Pilar Buendía

FISH screening of aneuploidies in preimplantation embryos to improve IVF outcome.

Preimplantation genetic diagnosis (PGD) has transformed the approach to the infertility patient in the IVF setting. Although the principal applications of PGD have been to prevent the transmission of sex-linked diseases, in time and with growing knowledge of the chromosomal abnormalities observed in preimplantation embryos, its applications have widened. Nowadays, apart from its implications in the prevention of transmission of chromosomal and genetic abnormalities, PGD is being used with increased frequency to improve the IVF outcome in patients with advanced maternal age (> or =38 years of age), recurrent miscarriage (> or =2 miscarriages), recurrent IVF failure (> or =3 failed IVF attempts) and severe male infertility. A high incidence of chromosomal abnormalities has been observed in these patient groups.

Redefining advanced maternal age as an indication for preimplantation genetic screening.

In this retrospective study, the utility of preimplantation genetic screening (PGS) in patients with advanced maternal age is evaluated. The patient population consisted of women aged 38-44years and included in a regular IVF programme with or without PGS analysis. Transfer rate, ongoing implantation rate and ongoing pregnancy rate were the main outcome parameters measured. A trend of better ongoing pregnancy rate per oocyte retrieval was observed in patients aged 38 and 39years in the non-PGS group when compared with PGS groups, but better ongoing pregnancy rate per oocyte retrieval was observed in patients 41-44years old in the PGS group. When patients with a low ovarian response accumulated oocytes in several stimulation cycles, clinical outcomes were comparable to those of normal-responder patients. These results show that, although PGS does not benefit patients less than 40years of age, reproductive success increases more than two-fold in patients over 40years, especially in patients with more than six metaphase II oocytes, as a result of a good ovarian response or gamete accumulation, suggesting a redefinition of advanced maternal age as indication for PGS. In this retrospective study, the utility of preimplantation genetic screening (PGS) in patients with advanced maternal age is evaluated. Patient population consisted of women aged 38-44 years and included in a regular IVF programme with or without PGS analysis. Transfer rate, ongoing implantation rate and ongoing pregnancy rate were the main outcome parameters measured. A trend of better ongoing pregnancy rate per ovarian stimulation cycle was observed in patients aged 38-39 years in the non-PGS group when compared with PGS groups, but better ongoing implantation rate was observed in patients aged 41-44 years old in the PGS group. When patients with a low ovarian response (low number of oocytes available for the IVF cycle) accumulated oocytes in several stimulation cycles, their reproductive possibilities were comparable to those of normal-responder patients. These results show that, although PGS does not benefit patients less than 40 years of age, reproductive success increases more than 2-fold in patients over 40 years, especially in patients with more than six metaphase II oocytes, as a result of a good ovarian response or gamete accumulation, suggesting a redefinition of advanced maternal age as indication for PGS.

Prognostic factors for preimplantation genetic screening in repeated pregnancy loss

The objective of this study was to identify specific subgroups of recurrent pregnancy loss (RPL) patients of unknown aetiology in whom the selection of chromosomally normal embryos for transfer improves reproductive outcome in preimplantation genetic screening (PGS). A total of 428 PGS cycles were included and chromosomes 13, 15, 16, 18, 21, 22, X and Y were evaluated. In RPL patients < or =37 years, a lower incidence of chromosomal abnormalities (P = 0.0004) and miscarriages (P = 0.0283) was observed, and there were significantly higher pregnancy (P < 0.0384) and implantation (P < 0.0434) rates than in patients >37 years. In the former subset, results showed: (i) significantly higher implantation rates (P = 0.0411) in couples that had experienced a previous aneuploid miscarriage; (ii) similar aneuploidy, pregnancy and implantation rates in couples suffering previous miscarriages during fertility treatments and in those with previous spontaneous pregnancies; (iii) no miscarriages after PGS in couples in whom a fluorescence in-situ hybridization assay showed the male partners sperm to be abnormal; and (iv) lower implantation rates in couples with > or =5 previous miscarriages, associated with a lower percentage of chromosomally abnormal embryos. It is concluded that PGS is to be strongly recommended when RPL is associated with miscarriages during infertility treatments, chromosomopathy in a previous miscarriage, up to five previous miscarriages and a high incidence of chromosomal abnormalities in spermatozoa.

Prosurvival effect of human wild-type α-synuclein on MPTP-induced toxicity to central but not peripheral catecholaminergic neurons isolated from transgenic mice

In the present work we report the generation of a new line of alpha-synuclein (alpha-SYN) transgenic mice in which the human wild-type alpha-SYN cDNA is expressed under the control of a tyrosine hydroxylase (TH) promoter. We provide evidence that the ectopic protein is found in TH expressing neurons of both central and peripheral nervous systems. The transgene is expressed very early in development coinciding with the activity of the TH promoter and in the adult brain the human protein distributes normally to the nerve endings and cell bodies of dopaminergic nigral neurons without any evidence of abnormal aggregation. Our results indicate that expression of human wild-type alpha-SYN does not affect normal development or maintenance of TH immunoreactive nigral neurons, striatal dopamine content, or locomotor activity. Systemic administration of the parkinsonian neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces a loss of TH immunoreactive nigral neurons and terminals and of dopamine levels to the same degree in both transgenic and non-transgenic adult mice. Intoxication also results in a similar loss of cardiac noradrenaline in both genotypes. Surprisingly, cultured transgenic ventral mesencephalic fetal dopaminergic neurons exhibit complete resistance to cell death induced by 1-methyl-4-phenylpyridinium ion (MPP(+)) intoxication, without changes in dopamine transporter (DAT) surface levels. Interestingly, this protection is not observed in other populations of catecholaminergic neurons such as peripheral sympathetic neurons, despite their high sensitivity to MPP(+)in vitro.

Vulnerability of peripheral catecholaminergic neurons to MPTP is not regulated by α-synuclein

Although generally considered a prototypical movement disorder, Parkinsons disease is commonly associated with a broad-spectrum of non-motor symptoms, including autonomic dysfunctions caused by significant alterations in catecholaminergic neurons of the peripheral sympathetic nervous system. Here we present evidence that alpha-synuclein is highly expressed by sympathetic ganglion neurons throughout embryonic and postnatal life and that it is found in tyrosine hydroxylase-positive sympathetic fibers innervating the heart of adult mice. However, mice deficient in alpha-synuclein do not exhibit any apparent alterations in sympathetic development. Sympathetic neurons isolated from mouse embryos and early postnatal mice are sensitive to the parkinsonian drug MPTP/MPP(+) and intoxication requires entry of the neurotoxin through the noradrenaline transporter. Furthermore, recovery of noradrenaline from cardiac sympathetic fibers is reduced in adult mice treated with MPTP systemically. However, MPP(+)-induced sympathetic neuron loss in vitro or MPTP-induced cardiac noradrenaline depletion in vivo is not modified in mice lacking alpha-synuclein. This is in clear contrast with the observation that dopaminergic neurons of the central nervous system are significantly less vulnerable to MPTP/MPP(+) in the absence of alpha-synuclein, suggesting different actions of this molecule in central and peripheral catecholaminergic neurons.