CLC-treated Sperm Research Articles

Cholesterol-loaded cyclodextrin improves motility and survival of cryopreserved zebrafish (Danio rerio) sperm

We studied the impact of modulating cholesterol levels in zebrafish sperm plasma membranes using cholesterol-loaded methyl-β-cyclodextrin (CLC) and unloaded methyl-β-cyclodextrin (MβC). Zebrafish sperm were treated with these substances before cryopreservation, and post-thaw sperm motility and in vitro fertilization (IVF) rates were compared between treated and untreated samples. Our findings indicate that adding cholesterol to sperm membranes increases post-thaw motility, motile cell count, and motile cell survival within a 0.5–4.0 mg per 1.2 × 108 cell concentration range. Conversely, depleting cholesterol using MβC at 1.0 and 2.0 mg per 1.2 × 108 cells reduced these parameters. On average, all CLC-treated sperm samples produced a 15 % higher IVF rate compared to untreated sperm. Including CLC in the extender before cryopreservation is beneficial for post-thaw sperm quantity and quality in zebrafish.

Effect of cholesterol-loaded cyclodextrin treatment on boar sperm cryopreservation.

This study investigated the efficacy of different concentrations of cholesterolloaded cyclodextrin (CLC) on cryopreservation in boar sperm quality. In this study, we treated boar sperm with different concentrations of CLC before freezing and analyzed the sperm cholesterol concentration, plasma membrane, acrosome integrity rate and total motility rate before and after freeze-thawing. We also investigated the levels of reactive oxygen species (ROS), malondialdehyde (MDA), adenosine triphosphate (ATP), and structural- and oxidative-damage related proteins in all groups after thawing. The results revealed that the cholesterol concentration of the CLC-treated groups was higher than that of the control group, both before freezing and after thawing (p<0.05). The plasma membrane integrity rate, acrosome integrity rate, and total motility rate of sperm were also enhanced after thawing in the CLC-treated group (all p<0.05). Moreover, ROS and MDA production and ATP loss were reduced in CLC-treated sperm during freezing and thawing (p<0.05). Finally, CLC pretreatment partially prevented the consumption of various proteins involved in metabolism including capping actin protein of muscle Z-line subunit beta (CAPZB), heat shock protein 90 alpha family class A member 1 (HSP90AA1) and phosphoglycerate mutase 2 (PGAM2) (p<0.05). The CLC treatment increased cholesterol concentration and decreased structural injury and oxidative damage during boar sperm freezing and thawing, improving the efficacy of sperm cryopreservation in boar.

Effect of cholesterol-loaded cyclodextrin treatment of bovine sperm on capacitation timing.

Pre-loading bovine sperm with cholesterol prior to freezing is known to increase cryosurvival, though the timing of capacitation in these sperm has not been evaluated. The objective of this study was to determine if there is a potential delay in capacitation timing in these sperm due to the increased cholesterol content. Flow cytometric evaluation was utilized to assess viability, and stain technology to assess acrosome intactness (Propidium Iodide/FITC-PNA), intracellular calcium levels (Propidium Iodide/FLUO 3-AM) and membrane fluidity (Merocyanine 540/YO-PRO-1). Cholesterol-loaded cyclodextrin (CLC) (2mg/mL) improved post-thaw viability to 61% from 45% in control sperm (p<.05). The addition of ionomycin (0.05 mM) induced capacitation in sperm by 1 h, resulting in increased intracellular calcium and increased acrosome reaction, and consequently viability loss by 3 h. Treatment with CLC significantly decreased membrane fluidity in sperm (p<.05). In conclusion, CLC-treated sperm required 1 h more to capacitate when compared with non-treated sperm based on percentage of live cells with high membrane disorder (p<.05). Increased cryosurvival and viability over time was observed, but longer time to capacitate may hinder fertilization capacity and/or require adjustments to timing of in vitro fertilization.

Cholesterol-loaded cyclodextrin attenuates dilution effect and improves quality of bovine low sperm insemination doses during cryopreservation.

In the present study, the effect of cholesterol-loaded cyclodextrin (CLC) on the quality of low sperm doses at post-thaw was evaluated. Twenty four ejaculates (6 from each bull) were collected and split into eight aliquots. First four aliquots were diluted up to 20-, 15-, 10- and 5-million sperm/0.25ml, and remaining four were treated with CLC at the rate of 1mg/120 million spermatozoa, followed by dilution up to 20-, 15-, 10- and 5-million sperm/0.25ml. The diluted semen was equilibrated, cryopreserved and evaluated post-thaw. The averages of total motility, progressive motility, average path velocity, straight linear velocity, membrane intact spermatozoa and noncapacitated spermatozoa were higher (p<.05) in CLC-treated sperm doses compared to control ones. However, the moribund spermatozoa, capacitated spermatozoa and acrosome-reacted spermatozoa were reduced (p<.05) in CLC-treated spermatozoa compared to control. The curvilinear velocity and linearity did not differ (p>.05) between control and CLC-treated sperm doses. In conclusion, treatment of spermatozoa with CLC at the rate of 1mg/120 million spermatozoon attenuates the dilution effect and improves the quality of bovine low sperm insemination doses during cryopreservation; hence it could be a favourable cryoprotectant for preserving bovine semen at higher dilutions.

Evaluation of cholesterol- treated dromedary camel sperm function by heterologous IVF and AI

Cholesterol (cholesterol-loaded cyclodextrins: CLC) treatment of dromedary camel sperm prior to freezing enhances cryosurvival. The present study first validated the efficacy of a heterologous zona-free goat oocyte assay (n=115 oocytes) to evaluate camel sperm function in vitro (Experiment 1: n=6 bulls), then examined the effects of CLC treatment (1.5mg/mL CLC; CLC+) versus no treatment (0 CLC) of fresh (Experiment 2: n=4 bulls) and frozen-thawed (Experiment 3: n=5 bulls) camel sperm to penetrate, de-condense and form pro-nuclei in in vitro-matured goat oocytes. Finally, the ability of fresh 0 CLC and CLC+ sperm to fertilize in vivo was studied by artificially inseminating super-ovulated females (n=7–9 per treatment) and examining embryo production (Experiment 4: n=4–5 bulls/treatment). Camel spermatozoa penetrated (60%) and formed pro-nuclei (33%) in goat oocytes demonstrating the utility of this heterologous system for assessing sperm function in vitro. For fresh spermatozoa, 0 CLC-treated sperm performed better than their CLC+ counterparts for all parameters measured (P<0.05). In contrast, cryopreservation resulted in a sharp decline in sperm-oocyte interaction in 0 CLC aliquots but remained unaltered in CLC+ aliquots demonstrating a protective effect of cholesterol treatment. There was no difference between treatments in the in vitro fertilizing ability of frozen-thawed sperm or in the numbers of embryos retrieved following AI with fresh 0 CLC or CLC+ sperm. We conclude that although CLC treatment of dromedary camel sperm improves sperm motility it fails to confer an advantage to them in terms of improved in vitro sperm-oocyte interaction or in vivo fertilization under the conditions tested.

Effect of cholesterol-loaded-cyclodextrin on sperm viability and acrosome reaction in boar semen cryopreservation

This study was undertaken to examine the effect of cholesterol-loaded-cyclodextrin (CLC) on boar sperm viability and spermatozoa cryosurvival during boar semen cryopreservation, and methyl-β-cyclodextrin (MBCD) was treated for comparing with CLC. Boar semen treated with CLC and MBCD before freezing process to monitor the effect on survival and capacitation status by flow cytometry with appropriate fluorescent probes. Sperm viability was higher in 1.5mg CLC-treated sperm (76.9±1.01%, P<0.05) than un-treated and MBCD-treated sperm before cryopreservation (58.7±1.31% and 60.3±0.31%, respectively). For CTC patterns, F-pattern was higher in CLC treated sperm than MBCD-treated sperm, for B-pattern was higher in CLC-treated sperm than fresh sperm (P<0.05). For AR pattern (an acrosome-reacted sperm) was lower in CLC-treated sperm than MBCD-treated sperm (P<0.05). Moreover, we examined in vitro development of porcine oocytes after in vitro fertilization using CLC-treated frozen–thawed semen, in which CLC treatment prior to freezing and thawing increased the development of oocytes to blastocyst stage in vitro. In conclusion, CLC could protect the viability of spermatozoa from cryodamage prior to cryopreservation in boar semen.

Egg Yolk and Glycerol Requirements for Freezing Boar Spermatozoa Treated with Methyl β-Cyclodextrin or Cholesterol-loaded Cyclodextrin

Egg yolk (EY) and glycerol are common constituents of extenders used for sperm cryopreservation. It has been demonstrated that using cholesterol-loaded cyclodextrins (CLC) improves sperm cryosurvival in several species. However, standard freezing extenders might not be the most appropriate for CLC-treated sperm. This study evaluated the EY and glycerol requirements for freezing CLC-treated boar spermatozoa. Semen samples from 34 ejaculates coming from 4 boars were used. Each ejaculate was split into three aliquots: one was used untreated (control), and the other two were treated with 1 mg of CLC or methyl-β-cyclodextrin/120 × 106 sperm for 15 min at 22 C prior to cryopreservation. Our results indicated that reducing the concentration of EY was detrimental for sperm viability after thawing (31.57 ± 2 vs. 19.89% ± 2 for 20 and 10% EY, respectively; P <0.05), even in semen treated with CLC. On the other hand, it was observed that the traditional concentration of glycerol (3%) was not the appropriate for freezing CLC-treated sperm (61.10 ± 3 vs. 47.87% ± 3 viable sperm for control and CLC-treated sperm, respectively; P <0.05). Thus, CLC-treated sperm showed a higher tolerance to high glycerol concentrations (5%) in terms of sperm viability (59.19% ± 3) than non-treated sperm (45.58% ± 3; P<0.05). Therefore, it could be necessary to modify the freezing extenders for CLC-treated sperm. Nevertheless, additional studies will be needed to evaluate alternative cryoprotectants and to determine the effect of high glycerol concentrations on sperm functionality.

Effect of cholesterol-loaded cyclodextrins on bull and goat sperm processed with fast or slow cryopreservation protocols

Cholesterol-loaded cyclodextrins (CLC) added to the sperm before cryopreservation enhance sperm quality after freeze-thawing in several cold shock-sensitive species, including cattle and goats. However, all studies conducted to date have used conventional protocols, in which sperm are cooled slowly to 5°C before freezing. As cholesterol plays a significant role in sperm cold shock resistance, it is possible that CLC-treated sperm can withstand cooling damage when the sperm are not cooled slowly to 5°C before freezing. In this study, we determined whether CLC-treated goat (1 mg CLC/120×106 sperm) and bull (2 mg CLC/120×106 sperm) sperm quality, after thawing, was different for sperm frozen using conventional protocols (including a slow cooling phase to 5ºC) and protocols in which the sperm were frozen from room temperature, without cooling the sperm slowly to 5°C before freezing. CLC-treated sperm exhibited higher percentages of plasma membrane-intact sperm than control sperm when cryopreserved using conventional protocols. In addition, CLC treatment enhanced both sperm motility and plasma membrane integrity when sperm were frozen directly from room temperature. However, this treatment did not fully prevent the damage of the sperm after cooling rapidly and subsequent freezing, as the sperm quality was lower than that presented by the samples frozen using the conventional protocol. The results are promising, but studies to optimize the protocols for freezing sperm directly from room temperature need to be conducted, as well as studies to determine how cryopreserving sperm in this manner affects other sperm functions.

In vivo fertilising ability of frozen-thawed boar sperm treated with cholesterol-loaded cyclodextrins prior to cryopreservation

The use of frozen-thawed (FT) sperm for the artificial insemination of pigs is rare. Treating boar sperm with cholesterol-loaded cyclodextrins (CLC) prior to cryopreservation enhances the penetration of immature oocytes in vitro, and this phenomenon has been positively correlated with in vivo fertilisation ability in pigs. The objective of this study was to compare the in vivo fertilising ability of boar sperm treated with 0 (control) or 1mg CLC/120×106 sperm (CLC) prior to freezing. The fertilising ability of the FT sperm was compared in hormonally treated (equine/human chorionic gonadotropin hormones; eCG/hCG) weaned sows inseminated once (cervical insemination) at the following fixed-times after hCG administration: 37h (experiment 1) or 30h (experiment 2). In experiment 1, both treatments exhibited similar fertility rates of 67.7 and 55.9% for the control and CLC, respectively (P>0.05); however, the CLC group had a smaller litter size (11.3±0.9) than the control group (13.6±0.8) (P<0.05). In experiment 2, the pregnancy and farrowing rates were 65.2 and 66.7% for the control and CLC groups, respectively, and the litter size was 12.9±1 and 11.3±1 for the control and CLC groups, respectively, which were similar (P>0.05) for both treatments. These results indicate that the timing of insemination developed for the FT control sperm may not be suitable for CLC-treated sperm and that CLC-treated sperm may benefit from a shorter time interval between the hCG treatment and insemination. Moreover, acceptable results can be obtained with FT boar sperm with a single artificial insemination performed 30h after hCG treatment, which is the time interval recommended for fresh sperm.

The Effect of Cholesterol Addition, Buffer, and pH on Equine Sperm Stored at 5°C

Cooled stallion semen has a short viable life, which ranges with acceptable motility and viability from 24 up to 48 hours. The purpose of this study was to compare the effects of storage pH, the ability of three different zwitterionic buffers, and cholesterol-loaded cyclodextrins (CLC) to preserve the motility and integrity of stallion sperm cooled to 5°C for 48 hours. Fourteen ejaculates were collected and split to receive CLC or not (control group). After incubation, each sample was split into six subsamples and diluted in KMT extender containing 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES), or 2-(N-morpholino)ethanesulfonic acid (MES) buffers, and the final pH was adjusted to either 7.0 or 6.6, totalizing 12 experimental groups as a function of CLC, buffer, and pH variables (2 × 3 × 2 factorial). The motility parameters and integrity of plasma and acrosome membranes (live cell index) were determined using computer-automated semen analysis and epifluorescence microscopy at 3, 6, 24, and 48 hours of cooling period. According to results, pH was not a significant source of variation for motility and live sperm over different cooling periods. However, samples diluted in BES exhibited higher progressive motility within 3 hours and higher percentages of total motile cells after 48 hours of incubation at 5°C (P < .05). After 24 hours of storage, CLC-treated sperm samples presented higher motility than control group (P < .05), and after 48 hours of incubation, CLC-treated sperm exhibited higher percentages of live, motile, and progressively motile sperms (P < .05). We inferred that equine semen diluted in KMT containing BES as buffer and CLC treatment improve the equine sperm survival during storage at 5°C for 48 hours.

Treating boar sperm with cholesterol-loaded cyclodextrins widens the sperm osmotic tolerance limits and enhances the in vitro sperm fertilising ability

Treating sperm with cholesterol-loaded cyclodextrins (CLC) improves the cryosurvival of the sperm of different cold-shock sensitive species. However, the response of boar sperm to this treatment is not fully understood. The aim of this study was to determine how CLC and methyl-β-cyclodextrin (MβCD, not loaded with cholesterol) affect the parameters for boar sperm functionality, including sperm osmotic resistance, and the ability of the sperm to capacitate and to penetrate the sow's immature oocytes in vitro. Samples treated with CLC or MβCD prior to freezing exhibited similar percentages of motile sperm, live sperm and sperm with intact acrosomes as the control samples ( P > 0.05). In addition, these treatments did not alter the response of the boar sperm to capacitating conditions. However, when compared to the controls and the MβCD-treated samples, the CLC-treated sperm maintained greater percentages of motile sperm and live sperm in a wide range of osmotic solutions including hypo- (50, 75 and 150 mOsm/kg) and hyper-osmotic (600, 800 mOsm/kg) conditions ( P < 0.05). In addition, the CLC-treated sperm exhibited greater oocyte penetration ability than the control and the MβCD-treated sperm ( P < 0.0001). In conclusion, the pre-freezing treatment of boar sperm with CLC does not alter the ability of the sperm to respond to capacitating conditions. Despite not increasing the cryosurvival of the sperm, this treatment widens the sperm osmotic tolerance limits and enhances the in vitro sperm fertilising ability.

Use of Cholesterol in Sperm Cryopreservation: Present Moment and Perspectives to Future

Sperm cryosurvival rates are not optimal for most species. Therefore, new cryopreservation strategies are needed with the objective of increasing the number of surviving sperm and the quality of those sperm after thawing. Cholesterol plays important roles in many sperm functions, including effects on membrane properties. One of these effects is to stabilize membranes at low temperatures. Thus, species that produce sperm which possess high membrane cholesterol : phospholipid ratios are more resistant to cold shock than sperm with low cholesterol : phospholipid ratios. Therefore, increasing the cholesterol content of sperm membranes may be a strategy that can improve sperm quality after freeze-thawing. In this review, information is presented related to using cyclodextrins pre-loaded with cholesterol for cryopreserving sperm from different species. The topics discussed include both in vitro and in vivo assessments of sperm quality after cryopreservation, as well as how increasing sperm cholesterol content affects other sperm functions.

Cholesterol-loaded-cyclodextrins and fertility potential of stallions spermatozoa

Irreversible damage occurs to spermatozoal membranes, during the phase transition, when spermatozoa are cooled from room temperature to 5 °C. Some of this damage can be ameliorated by adding cholesterol to the membrane, thereby altering membrane lipid composition. Adding cholesterol-loaded cyclodextrins (CLCs) to stallion spermatozoa prior to freezing, increases cell cryosurvival. However, the fertilizing potential of CLC-treated stallion spermatozoa is unknown. To address this, experiments were conducted which evaluated the ability of CLC-treated stallion spermatozoa to capacitate, acrosome react, and bind to the zona pellucida in vitro, and to fertilize oocytes in vivo. When CLC-treated cryopreserved stallion spermatozoa were treated with various agents to induce capacitation and the acrosome reaction (AR), dilauroylphosphatidylcholine (PC-12) and lysophosphatidylcholine (LPC) induced the AR in control cells (62% and 55%, respectively) but not in CLC-treated cells (17% and 14%, respectively, P < 0.05). However, the calcium ionophore A23187 induced the AR in both control- and CLC-treated cells equally well (39%, P > 0.05). Control- and CLC-treated stallion spermatozoa bound to ZP of cattle oocytes equally well (0.44 ± 0.16 vs. 0.25 ± 0.09, respectively; P > 0.05). In addition, the fertility rates of mares inseminated with control- and CLC-treated sperm were similar ( P > 0.05).

Treating ram sperm with cholesterol-loaded cyclodextrins improves cryosurvival

Acceptable fertility using cryopreserved ram sperm is currently only achieved using laparoscopic intrauterine insemination. Improving the cryosurvival of ram sperm may permit greater fertility rates using more practical techniques. This study was conducted to determine if treating ram sperm with six different cyclodextrins pre-loaded with cholesterol (CLC), prior to cryopreservation increases sperm cryosurvival and if this technology can be used with neat semen. Subsequent experiments evaluated how adding CLC to sperm affected sperm cholesterol content, sperm osmotic tolerance limits, sperm post-thaw survival after incubation and the capacity of sperm to bind to zona pellucidae of cattle and sheep oocytes. Sperm treated with 2-hydroxypropyl-β-cyclodextrin prior to cryopreservation exhibited greater percentages of motile sperm (62%) compared to the control (no CLC treatment) samples (43%, P < 0.05), after thawing. In addition, samples treated with methyl-β-cyclodextrin exhibited percentages of motile and viable sperm similar to samples treated with 2-hydroxypropyl-β-cyclodextrin. Other CLC-treated samples were similar to the control. The CLC concentration that optimized sperm cryosurvival was 2 mg CLC/120 × 10 6 sperm for both methyl-β- and 2-hydroxypropyl-β-cyclodextrin when added to neat semen prior to cryopreservation. Addition of 2 mg CLC not only maintained greater percentages of motile sperm compared to the control samples, but maintained greater percentages of motile sperm during a 3 h incubation after thawing. In addition, 2-hydroxypropyl-β-cyclodextrin pre-loaded with cholesterol maintained greater percentages of viable sperm (33%), than control sperm (18%; P < 0.05). Treating ram sperm with CLC increased the sperm cholesterol content > 1.9-fold and although some cholesterol was lost from the sperm during cooling and cryopreservation, the cholesterol content remained greater in CLC-treated sperm after cooling and after thawing than in control sperm ( P < 0.05). In addition, CLC-treated sperm maintained greater percentages of motile sperm through a wide range of osmotic solutions (150 and 425 mOsm) while control sperm lost motility in solutions outside a more narrow range (270 to 370 mOsm). Greater numbers of CLC-treated sperm bound to zona pellucida than control sperm ( P < 0.05), although number of sperm binding cattle and sheep oocytes, was similar ( P > 0.05). In conclusion, treating ram sperm with CLC increases sperm cryosurvival rates and sperm longevity after thawing. It also increases the cholesterol content, osmotic tolerance, and zona-binding capabilities of sperm. Finally, CLCs can be added to neat semen, making this technology feasible for practical application using current cryopreservation techniques for ram semen.

80 CHOLESTEROL-LOADED METHYL-BETA-CYCLODEXTRIN IMPROVES BOAR SPERMATOZOA CRYOPROTECTANT ADDITION AND REMOVAL TOLERANCE

Difficulties associated with the cryopreservation of boar sperm include their sensitivities to osmotic stresses and chilling sensitivity. We investigated the effects of cholesterol-loaded cyclodextrin (CLC) on boar sperm motility and membrane integrity following exposure to various osmolalities. Samples were collected using the gloved hand method from crossbred boars, and ejaculates having greater than 75% motility were extended 1:3 with Androhep (Minitube Inc., Verona, WI) for this study. Samples were centrifuged at 700g for 5 min, and the resulting pellets were resuspended to 1.2 × 108 cells mL–1 in Androhep. Samples were then treated with 0, 1.5, or 3.0 mg of CLC/1.2 × 108 cells mL–1 for 10 min at room temperature. In experiment 1, samples were aliquoted into 1.5-mL centrifuge tubes, centrifuged at 700g for 5 min and the sperm exposed to Dulbecco’s PBS at different osmolalities for 5 min before being returned to 300 mOsm by adding Dulbecco’s PBS solutions at differing osmolalities. After returning the sperm to isosmotic conditions, sperm motility was analyzed. In experiment 2, samples were treated as in experiment 1 and following exposure to the various osmolalities, sperm were stained with Alexa 488-PNA and propidium iodide to determine sperm membrane integrity. Ten thousand sperm per treatment were analyzed by flow cytometry. Data were analyzed by standard ANOVA. The CLC-treated sperm (normalized means ± SEM; 33 ± 16, 80 ± 8, 86 ± 5, 100, 64 ± 4, 7 ± 3, 0 ± 0, respectively) exhibited greater percentages of motile cells following hypo-isosmotic exposure than control sperm (4 ± 1.6, 33 ± 9.6, 84 ± 7.1, 100, 37 ± 5.5, 3 ± 1.6, 0 ± 0, respectively), and there was a tendency for CLC-treated sperm (P = 0.0225) to maintain motility following hyper-isosmotic exposure. In addition, CLC-treated sperm (87 ± 4, 93 ± 1, 95 ± 1, 93 ± 2, 88 ± 4, 83 ± 3, 41 ± 9, respectively; P &lt; 0.05) maintained greater percentages of membrane integrity following treatment with anisosmotic solutions compared with controls (29 ± 8, 63 ± 10, 81 ± 7, 92 ± 3, 73 ± 8, 44 ± 5, 21 ± 9, respectively). Using a combination of these osmotic tolerance data with previously published boar sperm membrane permeability characteristics, we mathematically modeled the number of steps needed for the addition or removal of cryoprotectants. Computer simulations indicate that an abrupt addition of 1 m glycerol will cause boar sperm to exceed their osmotic tolerance limits unless they are treated with 3 mg of CLC. Moreover, the addition of 1 m EG causes boar sperm to exceed all osmotic tolerance limits and therefore, the addition and removal of EG requires multiple-step protocols. However, the addition and removal of 1 m DMSO maintains volume excursions well within the osmotic tolerance limits with the addition of cholesterol (1.5 and 3 mg). Empirical data for addition of CPA have shown similar results as seen with the computer simulation. These data support the hypothesis that adding cholesterol to porcine sperm broadens their osmotic tolerance limits and potentially provide a mechanism to increase post-thaw survival of porcine sperm.

Effect of adding cholesterol to bull sperm membranes on sperm capacitation, the acrosome reaction, and fertility.

When cholesterol is added to sperm membranes before cryopreservation, higher percentages of motile and viable cells are recovered after thawing. However, because one of the first steps in sperm capacitation is cholesterol efflux from the sperm plasma membrane, adding cholesterol to enhance cryosurvival may retard sperm capacitation. These studies evaluated the ability of sperm treated with cholesterol-loaded cyclodextrins (CLC) to capacitate, acrosome react, and fertilize oocytes. Control (non-CLC-treated) and CLC-treated sperm were treated with heparin, dilauroylphosphatidylcholine (PC12), or calcium ionophore A23187 (A23187) to capacitate and induce the acrosome reaction. Sperm capacitation, assessed by an increase in intracellular calcium level, and acrosome-reacted sperm were measured using flow cytometry. Fresh CLC-treated sperm cells underwent capacitation and/or the acrosome reaction at rates different from control samples, and the differences detected were dependent on the method used to induce sperm capacitation and the acrosome reaction. After cryopreservation, however, CLC-treated and control sperm underwent capacitation and the acrosome reaction at similar rates regardless of the method used to induce capacitation and the acrosome reaction. The primary concern for CLC-treated sperm, however, is whether this treatment would affect in vitro or in vivo fertility. Adding either control or CLC-treated cryopreserved sperm to bovine oocytes in vitro resulted in similar oocyte cleavage rates and blastocyst formation rates. In addition, when inseminated into heifers, pregnancy rates for control and CLC-treated sperm were also similar. Therefore, treating bull sperm with CLC permits greater numbers of sperm to survive cryopreservation while preserving the fertilizing potential of each individual sperm.

An indirect immunofluorescence assay to assess sperm cryodamage using anti-bull sperm monoclonal antibodies

This study was undertaken to examine the effect of cholesterol-loaded-cyclodextrin (CLC) on boar sperm viability and spermatozoa cryosurvival during boar semen cryopreservation, and methyl-β-cyclodextrin (MBCD) was treated for comparing with CLC. Boar semen treated with CLC and MBCD before freezing process to monitor the effect on survival and capacitation status by flow cytometry with appropriate fluorescent probes. Sperm viability was higher in 1.5 mg CLC-treated sperm (76.9 ± 1.01%, P < 0.05) than un-treated and MBCD-treated sperm before cryopreservation (58.7 ± 1.31% and 60.3 ± 0.31%, respectively). For CTC patterns, F-pattern was higher in CLC treated sperm than MBCD-treated sperm, for B-pattern was higher in CLC-treated sperm than fresh sperm (P < 0.05). For AR pattern (an acrosome-reacted sperm) was lower in CLC-treated sperm than MBCD-treated sperm (P < 0.05). Moreover, we examined in vitro development of porcine oocytes after in vitro fertilization using CLC-treated frozen–thawed semen, in which CLC treatment prior to freezing and thawing increased the development of oocytes to blastocyst stage in vitro. In conclusion, CLC could protect the viability of spermatozoa from cryodamage prior to cryopreservation in boar semen.