Biology and spermatogonial stem cell niche: chinchila (Chinchila lanigera) as experimental model for mammals

Abstract

The Chilean chinchilla (Chinchilla lanigera) is threatened in its natural habitat and there is very little information concerning the reproductive biology of this species. The chinchilla is an endemic rodent found in the Andes region of South America and considered critically endangered due to the use of its fur in the fur market. Despite its economic and biological importance, there are few studies in the literature regarding the reproductive biology of this species. Among the published articles, there are studies developed at UFMG under the coordination of this proposal supervisor in which basic aspects related to the morphofunctional evaluation of the chinchilla testis were performed, particularly those concerning the postnatal testis development and spermatogenesis (Leal & França 2008, 2009). In these studies, it was found that puberty in male chinchillas occurs at 3 months of age, whereas sexual maturity occurs only at 17 months, and this time interval is relatively much longer than the ones observed in other mammalian species already investigated. Another very important and unique aspect observed was that the total number of germ cells per seminiferous tubule cross section, as well as the Sertoli cell efficiency and daily sperm production per testis increased continuously in the period between puberty and sexual maturity, without a corresponding increase in the total number of Sertoli cells per testis, the coefficient of spermatogonial mitoses efficiency and the meiotic index, which are classical parameters to evaluate the spermatogenic efficiency in mammals. In this regard, it was hypothesized that these very important findings probably were related to the formation of new spermatogonial stem cell niches/clones. Therefore, it is crutial to characterize the spermatogonial stem cells in chinchillas, as well as to functionally evaluate the environment (niches) where these cells are located and the possible role of the key testis somatic cells (Sertoli and Leydig cells) on this environment. Certainly, these important investigations will allow a better understanding of spermatogenic efficiency in mammals and even in vertebrates in overall. In this regard, this proposal aims to perform a functional evaluation of spermatogonial stem cells and their niches during postnatal testis development in chinchillas, using, among others, histomorphometric, immunohistochemical, ultrastructural and molecular techniques. We expect that, using the chinchilla as an experimental model, the results found will allow and accurate comprehension of the spermatogonial stem cells biology in mammals, providing also new knowledge that will eventually serve as a background for clinical application in approaches involving the restauration of fertility in infertile patients or those at risk of fertility. (AU)