Pretreatment of Addra gazelle (Nanger dama ruficollis) spermatozoa with cholesterol-loaded cyclodextrins improves cryosurvival

Addition of low concentration of cholesterol-loaded cyclodextrin (CLC) has a positive effect on cryopreserved canine spermatozoa evaluated by andrological and biophysical methods

BACKGROUND

This study was conducted to find the best concentration of cholesterol-loaded cyclodextrin (CLC) which has a positive impact on canine post thaw semen quality. Three different concentrations of CLC (0.83 mg/ml; 1.66 mg/ml; 3.32 mg/ml) and 2-hydroxylpropyl-beta-cyclodextrin (HBCD) (1.66 mg/ml) were used in addition to cryopreservation extender and compared with the control after thawing. Samples were assessed using computer-assisted semen analyzer (CASA), flow cytometry, fluorimeter by measuring the fluorescence anisotropy (ANISO) and determining the generalized membrane polarization (GP).

RESULTS

An addition of 0.83 mg/ml CLC significantly increased the percentage of progressive motile (PROG) and rapid spermatozoa (RAP) (P < 0.05). 1.66 mg/ml HBCD decreased progressive motility of spermatozoa and population with rapid movement relative to the control (P < 0.05). Furthermore, the groups with an addition of 1.66 mg/ml and 3.32 mg/ml of CLC, as well as the group with only cyclodextrin, increased percentage of dead spermatozoa without lipid peroxidation and decreased percentage of viable spermatozoa without LPO which was lower in these groups than in the control (P < 0.05). Other sperm parameters assessed on flow cytometer were not significantly different. The addition of CLC at 0.83 mg/ml and 3.32 mg/ml concentrations and 1.66 mg/ml of HBCD caused an increase in ANISO measured at 23 ºC (P < 0.05).

CONCLUSIONS

In conclusion, the results suggest that increasing cholesterol in the plasma membrane of canine spermatozoa can improve their freezability. However, only low concentrations of CLC may improve semen quality after thawing without adversely affecting other parameters.

Does Better Post-Thaw Motility of Dog Sperm Frozen with CLC Mean Better Zona Pellucida Binding Ability?

Even though the search for methods improving cryopreservation of canine spermatozoa led to an improvement of post-thaw quality, fertilizing results after insemination with frozen-thawed semen are still not satisfying. In this study, we focused on modification of spermatozoa membrane fluidity and investigated whether kinematic parameters as assessed by computer-assisted semen analyzer (CASA) can be improved. The primary aim of our study was to investigate whether the use of cholesterol-loaded cyclodextrins (CLC; 0.5 mg, 1 mg, 2 mg) and 2-Hydroxypropyl-ß-cyclodextrin (HBCD; 1 mg) positively influence capacitation status as examined by tyrosinphosphorylation, cholesterol efflux and zona binding assay (ZBA) of spermatozoa. The use of 0.5 mg of CLC increased the percentage of motile, progressive and rapid spermatozoa compared to the control. Addition of HBCD decreased motility and progressive motility of spermatozoa and the population with rapid movement in comparison to the control. The percentage of live spermatozoa without efflux of cholesterol compared to the control was increased when extender with 0.5 mg of CLC was used. There was no change in capacitation status. The zona binding ability of spermatozoa was significantly lower in the group with 0.5 mg of CLC than in the control. In conclusion, these results suggest that improvement of kinematic parameters does not necessarily coincide with better zona pellucida binding ability of spermatozoa.

Bilateral Intratesticular Spermatoceles in a Critically Endangered Dama Gazelle (Nanger dama mhorr)

Dama gazelles (Nanger dama mhorr) are considered critically endangered by the IUCN Red List of Threatened Species since the wild population is comprised of fewer than 200 animals. Several zoos in Europe and some private ranches in the US (Texas) maintain this species in captivity as a hedge against extinction. A routine reproductive exam on an adult male revealed bilateral cysts in the testicular parenchyma. The fluid in the cysts contained copious, moderately progressive motile spermatozoa. Following examination, the gazelle was diagnosed with bilateral intratesticular spermatoceles. Electroejaculation yielded 1.5 ml of semen containing 387 × 10⁶ total sperm with 50% motility and 45% morphologically normal sperm. The spermatoceles did not appear to cause pain or dysfunction, so no treatment was performed at this time. Since fewer than 10 animals are managed in captivity in the US, no intervention (castration/hemicastration) was considered.

Cyclodextrins or cholesterol-loaded-cyclodextrins? A better choice for improved cryosurvival of chicken spermatozoa

This study was designed to test if treating chicken sperm with i) the cyclodextrins 2-hydroxypropyl-β-cyclodextrin (HBCD) and methyl-β-cyclodextrin (MBCD) alone improve fresh, liquid-stored and cryopreserved semen quality, or ii) cholesterol-loaded cyclodextrins (CLCs): 2-hydroxypropyl-β-cyclodextrin loaded with cholesterol (HCLC) and methyl-β-cyclodextrin loaded with cholesterol (MCLC) enhance chicken semen quality for application to assisted reproductive technologies. Three consecutive experiments were performed with different concentrations of additives: Exp. 1: 1, 2, 4 mg of HBCD and MBCD in fresh and liquid stored semen; Exp. 2: 1, 2, 4 mg of HCLC and MCLC in fresh and liquid stored semen; and Exp. 3: 1, 2 mg of HBCD, HCLC, 1 mg MBCD, MCLC in cryopreserved and post-thaw storage semen. Sperm motility parameters were assessed by CASA system and comprehensive sperm characteristics were evaluated by flow cytometry. Supplementation with 4 mg HBCD, MBCD, HCLC and MCLC resulted in the lowest motility and functional parameters of fresh and stored spermatozoa for 24 h at 5 °C. After cryopreservation, spermatozoa stored with CLCs showed significantly lower progressive motility and velocity of movement, and exhibited the lowest percentage of cells with intact plasma membranes and acrosomes, mitochondrial activity and cells without apoptosis. These results indicated that CLCs did not improve chicken sperm viability after cryopreservation. However, spermatozoa treated with 2 mg HBCD showed higher proportion of motile sperm (28%; P < 0.01) together with higher proportion of sperm cells with high mitochondrial potential (25%; P < 0.05) compared to the control (18%; 21%, respectively) after 3 h of post-thaw storage. CLC, especially with methyl-β-cyclodextrin, appeared to be detrimental to chicken spermatozoa, causing apoptosis, impairment of mitochondrial potential, and damaged acrosomes and sperm plasma membranes.