Correlations among ultrasonographic and microscopic characteristics of prepubescent ram lamb testes

Abstract

The onset of spermatogenesis during prepubertal development is accompanied by dynamic changes in testicular microstructure. Computer-assisted analysis of scrotal ultrasonograms may allow us to track these changes in a noninvasive manner; however, the echotextural characteristics of different histomorphological variables remain unclear. Hence the objective of this study was to compare echotextural and microscopic attributes of the testis over the first wave of spermatogenesis in prepubescent ram lambs. Bi-weekly ultrasound examinations and weekly testicular biopsies were carried out in 22 ram lambs from 9.5–10 weeks of age or the attainment of 15 cm3 in testicular volume, respectively, to the first detection of elongated spermatids (ESt). Testicular echogenicity was highly variable with age; however, after the alignment of data to the first detection of ESt, there was an initial increase followed by a decline, corresponding to the mitotic and postmitotic phases of spermatogenesis in prepubescent ram lambs. Testicular echotextural attributes (mean numerical pixel values and pixel heterogeneity) correlated with seminiferous tubule (ST) diameter, the number of degenerating cells/ST cross-section (XS), and the number of ubiquitin C-terminal hydrolase L-1 (a marker for prespermatogonia and undifferentiated spermatogonia) staining cells/ST XS during the mitotic and postmitotic phases. Additionally, in the postmitotic phase, significant correlations were recorded between the quantitative echotextural characteristics and ST cell density, nuclear:ST area and percentages of STs with different spermatogenic cells as the most mature germ cell type present. These results indicate that ram testes exhibit distinctive echotextural characteristics during the mitotic and postmitotic phases of germ cell differentiation. It is concluded that scrotal ultrasonography in conjunction with computerized image analysis holds potential as a noninvasive alternative to testicular biopsy in monitoring the reproductive status throughout different stages of testicular development.