Undifferentiated Gonadal Tissue Research Articles

Germ Cell Tumors in the Intersex Gonad: Old Paths, New Directions, Moving Frontiers

The risk for the development of germ cell tumors is an important factor to deal with in the management of patients with disorders of sex development (DSD). However, this risk is often hard to predict. Recently, major progress has been made in identifying gene-products related to germ cell tumor development (testis-specific protein-Y encoded and octamer binding transcription factor 3/4) and in recognizing early changes of germ cells (maturation delay, preneoplastic lesions, and in situ neoplasia). The newly recognized "undifferentiated gonadal tissue" has been identified as a gonadal differentiation pattern bearing a high risk for the development of gonadoblastoma. It is expected that the combination of these findings will allow for estimation of the risk for tumor development in the individual patient (high risk/intermediate risk/low risk). This article reviews the recent literature regarding the prevalence of germ cell tumors in patients with DSD. Some major limitations regarding this topic, including a confusing terminology referring to the different forms of intersex disorders and unclear criteria for the diagnosis of malignant germ cells at an early age (maturation delay vs. early steps in malignant transformation) are discussed. Thereafter, an overview of the recent advances that have been made in our knowledge of germ cell tumor development and the correct diagnosis of early neoplastic lesions in this patient population is provided. A new classification system for patients with DSD is proposed as a tool to refine our insight in the prevalence of germ cell tumors in specific diagnostic groups.

Gonadoblastoma Arising in Undifferentiated Gonadal Tissue within Dysgenetic Gonads

The purpose of the study was to define the histological origin of gonadoblastomas, allowing the identification of high-risk patients. Sixty paraffin-embedded gonadectomy or gonadal biopsy samples of 43 patients with gonadal dysgenesis were selected from our archives. We studied the morphology and immunohistochemical properties of the germ cells in 40 samples without neoplastic transformation and compared these findings with the morphological and immunohistochemical characteristics of 20 samples containing gonadoblastoma/dysgerminoma. The overall incidence of germ cell tumors in our patient series was 35%. In dysgenetic gonads without germ cell neoplasia, besides the presence of areas with testicular and/or ovarian differentiation, areas of undifferentiated gonadal tissue were identified in 13 of 40 samples (32.5%). A subpopulation of germ cells within these undifferentiated areas stained positive for octamer binding transcription factor (OCT)3/4, the stem cell factor receptor, placental-like alkaline phosphatase, and testis-specific protein-Y encoded. Gonadoblastoma germ cells display identical staining results. Moreover, in gonads containing gonadoblastoma, adjacent to this lesion, areas of undifferentiated gonadal tissue with identical immunohistochemical characteristics were identified in 10 of 20 samples (50%). No adjacent tissue was available in five cases, whereas in the five remaining cases, it consisted of streak tissue. In three cases, an accumulation of OCT3/4-positive germ cells in the proximity of the malignant lesions was found, suggesting clonal expansion and final organization into gonadoblastoma nests. Based on these observations, we hypothesize that gonadoblastomas originate from surviving OCT3/4-positive germ cells in areas of undifferentiated gonadal tissue within the dysgenetic gonad. Supportive evidence was obtained that carcinoma in situ arises in regions with testicular differentiation.

Oocyte apoptosis during the transition from ovary-like tissue to testes during sex differentiation of juvenile zebrafish

Large numbers of apoptotic early diplotene oocytes were observed during the transition from ovary-like undifferentiated gonadal tissue to testes during sex differentiation in presumptive males of the zebrafish (Danio rerio). The percentage of terminal-deoxynucleotidyl-transferase-mediated dUTP nick-end labelling (TUNEL)-positive apoptotic oocytes in the gonads of presumptive males was approximately eight- to 12-fold higher than in genetic all-females. By 29 days post-hatching, all oocytes had disappeared from the gonads of presumptive males. In these males, we also observed apoptotic somatic cells in the ovarian cavity between 23 and 35 days post-hatching. Therefore, the disappearance of oocytes and the decomposition of the ovarian cavity caused by apoptosis during sex differentiation were male-specific events. In genetic all-females, apoptosis in a proportion of early diplotene oocytes was found in the undifferentiated gonads at 15-19 days post-hatching, probably as a result of programmed oocyte loss during ovarian development. These findings suggest that oocyte apoptosis is the mechanism of testicular and ovarian differentiation in zebrafish.

Anti-Müllerian hormone in early human development

Anti-Müllerian hormone (AMH) is a glycoprotein produced by immature Sertoli cells and responsible for the regression of Müllerian ducts in male fetuses. The ontogeny of the hormone in early human development was investigated. While no detectable AMH could be found in female fetal serum, in males, the mean ± S.E.M. AMH serum concentration was 40.5 ± 3.9 ng/ml from 19 to 30 weeks ( n = 13), and 28.4 ± 6.1 ng/ml from 30 weeks to term ( n = 9). The latter value is significantly different from the mean AMH concentration in serum from boys aged 2 months to 2 years (43.1 ± 3.7), suggesting that AMH production is sluggish during the perinatal period. The serum AMH concentration of a 46,XX male fetus was in the normal range for males. Using in situ hybridization, AMH transcripts were detected in the testicular tissue of all fetuses from 8 weeks onwards, but not in fetal ovaries nor in the yet undifferentiated gonadal tissue of a 7-week-old fetus bearing maledetermining DNA sequences. Together, these data indicate that AMH is a reliable marker for the presence of functional testicular tissue and, as such, may be helpful for the diagnosis of fetal sex, particularly in the presence.of sex chromosome abnormalities.

ANTI-MULLERIAN HORMONE IN EARLY HUMAN DEVELOPMENT

Anti-Mullerian hormone (AMH), also called Mullerian-inhibiting substance or factor, is a dimeric glycoprotein, produced by immature Sertoli cells, and responsible for Mullerian regress ion in male fetuses. To study the ontogeny of AMH production in the male against human recombinant AMH, the AMH concentration in 21 samples of amniotic fluid and 44 samples of fetal serum, initially collected for cytogenetical analysis in fetuses with sonographic abnormalities. No AMH was detectable in amnitotic fluid, whatever the fetal sex. Mean ± SEM AMH concentration was 40.5 ± 3.9 ng/ml in the serum of male fetuses from 19 to 30 weeks, and 28.4 ± 6.1 ng/ml in older ones. The AMH concentration in the serum of an male XX fetus, aged 24 weeks, 48.3 ng/ml, was the only biological indicator of fetal sex. No AMH was detectable in female serum at any time, allowing easy discrimination between male and female samples, even during the perinatal period, when mean scrum AMH concentration is decreased, compared to that of infants aged 2 months to 2 years (43.1 ± 3.7? P>0.05). AMH production in early fetal life was studied by in-situ hybridization, using AMH-specific sense and antisense riboprobes. AMH transcripts were detected in the Sertoli cells of fetuses aged 8 weeks or older, but not in ovarian tissue. Negative results were also found in the sexually undifferentiated gonadal tissue of one 7-week-old fetus, with detectable DMA SRY-specific sequences, confirming that AMH expression in the testis begins only after seminiferous tubule differentiation.