Effect of neonatal gonadotropin-releasing hormone antagonist administration on Sertoli cell number and testicular development in the marmoset: Comparison with the rat

The primary purpose of this study was to establish whether Sertoli cells pr oliferate in the neonatal period in the marmoset monkey (Callithrix jacchus ) and whether administration of a long-acting GnRH antagonist (GnRHa) durin g this phase induced any transient or permanent effects on Sertoli cell num ber or on any other aspect of testicular development. Male marmoset co-twin s (n = 9) were treated during Weeks 1-14 with either vehicle or GnRHa. Four sets of co-twins were examined at Weeks 18-22 (start of infancy) and 5 set s in adulthood (92+ wk), and Sertoli cell number was determined using eithe r the nucleator or optical disector methods; other testicular morphometric analyses (e.g., germ cell volume, Leydig cell volume) used standard point-c ounting. Data for the marmoset were compared with that obtained in similarl y treated rats. Sertoli cell number in marmosets treated neonatally with Gn RHa was reduced by 35% compared with that of controls at Weeks 18-22 but wa s comparable to control values in adulthood. However, seminiferous epitheli um volume was reduced significantly in adult marmosets treated neonatally w ith GnRHa, and there was a tendency for reduced germ cell volume per Sertol i cell. In the same animals, there was significant expansion of the interst itium and an increase in Leydig cell volume per testis when compared with c o-twin controls; a similar increase in Leydig cell volume was evident in ad ult rats treated neonatally with GnRHa. Comparison of Sertoli cell numbers in 6 infantile (18-24 wk) and 10 adult marmosets showed that adult numbers of Sertoli cells were present by the start of infancy but, unlike rats, mar mosets were still able to replicate Sertoli cells beyond this period. Howev er, marmoset Sertoli cells supported only similar to 20% of the germ cell v olume supported by rat Sertoli cells, indicative of poor efficiency of sper matogenesis, as shown previously in the human. This finding, together with the demonstration of a temporal pattern of Sertoli cell replication similar to that in the human, supports the use of marmosets as a model for human m ale testicular development and function.