Male and female differentiation of the human gonad

Unveiling the roles of Sertoli cells lineage differentiation in reproductive development and disorders: a review

In mammals, gonadal somatic cell lineage differentiation determines the development of the bipotential gonad into either the ovary or testis. Sertoli cells, the only somatic cells in the spermatogenic tubules, support spermatogenesis during gonadal development. During embryonic Sertoli cell lineage differentiation, relevant genes, including WT1, GATA4, SRY, SOX9, AMH, PTGDS, SF1, and DMRT1, are expressed at specific times and in specific locations to ensure the correct differentiation of the embryo toward the male phenotype. The dysregulated development of Sertoli cells leads to gonadal malformations and male fertility disorders. Nevertheless, the molecular pathways underlying the embryonic origin of Sertoli cells remain elusive. By reviewing recent advances in research on embryonic Sertoli cell genesis and its key regulators, this review provides novel insights into sex determination in male mammals as well as the molecular mechanisms underlying the genealogical differentiation of Sertoli cells in the male reproductive ridge.

Morphogenesis and fibronectin in sexual differentiation of rat embryonic gonads

The possible role of fibronectin in the organization of the sex-specific gonadal components was studied by immunocytochemistry combined with electron and light microscopy in rat fetuses at the ages of 12-15 days. Fibronectin was evenly distributed in both sexes under the basal lamina of the surface epithelium. Other basal laminae were not seen using light or electron microscopy inside the gonadal ridges at the age of 12 days. As the first sign of sexual differentiation, fibronectin-negative gonadal cords appeared in 13-day-old fetuses. In the males the cords were bigger than those in the females. The cords were clearly separated from the interstitium in 15-day-old fetuses of both sexes. A continuous layer of fibronectin had formed between the testicular surface epithelium and the elongated cords indicating the formation of a tunica albuginea. In females the surface epithelium-cord connection was maintained at all stages. Connections of the gonadal cords to mesonephric tubuli were seen in the rete region of both sexes. The electron optical basal lamina around the gonadal cords became continuous by the age of 15 days. The present results suggest that fibronectin is intimately involved in the sexual differentiation of the gonads, but not under the regulation of H-Y antigen or other testis-organizing factor.

Gonadal karyotyping in women with and without ovarian activity

Results of gonadal karyotyping on 26 patients with cyclic or acyclic ovarian activity and hypogonadotropic or hypergonadotropic hypogonadism are presented. Gonadal culture growth, with the exception of tissue from polycystic ovaries, was usually successful. With one exception, leukocytic and gonadal karyotypes were concordant. Normal ovarian function did not appear to be limited to ovaries of the 46,XX karyotype.

Ultrastructure of the indifferent gonad in male and female pig embryos

Pig embryos aged 24 days were obtained from artifically inseminated sows for ultrastructural study of the indifferent gonads. Sex was identified by chromosome analysis. The gonads are composed in both sexes of three different tissues: the surface epithelium, the gonadal blastema and the mesenchyme. The surface epithelial cells contained elongate mitochondria, granular endoplasmic reticulum, free polysomes, the Golgi complex, fine filaments and coated vesicles. The primitive cords were continuous with the surface epithelium and the interior of the gonad was occupied by blastema cells. They had prominent nucleoli, elongate mitochondria, granular endoplasmic reticulum, the Golgi complex, free polysomes, some lipid droplets and occasionally circular smooth membrane profiles resembling the agranular endoplasmic reticulum. Individual primordial germ cells were seen in all parts of the gonad. They were roundish with prominent nucleoli, globular mitochondria, granular endoplasmic reticulum, free polysomes, the Golgi complex, coated vesicles, lipid droplets and dense bodies. Degenerating cells and cells having pseudopods were also encountered. In comparison to the gonad at the age of 22 days, the primordium had grown into a longitudinal roundish protrusion and the number of primoridal germ cells had increased. Histological and ultrastructural observations showed that the pig gonads at the age of 24 days were similar in both sexes.

Ultrastructure of the early ovary and testis in pig embryos

Pig embryos aged 26-27 days were used for an ultrastructural study of the early ovary and testis. Sex was identified by both chromosomal analysis and gonadal histology, with consistent results. The gonads occupied their original site in the medial coelomic angles in both sexes. The female gonad was composed of three tissues: the surface epithelium, the gonadal blastema and the mesenchyme. The gonadal structure was similar to that seen earlier at the age of 24 days. At 26 days the testis had distinctly differentiated into four tissues. The new components were the testicular cords and the interstitium, both derived from the gonadal blastema. The testicular cords resembled anastomosing sheets more than cords. The ultrastructure of the tissues and their cell types are described and compared to the previous indifferent stage at the age of 24 days. The cells of the surface epithelium, of the primitive cords, of the mesenchyme, and the primordial germ cells had an ultrastructure that was similar in both sexes. The sustentacular cells of the testicular cords resembled the primitive cord cells and the spermatogonia were similar to the primordial germ cells. No Leydig cells were present yet. The process of testicular differentiation is described on the basis of the present and a previous study, and a new hypothesis, based on the vascular organization, is presented.