Endocrine Abstracts

JOINT1222

Both pigs and humans exhibit a triphasic pattern of Leydig cell development [1,2]. The second phase, termed "mini-puberty" in humans, is associated with penile growth, changes in body composition and cognitive development during the first six months of life [1]. In pigs, this phase begins around 2.5 weeks prenatally, peaks at 2.5 weeks after birth and ends seven weeks postnatally [2]. In contrast to humans, pigs have a functional gonadotropin-releasing hormone type II (GnRH-II)/GnRH-II receptor (GnRHR-II) system in the testes, the activation of which leads to luteinizing hormone (LH) independent testosterone secretion by Leydig cells [3]. This study aims to characterize the morphometric and transcriptomic changes in the porcine testes from 1 to 12 weeks of age to contribute to a better understanding of early testicular development and provide potential translational relevance. Testis samples were collected from pigs at 1, 3, 6 and 12 weeks of age (n = 6-10/group). The samples were fixed in Bouin’s solution and prepared for histomorphometric analysis. In addition, a portion of each sample was snap-frozen in liquid nitrogen for subsequent qPCR analysis. Histomorphometric analysis revealed a marked decrease in Leydig cell surface area and a progressive increase in nucleoplasmic index in 6- and 12-week-old animals compared with animals aged 1 and 3 weeks. Distinct age-dependent expression patterns were established for androgen receptor (AR), estrogen receptor 2 (ESR2), follicle-stimulating hormone receptor (FSHR), GnRH-II, GnRHR-II, inhibin subunit alpha (INHA), steroidogenic acute regulatory protein (STAR) and betaine-homocysteine S-methyltransferase (BHMT). Expression levels of transcripts for steroidogenic pathway proteins, i.e., HSD3B1, increased with age, whereas the expression of STAR progressively decreased. Upregulation of FSHR, ESR2, GnRH-II and INHA was observed from week 6 and of GnRHR-II, AR and BHMT from week 12. Expression of the LH/choriogonadotropin receptor was comparable across groups. Observed morphometric changes are consistent with the three-phase developmental pattern of Leydig cells and are associated with a reduced requirement for steroidogenesis at the end of mini-puberty, as shown by the reduced expression of STAR. The expression data also suggests that the GnRH-II/GnRHR-II system is not activated in the porcine testis during mini-puberty. Taken together, these preliminary results emphasize the interplay between structural adaptations and transcriptome changes that control testicular maturation in pigs. Reference[1] Becker M et al. Horm Res Paediatr, 2020; 93(2). [2] Van Straaten HWM et al. Biology of Reproduction, 1978; 19(1). [3] Morgan K et al. J Neuroendocrinol, 2024; 36(10).