A new approach to quantification of spermatogenesis and its application to germinal cell attrition during human spermiogenesis.

Abstract

A new approach to quantification of spermatogenesis has been applied to human testes to investigate germinal cell attrition during spermiogenesis and to derive an appropriate time divisor for the determination of daily sperm production from numbers of homogenization-resistant spermatids in unfixed human testes. Glutaraldehyde fixation of testes from 10 men rendered nuclei of even the most immature germinal cells resistant to homogenization. Prevention of dissolution of cell nuclei during homogenization permitted enumeration of the entire constellation of germinal cell nuclei by phase-contrast microscopy. Thus, investigation of attrition during spermatogenesis became possible. Since daily sperm production per gram of parenchyma (DSP/g) was similar (P>0.05) when based on enumeration of round spermatids (5.5 X 10’), maturation-phase spermatids (5.8 X 106), and all spermatids (5.9 X 106), no attrition was detected during human spermiogenesis. Agreement (P>0.05) between these three estimates and DSP/g based on histometric analysis of round spermatids in the same testes (5.9 X 106) validated the new technique for quantifying spermatogenesis. The number of homogenization-resistant spermatids in unfixed tissue was only 37% of the number of maturation-phase spermatids in homogenates of fixed, contralateral testes. Thus, previous estimates of DSP/g in humans from homogenates of unfixed testis are low and should be approximated by multiplying published data by the reciprocal of 0.37 (i.e., 2.7). When the corrected time divisor of 2.9 days (7.9-day time divisor for maturation-phase spermatids multiplied by the correction factor of 0.37) was employed to convert numbers of homogenization-resistant spermatids from unfixed testes to DSP, a value of 5.6 X 106 was obtained for these 10 men. No difference (P>0.05) was found among the five estimates of DSP/g.