A comparison between in vitro fertilization and microinjection of immobilized spermatozoa from bulls producing spermatozoa with defects

Microfluidic jet injection for delivering macromolecules into cells

We present a microfluidic based injection system designed to achieve intracellular delivery of macromolecules by directing a picoliter-jet of a solution towards individual cells. After discussing the concept, we present design specification and criteria, elucidate performance and discuss results. The method has the potential to be quantitative and high throughput, overcoming limitations of current intracellular delivery protocols.

Microfluidic based single cell microinjection

We report a microfluidic based approach for single cell microinjection in which fluid streams direct a cell onto a fixed microneedle in contrast to moving a microneedle towards an immobilized cell, as done in conventional methods. The approach simplifies microinjection and offers the potential for flow through automated microinjection of cells.

Effect of centrifugation and electrical activation on male pronucleus formation and embryonic development of porcine oocytes reconstructed with intracytoplasmic sperm injection

Oocyte centrifugation and electrical activation are commonly used in intracytoplasmic sperm injection (ICSI) of bovine and porcine oocytes, to facilitate visual identification of sperm release into the ooplasm and to support oocyte activation following injection with tail membrane-damaged sperm. The present study evaluated the necessity of these steps in porcine modified ICSI. In the first series of experiments, in vitro-matured gilt oocytes with or without centrifugation were injected with head membrane-damaged spermatozoa aspirated tail first. Oocytes without centrifugation exhibited a significantly higher normal fertilisation rate, defined as male pronucleus (MPN) and female pronucleus (FPN) formation and the presence of two polar bodies, than centrifuged oocytes (40% v. 9%, respectively; P < 0.05). The rate of MPN formation was significantly higher in uncentrifuged oocytes compared with centrifuged oocytes (48% v. 17%, respectively; P < 0.05). The rates of survival, cleavage, blastocyst formation and total cell number in blastocysts did not differ between the two groups of oocytes. Next, the effect of electrical activation after ICSI on uncentrifuged oocytes injected with head membrane-damaged spermatozoa was determined. No significant differences were observed in the rate of MPN formation in sperm-injected oocytes regardless of electrical activation. However, the survival rates of sperm-injected or control oocytes without electrical activation were significantly higher than those of sperm-injected or control oocytes with electrical activation (88% and 84% v. 77% and 64%, respectively; P < 0.05). The cleavage rates of sperm-injected oocytes were significantly higher than those of control oocytes, regardless of electrical activation (77% and 81% v. 47% and 61% in sperm-injected and control oocytes with or without electrical activation, respectively; P < 0.05). Although development to blastocysts was similar in all experimental groups, the total cell numbers in blastocysts from control oocytes were significantly higher than those in sperm-injected oocytes, regardless of electrical activation (40 and 44 v. 22 and 26 in control and sperm-injected oocytes with or without electrical activation, respectively; P < 0.05). In conclusion, the present study clearly demonstrated that oocyte centrifugation before sperm injection is not beneficial to normal fertilisation and that electrical activation is not necessary in the modified porcine ICSI.

Production of piglets using intracytoplasmic sperm injection (ICSI) with flowcytometrically sorted boar semen and artificially activated oocytes

The purpose of the present study was to develop a protocol for the successful production of piglets employing intracytoplasmic sperm injection (ICSI) with flowcytometrically sexed spermatozoa and artificially activated porcine oocytes. In vitro matured oocytes were fertilized by ICSI using non-sorted frozen/thawed epididymal semen. Oocytes were either activated by CaCl(2), Ca(2+)-ionophore or electrical pulse. Activation and fertilization rates of sperm injected oocytes stimulated by CaCl(2)-injection were significantly higher than those without activation (70.4% versus 45.9%; 49.9% versus 33.2%, respectively; P<0.001). Activation rate of sham injected oocytes increased in parallel (11.2% versus 26.3%, P<0.05), parthenogenetic development remained low (2.8% versus 8%). Co-incubation in Ca(2+)-ionophore did not improve activation rates as compared to non-activated oocytes (44.8% versus 42.5%). Fertilization rate decreased as compared to non-treated sperm injected oocytes (36.8% versus 24.5%, P<0.05). Activation of oocytes with a single electrical pulse resulted in significantly higher activation rates in all groups of oocytes as compared to non-stimulated ones (sperm injected oocytes: 65.6% versus 43.1%, P<0.001; sham injected oocytes: 48.5% versus 5.6%, P<0.001; control oocytes: 50.7% versus 0.0%, P<0.001). Fertilization rates (32.3% versus 48.2%) and parthenogenetic development (0.7% versus 38.9%, 0.0% versus 30.9%, P<0.001) increased significantly in parallel. In addition, in four replicates of flowcytometrically sorted Y-chromosome bearing spermatozoa were injected into in vivo matured oocytes, activated with 1.2 pl of a 30 mM CaCl(2) solution. On average 85.3 fertilized oocytes were transferred surgically into four recipients. Pregnancies delivered a total of 13 male piglets. These are the first piglets born from ICSI with sorted spermatozoa.

Fertility estimation: a review of past experience and future prospects

Fertility has many components and stages which require that males and females be functionally capable of carrying out all critical stages if each generational reproductive cycle is to be completed. To accomplish this, the male must produce and ejaculate normal fertile sperm. The female must produce, store and ovulate normal fertilizable oocytes. Furthermore, the female must provide a reproductive system compatible with sperm transport, capacitation, and fertilization of the oocytes, embryo and fetal development, and finally birth of healthy young. Reproductive success or failure at several of these points can be estimated quantitatively on a population basis, and in a few situations on an individual basis. It is important that fertility estimates be determined accurately and with precision to be most useful to researchers and managers of animal enterprises. Many studies have underestimated the biological relationship of fertility to other traits because the estimates lacked precision. Many in vitro manipulations of sperm in artificial insemination, of gametes in various assisted reproductive technologies, and of embryos in embryo transfer are utilized in animal breeding programs. Accurate estimation of reproductive efficiency of these in vitro procedures also is important. Conditions surrounding different sets of fertility estimates almost certainly will be different. These conditions should be described as precisely as possible, and appropriate controls included in all experiments. When possible, experiments should be replicated over time and place to determine the repeatability of the various criteria used to estimate fertility and reproductive efficiency. Advances in genomic information and molecular biology should facilitate characterizing more fully inherent potential fertility of animals at birth. In vitro tests will improve, and automated techniques will facilitate making multiple determinations possible on a large scale. Reliability of fertility estimates will increase, with the potential for enhanced animal reproductive performance through more accurate selection, genetic engineering, and enlightened animal care. Simultaneously, it is important to recognize that prediction of future fertility is more hazardous than estimating fertility, as a completely new set of circumstances may occur which are not predictable. Because fertility estimation may be applied under a myriad of conditions, principles and factors affecting fertility will be emphasized in this review as being more useful than a compilation of numerical examples.

Birth of normal calves after intracytoplasmic sperm injection of bovine oocytes: a methodological approach

Intracytoplasmic sperm injection (ICSI) is advantageous when only very few spermatozoa are available for insemination. Bovine spermatozoa were injected individually into matured oocytes using a piezo electric actuator. Spermatozoa were "immobilized", by scoring their tails immediately before injection, or "killed", by repeated freezing and thawing. About 4 h after ICSI, the oocytes with two polar bodies (activated by sperm injection) were selected and treated 5 min with 7% ethanol before further culture. When examined 19-21 h after ICSI, nearly 90% of the oocytes were fertilized normally (two pronuclei and two polar bodies) irrespective of the sperm treatment (immobilization or killing) prior to ICSI, but subsequent preimplantation embryo development was much superior (cleavage 72%: blastocysts 20%) after ICSI with immobilized spermatozoa than by using killed spermatozoa (cleavage 28%; blastocysts 1%). Ethanol activation of bovine oocytes with two polar bodies 4 h after ICSI improved the cleavage (33% versus 72%) and blastocyst (12% versus 20%) rates markedly (P < 0.05). Five normal calves were born after transplantation of ten blastocysts to ten surrogate cows. These results show that piezo-ICSI using immobilized spermatozoa, combined with ethanol treatment of sperm-injected oocytes, is an effective method to produce bovine offspring.

Induction of the acrosome reaction and zona-free hamster oocyte penetration by a bull with complete teratospermia versus a half brother with normal sperm

A fertile bull producing normal sperm and a sterile half brother exhibiting 100% teratospermia were available to study an induced sperm acrosome reaction and oocyte penetration. Pedigree analysis indicated that this condition was inherited. Experiments were undertaken to study the induction of the acrosome reaction using dilaurylphosphatidylcholine (PC12) liposomes, because this procedure was previously established to be highly correlated with bull fertility. The sperm from each bull were incubated with several PC12 concentrations for varying time periods. The initial percentages of sperm from the sterile bull with intact, partially intact, and lost acrosomes were 67%, 18%, and 14%, respectively, vs 82%, 13%, and 5% for the fertile bull (P < .05). After incubation for 15 minutes with 50 microM PC12 liposomes the corresponding values were, respectively, 51%, 26%, and 19%; and 60%, 28%, and 12%. Thus, the differences after induction of the acrosome reaction, although significant (P < .05), were small. The number of sperm adhered to each oocyte averaged 22 and 10, respectively, for the fertile and sterile bulls, whereas 74% of the fertile bull sperm and only 11% of the sterile bull sperm penetrated oocytes. Mixing the sperm-oocyte complex during incubation and increasing the sperm concentration during incubation to compensate for differences in sperm motility did not markedly affect oocyte penetration by teratogenic sperm, which is consistent with this bull being sterile. In other studies, microinjection of this type of sperm was demonstrated to induce fertilization, so the consequences of using sperm with hereditary defects in assisted reproductive programs to overcome human male sterility may be a concern.

Use of semen from a bull heterozygous for the translocation in an IVF program

In cattle, a translocation of the Robertsonian type between the largest and smallest chromosome leads to a reduction in fertility. This is substantiated by reduced nonreturn rates in daughter groups of bulls carrying the 1 29 translocation and in the heterozygous bulls themselves. This reduction in fertility is thought to be due to the early death of embryos with unbalanced karyotypes. The influence of semen from a bull known to be heterozygous for the 1 29 translocation on the outcome of a bovine IVF program was investigated. There was a significant difference (P<0.005) in terms of cleavage rate (59.8 vs 71.1%) and blastocyst rate (12.0 vs 20.0%) between the carrier and control bull, respectively. There was no difference in blastocyst quality as measured by cell number. The results observed in vitro are consistent with the field fertility records of the 2 bulls in terms of nonreturn rates (59.2 vs 70.6%, for the carrier and control bull, respectively).