Successful Cryopreservation of Domestic Cat (Felis catus) Epididymal Sperm after Slow Equilibration to 15 or 10°C

Effect of the addition of antifreeze protein type I on the quality of post-thawed domestic cat epididymal sperm

Cryopreservation of domestic cat semen is mainly performed as a model for the establishment of endangered wild feline protocols. The supplementation of antifreeze protein type I (AFP I) to cryopreservation medium has shown improvement in frozen-thawed sperm quality in other species, but its effect on cat semen has not yet been tested. This study aimed to assess the addition of AFP I to cryopreservation medium in domestic cats. Sperm was obtained from the cauda epididymis of orchiectomized cats; sperm was then pooled in Tris buffer and allocated into three treatments, according to AFP I final concentration: 0 (control), 0.1, and 0.5 µg/ml. Nine replicates were cryopreserved in a two-step protocol and subsequently thawed at 37°C for 30 s. There was no difference (P > 0.05) among the control, 0.1 and 0.5 µg/ml groups for parameters such as motility, vitality, functional membrane integrity, mature chromatin, normal morphology, and sperm binding to egg perivitelline membrane. In the 0.5 μg/ml group only, percentages of live sperm with intact acrosome and of sperm with most inactive mitochondria (DAB III) showed a significant reduction, along with a tendency (P = 0.053) to an increase in the percentage of sperm with most active mitochondria (DAB II). In conclusion, the supplementation of 0.1 and 0.5 µg/ml of AFP I did not promote consistent beneficial effects on the overall sperm cryotolerance in domestic cats.

Current State of In Vitro Embryo Production in African Lion (Panthera leo)

In the last 30–40 years, in vitro maturation (IVM) and fertilization (IVF) of domestic cat oocytes have been established as part of the panel of assisted reproduction technologies. As a representative of wild felids, the African lion is not yet considered endangered. Nevertheless, the zoo population management of the African lion itself as well as other closely related felids would benefit from the establishment of an IVF system. Here, we aimed to investigate the transferability of domestic cat IVF technology to the African lion. From the ovaries of 42 lionesses aged between 0.75 and 15 years, a total of 933 IVF-suitable oocytes were retrieved and subjected to IVM and IVF. The overall maturation rate was 40.6% and 18.9% of these oocytes cleaved after fertilization, respectively. Embryos were generated by intracytoplasmic sperm cell injection as well as co-culture with epididymal sperm. Improvements in the model system also led to an improved outcome with in vitro produced embryos in the lion. Compared to domestic cats, the transportation of gonads to a specialized laboratory was time-consuming and influenced oocyte quality negatively. In conclusion, the domestic cat IVF system is adoptable for the African lion, although success rates are still lower.

IGF-I Medium Supplementation Improves Singly Cultured Cat Oocyte Maturation and Embryo Development In Vitro

Embryo production is a routine procedure in several species. However, in felids, the effectiveness of this approach is far behind that in the majority of laboratory species. The development of a suitable environment starts with the proper composition of culture media. Therefore, for the improvement of assisted reproduction techniques and their outcome in cats, this is an urgent task. As the addition of insulin-like growth factors (IGF-I, IGF-II) or granulocyte-macrophage colony-stimulating factor (GM-CSF) was beneficial in other mammalian species, this study aims to check whether these components, combined with other factors (such as type of fertilisation or type of culture) can provide a benefit in the felid culture system in current use. Thus, these supplements, in different concentrations and combinations, were merged with the use of two fertilisation techniques and randomly assigned to single or group culturing. The results showed that the addition of IGF-I and/or GM-CSF produced an increase in morula and blastocyst rate in a single culture system. In particular, the supplementation with 20 ng/mL of IGF-I incremented the maturation rate by 10% and significantly increased the morula and blastocyst rates in single culturing. This result is especially remarkable for wild felids, where only a few oocytes and/or embryos are available.

Maturation and fertilization of African lion (Panthera leo) oocytes after vitrification

The African lion is an excellent model species for the highly endangered Asiatic lion. African lions reproduce well in zoos, leading to the fact that occasionally ovaries and testis are available for in-vitro experiments. We previously performed in-vitro maturation (IVM) and fertilization of lion oocytes and were able to produce advanced embryos after intracytoplasmic sperm injection (ICSI) with cryopreserved sperm. Here we examined whether our in-vitro method is also applicable after vitrification of immature oocytes. Oocytes of four lionesses (5-7 years old) were obtained after euthanasia and immediately processed on site. Half of the oocytes (n = 60) were subjected to IVM for a total of 32-34 h at 39 °C, 5% CO₂ and humidified air atmosphere. The second group (59 oocytes) was vitrified instantly using the Cryotop method. Following 6 days of storage in liquid nitrogen, oocytes were warmed and subjected to IVM as well. Mature oocytes of both groups were fertilized with frozen-thawed African lion sperm using ICSI. Maturation rate was 55% and 49.2% for the control and vitrified group, respectively. In the control group, three oocytes cleaved and another three were arrested at the pronuclei stage. Due to the low fertilization result, a sperm sample of another male was used for the vitrified group. Of the vitrified oocytes 7 cleaved and 9 more oocytes stopped at pronuclei stage. All embryos of the vitrified group did not develop beyond 4 cell stage. This is the first time that African lion in-vitro-derived embryos have been produced following oocyte vitrification.

Equilibration in freezing extender alters in vitro sperm-oviduct binding in the domestic cat (Felis catus)

For the preservation of endangered felid species, epididymal sperm may be received from valuable individuals after castration or death and they need to be cryopreserved for storage. However, pregnancy rates with epididymal or cryopreserved sperm are lower than with ejaculated and non-frozen semen even if insemination is surgically performed into the oviduct. To investigate whether equilibration, the first step of the cryopreservation procedure, has an impact on sperm-oviduct binding, we generated oviduct epithelial cell vesicles from isthmus segments of preovulatory domestic cats. Binding assays were performed with epididymal sperm in a cell culture medium (M199) without supplements, or after cooling to 15 °C in a freezing extender (TestG), supplemented with glycerol and the water-soluble fraction of hen's egg yolk mainly comprising LDL. The sperm-oviduct binding was assessed both quantitatively and qualitatively (head or tail binding of sperm with active or inactive mitochondria). Most of the bound sperm prepared in M199 had active mitochondria and were attached to the vesicles by their heads. In equilibrated samples, the proportion of bound sperm with active mitochondria and the proportion of head-bound spermatozoa were reduced. The total motility of the sperm after 1 h of incubation in the absence or presence of vesicles were also affected by the preparation (higher in equilibrated) and the incubation (lower in co-incubated), while mitochondrial activity was influenced just by the preparation. Obviously, LDL has a beneficial effect on sperm motility, but we suggest that it interferes with the molecular sperm-oviduct crosstalk and causes a reduced binding of "good" sperm.

Assisted reproduction for felid species conservation-Sperm competences at risk

Cryobanking of gametes in combination with artificial insemination is an essential option to support conservation programmes for endangered and threatened species. About two-thirds of the felid species are classified as 'near threatened', 'vulnerable' or 'endangered' (www.cites.org), and mostly, epididymal sperm are collected from euthanized or castrated male felids and cryopreserved. However, epididymal compared with ejaculated and cryopreserved compared with fresh sperm have a limited potential to fertilize if vaginal non-surgical insemination is applied in feline species. Missing or highly diluted seminal fluid in epididymal and cryopreserved sperm, as well as a potential interference of extender ingredients with the natural interactive properties of sperm in the female genital tract is discussed as potential drawback which hampers a proper sperm transit and fertilization besides the limited longevity of cryopreserved feline sperm. Individual components in seminal fluid as well as cryoextenders may adversely alter sperm properties and have a different impact on fertility and preservation success. The identification and investigation of beneficial as well as detrimental components is a precondition to deduce options for improving the process of cryopreservation in felids, particularly, if only epididymal sperm are available.

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.

Brilliant cresyl blue staining allows the selection for developmentally competent immature feline oocytes

The outcome of in-vitro-maturation and in-vitro-fertilization of feline oocytes depends on the selection of high quality oocytes, and is often restricted to morphological criteria. The aim of this study was to test whether the Brilliant cresyl blue (BCB) staining is suitable for pre-selection of feline oocytes before in-vitro-maturation. Cumulus-oocytes-complexes (COC) were released from domestic cat ovaries obtained after ovariectomy and were subjected to BCB staining. BCB+ stained oocytes were characterized by a violet/pale blue staining of the ooplasma, BCB- oocytes remained unstained. Transmission electron microscopy indicated for a slightly advanced stage of BCB- oocytes within the maturation process. After 24 h in-vitro-maturation, almost 75% of BCB+ and 21.5% of BCB- oocytes were able to reach metaphase II. Also, after in-vitro-fertilization, significantly more oocytes developed to morulae (19.2%) if oocytes were preselected for BCB staining, although 8% of unstained COC still reached advanced embryo stages. Prolonged storage of ovaries before COC retrieval for 16-20 h at 4 °C was accompanied by reduced number of BCB+ oocytes (96 of 210, 45.7%) in comparison to freshly isolated COC (151 of 225, 67.1%), and impaired cleavage rate (19.8%) and morula rate (9.4%) of BCB+ oocytes but the rate of embryos which developed to advanced stages remained unchanged (∼50%). To conclude, BCB staining is a very useful tool to preselect immature COC of feline species ensuring higher developmental rates.