Morphological differences in human spermiogenesis compared with rodent model: A light microscopy study

Objective Spermiogenesis is the final stage of spermatogenic differentiation during which round spermatids transform into mature spermatozoa. This process involves a sequence of morphological and biochemical changes that generally conserved among different species. Although minor biochemical and biophysical variations have been reported, detailed morphological deviations among mammals remains poorly defined. This study aimed to observe morphological differences between human spermiogenesis and the widely accepted mammalian model derived primarily from rodents. Methods Isolated germ cells were cultured for three weeks in Dulbecco's Modified Eagle Medium/Nutrient Mixture F-12 (DMEM/F12), supplemented with 10% Fetal Bovine Serum, MEM vitamins, L-Glutamine and Penicillin-Streptomycin. Cultures were examined at different time intervals to document spermiogenic stages. Results In humans, spermatid elongation is not as prominent as in rats, as the head is in pyriform in shape. In contrast to rodents, the human sperm head protrudes out from the cytoplasm immediately after completion of head development, followed by uncoiling the tail. Shedding of excess cytoplasm is not readily visible under the light microscope but is indirectly evident by presence of small droplets attached to some spermatozoa, particularly in morphologically abnormal sperm. Conclusion These findings support a revised morphological model of human spermiogenesis based on light microscopic observations.