Cyclodextrin-Loaded Cholesterol Increases the Resistance of Goat Sperm to Cold Shock and Cryopreservation in Skim Milk but Not Egg Yolk Extender.
Bibliographic record
Abstract
The demand for goat produce in North America has spectacularly increased over the past decade, however, the productivity of the herd does not meet industry requirements. Artificial insemination (AI) using semen from genetically-superior males is a well-established strategy for herd improvement and greatly benefited the goat industry in France and the dairy cattle industry worldwide. Cryopreservation, however, decreases the viability and motility of goat sperm while inducing spontaneous capacitation (“cryo-capacitation”) and acrosome reactions (AR). Sperm from species with high membrane cholesterol:phospholipid ratios can resist cooling. To test the hypothesis that enhancing the cholesterol content of goat sperm would improve cold tolerance, fresh semen aliquots were treated with 0, 0.2, 1, 2.5 or 5 mg/mL cholesterol-loaded methyl-beta-cyclodextrin (CLC; corresponding to 0, 9.8, 49, 122.5 and 245 μg/mL cholesterol) in PBS and cold shocked (20 min, −20C). Spontaneous AR increased due to cold shock but were completely prevented by >1 mg/mL CLC (P < 0.05; n = 3), suggesting that CLC increases membrane cholesterol: phospholipid ratio to moderate phase transitions associated with cold shock. To confirm that CLC increases sperm cholesterol content, fresh sperm in PBS were treated with or without 150 μg/mL cholesterol alone, 3 mg/mL cyclodextrin alone, or 3 mg/mL CLC (corresponding to 150 μg/mL cholesterol). Lipids were extracted by the Folch method adapted for sperm and cholesterol was assayed using Lieberman-Burchard reagent. CLC increased sperm cholesterol levels 3-fold compared to other treatments (P < 0.05; n = 3), indicating that higher cholesterol is indeed related to the cold-resistance of these CLC-treated sperm. Furthermore, cholesterol incorporation requires cyclodextrin as a carrier-molecule. These results suggest that that enriching sperm cholesterol levels using CLC would improve sperm resistance to cryopreservation. Work on other species, however, demonstrates only modest increases in sperm quality and no improvement in fertility following CLC treatment in traditional egg yolk-based extenders. We hypothesised, therefore, that a skim milk-based extender would more effectively permit the CLC to exchange with and protect sperm. Semen aliquots were treated with 0, 0.5, 1, 2, 3 and 4 mg/mL CLC (corresponding to 0, 24.5, 49, 122.5, 147 and 196 μg/mL cholesterol) and then cryopreserved in egg yolk- or skim milk-based extender (8 treatments/ejaculate; n=8). Without CLC, there was no difference in sperm quality between extenders after thawing. However, the percentages of motile, progressively motile, or uncapacitated sperm (“pattern F” according to the chlortetracycline fluorescence assay) increased with 1, 2 and 3 mg/mL CLC in skim milk extender even during incubation after thawing for 3 h at 38.5°C (P < 0.05), with 3 mg/mL being optimal (P < 0.05). In contrast, CLC treatment did not alter the post-thaw quality of sperm in egg yolk extender. Together, our data indicate that cyclodextrin-mediated delivery of exogenous cholesterol improves the tolerance of goat sperm to cold temperatures and that this transfer is biologically more effective in skim milk-based relative to egg yolk-based extenders. Therefore, it is tempting to speculate that in vivo fertility could be improved for semen cryopreserved with between 1 and 3 mg/mL CLC in skim milk-based extender. Thanks to CRSAD for animal support. Financed by NSERC & MAPAQ.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".