Injection Of Sperm Extract Research Articles

32 A CLONED FOAL PRODUCED USING OOCYTES RECOVERED BY TRANSVAGINAL ASPIRATION OF IMMATURE FOLLICLES

Closure of all the horse slaughterhouses in the US has reduced the availability of equine oocytes in this country. We investigated the use of oocytes collected from immature follicles of live mares for cloning research. Because blastocyst development of equine cloned embryos is typically low (<10%), we also investigated the effect of Scriptaid, a histone deacetylase inhibitor that increases blastocyst development, live birth rate, and neonatal health in cloned mice and pigs. Immature oocytes were transvaginally aspirated from all follicles ≥8 mm diameter in a herd of 11 mares. The oocytes were cultured in modified M199 for 24 to 26 h. Donor fibroblasts from a 27-year old stallion were treated with roscovitine for 24 h, then were directly injected into enucleated oocytes using the Piezo drill. Reconstructed oocytes were activated with ionomycin followed by injection of sperm extract and culture with 6- dimethylaminopurine (6-DMAP) for 4 h. Recombined oocytes in the Scriptaid treatment were cultured in the presence of Scriptaid, 250 nM, starting at the onset of 6-DMAP treatment and continuing for a total of 18 to 20 h. After embryo culture, blastocysts were shipped for transfer to recipient mares. Overall, each oocyte donor mare underwent aspiration up to 10 times; 653 follicles were aspirated and 271 oocytes were recovered. The in vitro maturation rate was 65% (172/263). After nuclear transfer procedures, 147 oocytes survived; 130 were used for the study. The blastocyst development rate was 2/47 (4%) in the control treatment and 1/83 (1%) in the Scriptaid treatment. All 3 blastocysts yielded pregnancies after transfer. Both control pregnancies were lost, 1 at 30 days and other at 9 months. The mare pregnant with the embryo from the Scriptaid treatment foaled at 326 days of gestation. The foal had medical issues at birth similar to those seen in some cloned foals previously, including maladjustment, patent urachus, and poor oxygenation. These issues were resolved with medical care; the foal is 3 months of age and healthy at the time of writing. These results indicate that immature oocytes obtained from a limited number of mares can be used successfully for nuclear transfer, providing the opportunity to control the mitochondrial identity of the host cytoplast. Scriptaid treatment did not improve the rate of blastocyst development or prevent health problems at birth; however, transfer of 1 embryo in this treatment produced a viable foal. More work is needed to determine the effect of histone deacetylase treatment on efficiency of cloning in the horse. This work was supported by the Link Equine Research Endowment Fund, Texas A&M University, and by Ms. Kit Knotts. We thank Drs. Malgorzata Pozor, Margo Macpherson, and the Medicine team at the University of Florida for medical care of the foal.

Effect of Sperm Extract Injection Volume, Injection of PLCζ cRNA, and Tissue Cell Line on Efficiency of Equine Nuclear Transfer

We evaluated the effect of different activation methods on blastocyst development after equine nuclear transfer. All activation treatments were followed by incubation in 2 mM 6-dimethylaminopurine for 4 h. In Experiment 1, reconstructed oocytes were injected with sperm extract for 0.1, 0.2, 0.4, 0.8, or 1.6 sec using a FemtoJet injection device, then treated with ionomycin. The blastocyst rate (9.8%) for 0.1-sec injection was significantly higher than that for 0.2 sec (0%) or 0.8 sec (1.4%). In Experiment 2, injection of murine PLCzeta cRNA before or after ionomycin treatment did not increase blastocyst development (0 and 4.5%) over a control treatment (injection of sperm extract after ionomycin exposure; 5.6%). Transfer of 10 blastocysts produced in Experiments 1 and 2 resulted in five pregnancies, all lost before 70 days of gestation. In Experiment 3, cells from a second biopsy sample from the same horse produced significantly more blastocysts than did the original sample (4/44 vs. 0/58; p < 0.05). Transfer of these four blastocysts produced two viable foals. In Experiment 4, blastocyst development rates did not differ between oocytes in metaphase I or II at the time of nuclear transfer (16.7 and 3.0%, respectively). A healthy foal was produced from a blastocyst originating from a metaphase I oocyte.

P34cdc2Kinase and MAP Kinase Activities and Parthenogenetic Activation in Porcine Oocytes after Injection of Miniature Pig Sperm Extracts

ABSTRACT The aim of the present study was to examine the rate of activation and time-dependent changes in p34cdc2 kinase and MAP kinase activities in porcine oocytes after injection of sperm extracts (SE) or treatment with Ca2+ ionophore to clarify whether SE injection is useful for porcine oocyte activation. SE was prepared from miniature pig sperm by non-ionic surfactant. Oocytes that were treated with Ca2+ ionophore and injected with SE were activated at rates of 41% and 46%, respectively. The activities of p34cdc2 kinase and MAP kinase in each culture period (4, 8 and 12 h) in the Ca2+ ionophore group and SE injection group were significantly lower than those in the control group. These results suggest that SE injection induces decrease of p34cdc2 kinase and MAP kinase activity, and induces oocyte activation, as well as Ca2+ ionophore treatment, but the induction was comparatively limited.

27 EFFECT OF ACTIVATION METHODS AND BIOPSY SAMPLING ON NUCLEAR TRANSFER BLASTOCYST PRODUCTION AND CLONING EFFICIENCY IN A HORSE

In the horse, rates of blastocyst production after nuclear transfer are low. This study was conducted to examine the effect of activation via injection of different volumes of sperm extract or via injection of murine mRNA for PLC-ζ, a sperm-specific protein which induces Ca2+ oscillations in all species thus far studied, on blastocyst development after nuclear transfer. Two biopsy samples from the same horse were also examined for cloning efficiency. Donor fibroblasts cultured from a skin biopsy taken from a 19-year-old mare were treated with 15 µm R-roscovitine for 18 to 24 h before direct injection into enucleated ooplasts. Ionomycin treatment, 5 µm for 4 min, was used in all activation treatments, as the combination of ionomycin with sperm extract provided the highest blastocyst development and foaling rates in our previous report (Hinrichs et al. 2007 Reproduction 134, 319–325). All treatments were followed by incubation in 2 mm 6-dimethylaminopurine for 4 h. Differences in blastocyst development between treatments were analyzed using Fisher's exact test. In Experiment 1, reconstructed oocytes were injected with sperm extract for 0.1, 0.2, 0.4, 0.8, or 1.6 s at a fixed pipette diameter and injection pressure, and then treated with ionomycin. The blastocyst rate (9.8%) for 0.1 s was significantly higher than that for 0.2 s (0%) or 0.8 s (1.4%). In Experiment 2, murine PLC-ζ mRNA (0.25 µg µL–1) was injected into reconstructed oocytes 20 to 30 min before or after ionomycin treatment and compared with a control treatment (injection of 2 to 4 pL sperm extract 20 to 50 min after ionomycin exposure). There were no differences in blastocyst development among treatments (0, 4.5, and 5.6%, respectively). Transfer of 10 blastocysts produced in Experiments 1 and 2 resulted in 5 pregnancies: however, all were lost before 70 days of gestation. In Experiment 3, a second skin biopsy was obtained from the same mare and cells from this tissue sample were used for nuclear transfer concurrently with cells from the first sample, using the control method above. Blastocyst production was higher using cells from the second biopsy sample (4/23 v. 0/23; P = 0.05). Transfer of these four blastocysts yielded four pregnancies, two of which continued to term and produced viable foals. These results indicate that blastocyst development after injection of sperm extract is dependent upon the volume injected, that injection of murine PLC-ζ mRNA does not improve blastocyst formation under the given conditions, and that the efficiency of cloning may vary with biopsy sample even from the same animal.

Production of horse foals via direct injection of roscovitine-treated donor cells and activation by injection of sperm extract

We evaluated the effects of different donor cell treatments and activation methods on production of blastocysts after equine nuclear transfer. Nuclear transfer was performed by direct injection of donor cells, using a piezo drill, and standard activation was by injection of sperm factor followed by culture with 6-dimethylaminopurine. There was no difference in blastocyst development between embryos produced with roscovitine-treated or confluent donor cells (3.6% for either treatment). Addition of injection of roscovitine or culture with cycloheximide at the time of activation did not affect blastocyst development. Overall, transfer of eight blastocysts produced using roscovitine-treated donor cells and our standard activation protocol yielded three pregnancies, of which two (25% of transferred embryos) resulted in delivery of viable foals. Flow cytometric evaluation showed that roscovitine treatment significantly increased the proportion of cells classified as small, in comparison to growth to confluence or serum deprivation, but did not significantly affect the proportion of cells in G0/G1 (2N DNA content). Transfer of one blastocyst produced using roscovitine-treated donor cells, with addition of roscovitine injection at activation, yielded one pregnancy which was lost before 114 days' gestation. Transfer to recipients of two blastocysts produced using confluent donor cells with addition of cycloheximide at activation gave no resulting pregnancies. We conclude that roscovitine treatment of donor cells yields equivalent blastocyst production after nuclear transfer to that for confluent donor cells, and that direct injection of roscovitine-treated donor cells, followed by activation using sperm extract, is compatible with efficient production of viable cloned foals.

Effects of Miniature Pig Sperm Extracts and Their Treatments on Porcine or Bovine Oocyte Activation

This study investigated the activation of oocytes after microinjection of sperm extracts (SE) from miniature pig spermatozoa. SE was prepared from miniature pig sperm by sonication for 35 min and centrifugation 100,000 g for 1 h. Injection of SE 0.3 mg/ml into porcine oocytes produced the highest activation rate (41.8%). SE injection into bovine oocytes induced similar activation (43.3%). The porcine oocyte activation rate (63.4%) was significantly (p<0.05) improved when SE was purified with a 2-D clean-up kit. When SE was heat treated at 60°C for 30 min, it failed in activation. However, SE succeeded in activation when stored at 4°C for 48 h or was freeze-thawed 5 times using liquid nitrogen. The activation rates were 42.1% and 31.4%, respectively. The results indicate that SE from miniature pig sperm might have an oocyte activation factor, and that the factor might have stability at low temperatures, though it appears to be inactivated at high temperatures.

Equine blastocyst development after intracytoplasmic injection of sperm subjected to two freeze-thaw cycles

This study was conducted to evaluate the effects of thawing, division into aliquots and refreezing on fertilizing capacity (ability to support embryo development after intracytoplasmic sperm injection; ICSI) of frozen stallion semen. Frozen semen from a fertile stallion was thawed, diluted 1:100 with freezing extender, and refrozen (2F treatment). Control semen was frozen only once. In vitro matured equine oocytes were injected with: (1) motile control spermatozoa; (2) motile 2F spermatozoa; (3) non-motile 2F spermatozoa; or (4) non-motile 2F spermatozoa, followed by injection of sperm extract. Blastocyst development after ICSI was equivalent between control spermatozoa and motile 2F spermatozoa (27 and 23%, respectively). Blastocyst development after injection of non-motile 2F spermatozoa (13%) tended ( P = 0.07) to be lower than that for control spermatozoa. Injection of sperm extract into oocytes that received non-motile 2F spermatozoa resulted in a significant decrease in blastocyst development (to 2%) compared with injection of non-motile 2F spermatozoa alone. Spermatozoa from a subfertile stallion was similarly processed and used for ICSI; blastocyst development for both motile control (once frozen) spermatozoa and motile 2F spermatozoa was 9%. In conclusion, frozen stallion semen may be thawed, diluted, and refrozen without effect on the ability of motile spermatozoa to initiate embryo development after ICSI. Non-motile spermatozoa from reprocessed semen may also achieve embryo development after ICSI. To our knowledge, this is the first report evaluating the ability of refrozen spermatozoa to produce embryos by ICSI in any species.

Recombinant phospholipase Czeta has high Ca2+ sensitivity and induces Ca2+ oscillations in mouse eggs.

Sperm-specific phospholipase Czeta (PLCzeta) is known to induce intracellular Ca(2+) oscillations and subsequent early embryonic development when expressed in mouse eggs by injection of RNA encoding PLCzeta (Saunders, C. M., Larman, M. G., Parrington, J., Cox, L. J., Royse, J., Blayney, L. M., Swann, K., and Lai, F. A. (2002) Development 129, 3533-3544). The present study addressed characteristics of purified mouse PLCzeta protein that was synthesized using the baculovirus/Sf9 cell expression system. Microinjection of recombinant PLCzeta protein into mouse eggs induced serial Ca(2+) spikes quite similar to those produced by the injection of sperm extract, probably because of repetitive Ca(2+) release from the endoplasmic reticulum caused by continuously produced inositol 1,4,5-trisphosphate. Recombinant PLCdelta1 also induced Ca(2+) oscillations, but a 20-fold higher concentration was required compared with PLCzeta. In the enzymatic assay of phosphatidylinositol 4,5-bisphosphate hydrolyzing activity in vitro at various calcium ion concentrations ([Ca(2+)]), PLCzeta exhibited a significant activity at [Ca(2+)] as low as 10 nm and had 70% maximal activity at 100 nm [Ca(2+)] that is usually the basal intracellular calcium ion concentration level of cells. On the other hand, the activity of PLCdelta1 increased at a [Ca(2+)] between 1 and 30 microm. EC(50) was 52 nm for PLCzeta and 5.7 microm for PLCdelta1. Thus, PLCzeta has an approximately 100-fold higher Ca(2+) sensitivity than PLCdelta1. The ability of purified PLCzeta protein to induce Ca(2+) oscillations qualifies PLCzeta as a proper candidate of the mammalian egg-activating sperm factor. Furthermore, such a high Ca(2+) sensitivity of PLC activity as PLCzeta that can be active in cells at the resting state is thought to be an appropriate characteristic of the sperm factor, which is introduced into the ooplasm upon sperm-egg fusion, triggers Ca(2+) release first, and maintains Ca(2+) oscillations.

Activation of equine nuclear transfer oocytes: methods and timing of treatment in relation to nuclear remodeling.

Early development of embryos produced by transfer of equine nuclei to bovine cytoplasts is superior to that of intraspecies equine nuclear transfer embryos. This may be related to differences in chromatin remodeling or efficiency of activation between the two oocyte types. The pattern of donor nucleus remodeling was examined in equine-equine and equine-bovine reconstructed oocytes. Chromosome condensation occurred in equine cytoplasts by 2 h but was not seen in bovine cytoplasts until 4 h. We investigated the effect of activation of equine-equine reconstructed oocytes at <30 min or at 2 h after reconstruction. Four activation treatments were evaluated at each time point: injection of sperm extract alone, or in combination with 6-dimethylaminopurine (6-DMAP), cytochalasin B, or 1% dimethylsulphoxide. There was no significant difference in normal cleavage rate or average nucleus number of embryos between equine oocytes activated <30 min or at 2 h after reconstruction. The combination of 6-DMAP with sperm extract significantly (P < 0.01) improved cleavage rate compared with the other three treatments. Activation with sperm extract and 6-DMAP 2 h after donor nucleus injection gave the highest cleavage (79%) and the highest cleavage with normal nuclei (40%). Sperm extract and 6-DMAP also effectively activated oocytes parthenogenetically, yielding 83% cleavage and 73% cleavage with normal nuclei. These results indicate that although nuclear remodeling occurs rapidly in equine cytoplasts, early activation does not improve embryonic development after reconstruction.

Analysis of Mn2+/Ca2+influx and release during Ca2+oscillations in mouse eggs injected with sperm extract

Repetitive Ca2+release from the endoplasmic reticulum (ER) is necessary for activation of mammalian eggs. Influx and release of Mn2+and Ca2+during Ca2+oscillations induced by injection of sperm extract (SE) into mouse eggs were investigated by Mn2+-quenching of intracellular Fura-2 after adding Mn2+to external medium. Mn2+/Ca2+influx was detected at the resting state. A marked Mn2+/Ca2+influx occurred during the first Ca2+release upon SE injection, and persistently facilitated Mn2+/Ca2+influx was observed during steady Ca2+oscillations. As intracellular Mn2+concentration ([Mn2+]i) increased progressively, periodic [Mn2+]irises appeared, corresponding to each Ca2+transient but taking a slower time course. A numerical simulation based on continuous Mn2+/Ca2+influx-extrusion across the plasma membrane and release-uptake across the ER membrane in a competitive manner mimicked well the Mn2+oscillations calculated from experimental data, strongly suggesting that repetitive Mn2+release develops after Mn2+entry and uptake into the ER. In other experiments, a marked Mn2+influx occurred upon Mn2+addition to Ca2+-free medium after depletion of the ER using an ER Ca2+pump inhibitor plus repeated injection of inositol 1,4,5-trisphosphate (InsP3). No significant increase in Mn2+influx was induced by injection of SE, InsP3, or Ca2+, when Ca2+release was prevented by pre-injection of an antibody against the InsP3receptor. We concluded that Ca2+influx is activated during the initial large Ca2+release possibly by a capacitative mechanism and kept facilitated during steady Ca2+oscillations. The finding that repetitive Mn2+release is caused by continuous Mn2+entry suggests that continuous Ca2+influx may play a critical role in refilling the ER and, thereby, maintaining Ca2+oscillations in mammalian fertilization.

Soluble extracts from ascidian spermatozoa trigger intracellular calcium release independently of the activation of the ADP ribose channel.

We have injected soluble extracts of sperm from the ascidian Ciona intestinalis into oocytes of the same species to test whether these extracts can mimic the events of fertilisation. Injection of ascidian sperm extracts leads, after a delay of approximately 60 s, to a large calcium transient and repetitive pattern of calcium oscillations, mimicking the normal fertilisation response. The response was concentration-independent, suggesting a stimulatory mechanism in triggering the fertilisation response. We tested the pathway of calcium release in ascidian oocytes after injection of sperm extracts by preinjection of calcium release inhibitors. The data demonstrate that dual pathways to calcium release act at fertilisation in ascidians, as in other species. C. intestinalis oocytes are characterised by a ion channel in the plasma membrane that is gated uniquely by ADP ribose. We show that this channel is not gated by the injection of ascidian sperm extracts. Our data suggest that one metabolic pathway triggered by sperm, the release of nitric oxide, is not stimulated by sperm extracts and that several metabolic pathways are stimulated at fertilisation by more than one factor within sperm.

Ca 2+ oscillations and sensitization of Ca 2+ release in unfertilized mouse eggs injected with a sperm factor

The mechanisms by which a sperm factor caused Ca 2+ oscillations in unfertilized mouse eggs was investigated by monitoring the fluorescence of intracellular Fluo-3. Injecting sperm extracts triggered Ca 2+ oscillations that varled in number and frequency rather than amplitude. All the sperm factor-induced Ca 2+ transients showed a characteristic rapid increase and decline. The oscillations persisted for varlable times in eggs bathed in Ca 2+ free media and were distinct in character from those caused by inserting pipettes containing inositol 1,4,5-trisphosphate (InsP 3). InsP 3-induced Ca 2+ oscillations were always of high frequency but varied considerably in form and amplitude depending upon InsP 3 concentration. The oscillations produced by injecting Ca 2+ into unfertilized eggs were similar to those produced with low doses of InsP 3 but different from those caused by sperm extract injection. After injection of sperm extracts further injection of InsP 3, or Ca 2+, produced high frequency large amplitude Ca 2+ transients. It is concluded that the sperm factor mediates its effects by sensitizing Ca 2+ release mechanisms.