Submitted to: Biology of Reproduction
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/15/2002
Publication Date: 1/1/2003
Citation: LUNSTRA, D.D., WISE, T.H., FORD, J.J. 2003. SERTOLI CELLS IN THE BOAR TESTIS: CHANGES DURING DEVELOPMENT AND COMPENSATORY HYPERTROPHY AFTER HEMICASTRATION AT DIFFERENT AGES. BIOLOGY OF REPRODUCTION. v. 68(1). p. 140-150. Interpretive Summary: Sertoli cells play an important role in both pubertal development and mature testicular function because they provide an environment that protects and nurtures germ cells and assists their development into viable sperm. In addition, Sertoli cell number determines mature testicular size and capacity to produce sperm. The rapid increase in use of artificial insemination in the swine industry has placed greater importance on larger testicular size and increased sperm production in stud boars. However, Sertoli cell numbers in the boar testis have not been enumerated during development. The present study enumerated Sertoli cells and assessed testicular structure in crossbred boars at 1, 10, 56 , 112 and 220 days of age. In addition, the effects of unilateral castration on growth and structure of the remaining testis was assessed. At 220 days of age, testis weight and Sertoli numbers were highly correlated (r = .83; P < .001), confirming that Sertoli numbers are related to mature testis size in the boar. In boars destined to have small testis at maturity, Sertoli cell proliferation had ceased by 56 days of age, but proliferation continued through 112 days of age in boars with large testis at maturity. Unilateral castration demonstrated that the remaining testis increased in mass, but little or no increase in Sertoli cell numbers occurred; these findings demonstrate that the programming of Sertoli cell proliferation occurs before birth in swine. Thus, these results indicate that boars destined to have large or small testis at maturity display intriguing differences during development. In addition, large and small testis boars provide a unique animal model for further studies of factors that program and control Sertoli cell proliferation. Identification of these factors may ultimately allow manipulation of mature testis size, sperm production and reproductive efficiency among boars used as sires in the swine industry.
Technical Abstract: Changes in Sertoli cell numbers and testicular structure during normal development and during compensatory hypertrophy were assessed in crossbred Meishan x White Composite males. Boars were assigned at birth to unilateral castration at 1, 10, 56 or 112 days, or remained as intact controls through 220 days. The first testis removed were compared to assess testicular development. At 220 days, testicular structure was evaluated in boars representing the 25% with the largest testis (Lg) and 25% with the smallest testis (Sm) in each treatment group. Number of Sertoli cells per testis reached a maximum by Day 56 in Sm but not until Day 112 in Lg testis boars, indicating a longer duration of Sertoli proliferation in Lg testis boars. Unilateral castration of Lg testis boars on Days 1, 10, 56 and 112 caused the weight of the remaining testis to hypertrophy 149%, 135%, 119% and 120% and total sperm production to increase to 127%, 128%, 97% and 106%, respectively. However, Sertoli cell numbers changed little in hemicastrate boars. In Lg testis boars, compensatory hypertrophy primarily involved proliferation of Leydig cells and expansion of existing Sertoli cells with little increase in Sertoli cell numbers, but involved expansion of existing Leydig and Sertoli cells without increase in cell numbers in Sm testis boars. These results indicate that Lg and Sm testis boars display intriguing differences both during development and compensatory hypertrophy, and identify a unique animal model for further studies of factors that program and control Sertoli cell proliferation.