Pluripotent Embryonic Stem cell (ESC) lines can be derived from a variety of sources. Mouse lines derived from the early blastocyst and from primordial germ cells (PGCs) can contribute to all somatic lineages and to the germ line, whereas cells from slightly later embryos (EpiSC) no longer contribute to the germ line. In chick, pluripotent ESCs can be obtained from PGCs and from early blastoderms. Established PGC lines and freshly isolated blastodermal cells (cBC) can contribute to both germinal and somatic lineages but established lines from the former (cESC) can only produce somatic cell types. For this reason, cESCs are often considered to be equivalent to mouse EpiSC. To define these cell types more rigorously, we have performed comparative microarray analysis to describe a transcriptomic profile specific for each cell type. This is validated by real time RT-PCR and in situ hybridisation. We find that both cES and cBC cells express classic pluripotency-related genes (including cPOUV/OCT4, NANOG, SOX2/3, KLF2 and SALL4), whereas expression of DAZL, DND1, DDX4 and PIWIL1 defines a molecular signature for germ cells. Surprisingly, contrary to the prevailing view, our results also suggest that cES cells resemble mouse ES cells more closely than mouse EpiSC.

Sperm parameters are known to be impaired in men with sickle cell disease (SCD). Although treatment with hydroxyurea (HU) impacts sperm quality, sperm preservation is impossible before puberty. The present study's primary objective was to analyze and compare sperm parameters in male SCD patients exposed (or not) to HU before puberty. Twenty-six sperm samples from 15 patients (median (range) age: 17 (16-23)) treated with HU during childhood were compared with 46 samples from 23 HU-naïve patients (median (range) age: 20 (16-24)). The median (range) age at HU initiation was 6 years (1-14), the median duration of HU treatment was 4 years (0.5-10) and the mean ± standard deviation dose of HU was 22.4 ± 3.7 mg/kg/day. Although we observed substantial quantitative and qualitative semen abnormalities in all patients, there were no significant differences in semen volume, sperm concentration, total sperm count, and spermatozoa motility, morphology and vitality between the HU-exposed and HU-naïve groups. At the time of the semen analysis, respectively 100% and 52% of the patients in the HU-exposed and HU-naïve groups were on transfusion therapy. Hydroxyurea's specific effect on spermatogenesis in very young infants and the putative value of transfusion for reversing HU's toxicity warrant further investigation.