Preimplantation Genetic Diagnosis and Screening (PGD/PGS) for monogenic diseases and/or numerical/structural chromosomal abnormalities is a tool for embryo testing aimed at identifying nonaffected and/or euploid embryos in a cohort produced during an IVF cycle. A critical aspect of this technology is the potential detrimental effect that the biopsy itself can have upon the embryo. Different embryo biopsy strategies have been proposed. Cleavage stage blastomere biopsy still represents the most commonly used method in Europe nowadays, although this approach has been shown to have a negative impact on embryo viability and implantation potential. Polar body biopsy has been proposed as an alternative to embryo biopsy especially for aneuploidy testing. However, to date no sufficiently powered study has clarified the impact of this procedure on embryo reproductive competence. Blastocyst stage biopsy represents nowadays the safest approach not to impact embryo implantation potential. For this reason, as well as for the evidences of a higher consistency of the molecular analysis when performed on trophectoderm cells, blastocyst biopsy implementation is gradually increasing worldwide. The aim of this review is to present the evidences published to date on the impact of the biopsy at different stages of preimplantation development upon human embryos reproductive potential.

In the past, different protocols of ovulation induction, aimed to overcome problems of anovulatory infertility in humans, have been developed during IVF programmes. However, administration of exogenous hormones may cause severe health problems, e.g. ovarian hyperstimulation syndrome. To overcome this problem an attractive alternative is to develop in-vitro systems that allow follicle and oocyte growth and maturation. This paper reviews the current status of research on oocyte-granulosa cell interactions and on the autocrine and paracrine factors involved in follicle development. The ovarian follicle is a morphological and functional unit in which the somatic and germ cell components are intimately associated and interdependent. The co-ordinate development of follicle and oocyte leads to a number of modifications in the growing oocyte necessary for the acquisition of competence to mature correctly and to undergo fertilization and embryo development. The search for the optimal culture conditions and the correct balance of hormones necessary to obtain a fertilizable oocyte in vitro is extremely important for clinical and agricultural applications.

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Transforming growth factor beta (TGF) is a well-known inhibitor of myogenic differentiation as well as an autocrine product of rhabdomyosarcoma cells. We studied the role of the TGF-beta autocrine loop in regulating growth and myogenic differentiation in the human rhabdomyosarcoma cell line, RD. We previously reported that the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) induces growth arrest and myogenic differentiation in these cells, which constitutively express muscle regulatory factors. We show that TPA inhibits the activation of secreted latent TGF-beta, thus decreasing the concentration of active TGF-beta to which the cells are exposed. This event is mediated by the TPA-induced alteration of the uPA/PAI serine-protease system. Complete removal of TGF-beta, mediated by the ectopic expression of a soluble type II TGF-beta receptor dominant negative cDNA, induces growth arrest, but does not trigger differentiation. In contrast, a reduction in the TGF-beta concentration, to a range of 0.14-0.20 x 10(-2) ng/ml (which is similar to that measured in TPA-treated cells), mimics TPA-induced differentiation. Taken together, these data demonstrate that cell growth and suppression of differentiation in rhabdomyosarcoma cells require overproduction of active TGF-beta; furthermore, they show that a 'critical' concentration of TGF-beta is necessary for myogenic differentiation to occur, whereas myogenesis is abolished below and above this concentration. By impairing the TGF-beta autocrine loop, TPA stabilizes the factor concentration within the range compatible for differentiation to occur. In contrast, in human primary muscle cells a much higher concentration of exogenous TGF-beta is required for the differentiation inhibitory effect and TPA inhibits differentiation in these cells probably through a TGF-beta independent mechanism. These data thus clarify the mechanism underlying the multiple roles of TGF-beta in the regulation of both the transformed and differentiated phenotype.