Cryopreservation of rhesus macaque (Macaca mulatta) spermatozoa and their functional assessment by in vitro fertilization

Semen collection by urethral catheterization and electro-ejaculation with different voltages, and the effect of holding temperature and cooling rate before cryopreservation on semen quality in the Japanese macaque (Macaca fuscata)

In the Japanese macaque, semen has been collected by electro-ejaculation (EE), using the higher voltage stimuli compared to other species including genus Macaca. Semen coagulate immediately after ejaculation, which makes difficult to produce high-quality semen for artificial insemination. Recently, semen collection using urethral catheterization (UC) has been reported in carnivore and this technique may allow semen collection without coagulation in a less invasive manner. Further, the temporal preservation temperature and cooling rate of semen during cryopreservation affect post thawing sperm quality. In this study, to improve semen quality and quantity, as well as the animal welfare, semen collection was performed by EE with high (5-15 V) or low (3-6 V) voltage, UC and a combination of the two (EE-UC). It has been suggested that a high voltage is necessary for semen collection, but 10 V stimulation was effective enough and 15 V is for additional sperm collection. Also, liquid semen was collected by EE-UC and this could increase the total number of sperm. Further, to improve the post thawing sperm motility, semen was kept at four temperatures (4, 15, 25 and 37˚C) for 60 min, and processed with two cooling procedures (slow cooling before second dilution and fast cooling after second dilution). Holding semen at 25˚C and fast cooling after the second dilution maintained progressive motile sperm rate. The present results will contribute to the improvement of semen collection and animal welfare of Japanese macaques.

Male reproductive systems of Macaca mulatta: Gonadal development, spermatogenesis and applications in spermatogonia stem cell transplantation

Rhesus macaque (Macaca mulatta) is widely applied in animal model construction of infertility, spermatogonia stem cell transplantation and male reproductive diseases. In this review, we describe the seasonal changes of the reproductive system in rhesus macaques, the regular pattern of spermatogenesis and spermatozoa maturation, and the differentiation of spermatogonia and spermatocytes. The duration of the M. mulatta spermatogenesis is approximately 10 days and seminiferous epithelium cycles mainly consist of 12 stages, which provide a suitable model for reproductive studies in non-human primates. Here, we summarize the features of gonadal development and sperm maturation in the rhesus monkeys, which provide important information in the studies of reproductive biology. Rhesus macaque is an excellent animal model in spermatogonia stem cell transplantation. We discuss the applications and progresses of assisted reproductive technologies in sperm liquefaction, semen cryopreservation and spermatogonia stem cell transplantation of rhesus macaques. Besides, we sort out recent proteomic analyses of male reproductive systems and semen samples in rhesus macaques. This review mainly focuses on male reproductive biology and application studies using M. mulatta, which would promote the development of new therapeutic interventions on assisted reproduction and reproductive disease studies in the future.

Archiving genetically altered animals: a review of cryopreservation and recovery methods for genome edited animals

With the ever-expanding numbers of genetically altered (GA) animals created in this new age of CRISPR/Cas, tools for helping the management of this vast and valuable resource are essential. Cryopreservation of embryos and germplasm of GA animals has been a widely used tool for many years now, allowing for the archiving, distribution and colony management of stock. However, each year brings an array of advances, improving survival rates of embryos, success rates of in-vitro fertilisation and the ability to better share lines and refine the methods to preserve them. This article will focus on the mouse field, referencing the latest developments and assessing their efficacy and ease of implementation, with a brief note on other common genetically altered species (rat, zebrafish, Xenopus, avian species and non-human Primates).

Sexual selection and sperm diversity in primates

Many aspects of primate sperm physiology and reproductive behavior have been influenced by sexual selection, especially in taxa exposed to sperm competition where females mate with multiple partners. Primate sperm diversity reflects therefore the evolutionary divergences of the different primate species and the impact of a combination of variables exerting selection pressures on sperm form, function, and competition. Thereby, mating systems, life cycle or ecological variables are some of the important factors driving sperm diversity and explaining variation in terms of sperm morphology, parameters or male sexual characters. Here, we address primate sperm diversity through a compilation of all data available in the literature concerning primate sperm parameters and relationships between them. We also review the factors that can influence primate sperm diversity (e.g. mating systems, trade-off between investments in precopulatory and postcopulatory sexual traits, male and female sexual behaviors, seasonality, social constraints, testosterone levels), and discuss also their relevance to our understanding of human reproduction.

Cryopreservation of Mauritian Cynomolgus Macaque (Macaca fascicularis) Sperm in Chemically Defined Medium

The objective of this study was to optimize cryopreservation of sperm from Mauritian cynomolgus macaques (MCM) in defined conditions. Sperm viability and motility were compared between sperm cryopreserved in chemically-defined freezing media with variable osmolarity and the presence of either ethylene glycol or glycerol. The highest percentage viability (after freeze-thaw) was seen in sperm samples that were cryopreserved in medium with an osmolarity of 310 mOsm, while higher osmolarities markedly decreased sperm viability. Ethylene glycol and glycerol at concentrations of 4.6% and 5%, respectively, preserved sperm viability to an equivalent degree. Although higher motility rates and higher straight-line velocities were observed in sperm samples frozen in glycerol compared with ethylene glycol, these differences were not statistically significant. Thawed sperm frozen in defined conditions with glycerol were capable of fertilizing MCM oocytes in vitro, with development to the blastocyst stage. The protocol described here provides an effective method for cryopreservation of sperm to facilitate subsequent in vitro fertilization and genome editing of embryos in MCM species.

Strong Heterogeneity in Advances in Cryopreservation Techniques in the Mammalian Orders

Between 1970 and 2012, vertebrate abundance has declined by 58% with an average annual decline of 2%, calling for serious action to prevent a mass extinction and an irreversible loss of biodiversity. Cryobanks and cryopreservation have the potential to assist and improve ex situ and in situ conservation strategies by storing valuable genetic material. A great deal of studies concerning cryopreservation have been performed within the class Mammalia, although no systematic overview has previously been presented. The objective of this study is therefore to evaluate the status, pattern and future of cryopreservation within Mammalia. A strong disproportional distribution of studies in examined orders is displayed. For the majority of examined orders less than 10% of species has been examined. However, the cryopreservation of germplasm has in several cases been successful and resulted in successful applications of assisted reproductive techniques (ARTs). Various obstacles are associated with the development of cryopreservation protocols, and among them the most prominent is interspecific differences in cryotolerance. Extrapolation of protocols in closely related species is considered the most applicable procedure, and a future supplement to overcome this problem is the examination and comparison of cryobiological traits. Successful protocols have been developed for the vast majority of domesticated mammals, which gives incentive for the further extrapolation of protocols in threatened species.

Cryopreservation of transgenic Huntington's disease rhesus macaque sperm-A Case Report

The cryoprotective effects of glycerol in three different semen freezing extenders, Tris-citrate (TRIS), TEST, and Tes-Tris-Egg yolk (TTE), on wild-type (WT) rhesus monkey (Macaca mulatta) sperm cryopreservation have been tested. Sperm motility and viability were examined to evaluate the integrity of frozen-thawed sperm, and the best extender was selected to cryopreserve sperm from transgenic Huntington's disease (HD) rhesus monkey. The results showed no post-thaw motility difference among the freezing extender tested (P>0.05). However, sperm membrane integrity in TEST and TTE were significantly better than in TRIS extender (P<0.05). TEST was chosen for HD rhesus monkey sperm cryopreservation. The results showed that post-thawed HD sperm motility and viability was not different compared with WT control group (P>0.05). The present study demonstrates that TEST and TTE were excellent extenders and suitable for rhesus monkey sperm cryopreservation and no detectible differences of post-thaw sperm motility and viability between HD and WT rhesus monkeys resulted from TEST extender.

[Effects of some extenders and monoamines on sperm cryopreservation in tree shrews (Tupaia belangeri)]

The tree shrew may be an important experimental animal for disease models in humans. The effects of some extenders and momamines on sperm cryopreservation will provide helpful data for experimentation of strains and conservation of genetic resources in tree shrews. Epididymal sperm were surgically harvested from male tree shrews captured around Kunming, China and sperm motility, acrosome integrity and fertility were assessed during cryopreservation. In Experiment 1 eight extenders (TTE, TCG, TCF, TTG, BWW, BTS, DM, and SR) supplemented with 0.4 mol/L DMSO were used to dilute the sperm: only TTE, DM and SR showed no differences in motility and acrosome integrity compared to fresh controls after equilibration. After freezing and thawing, sperm in any extender showed lower motility than fresh control and sperm in DM showed higher motility than other groups. However, BWW produced the lowest motility. For acrosome integrity, TTE and DM showed higher than BWW, BTS and SR after equilibration. The parameter in DM was higher than other groups (except TTE) after thawing. In Experiment 2 four penetrating cryoprotectant agents (CPA) [dimethyl-formamide (DF), formamide (F), dimethylacetamide (DA), and acetamide (A)] at 0.2 mol/L, 0.4 mol/L, 0.8 mol/L, and 1.2 mol/L, respectively were added to the DM extender. Motility showed no difference among CPA groups and non-CPA group (control) after equilibration, but all thawed sperm showed lower values in motility and acrosome integrity than pre-freezing groups. However, sperm in 0.8 mol/L DF and 0.4 mol/L DMSO showed higher values in both parameters than that in other CPA groups (P>0.05). In Experiment 3 the fertilization rate of oocytes inseminated with 0.4mol/L DMSO (50%) were higher than that with 0.8mol/L DF (16%). In conclusion, non-ion extenders supplemented with egg yolk may be better for sperm cryopreservation in tree shrews and cryoprotectant effects of monoamines agents should be further studied in this species.

[Morphological characteristics and cryodamage of Chinese tree shrew (Tupaia belangeri chinensis) sperm]

The tree shrew (Tupaia belangeri chinensis) is a small non-rodent mammal, which is a relatively new experimental animal in medicine due to its close evolutionary relationship to primates and its rapid propagation. Sperm characteristics and cryopreservation in the tree shrew were the main contents of our spermatological research. Epididymal sperm were surgically harvested from male tree shrews captured from the Kunming area. The rate of testis weight to body weight was (1.05±0.07)%, volume of both testis was (1.12 ± 0.10) mL, total sperm from epididymis and vas deferens were 2.2-8.8×10(7), and sperm motility and acrosome integrity were (68.8 ± 3.9)% and (90.0 ± 2.1)%, respectively. Sperm ultrastructure of the tree shrew was examined by scanning electron microscopy and transmission electron microscopy. Tree shrew sperm had a round or oval shaped head of approximately 6.65×5.82 μm, and midpiece, principal piece, tail, and total sperm lengths were 13.39, 52.35, 65.74, and 73.05 μm, respectively. The mitochondria in the midpiece consisted of approximately 48 gyres and had a 9+9+2 axonemal pattern. After freezing and thawing, sperm showed partly intact acrosomes and plasma membrane defects, and sperm breakages, twists, and swellings were found. The tree shrew had similar ultrastructure with other mammalians except for the mitochondria number and the sperm size. Ultrastructural alteration is still the main cause resulting in poor sperm after cryopreservation.

Optimization of ethylene glycol concentrations, freezing rates and holding times in liquid nitrogen vapor for cryopreservation of rhesus macaque (Macaca mulatta) sperm

Ethylene glycol (EG) has been speculated to be the most appropriate penetrating cryoprotectant for cryopreservation of rhesus macaque sperm due to its higher permeability coefficient. The present study aimed to determine the optimal EG concentration, freezing rate and holding time in liquid nitrogen (LN(2)) vapor for rhesus sperm cryopreservation. Among six tested EG concentrations (0, 0.18, 0.35, 0.7, 1.4 and 2.1 M), 0.7 M EG showed the most effective cryoprotection (P<0.05). Sperm frozen with 0.7 M EG at -183°C/min showed higher post-thaw motility than sperm frozen at -10, -67 or -435°C/min (P<0.05). Sperm frozen in LN(2) vapor at -183°C/min with 0.7 M EG and a holding time of 10 min showed higher post-thaw motility compared with a holding time of 5 or 15 min (P<0.05). The function of sperm cryopreserved at the optimized EG concentration, freezing rate and holding time was further evaluated by in vitro fertilization. Of the 36 oocytes collected from gonadotropin-stimulated rhesus macaques, 61.1% were fertilized, and 61.1, 44.4 and 36.1% of the oocytes developed to 2 cells, morulae and blastocysts, respectively. Our findings provide an alternative penetrating cryoprotectant and optimal protocol for genetic preservation purposes in this important species.

Transgenic rhesus monkeys produced by gene transfer into early-cleavage-stage embryos using a simian immunodeficiency virus-based vector

The development of transgenic technologies in monkeys is important for creating valuable animal models of human physiology so that the etiology of diseases can be studied and potential therapies for their amelioration may be developed. However, the efficiency of producing transgenic primate animals is presently very low, and there are few reports of success. We have developed an improved methodology for the production of transgenic rhesus monkeys, making use of a simian immunodeficiency virus (SIV)-based vector that encodes EGFP and a protocol for infection of early-cleavage-stage embryos. We show that infection does not alter embryo development. Moreover, the timing of infection, either before or during embryonic genome activation, has no observable effect on the level and stability of transgene expression. Of 70 embryos injected with concentrated virus at the one- to two-cell stage or the four- to eight-cell stage and showing fluorescence, 30 were transferred to surrogate mothers. One transgenic fetus was obtained from a fraternal triple pregnancy. Four infant monkeys were produced from four singleton pregnancies, of which two expressed EGFP throughout the whole body. These results demonstrate the usefulness of SIV-based lentiviral vectors for the generation of transgenic monkeys and improve the efficiency of transgenic technology in nonhuman primates.

SINGLE UV EXCITATION OF HOECHST 33342 AND PROPIDIUM IODIDE FOR VIABILITY ASSESSMENT OF RHESUS MONKEY SPERMATOZOA USING FLOW CYTOMETRY

Many fluorescent probes excited by visible light have been used to assess sperm quality by flow cytometry. Developing a viability evaluation method using UV excited stains would be useful for multiparameter analysis of sperm function. This investigation was conducted to determine the efficacy of Hoechst 33342 (H342) and propidium iodide (PI) dual staining for evaluating rhesus monkey sperm viability through use of flow cytometry and excited by a single UV laser. The results showed that the live cells stained only with H342 strongly correlated with expected sperm viability, and flow cytometric analyses were highly correlated with fluorescence microscopic observation. Using H342/PI/SYBR-14 triple staining method, it was found that the live/dead sperm distributions were completely concordant in both H342/PI and SYBR-14/PI assays. In addition, this dual staining was extended with fluorescein isothiocyanate-conjugated peanut agglutinin (FITC-PNA) to simultaneously analyze viability and acrosome integrity of sperm cryopreserved using two different extenders, TTE and TEST, and indicated that TTE offered better preservation of plasma and acrosome integrity than TEST. Therefore, the H342/PI dual staining provides an accurate technique for evaluating viability of rhesus monkey sperm and should be valuable for multiparameter flow cytometric analysis of sperm function.

Rhesus macaque blastocysts resulting from intracytoplasmic sperm injection of vacuum-dried spermatozoa

BACKGROUND

Sperm desiccation is an attractive approach for sperm preservation. In this study, we examined the feasibility and efficiency of intracytoplasmic sperm injection using vacuum-dried rhesus macaque sperm in CZB medium supplemented with 10% fetal bovine serum.

METHODS

A total of 109 MII oocytes were injected with 69 fresh ejaculated sperm and 40 vacuum-dried sperm.

RESULTS

Cleavage occurred in 97% of oocytes injected with fresh, motile sperm and in 88% of oocytes injected with vacuum-dried sperm. Of the cleaved oocytes, 68% fresh sperm-injected oocytes and 74% of dried sperm-injected oocytes developed to the compact morula stage. Blastocyst development was comparable between fresh-injected (16%) and vacuum-dried-injected (17%) oocytes. Differences between treatment groups were not significant. Transmission electron microscopic observation of the blastocysts indicated no detectable differences between fresh sperm and dried sperm-derived embryos.

CONCLUSIONS

We conclude that vacuum-dried rhesus macaque sperm are capable of inducing fertilization and development of pre-implantation embryos when sperm were dried under vacuum and microinjected into normal viable oocytes.

Male-to-male differences in post-thaw motility of rhesus spermatozoa after cryopreservation of replicate ejaculates

BACKGROUND

The efficiency of controlled propagation to produce rhesus monkeys of particular genotypes can be maximized by use of cryopreserved spermatozoa collected from specific males to inseminate appropriate females. But this assumes that semen from males with different genotypes can be cryopreserved with equal effectiveness.

METHODS

To investigate whether spermatozoa from different Macaca mulatta males can be effectively cryopreserved when frozen under identical conditions, we collected and froze semen specimens from 13 adult, fertile males maintained at three primate research centers.

RESULTS

Survival, based on post-thaw motility normalized to the pre-freeze value, was assayed within 30 minutes after thawing; it varied from 50% to 70% but declined thereafter. To examine the response of semen from individual males, we collected and froze three to six ejaculates per male from each of seven males.

CONCLUSIONS

In general, semen from a given male responded reproducibly to freezing, but there were significant differences among males. The cause of these differences among M. mulatta males in post-thaw sperm survival remains unidentified.

Light Microscopical and Ultrastructural Characterization of Black Howler Monkey (Alouatta caraya) Ovarian Follicles

The present study describes the morphological characteristics of black howler monkey (Alouatta caraya) ovarian follicles. One ovary of an adult healthy black howler monkey was collected and processed for light and electron microscopy. Primordial, primary, secondary, tertiary and pre-ovulatory follicles were evaluated for their morphometrical aspects. The ovary of black howler monkey presented a distinct conformation with a uniform distribution of the follicles mostly in the peripheric cortex. This black howler monkey ovary presented a total of 59 921 ovarian follicles. From this amount, 71.1% were classified as primordial, 18.9% as primary, 8.1% as secondary, 1.4% as tertiary and 0.5% as pre-ovulatory follicles. From all these developmental stages, the mean diameters of follicles, oocytes, oocytes nuclei and the mean number of granulosa cells are described. Moreover, primordial, primary and secondary follicles have been observed by electron microscopy.

Comparative studies with six extenders for sperm cryopreservation in the cynomolgus monkey (Macaca fascicularis) and rhesus monkey (Macaca mulatta)

Ejaculated spermatozoa from cynomolgus monkeys and rhesus monkeys were frozen in straws with six different extenders (TTE, DM, mDM, LG-DM, G-DM, and TCG) containing glycerol. Sperm motility and head membrane and acrosomal integrity were evaluated after freezing and thawing, and the cryoprotective effects were compared among the extenders and the two species studied. The results showed that sperm motility and motility recovery with the six extenders were comparable for the cynomolgus and rhesus monkeys. There was no significant difference in sperm motility and head membrane integrity among the six extenders in either the cynomolgus or rhesus monkeys (P>0.05). However, a slightly but statistically lower percentage of acrosomal integrity was found with TCG in both species compared to the other extenders (P<0.05). These findings demonstrate that TTE, DM, mDM, LG-DM, G-DM, and TCG are equally suitable extenders for the cryopreservation of spermatozoa from cynomolgus and rhesus monkeys.

Comparison of protocols for cryopreservation of rhesus monkey spermatozoa by post-thaw motility recovery and hyperactivation

Cryopreservation of spermatozoa is useful for gene banking and for in vitro fertilisation (IVF). This study compared several published cryopreservation techniques to find the most efficient for rhesus macaques. Effectiveness was assessed by sperm longevity (post-thaw motility % and duration) and ability to hyperactivate in response to chemical activators (caffeine, dibutyryl cyclic AMP). Each ejaculate from three males was treated with four published cryopreservation protocols (Seier et al. 1993; Sanchez-Partida et al. 2000; Si et al. 2000; Isachenko et al. 2005). Upon thawing, each sub-sample was incubated either at 37°C in 5% CO2 in air with or without activators or at ~22°C in atmospheric air without activators for 0–24 h. Samples cryopreserved using one method showed zero motility and were not included in the 2 × 2 G-test statistical analysis. The other methods all demonstrated good immediate post-thaw motility rates (68%, 73% and 62% respectively) and underwent capacitation after exposure to activators. Sperm motility in each treatment decreased over time at both temperatures but overall, incubation at 22°C preserved motility better in all three methods. In summary, cryopreservation of rhesus spermatozoa using the method published by Sanchez-Partida et al. or Seier et al. appeared best, potentially supporting gene banking as well as allowing for multiple IVF uses from the same sample.

Low temperature storage of rhesus monkey spermatozoa and fertility evaluation by intracytoplasmic injection

The objective was to develop a sperm freezing procedure suitable for use in the propagation of valuable founder animals by assisted reproductive technologies. Here, we report a comparison of processing methods by measuring the motility of fresh and frozen-thawed rhesus monkey spermatozoa and fertility via intracytoplasmic spermatozoa injection (ICSI) of sibling oocytes. Washed spermatozoa were frozen in straws or in pellets using different cryoprotective media and processed post-thaw with or without a density gradient centrifugation step. Among the four study series, motility post-thaw was improved with density gradient centrifugation (17-24% versus 75%, P<0.01) achieving levels similar to fresh spermatozoa. Spermatozoa injected oocytes (total n=377) were co-cultured on BRL cells and observed for fertilization and development. With spermatozoa frozen in straws in liquid nitrogen vapors, the fertilization rate after ICSI was lower than with fresh spermatozoa (40-44% versus 77-86%, P<0.05), even with the Percoll-enriched fraction that exhibited robust motility. In contrast, somewhat slower freezing of spermatozoa in pellets on dry ice supported fertilization rates (73%) that were similar to the fresh counterpart. Developmental rates of fertilized eggs were similar in all experiments. A total of 106 embryo transfers has resulted in the first primate born after ICSI with F/T ejaculated spermatozoa plus 22 other infants to date. Additionally, a 3-4 h incubation after thawing improved the fertilization rate with spermatozoa from a male with poor post-thaw recovery of sperm motility. In conclusion, an acceptable fertilization rate after ICSI with motile, frozen-thawed primate spermatozoa was observed comparable to that obtained with fresh spermatozoa allowing small quantities of competent spermatozoa to be used with ICSI to facilitate propagation of desirable primate genotypes.

Osmotic tolerance and membrane permeability characteristics of rhesus monkey (Macaca mulatta) spermatozoa

Biophysical characteristics of the plasma membrane, such as osmotic sensitivity and water and cryoprotectant permeability are important determinants of the function of spermatozoa after cryopreservation. A series of experiments was conducted with rhesus macaque spermatozoa at 23 degrees C to determine their: (1) cell volume and osmotically inactive fraction of the cell volume; (2) permeability coefficients for water and the cryoprotectants dimethyl sulfoxide, glycerol, propylene glycol, and ethylene glycol; (3) tolerance to anisosmotic conditions; and (4) motility after a one step addition and removal of the four cryoprotectants. An electronic particle counter and computer aided semen analysis were used to determine the cell volume and permeability coefficients, and motility, respectively. Rhesus spermatozoa isosmotic cell volume was 27.7+/-3.0 microm3 (mean+/-SEM) with an osmotically inactive cell fraction of 51%. Hydraulic conductivity in the presence of dimethyl sulfoxide, glycerol, propylene glycol, and ethylene glycol was 1.09+/-0.30, 0.912+/-0.27, 1.53+/-0.53, and 1.94+/-0.47 microm/min/atm, respectively. Cryoprotectant permeability was 1.39+/-0.31, 2.21+/-0.32, 3.38+/-0.63, and 6.07+/-1.1 (x10(-3)cm/min), respectively. Rhesus sperm tolerated all hyposmotic exposures. However, greater than 70% motility loss was observed after exposure to solutions of 600 mOsm and higher. A one step addition and removal of all four cryoprotectants did not cause significant motility loss. These data suggest that rhesus sperm are tolerant to hyposmotic conditions, and ethylene glycol may be the most appropriate cryoprotectant for rhesus sperm cryopreservation, as it has the highest permeability coefficient of the tested cryoprotectants.

Effect of glycerol and dimethyl sulfoxide on cryopreservation of rhesus monkey (Macaca mulatta) sperm

Glycerol and dimethyl sulfoxide (DMSO) are widely used as penetrating cryoprotectants in the freezing of sperm, and various concentrations are applied in different species and laboratories. The present study aimed to examine the effect of these two cryoprotectants at different concentrations (2%, 5%, 10%, and 15% glycerol or DMSO) on rhesus monkey sperm cryopreservation. The results showed that the highest recovery of post-thaw sperm motility, and plasma membrane and acrosome integrity was achieved when the sperm was frozen with 5% glycerol. Spermatozoa cryopreserved with 15% DMSO showed the lowest post-thaw sperm motility, and spermatozoa cryopreserved with 15% glycerol and 15% DMSO showed the lowest plasma membrane integrity among the eight groups. The results achieved with 5% glycerol were significantly better for all parameters than those obtained with 5% DMSO. The functional cryosurvival of sperm frozen with 5% glycerol was further assessed by in vitro fertilization (IVF). Overall, 85.7% of the oocytes were successfully fertilized, and 51.4% and 5.7% of the resulting zygotes developed into morulae and blastocysts, respectively. The results indicate that the type and concentration of the penetrating cryoprotectant used can greatly affect the survival of rhesus monkey sperm after it is frozen and thawed. The suitable glycerol level for rhesus monkey sperm freezing is 5%, and DMSO is not suitable for rhesus monkey sperm cryopreservation.

Long-acting depot formulation of luprolide acetate as a method of hypothalamic down regulation for controlled ovarian hyperstimulation and oocyte production in Macaca fascicularis

Reproductive function in some nonhuman primate species parallels that of the human. As a result, studies addressing aspects of reproductive function primarily involve the use of nonhuman primate models. The objective of the present study was to assess the efficiency of two hypothalamic down-regulation techniques combined with a single controlled ovarian hyperstimulation protocol for mature oocyte production in the cynomolgus macaque (Macaca fascicularis). Hypothalamic GnRH down regulation was first induced using the clinical long protocol of the short-acting GnRH-agonist luprolide acetate combined with controlled ovarian hyperstimulation and oocyte retrieval. Resulting oocyte yield and maturity with this regimen was insufficient for further evaluation of oocyte competency. Hypothalamic down regulation was induced in the second experiment using the long-acting depot formulation of luprolide acetate in conjunction with controlled ovarian hyperstimulation. This regimen allowed for the consistently efficient production of oocytes (15.5 oocytes per oocyte retrieval) and an oocyte maturity rate of 56%. Oocyte competence, as determined by the ability to undergo fertilization or parthenogenic activation and to reach specific cleavage stages at appropriate time intervals, was evaluated. Intracytoplasmic sperm injection resulted in a 59% fertilization rate and a 91% cleavage rate. Parthenogenic activation resulted in a 70% activation rate and an 86% cleavage rate. These data suggest that use of the long-acting form of luprolide acetate in conjunction with controlled ovarian hyperstimulation results in the production of competent, mature oocytes and allows the efficient use of nonhuman primate resources in studies of reproductive function in cynomolgus macaques.

Effect of age and breeding season on the developmental capacity of oocytes from unstimulated and follicle-stimulating hormone-stimulated rhesus monkeys

Effects of age and season on the developmental capacity of oocytes from unstimulated and FSH-stimulated rhesus monkeys were examined. Immature cumulus-oocyte complexes were matured in vitro in modified CMRL-1066 medium containing 20% bovine calf serum and subjected to in vitro fertilization followed by embryo culture. After fertilization, ova from unstimulated prepubertal monkeys displayed lower development to morula (4%) than those from unstimulated adult females (18% in breeding season and 22% in nonbreeding season). No developmental difference was found between ova from unstimulated adult monkeys in breeding and nonbreeding seasons. However, ova from FSH-primed prepubertal monkeys displayed greater development to blastocyst stage (54%) than those from adult monkeys in the breeding season (16%) and nonbreeding season (0%); and ova from FSH-primed adult females in the breeding season had significantly (P < 0.05) greater developmental competence than those obtained in the nonbreeding season (> or = morula stage, 54% vs. 3%; blastocyst stage, 16% vs. 0%). These data indicate that 1) rhesus monkey oocytes acquire developmental competence in a donor age-dependent manner, and 2) animal age and breeding season modulate the effect of FSH on oocyte developmental competence in the rhesus monkey.