Sertoli cell differentiation in pubertal boars.

Meishan boars experience puberty at a younger age than crossbred boars in association with earlier expansion of seminiferous tubules and smaller postpubertal testicular size. The current study defined changes in expression, assessed by immunohistochemistry, of anti-Mullerian hormone (AMH) and CDKN1B, markers of Sertoli cell differentiation, in prepubertal Meishan and crossbred (BX) boars and related these changes with the pubertal expansion of seminiferous tubules. Expression of AMH in tubules of Meishan and BX boars increased (P < 0.002) from 7 to 28 d of age. Pubertal development was characterized by declining AMH expression (P < 0.001), followed by increasing (P < 0.001) expression of CDKN1B in Sertoli cell nuclei and subsequent expansion of tubules. These pubertal changes occurred at younger (P < 0.001) ages in Meishan than in BX boars. In testes of 90-d-old BX boars, expression of CDKN1B in Sertoli cell nuclei and tubular diameter increased (P < 0.001) from the mediastinum outwardly toward the tunica. Evaluation of the same tubules in adjacent sections established that expression of AMH decreased followed by expression of CDKN1B in Sertoli cell nuclei; both changes occurred before tubular diameter achieved 90 microm. In BX boars unilaterally castrated at 90 d of age, tubular diameter was inversely related to weight of the remaining testis at 10 mo (P < 0.05), supporting terminal differentiation of Sertoli cells in a subpopulation of these boars. These studies established temporal relationships of AMH, CDKN1B, and seminiferous tubule diameter in pubertal boars of 2 genetically diverse lines and determined that differentiation of Sertoli cells during pubertal development progresses as a gradient from the mediastinum outwardly toward the tunica.