Changes in the testicular histomorphometry and their association with genes expression pattern of testes from birth to puberty in Beetal goat kids

Abstract

In the present study, twenty-eight (n = 28) longitudinally rear male goat kids were slaughtered at monthly intervals (n = 4/group) till the 6th month of age; to examine the testicular development and establishment of spermatogenesis through histo-architecture along with mRNA expression of related genes. The results showed that seminiferous tubular diameter was linearly increased (P < 0.001) at birth (40 µm) to 6th months (200 µm). The epithelial height was 18.41 ± 0.65 µm at birth and 164 ± 2.82 µm at 6th months. Whereas, at 3rd months age greatest increase was observed (74.08 ± 1.66 µm), possibly due to a rapid increase in the numbers of spermatocytes and spermatids (4.0 ± 0.3 and 0.9 ± 0.04, respectively). At the same time point (4–6 months of age), a dramatic increase (P < 0.001) was observed in the mRNA level of genes expressed in haploid germ cells including Protamine (PRM1), Outer dense fiber protein (ODF2) and Stimulated by Retinoic Acid (STRA8). In addition, the maturation of Sertoli cells (SCs) was appeared to be completed at the start of 1st month (5.6 ± 0.5), which was further validated by sudden repression (P < 0.001) of SC-specific SOX9 and FSHR mRNA levels during this period. The spermatids that appeared at the end of the 3rd month reflect the start of spermatogenesis. However, a significant (P < 0.001) number of elongated spermatids and mature spermatozoa was observed at the end of 6 months, which indicated pubertal onset (9.8 ± 0.7 and 9.9 ± 0.9, respectively). The mRNA expression of other genes altered during this developmental phase was Heat-shock Protein 8 (HSPA8) and Aromatase (CYP19A1), both was important in sperm maturation and testosterone level. In conclusion, marked changes in cellular and molecular events were observed from the 3rd month; when active spermatogenesis initiated, and mature spermatozoa appeared in the 6th month at pubertal onset in Beetal bucks.