Complete Human and Rat Ex Vivo Spermatogenesis from Fresh or Frozen Testicular Tissue.

Until now, complete ex vivo spermatogenesis has been reported only in the mouse. In this species, the duration of spermatogenesis is 35 days, whereas it is 54 days in the rat and 74 days in humans. We performed long-term (until 60 days) cultures of fresh or frozen rat or human seminiferous tubule segments in a bioreactor made of a hollow cylinder of chitosan hydrogel. Testicular tissues were obtained from 8- or 20-day-old male rats or from adult human subjects who had undergone hormone treatments leading to a nearly complete regression of their spermatogenesis before bilateral orchiectomy for gender reassignment. The progression of spermatogenesis was assessed by cytological analyses of the cultures; it was related to a dramatic increase in the levels of the mRNAs specifically expressed by round spermatids, Transition protein 1, Transition protein 2, and Protamine 3 in rat cultures. From 2% to 3.8% of cells were found to be haploid cells by fluorescence in situ hybridization analysis of human cultures. In this bioreactor, long-term cultures of seminiferous tubule segments from prepubertal rats or from adult men allowed completion of the spermatogenic process leading to morphologically mature spermatozoa. Further studies will need to address the way of optimizing the yield of every step of spermatogenesis by adjusting the composition of the culture medium, the geometry, and the material properties of the chitosan hydrogel bioreactors. Another essential requirement is to assess the quality of the gametes produced ex vivo by showing their ability to produce normal offspring (rat) or their biochemical normality (human).

[Semen cryopreservation in adolescent with cancer: at which age can it be proposed?]. / Cryopréservation de sperme chez l'adolescent atteint de cancer: à partir de quel âge?

The increased incidence of tumors in children and adolescents (Lacour, 2010), as well as therapeutic advances in recent decades, have led to an increase of fertility disorders in young adult cancer survivors. In pubescent boys, the use of cryopreserved sperm and assisted reproductive technology (ART) is a validated preventive option. Currently, there is no consensus on the age at which the semen cryoconservation has to be proposed. There is a wide disparity of care among centers in France. Based on the observation of Nathan,11 years old, in whom semen cryopreservation was performed at his request, we analyze local practices and discuss the indications for cryopreservation of sperm in young teenagers with cancer treated by potentially sterilizing treatment.

Epigenetic marks at BRCA1 and p53 coding sequences in early human embryogenesis.

In the vertebrate genome, methylation of deoxycytosine residues of CpGs dinucleotide has been associated with transcriptional silencing of genes, parental imprinting, X-inactivation and chromatin remodelling. In human somatic tissues, the 5' end of the BRCA1 CpG island is methylated, whereas this region is unmethylated in mature germ cells and early embryos. In gametes, as in somatic tissues, the CpG sites in the coding region are methylated. We took advantage of this bimodal distribution as a model to analyse the epigenetic reprogramming of coding regions during early human embryogenesis using the bisulphite-based genomic sequencing method. During preimplantation divisions, exon 11 of BRCA1 was slowly demethylated and retained approximately 30% of its methylated residues at the blastocyst stage. Moreover, the change in the distribution of methylated residues was not restricted to the BRCA1 gene, since for another gene, p53, a relatively high level of methylation (50%) of exon 4 was observed in blastocysts. Taken together, these data suggest that a significant part of the methylated residues of coding sequences might be conserved during preimplantation development.