Infertility
Fertility enhanced with Vitamin E- Galactose hybrid polymer
By University of Oxford
Sep 29, 2005, 20:56

The sperm vitality of pigs can be enhanced and fertility rates increased through the use of a new hybrid polymer, according to research led by Dr Ben Davis of the Department of Chemistry. The approach might be used to increase sperm vitality and lifespan in other mammals, for example during human infertility treatment.

During artificial insemination procedures mammalian sperm is particularly vulnerable to damage through exposure to oxygen. The antioxidant vitamin E is a powerful defence against oxidative damage, but is difficult to deliver to cells. In a paper published in the October issue of Nature Chemical Biology the researchers report the design and application of a new hybrid polymer to deliver vitamin E to sperm, boosting its vitality and lifespan.

The approach takes advantage of highly specific carbohydrate-binding proteins present on the surface of mammalian sperm cells which recognize galactose, a simple sugar. In collaboration with colleagues at the University of Durham and JSR Healthbred, Dr Davis designed a polymer that combines vitamin E with galactose. The galactose acts as a targeting agent, helping to deliver the vitamin E to the surface of the sperm cell. When the polymer binds to the surface of the sperm cell, it is transported across the cell membrane, whereupon the vitamin E is released.

Using polymers labelled with fluorescent dye, the researchers were able to visualize the galactose-containing polymers crossing the cell membrane. However, a galactose-free polymer was not internalised, demonstrating that polymer internalisation depends on the galactose interaction with the sperm cell surface.

The sperm cells treated with the new hybrid polymer had enhanced physiological properties and a longer life-span, resulting in enhanced fertilization rates after artificial insemination. Further application of the technique could potentially enhance fertility in other mammals in situations when sperm may have to be stored outside the body for long periods, such as in human infertility treatment or in breeding of rare and endangered species.

Dr Davis said: �Our results indicate that hybrid polymer delivery systems can prolong the functional viability of mammalian sperm and can improve fertility rates. In addition, the further application of this technique could provide a useful means to discover new carbohydrate-protein interactions. Most carbohydrate-binding proteins are characterized in terms of simple sugars but the genuine ligands are more likely to be much more complex cell-surface conjugates. This polymer is just one of several systems that we think could act as good functional mimics of these more complex sugar systems. With these types of biological mimics in hand we can really start to unpick the role of complex carbohydrates in nature.�

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