Abstract
Spermatogenesis, which is a continuous process from undifferentiated spermatogonia to spermatozoa in the seminiferous tubules, declines with age. To investigate changes in spermatogenesis with aging, we reconstructed the seminiferous tubules of 12 mice aged 12 to 30 months from serial sections and examined age-related and region-specific alterations in the seminiferous epithelium and spermatogenic waves in three dimensions. The basic structure of the seminiferous tubules, including the numbers of tubules, terminating points, branching points, and total tubule length, did not change with age. Age-related alterations in spermatogenesis, primarily assessed by the formation of vacuoles in Sertoli cells, were detected in the seminiferous tubules at 12 months. The proportion of altered tubule segments with impaired spermatogenesis further increased by 24 months, but remained unchanged thereafter. Altered tubule segments were preferentially distributed in tubule areas close to the rete testis and those in the center of the testis. Spermatogenic waves became shorter in length with age. These results provide a basis for examining the decline of spermatogenesis not only with aging, but also in male infertility.
Highlights
Spermatogenesis, which is a continuous process from undifferentiated spermatogonia to spermatozoa in the seminiferous tubules, declines with age
All seminiferous tubule areas observed in each testis section were classified into two types according to the cell association pattern and the presence or absence of vacuoles formed in Sertoli cells: normal, normal spermatogenesis and the absence of vacuoles; altered, the presence of vacuoles (Fig. 1e–j) and/or impaired spermatogenesis (Fig. 1k,l)
The present study revealed that the extent of age-related alterations in the seminiferous epithelium represented by vacuoles formed in Sertoli cells, which were already found at 12 months, increased significantly by 24 months, but remained unchanged thereafter
Summary
Spermatogenesis, which is a continuous process from undifferentiated spermatogonia to spermatozoa in the seminiferous tubules, declines with age. To investigate changes in spermatogenesis with aging, we reconstructed the seminiferous tubules of 12 mice aged 12 to 30 months from serial sections and examined age-related and region-specific alterations in the seminiferous epithelium and spermatogenic waves in three dimensions. Age-related alterations in spermatogenesis, primarily assessed by the formation of vacuoles in Sertoli cells, were detected in the seminiferous tubules at 12 months. Spermatogenic waves became shorter in length with age These results provide a basis for examining the decline of spermatogenesis with aging, and in male infertility. Spermatogenesis is a continuous process from undifferentiated spermatogonia to spermatozoa in the seminiferous tubules[1,2,3]. The decline in spermatogenesis with age is gradual and the complete cessation of reproductive capacity never
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