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Infancy is not a quiescent period of testicular development
1Laboratory of Testicular Physiology and Pathology, Buenos Aires Children's Hospital, Buenos Aires, Argentina. hchemes@cedie.guti.gov.ar
Insights
The primate testis is not quiescent during infancy but shows significant growth and cellular activity. Successful completion of these developmental changes is crucial for adult fertility.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Endocrinology
Background:
- The infantile period in higher primates separates neonatal activation from pubertal development.
- This phase was traditionally viewed as quiescent but exhibits substantial underlying activity.
Purpose of the Study:
- To investigate the dynamic changes in the primate testis during the infantile period.
- To understand the cellular and hormonal events preceding pubertal maturation.
Main Methods:
- Histological examination of testicular development.
- Analysis of hormonal profiles and receptor expression (FSH receptors).
- Observation of cellular proliferation and differentiation (Sertoli and Leydig cells).
Main Results:
- Significant postnatal testicular growth driven by seminiferous cord elongation and Sertoli cell proliferation.
- Infantile Sertoli cells exhibit unique functions including hormone secretion and FSH responsiveness.
- Leydig cell activity and testosterone secretion increase post-birth, with fluctuations during late infancy.
- Puberty onset involves Leydig cell reactivation and germ cell maturation, with increased seminiferous tubule diameter.
Conclusions:
- The infantile primate testis is a period of intense, albeit subtle, developmental activity, not quiescence.
- Successful completion of infantile testicular changes, including Sertoli cell differentiation and hormonal regulation, is essential for achieving adult fertility.
Abstract:
Postnatal evolution of the testis in most laboratory animals is characterized by the close continuity between neonatal activation and pubertal development. In higher primates, infancy, a long period of variable duration, separates birth from the beginning of puberty. This period has been classically considered as a quiescent phase of testicular development, but is actually characterized by intense, yet inapparent activity. Testicular volume increases vigorously shortly after birth and in early infancy due to the growth in length of seminiferous cords. This longitudinal growth results from active proliferation of infantile Sertoli cells which otherwise display a unique array of functional capabilities (oestrogen and anti-müllerian hormone secretion, increase of FSH receptors and maximal response to FSH). Leydig cells also show recrudescence after birth, possibly determined by an active gonadotrophic-testicular axis which results in increased testosterone secretion of uncertain functional role. This postnatal activation slowly subsides during late infancy when periodic phases of activation of the hypothalamo-pituitary-testicular axis are paralleled by incomplete spermatogenic spurts. The beginning of puberty is marked by the simultaneous reawakening of Leydig cell function and succeeding phases of germ cell differentiation/degeneration which ultimately lead to final spermatogenic maturation. The marked testicular growth in this stage is due to progressive increase at seminiferous tubule diameter. Sertoli cells, which have reached mitotic arrest, develop and differentiate, establishing the seminiferous tubule barrier, fluid secretion and lumen formation, and acquiring cyclic morphological and metabolic variations characteristic of the mature stage. All of these modifications indicate that, far from being quiescent, the testis in primates experiences numerous changes during infancy, and that the potential for pubertal development and normal adult fertility depends on the successful completion of these changes.