Immunohistochemical and Ultrastructural Evaluation of Human Fetal Testicular Development Across Different Gestational...

Introduction Human fetal testicular development is a tightly regulated process involving coordinated cellular differentiation and structural maturation. However, comprehensive immunohistochemical and ultrastructural characterization across different gestational ages remains limited, restricting a detailed understanding of normal testicular development. Materials and methods Testicular tissue samples obtained from aborted human fetuses of varying gestational ages were studied. The tissues were subjected to Ki-67 antibodies for immunohistochemistry, examined through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to assess cellular organization and ultrastructural features. Results The fetal testis consisted of solid seminiferous (testis) cords lacking a central lumen, with no distinct basal and adluminal compartments due to the absence of Sertoli cell tight junctions and the blood-testis barrier. The cords were lined by immature Sertoli cells enclosing centrally located gonocytes. The interstitial tissue contained abundant fetal Leydig cells arranged singly or in small clusters. Ultrastructurally, fetal Leydig cells exhibited abundant smooth endoplasmic reticulum, numerous mitochondria with tubular cristae, prominent Golgi complexes, and lipid droplets, consistent with their active steroidogenic function during fetal development. Conclusion Human fetal testicular development is characterized by progressive structural organization of seminiferous cords and differentiation of immature Sertoli and fetal Leydig cells. The immunohistochemical and ultrastructural findings demonstrate the establishment of the cellular architecture required for future spermatogenesis while confirming the active steroidogenic role of fetal Leydig cells during gestation. These observations provide a comprehensive baseline for understanding normal fetal testicular development and may serve as a reference for investigating disorders of testicular differentiation and development.