Abstract
Colloid centrifugation can be used to separate heterogeneous populations of cells particularly semen samples, which typically contain mixtures of spermatozoa at different stage of maturity together with dead and dying spermatozoa and also non-sperm cells. Colloids can be used to enrich the population of spermatozoa that are viable and functional; these are the spermatozoa that are needed for fertilization in Assisted Reproduction. Sperm samples obtained after colloid centrifugation may be enriched for motile, morphologically normal spermatozoa with intact chromatin. Insemination of mares with stallion sperm samples prepared by colloid centrifugation resulted in a higher pregnancy rate per cycle than controls, confirming that the good sperm attributes observed in the laboratory were indicative of functional spermatozoa. The method does not simply enrich for viable spermatozoa by inhibiting dead or dying spermatozoa from passing through the colloid since emerging evidence shows that colloid centrifugation can select for spermatozoa with certain properties such as metabolic activity. Other reproductive cells, such as spermatids or progenitor cells, may also be purified by colloid centrifugation. This review describes the history of colloid centrifugation for selecting spermatozoa, compares colloid centrifugation with alternative techniques, and finally describes some of the applications of the technique within the animal breeding industry.
Highlights
Colloid centrifugation is a technique for separating different types of cells from heterogeneous suspensions [1]
Specialist laboratories may use in vitro fertilization (IVF), for cattle, where sperm samples are added to oocytes in the laboratory and incubated to allow the fertilized oocytes to develop; and intracytoplasmic sperm injection (ICSI) e.g. in horses, where an individual spermatozoon is injected into an oocyte
These results suggest that either superoxide is not converted to hydrogen peroxide, as previously, thought or that Single Later Centrifugation (SLC) may allow the passage of a sperm sub-population that metabolise differently to the main population
Summary
Colloid centrifugation is a technique for separating different types of cells from heterogeneous suspensions [1]. In addition to practical applications in ART, colloid centrifugation is a useful research tool in the elucidation of the mechanisms occurring in spermatozoa during maturation, capacitation and the acrosome reaction These events are all necessary before spermatozoa can bind to the zona pellucida prior to fertilization of the oocyte. It may be necessary to use epididymal spermatozoa, either post-castration or after the death of the animal [7] This is relevant for conservation biology, when recovery of epididymal and testicular spermatozoa may represent the last chance to recover genetic material from a particular individual. Such tissue is usually contaminated with blood and cellular debris, both of which have a detrimental effect on sperm survival. Species-specific applications of colloid centrifugation will be discussed, for the equine, porcine and bovine breeding industries, as well as in conservation breeding
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