Intracytoplasmic sperm injection

Older mothers have healthier babies if they conceive using IVF

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Babies born to older mothers are more likely to be healthy if they have been conceived through IVF rather than naturally, a major new study has found.

A survey of more than 300,000 live births revealed that women aged 40 or over were more than twice as likely to have a child with birth defects than those of the same age who had undergone a widely used method of assisted reproduction.

Scientists behind the study say the “remarkable” findings may be explained by a hormonal stimulation provided by IVF that helps reverse the decline in ovulation control experienced as women get older.

There is something quite remarkable occurring with women over the age of 40 who use assisted reproductionProf Michael Davies
 IVF in action

The team from the University of Adelaide collated data from every live birth in South Australia between 1986 and 2002, which revealed that the overall proportion of birth defects among naturally conceived babies across all age groups was 5.7 per cent, compared to 9.9 per cent for traditional IVF births.

For babies conceived using Intracytoplasmic sperm injection (ICSI), a variety of IVF used in about 70 per cent of cases worldwide, just under 10 per cent had birth defects.

For women aged 40 or over, however, the relative likelihood of having a healthy baby reversed, with an 8.2 per cent chance of birth defects for those conceived naturally against just a 3.6 per cent chance for those conceived using ICSI.

Professor Michael Davies, who led the research, said: “There is something quite remarkable occurring with women over the age of 40 who use assisted reproduction.

“There is some aspect of IVF treatment in particular that could be helping older women to redress the maternal age issues we see among natural conception, where we observe a transition at around the age of 35 towards a steadily increasing risk of birth defects.

“We don’t know what that is quite yet – it could be an aspect of hormonal stimulation that helps reverse the age-related decline in control of ovulation.”

The study also revealed that the age at which women who are treated with both IVF and ICSI combined are most at risk of giving birth to an unhealthy child is 29, with a 9.4 per cent chance.

Professor Davies said his findings could have significant implications for infertility treatment if researchers can understand why older women do better on assisted reproduction.

However, Yacoub Khalaf, a consultant gynaecologist at Guys and St Thomas’s hospitals in London, pointed out that, despite the size of the overall study, the number of births in the over 40 group were “relatively small”, and said Professor Davies’ inferences could be the result of a statistical anomaly.

Cloning Mice.

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For the First Time, a Donor Mouse Has Been Cloned Using a Drop of Peripheral Blood from Its Tail.

From obesity to substance abuse, from anxiety to cancer, genetically modified mice are used extensively in research as models of human disease. Researchers often spend years developing a strain of mouse with the exact genetic mutations necessary to model a particular human disorder. But what if that mouse, due to the mutations themselves or a simple twist of fate, was infertile?

Currently, two methods exist for perpetuating a valuable strain of mouse. If at least one of the remaining mice is male and possesses healthy germ cells, the best option is intracytoplasmic sperm injection (ICSI), an in vitro fertilization procedure in which a single sperm is injected directly into an egg.

However, if the remaining mice cannot produce healthy germ cells, or if they are female, researchers must turn to cloning. Somatic-cell nuclear transfer (SCNT) produces cloned animals by replacing an oocyte’s nucleus with that of an adult somatic cell. An early version of this process was used to produce Dolly the sheep in 1996.

Since then, SCNT techniques have continued to advance. Earlier this year, researchers at the RIKEN Center for Developmental Biology in Kobe, Japan, even devised a technique to avoid the diminishing returns of recloning the same cell; success rates increased from the standard three percent in first-generation clones to ten percent in first-generation and 14 percent in higher-generation clones.

The type of somatic cell used for this process is critical and depends largely on its efficiency in producing live clones, as well as its ease of access and readiness for experimental use. While cumulus cells, which surround oocytes in the ovarian follicle and after ovulation, are currently the preferred cell type, Drs. Satoshi Kamimura, Atsuo Ogura, and colleagues at the RIKEN BioResource Center in Tsukuba, Japan, questioned whether white blood cells (a.k.a., leukocytes) collected from an easily accessed site, such as a tail, would be effective donor cells. Such cells would allow for repeated sampling with minimal risk to the donor mouse.

There are five different types of white blood cells and, as expected, the researchers found that lymphocytes were the type that performed the most poorly: only 1.7 percent of embryos developed into offspring. The physically largest white blood cells, and thus the easiest to filter from the blood sample, were granulocytes and monocytes. The nuclei of these cells performed better, with 2.1 percent of the embryos surviving to term, compared to 2.7 percent for the preferred cell type, cumulus cells.

The granulocytes’ performance was poorer than expected due to a much higher rate of fragmentation in early embryos (22.6 percent): twofold higher than that of lymphocyte cloning and fivefold higher than cumulus cell cloning. The researchers were unable to determine what could be causing the fragmentation and intend to perform further studies to improve the performance of granulocyte donor cells.

Although the blood cells tested did not surpass the success rate of cumulus cells in this study, the researchers have demonstrated, for the first time, that mice can be cloned using the nuclei of peripheral blood cells. These cells may be used for cloning immediately after collection with minimal risk to the donor, helping to generate genetic copies of mouse strains that cannot be preserved by other assisted reproduction techniques.