Recent advances in ovulation synchronization and superovulation in ...

Abstracts. II International Symposium on Animal Biology of Reproduction, Nov. 19-22, 2008, São Paulo, SP, Brazil.
Apoptosis and autophagy are required during the follicular atresia in teleost ovary
R. Thomé 1 , H. Santos 1 , F. Arantes 1 , Y. Sato 2 , N. Bazzoli 3 , E. Rizzo 1
1
Laboratory of Ictiohistology, Morphology Department, ICB/UFMG, CP 486, Belo Horizonte, MG, Brazil; Hydrobiology and
Hatchery Station of Três Marias – CODEVASF; 3 Graduate Program on Zoology of Vertebrates – PUC Minas, Belo Horizonte,
MG, Brazil.
Introduction
Follicular atresia is a hormonally controlled degenerative process by which vertebrate ovarian follicles lose their
integrity and are eliminated prior to ovulation. Apoptosis or type I cell death is a well-characterized pathway to cell
death essential to maintenance of tissue homeostasis in multicellular organisms. Autophagic or type II cell death has
been considered as an alternative route of programmed cell death, distinct from apoptosis and characterized by the
formation of many large autophagic vacuoles (1). The purpose of the present study was to investigate the
contribution of apoptosis and autophagy during follicular atresia in two freshwater teleost species from the São
Francisco River basin, Brazil: curimatã-pacu, Prochilodus argenteus and piau-jejo, Leporinus taeniatus.
Material and Methods
Fishes were maintained in captivity after the reproductive period and follicular atresia was assessed for three stages:
early, advanced, and late atresia. The morphological features of the atretic follicles were histologically examined in
ovarian samples fixed in Bouin’s fluid for 8 h at room temperature, embedded in paraffin, sectioned, and stained
with hematoxylin-eosin. For the identification of autophagy in the follicular cells, the ovarian samples were fixed in
Karnovsky, post-fixed in 1% osmium tetroxide with 1.5% potassium ferrocyanide for 2 h, and then embedded in
Epon/Araldite plastic resin. Ultrathin sections were stained with uranyl acetate and lead citrate and examined using a
transmission electron microscope. The TUNEL in situ technique was used to assess apoptosis during the follicular
atresia in ovaries of the P. argenteus and L. taeniatus.
Results and Discussion
The atretic follicles exhibited zona pellucida breakdown, yolk degeneration, and hypertrophied follicular cells,
common features of the follicular atresia in most of the teleosts (2). Morphometric analyses of the ovarian regression
showed decreased atretic vitellogenic follicles and increased perinucleolar follicles for the future reproductive cycles
and yellow bodies to both species. In contrast to mammals, oogonia continue to proliferate in adult females and
produce perinucleolar follicles, which stock oocytes for the next reproductive cycle (3). Intense heterophagy to
engulf the yolk, and autophagy were detected in the follicular cells during advanced and late atresia. The TUNEL
assay detected DNA fragmentation, mainly in late follicular atresia. Differently, the apoptosis contribute greatly for
the rapid elimination of the postovulatory follicles in spawned ovaries of P. argenteus (4). We inferred that
heterophagy, autophagy, and apoptosis contributed to follicular atresia in teleost ovaries, thereby achieving a more
efficient removal of the degenerating oocyte and dying follicular cells.
References
(1) Lockshin RA, Zakeri Z. 2004. Int J Biochem Cell Biol, 36:2405-2419; (2) Bazzoli, N. 2003. In: Godinho HP.
Godinho AL. Waters, fishes and fishers of the São Francisco in Minas Gerais. Belo Horizonte, MG: PUC-Minas [in
Portuguese]; (3) Jalabert B. 2005. Reprod Nutr Dev, 45: 261-279; (4) Santos et al. 2008. Tissue Cell, 332:159-170.
Support: FAPEMIG, CNPq and CODEVASF.
E-mail: ictio@mono.icb.ufmg.br
Anim. Reprod., v.6, n.1, p.211, Jan./Mar. 2009 211