impact of four antioxidants: β-mercaptoethanol (β-ME), chlorogenic acid (CGA), curcumin and sericin, when applied individually or in combinations, during oocyte maturation on development of porcine oocytes. Cumulus-oocyte complexes were collected, cultured in maturation medium supplemented with antioxidants for 44 hr and subsequently subjected to in vitro fertilization (IVF) and culture for 7 days. Combining all four (β-ME + CGA + curcumin + sericin) or three (β-ME + CGA + curcumin) antioxidants increased blastocyst formation rates. However, sericin supplementation alone, or in combination with β-ME or CGA, failed to improve blastocyst formation rates. The total cell numbers of blastocysts from the group supplemented with three antioxidants (β-ME + CGA + curcumin) were significantly higher than those from the other groups, except for the curcumin-supplement group. There were no differences in the maturation rates and proportions of oocytes with fragmented DNA between the antioxidant-supplemented and the non-supplemented control groups. In conclusion, supplementation with three antioxidants (β-ME + CGA + curcumin) during the maturation culture enhanced blastocyst formation and improved blastocyst quality.

Zona pellucida treatment before CRISPR/Cas9-mediated genome editing of porcine zygotes

Background

Increasing the permeability of the zona pellucida (ZP) of oocytes before CRISPR/Cas9 electroporation may improve the efficiency of gene editing; however, the effects of this approach on subsequent developmental processes are unclear. In this study, the effects of ZP treatment before electroporation on embryonic development and gene editing in porcine embryos were evaluated.

Methods

The ZP of zygotes was weakened or removed by exposure to 0.5% actinase E, followed by electroporation of the Cas9 protein with guide RNA targeting GGTA1.

Results

The blastocyst formation rate of ZP‐free zygotes after electroporation was significantly lower (p < 0.05) than that of ZP‐intact zygotes. The mutation rate in blastocysts from ZP‐weakened zygotes was similar to that in ZP‐intact zygotes, whereas ZP removal increased the mutation rate. The mutation efficiency in blastocysts from electroporated zygotes did not differ among ZP treatment groups.

Conclusions

Our results indicate that weakening the ZP does not affect the developmental competence, mutation rate, or mutation efficiency of electroporated zygotes, whereas ZP removal has a detrimental effect on embryonic development but may increase the mutation rate.

Timing and duration of lipofection-mediated CRISPR/Cas9 delivery into porcine zygotes affect gene-editing events

OBJECTIVE

Lipofection-mediated introduction of the CRISPR/Cas9 system in porcine zygotes provides a simple method for gene editing, without requiring micromanipulation. However, the gene editing efficiency is inadequate. The aim of this study was to improve the lipofection-mediated gene editing efficiency by optimizing the timing and duration of lipofection.

RESULTS

Zona pellucida (ZP)-free zygotes collected at 5, 10, and 15 h from the start of in vitro fertilization (IVF) were incubated with lipofection reagent, guide RNA (gRNA) targeting GGTA1, and Cas9 for 5 h. Lipofection of zygotes collected at 10 and 15 h from the start of IVF yielded mutant blastocysts. Next, ZP-free zygotes collected at 10 h from the start of IVF were incubated with lipofection reagent, gRNA, and Cas9 for 2.5, 5, 10, or 20 h. The blastocyst formation rate of zygotes treated for 20 h was significantly lower (p < 0.05) than those of the other groups, and no mutant blastocysts were obtained. Moreover, the mutation rates of the resulting blastocysts decreased as the incubation time increased. In conclusion, a lipofection-mediated gene editing system using the CRISPR/Cas9 system in ZP-zygotes is feasible; however, further improvements in the gene editing efficiency are required.

Improvement of the in vitro fertilization and embryo development using frozen-thawed spermatozoa of microminipigs

This study aimed to compare the quality and the penetration ability of frozen–thawed spermatozoa from three microminipigs and Large White boars and to evaluate the effects of caffeine and heparin as well as the sperm–oocyte co-incubation length on the fertilization and embryonic development in vitro. Results showed that the fertilization rates of spermatozoa from three microminipig boars were significantly lower than those of a Large White boar. In the post-thaw spermatozoa from one of three microminipig boars, the sperm quality, penetration ability, and the oocyte development after in vitro fertilization were significantly lower than those of the spermatozoa from other boars. The caffeine supplementation in the fertilization media increased the rates of fertilization and blastocyst formation for the microminipig spermatozoa with low sperm quality. In addition to caffeine supplementation, the rates of fertilization and blastocyst formation after using microminipig spermatozoa were significantly higher with a 10 h sperm–oocyte co-incubation than with 3 h of co-incubation length. Our results indicate that the differences between the males and the breed influence the quality and fertility of frozen–thawed boar spermatozoa. In conclusion, the presence of caffeine in the in vitro fertilization (IVF) medium and adequate length of sperm–oocyte co-incubation may have beneficial effects for improving IVF results when using microminipig spermatozoa with low quality.

Enrichment of bovine X-sperm using microfluidic dielectrophoretic chip: A proof-of- concept study

The microfluidic dielectrophoretic (MF-DEP) chip is a new, economical and readily-available technology that might be used to enrich X-sperm for increasing female offspring in dairy farms. In this study, we sought to develop an MF-DEP chip to enrich X bovine sperm. The MF-DEP chip was composed of an electrode attached to a glass slide and a microchannel made from polydimethylsiloxane. Sex-sorted sperm from flow cytometry were used to identify optimal electric field conditions while unsorted sperm were later tested for sorting efficiency. The results show that during dielectrophoresis some sperm attached to the electrode (called positive DEP; pDEP) whereas other moved away from the electrode (called negative DEP; nDEP). X and Y-sperm responded to dielectrophoresis differently depending on various factors such as buffers, voltages, and frequencies. We found that the condition 4 V 1 MHz significantly reduced (P < 0.05) the percentage of Y-sperm to nearly 30 and therefore enriched X-sperm. The sorting efficiency was dependent on buffer, bull, sorting cycle, flow rate, electrical voltage, and frequency. Notably, the best sorting buffer found in this experiment was the conducting buffer, but this buffer significantly reduced sperm viability and motility. Other sperm-friendly buffers, TRIS and mHTF, were also used, but could not enrich X-sperm. In conclusion, this is a proof of concept that the MF-DEP chip can be effectively used to enrich bovine X-sperm. However, more research must be performed particularly to find the best sorting buffer to effectively sex-sort sperm while providing high motility and sperm viability.

Development of IFN-Stimulated Gene Expression from Embryogenesis through Adulthood, with and without Constitutive MDA5 Pathway Activation

Pathogen-associated molecular patterns (e.g., dsRNA) activate expression of IFN-stimulated genes (ISGs), which protect hosts from infection. Although transient ISG upregulation is essential for effective innate immunity, constitutive activation typically causes harmful autoimmunity in mice and humans, often including severe developmental abnormalities. We have shown that transgenic mice expressing a picornavirus RNA-dependent RNA polymerase (RdRP) outside the viral context (RdRP mice) exhibit constitutive, MDA5-dependent, and quantitatively dramatic upregulation of many ISGs, which confers broad viral infection resistance. Remarkably, RdRP mice never develop autoinflammation, interferonopathy, or other discernible abnormalities. In this study, we used RNA sequencing and other methods to analyze ISG expression across five time points from fetal development to adulthood in wild-type and RdRP mice. In RdRP mice, the proportion of upregulated ISGs increased during development, with the most dramatic induction occurring 2 wk postnatally. The amplified ISG profile is then maintained lifelong. Molecular pathways and biological functions associated with innate immune and IFN signaling are only activated postnatally, suggesting constrained fetal responsiveness to innate immune stimuli. Biological functions supporting replication of viruses are only inhibited postnatally. We further determined that the RdRP is expressed at low levels and that blocking Ifnar1 reverses the amplified ISG transcriptome in adults. In conclusion, the upregulated ISG profile of RdRP mice is mostly triggered early postnatally, is maintained through adulthood, and requires ongoing type I IFN signaling to maintain it. The model provides opportunities to study the systems biology of innate immunity and to determine how sustained ISG upregulation can be compatible with robust health.

Cilostamide and forskolin maintain gap junction function of incubated dog follicles

Disruption of the communication between the oocyte and granulosa cells is one of the major causes of poor development of in vitro grown ovarian follicles and oocytes. The present study investigated the effect of two cAMP modulators, cilostamide and forskolin, on in vitro growth of isolated dog secondary follicles and enclosed oocytes, communication between the gamete and surrounding granulosa cells, expression of GJA1 and GDF9, as well as cAMP level. Secondary follicles were incubated with cilostamide or forskolin alone or a combination of 20 μM cilostamide +1 μM forskolin, and the diameter of the incubated follicles and enclosed oocytes assessed every 72 h. Gap junction activity, GJA1 and GDF9 expression and cAMP level were assessed on Days 6 and 12 and transzonal projection (TZP) density was evaluated on Day 12. Neither cilostamide nor forskolin alone enhanced in vitro growth of dog follicles and the enclosed oocytes (P > 0.05). However, these two cAMP modulators dose dependently sustained gap junction activity and stimulated cAMP production compared with the non-supplemented control. Cilostamide at the high dosage (20 μM) also upregulated GJA1 expression. The combination of cilostamide and forskolin supported oocyte growth during the first 9 days and upregulated GJA1 and GDF9 expression at Day 12 of in vitro culture. This combination treatment also sustained gap junction activity, cAMP production, and increased TZP function (calcein intensity: TZP density ratio). The findings indicated that a combination of cilostamide and forskolin supported growth and survival of oocytes enclosed within cultured follicles by sustaining cAMP production and gap junction activity.

Insulin promotes preantral follicle growth and antrum formation through temporal expression of genes regulating steroidogenesis and water transport in the cat

The aims of the present study were to determine the effects of insulin, invitro, on: (1) the viability and growth of domestic cat ovarian follicles; (2) mRNA expression of genes regulating steroidogenesis (cytochrome P450 family 17 subfamily, A polypeptide 1 (Cyp17a1), cytochrome P450 family 19 subfamily, A polypeptide 1 (Cyp19a1) and steroidogenic acute regulatory protein (Star)) and water transport (aquaporins (AQPs) Aqp1, Aqp3, Aqp7, Aqp9); and (3) steroid production (17β-oestradiol (E2), progesterone (P4), androstenedione (A4)). Cat secondary follicles were isolated from ovarian cortices and cultured in 0 (Control), 1 or 10µgmL-1 insulin for 14 days (Day 0=culture onset). Follicle and oocyte viability (based on neutral red staining), diameter and antrum formation were assessed every 72h and at the end of incubation (Day 14). Expression of steroidogenic and water transport genes was evaluated on Days 0, 6 and 12, and E2, P4 and A4 concentrations in the culture medium were determined on Day 12. By Day 14, 1 and 10µgmL-1 insulin had significantly promoted (P<0.05) both antrum formation in a mean (±s.e.m.) 26.9±9.0% and 78.0±10.0% of follicles respectively, and follicle growth (diameter 151.4±4.5 and 169.9±10.5µm respectively) compared with Control (antrum formation in 3.3±3.3% of follicles and follicle diameter 129.1±6.6µm). High insulin (10µgmL-1) treatment increased follicle viability compared with Control (86.0±9.8% vs 38.1±10.9% respectively; P<0.05). However, insulin had no beneficial effect (P>0.05) on oocyte diameter. Cyp17a1 expression on Days 6 and 12 was higher (P<0.05) in follicles cultured in the low (1µgmL-1) compared with high (10µgmL-1) insulin treatment, with no significant difference between low or high insulin vs Control groups. Star expression was higher (P<0.01) in the low insulin compared with Control group on Day 6, but Star was undetectable in the high insulin group by Day 12. Compared with high insulin, low insulin increased (P<0.05) Aqp1 expression on Day 6, but there were no significant differences between these two groups on Day 12. In contrast, high insulin decreased (P<0.05) Aqp9 transcript levels compared with Control. Only P4 production was affected by insulin, with P4 concentrations in the medium being higher (P<0.05) in the low compared with high insulin and Control groups. In summary, the findings indicate that insulin promotes cat ovarian follicle growth and survival invitro, including enhanced antrum formation, with the likely mechanism involving temporal expression of Cyp17a1, Star and Aqp9 genes.

Effect of anti-apoptotic drug Z-VAD-FMK on in vitro viability of dog follicles

It is recognized that ovarian follicular atresia is associated with apoptosis, and the most important effector of cell death is caspase-3. The aim of this study was to investigate the influence of anti-apoptotic drug Z-VAD-FMK on in vitro follicle growth in the domestic dog. Ovaries were obtained from peri-pubertal and adult domestic dogs, and cortical fragments recovered and incubated on 1.5% (w/v) agarose gel blocks within a 24-well culture plate containing Minimum Essential Medium Eagle-Alpha Modification (αMEM) supplemented with 4.2 μg/mL insulin, 3.8 μg/mL transferrin, 5 ng/mL selenium, 2 mM L-glutamine, 100 μg/mL of penicillin G sodium, 100 μg/mL of streptomycin sulfate, 0.05 mM ascorbic acid, 10 ng/mL of FSH and 0.1% (w/v) polyvinyl alcohol in humidified atmosphere of 5% CO₂ and 5% O₂. The cortices were randomly allocated in six treatments: 1) 10 ng/mL EGF (EGF V0); 2) 10 ng/mL of EGF plus 1 mM Z-VAD-FMK (EGF V1); 3) 10 ng/mL of EGF and 10 mM Z-VAD-FMK (EGF V10); 4) 1 mM Z-VAD-FMK; 5) 10 mM Z-VAD-FMK and (6) no EGF and Z-VAD-FMK supplementation (Control). The cortices were processed for histology and assessed for viability (based on morphology), density of structurally normal follicles, and diameter immediately after collection (non-culture Control) or after 3 or 7 days of in vitro incubation. Evaluation of mRNA expression of Cas3 in fresh cortices and those incubated for 3 days was performed using real-time PCR. Histological analysis revealed that in vitro incubation decreased (P < 0.05) follicle viability and density compared to the fresh, non-culture control. Addition of 10 μM of Z-VAD-FMK alone to the culture medium sustained follicle viability at Day 3, but did not impact follicle diameter when compared to the other treatment groups (p < 0.001); however, the beneficial benefit of this anti-apoptotic drug diminished after 7 days of incubation. Furthermore, Z-VAD-FMK supplementation did not impact Cas3 expression. The findings demonstrated that dog ovarian tissues are highly susceptible to in vitro incubation and Z-VAD-FMK supported short-term survival of dog follicles enclosed within the ovarian cortex.

Short-term hypertonic exposure enhances in vitro follicle growth and meiotic competence of enclosed oocytes while modestly affecting mRNA expression of aquaporin and steroidogenic genes in the domestic cat model

Using the domestic cat as a non-rodent, larger animal model, the objective was to determine the impact of a brief incubation in a hypertonic microenvironment on (1) ovarian follicle and oocyte growth in vitro, (2) developmental capacity of the resident oocyte, and (3) expression of aquaporin (AQP) genes in parallel with genes involved in regulation of folliculogenesis. In Study 1: Secondary or early antral follicles encapsulated in 0.5% alginate were allocated to one of three treatment groups: 1) culture in standard medium at 290 mOsm for 15 d (Control); 2) incubation in 350 mOsm medium for 1 h followed by culture in standard medium for 15 d (Hypertonic-1h); or 3) incubation in 350 mOsm medium for 24 h followed by incubation in standard medium for additional 14 d (Hypertonic-24h). After measuring follicle and oocyte diameters on Day 15, in vitro-grown oocytes were incubated for 24 h before assessing nuclear status. In Study 2: secondary or early antral follicles were subjected to one of the three treatments: 1) culture in standard medium at 290 mOsm for 48 h; 2) incubation in 350 mOsm medium for 1 h followed by culture in standard medium for additional 47 h; or 3) incubation in 350 mOsm medium for 24 h followed by culture in standard medium for additional 24 h. At the end of the culture period, all follicles were assessed for mRNA level of Cyp17a1, Cyp19a1, Star, Aqp1, 3, 5, 7 and 8 as well as Fshr using qPCR. Freshly collected follicles also were subjected to gene expression analysis and served as the 'Non-cultured control'. Hypertonic-24h follicles grew larger (P < 0.05) than the control, whereas those in Hypertonic-1h group exhibited intermediate growth, especially when the culture started at the early antral stage. Oocytes in the Hypertonic-24h group were larger and resumed meiosis at a higher rate than in the other treatments. In vitro culture affected (P < 0.05) mRNA expression of Cyp19a1, Star, Aqp1, and Aqp7 in both the secondary and early antral stage while Fshr was only affected in the former compared to the non-cultured control. Pre-incubating follicles in 350 mOsm medium for 24 h enhanced (P < 0.05) Star and Aqp7 while decreasing (P < 0.05) Aqp1 expression compared to the control in secondary follicles, but not in the early antral stage. In summary, short-term hypertonic exposure promoted cat follicle development in vitro (including the meiotic competence of the enclosed oocyte) possibly through a mechanism that does not involve water transport genes.

137 DYNAMIC SHIFT IN CYTOPLASMIC LIPIDS IN CAT OOCYTES DURING OVARIAN FOLLICLE DEVELOPMENT

Cytoplasmic lipids play key roles during oocyte and embryo development. However, there is little information on the changes in lipid types during intraovarian follicular and oocyte growth. Here, we used matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry to understand lipid composition in the cat oocyte during differing stages of folliculogenesis. Follicles at different developmental stages were mechanically isolated from cat ovaries within 4 h after routine ovariohysterectomy. Oocytes with granulosa cells were recovered from secondary (preantral stage, n = 387), early antral (<0.5 mm diameter, n = 177), small antral (0.5–1 mm, n = 144), and antral (>1 mm, n = 120) follicles, then subjected to lipid extraction and MALDI-TOF analysis (n = 3 replicates). Resulting mass spectra data were evaluated using MALDIquant in R package to eliminate baseline (background) and to identify peak values. The latter maximal values for each follicle stage were selected and subjected to principal component analysis to identify similarities and differences in mass spectra profile among oocytes from varying developmental stages. Peaks were compared to those calculated molecular formulae available in the Lipid MAP database. Error estimates were calculated using Excel (Microsoft Corp., Redmond, WA), and lipid species identification performed using Lipid MS Predict. Twenty-nine lipid species from six glycerophospholipids groups (glycerophosphates, PA; glycerophosphoserines, PS; glycerophosphoinositols, PI; glycerophosphoglycerols, PG; glycerophosphoinositol monophosphates, PIP; and glycerophosphoethanolamines, PE) were identified, 15 being found in more than 1 developmental stage. Two species in particular, [PI(29:4)+Na]+ and [PIP(23:0)+Na]+, were the most abundant lipids and were identified in oocytes from all developmental stages. There were dynamic shifts in lipid species expressed at different follicle stages. Oocytes from secondary and antral follicles contained more lipid types (15 and 22, respectively) than early (10) and small antral (4) counterparts. Four (PA, PS, PI, and PIP) of the 6 glycerophospholipids were found only in oocytes from secondary and antral follicles. Oocytes from small antral follicles also lacked PA, PS, and PG, whereas PG was not found in early antral stage oocytes. In summary, we showed for the first time in the cat that, similar to goats and rats, there are temporal changes in lipid types within the oocyte during folliculogenesis. We suspect that these changing dynamics, including shifts in presence or absence of lipid species with follicle stage, may be playing key roles in oocyte growth and viability. Our findings also serve as in vivo benchmarks for parallel studies focused on enhancing an in vitro culture system for early-stage ovarian follicles to preserve fertility of genetically valuable domestic and wild felids.

Epidermal growth factor improves developmental competence and embryonic quality of singly cultured domestic cat embryos

This study examined the influence of EGF on the expression of EGF receptors (EGFR) and developmental competence of embryos cultured individually versus those cultured in groups. Cat oocytes were in vitro matured and fertilized (IVM/IVF), and cleaved embryos were randomly assigned to one of seven culture conditions: one group each in which embryos were subjected to group culture supplemented with or without 5 ng/ml EGF and five groups in which embryos were subjected to single-embryo culture supplemented with EGF (0, 5, 25, 50 or 100 ng/ml). Morulae, blastocysts and hatching blastocysts were assessed at days 5 and 7; post IVF, respectively, and total blastocyst cell numbers were assessed at day 7. Relative mRNA expressions of EGFR of 2–4-cell embryos, 8–16-cell embryos, morulae and blastocysts cultured in groups or singly with or without EGF supplementation were examined. OCT3/4 and Ki67 in blastocysts derived from the group or single-embryo culture systems with or without EGF supplementation were localized. A higher rate of embryos cultured in groups developed to blastocysts than individually incubated cohorts. Although EGF increased blastocyst formation in the single-embryo culture system, EGF did not affect embryo development in group culture. Expression levels of EGFR decreased in morulae and blastocysts cultured with EGF. An increased ratio of Ki67-positive cells to the total number of cells in the blastocyst was observed in singly cultured embryos in the presence of EGF. However, EGF did not affect the expression of OCT3/4. These findings indicate that EGF enhanced developmental competence of cat embryos cultured singly by stimulating cell proliferation and modulating the EGFR expression at various developmental stages.

Selective TGF-β1/ALK inhibitor improves neuronal differentiation of mouse embryonic stem cells

The transforming growth factor-β1 (TGF-β1), a polypeptide member of the TGF-β superfamily, has myriad cellular functions, including cell fate differentiation. We hypothesized that suppression of TGF-β1 signaling would improve the efficacy of neuronal differentiation during embryoid body (EB) development. In this study, mouse embryonic stem cells (ESCs) were allowed to differentiate into their neuronal lineage, both with, and without the TGF-β1 inhibitor (A83-01). After 8 days of EB suspension culture, the samples were examined by morphological analysis, immunocytochemistry and immunohistochemistry with pluripotent (Oct4, Sox2) and neuronal specific markers (Pax6, NeuN). The alteration of gene expressions during EB development was determined by quantitative RT-PCR. Our results revealed that the TGF-β1/ALK inhibitor potentially suppressed pluripotent gene (Oct4) during a rapidly up-regulation of neuronal associated genes including Sox1 and MAP2. Strikingly, during EB development, the expression of GFAP, the astrocyte specific gene, remarkably decreased compared to the non-treated control. This strategy demonstrated the beneficial function of TGF-β1/ALK inhibitor that rapidly and uniformly drives cell fate alteration from pluripotent state toward neuronal lineages.

Insulin-like growth factor-1 (IGF-1) enhances developmental competence of cat embryos cultured singly by modulating the expression of its receptor (IGF-1R) and reducing developmental block

OBJECTIVE

The aim of this study is to determine the effects of insulin-like growth factor-1 (IGF-1) and the mRNA expression of IGF-1 receptor (IGF-1R) during the in vitro development of cat embryos cultured in groups versus singly.

METHODS

Cumulus-oocyte complexes (COCs) were matured and fertilized in vitro with frozen-thawed semen. Cleaved embryos (48h post-fertilization) were randomly assigned to one of the following treatments: 1) group embryo culture without IGF-1 (10 embryos per 50μl droplet), 2) single-embryo culture without IGF-1, and 3) to 6) single-embryo culture (50μl droplet per embryo) supplemented with different concentrations of IGF-1 (5, 25, 50 and 100ng/ml, respectively). During in vitro culture, the embryos were analyzed for development to the morula, blastocyst and hatching blastocyst stage. Relative mRNA expression of IGF-1R was also examined by qPCR at the morula and blastocyst stages. In addition, the mRNA expression of IGF-1R in morula-stage embryos treated with IGF-1 was determined. The influence of IGF-1 to preimplantation embryo development was then explored by co-incubation with 0.5μM IGF-1R inhibitor (Picropodophyllin; PPP).

RESULTS

Group embryo culture led to a significantly higher blastocyst development rate compared with single-embryo culture (P<0.05). The poor development of singly cultured embryos coincided with the significantly lower IGF-1R expression in morulae than in group-cultured morulae. IGF-1 (25 or 50ng/ml) supplementation significantly improved the blastocyst formation rate of single embryos to a level similar to group culture by promoting the morula-to-blastocyst transition. IGF-1 supplementation (25 or 50ng/ml) of singly cultured embryos upregulated the expression of IGF-1R mRNA in morula-stage embryos to the same level as that observed in group-cultured embryos (without IGF-1). The beneficial effects of IGF-1 on singly cultured embryo were (P<0.05) suppressed by PPP even in the group culture embryo without growth factor supplementation.

CONCLUSION

IGF-1 supplementation improves the developmental competence of feline embryos cultured individually and also increases IGF-1R gene expression to levels similar to group-cultured embryos.

Birth of kittens after the transfer of frozen-thawed embryos produced by intracytoplasmic sperm injection with spermatozoa collected from cryopreserved testicular tissue

The aim of this study is to produce live kittens from oocytes fertilized by intracytoplasmic sperm injection (ICSI) with frozen/thawed testicular spermatozoa. Spermatozoa were collected from thawed testicular tissue and subsequently injected into in vitro matured cat oocytes. At 24 h post-ICSI, presumptive zygotes/cleaved embryos were treated with 10 μm forskolin for 24 h to reduce intracellular lipid content of embryos (delipidation). At 48 h after oocyte injection, cleaved embryos (2- to 8-cell stage) were frozen in 10% (v/v) ethylene glycol-based medium by a slow controlled rate method and stored in liquid nitrogen. To evaluate in vitro and in vivo developmental competence, frozen embryos were thawed and then cultured for 6 days (n = 155) or cultured for 2 h before transferred (n = 209) to hormonal (equine chorionic gonadotropin/hCG)-treated cat recipients. Cleavage frequency at day 2 after ICSI with frozen/thawed testicular spermatozoa was ~30%. The percentages of frozen/thawed embryos that developed to morula and blastocyst stage (on day 3 and day 6 of in vitro culture, respectively) were significantly lower than that of fresh ICSI embryos (22.6 vs 45.2% and 21.3 vs 38.7%, respectively; p < 0.05). However, no difference was found in the number of blastomeres between frozen/thawed (242.5 ± 43.1) and fresh (320.2 ± 28.1) blastocysts. Three of seven cat recipients were pregnant and one pregnant cat delivered two healthy kittens. This is the first report of the birth of kittens after the transfer of frozen-thawed embryos produced by ICSI with frozen/thawed testicular sperm.

Characterization and in vitro culture of putative spermatogonial stem cells derived from feline testicular tissue

Spermatogonial stem cells (SSCs) function to regulate the balance of self-renewal and differentiation of male gametes. SSCs have been successfully isolated and cultured in vitro in several species, but not in feline. Therefore, in this study, we aimed to culture and characterize feline SSCs. In experiment 1, testes (n=5) from different pubertal domestic cats were cryosectioned and fluorescently immunolabeled to examine the expression of SSC (GFRα-1), differentiated spermatogonium (c-kit) and germ cell (DDX-4) markers. In experiments 2 and 3, testicular cells were digested and subsequently cultured in vitro. The resultant presumptive SSC colonies were then collected for SSC identification (experiment 2), or further cultured in vitro on feeder cells (experiment 3). Morphology, gene expression and immunofluorescence were used to identify the SSCs. Experiment 1 demonstrated that varying types of spermatogenic cells existed and expressed different germ cell/SSC markers. A rare population of putative SSCs located at the basement membrane of the seminiferous tubules was specifically identified by co-expression of GFRα-1 and DDX-4. Following enzymatic digestion, grape-like colonies formed by 13-15 days of culture. These colonies expressed GFRA1 and ZBTB16, but did not express KIT. Although we successfully isolated and cultured feline SSCs in vitro, the SSCs could only be maintained for 57 days. In conclusion, this study demonstrates, for the first time, that putative SSCs from testes of pubertal domestic cats can be isolated and cultured in vitro. These cells exhibited SSC morphology and expressed SSC-specific genes. However, long-term culture of these putative SSCs was compromised.