title: Effect of heat stress on the survival and development of in vitro cultured bovine preantral follicles and on in vitro maturation of cumulus-oocyte complex.
abstract: The deleterious effect of heat stress (HS) on competence of oocytes from antral follicles is well recognized, but there is a lack of data regarding its impact on the viability and growth of preantral follicles. In this study, we used in vitro preantral follicle cultures to investigate the effects of HS on the following parameters: survival and development of primordial follicles after in vitro culture of ovarian fragments (experiment I); growth and antrum formation of isolated advanced secondary follicles (experiment II); and maturation rates after in vitro maturation (IVM) of cumulus-oocyte complexes (COCs) from antral follicles (>2-6 mm) grown in vivo (experiment III). Furthermore, the following end points were evaluated in all experiments: follicle/oocyte survival, reactive oxygen species (ROS), estradiol (E2) and progesterone (P4) production, as well as mRNA expression for select genes related to stress (HSP70) and apoptosis (MCL1 and BAX). In all experiments, HS consisted of exposing the structures (ovarian fragments, isolated preantral follicles and COCs) to 41 °C for 12 hours and then to 38.5 °C until the end of the culture (7 days for experiments I and II and 24 hours for experiment III). The temperature for the control group was held at 38.5 °C for the entire culture period. Heat stress increased (P < 0.05) the percentage of developing follicles (intermediate, primary, and secondary follicles) at 12 hours and increased levels of ROS at all evaluated time points (12, 24 hours, and D7), when compared to the control (experiment I). Heat stress did not affect (P > 0.05) any identified end points when preantral follicles were cultured in their isolated form (experiment II). However, in experiment III, HS decreased (P < 0.05) both the rates of metaphase II after 24 hours and E2 production at 12 hours of IVM. Moreover, HS increased (P < 0.0001) levels of P4 after IVM and ROS production at every evaluated time point, compared with the control (12 and 24 hours). In conclusion, HS caused: (1) early activation of primordial follicles; (2) an increase in ROS production by early preantral follicles enclosed in ovarian tissue and by COCs; (3) a short-term reduction of E2 production by COCs; and (4) an increase in P4 secretion from COCs. However, HS did not affect in vitro culture of advanced isolated secondary follicles. Experimental evidence indicates that preantral follicles are less sensitive to HS than COC.
authors.affiliation: Laboratory of Manipulation of Oocyte and Preantral Follicles (LAMOFOPA), State University of Ceará, Fortaleza, CE, Brazil.
authors.forename: V M
authors.initials: VM
authors.lastname: Paes
authors.affiliation: Laboratory of Manipulation of Oocyte and Preantral Follicles (LAMOFOPA), State University of Ceará, Fortaleza, CE, Brazil.
authors.forename: L A
authors.initials: LA
authors.lastname: Vieira
authors.affiliation: Laboratory of Manipulation of Oocyte and Preantral Follicles (LAMOFOPA), State University of Ceará, Fortaleza, CE, Brazil.
authors.forename: H H V
authors.initials: HHV
authors.lastname: Correia
authors.affiliation: Laboratory of Manipulation of Oocyte and Preantral Follicles (LAMOFOPA), State University of Ceará, Fortaleza, CE, Brazil.
authors.forename: N A R
authors.initials: NAR
authors.lastname: Sa
authors.affiliation: Laboratory of Animal Reproduction, Federal University Ceará, Fortaleza, CE, Brazil.
authors.forename: A A A
authors.initials: AAA
authors.lastname: Moura
authors.affiliation: Laboratory of Manipulation of Oocyte and Preantral Follicles (LAMOFOPA), State University of Ceará, Fortaleza, CE, Brazil.
authors.forename: A D
authors.initials: AD
authors.lastname: Sales
authors.affiliation: Laboratory of Manipulation of Oocyte and Preantral Follicles (LAMOFOPA), State University of Ceará, Fortaleza, CE, Brazil.
authors.forename: A P R
authors.initials: APR
authors.lastname: Rodrigues
authors.affiliation: Postgraduate biotechnology, Potiguar University/Laureate International Universities, Natal, RN, Brazil.
authors.forename: D M
authors.initials: DM
authors.lastname: Magalhães-Padilha
authors.affiliation: Laboratory of Reproduction Biotechnology (Biotech), State of University of Pampa, Uruguaiana, RS, Brazil.
authors.forename: F W
authors.initials: FW
authors.lastname: Santos
authors.affiliation: Department of Animal Science, Food and Nutrition, Southern Illinois University, Carbondale, Illinois, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Apgar
authors.affiliation: Laboratory of Manipulation of Oocyte and Preantral Follicles (LAMOFOPA), State University of Ceará, Fortaleza, CE, Brazil.
authors.forename: C C
authors.initials: CC
authors.lastname: Campello
authors.affiliation: Dairy Cattle Research Center, EMBRAPA, Juiz de Fora, MG, Brazil.
authors.forename: L S A
authors.initials: LSA
authors.lastname: Camargo
authors.affiliation: Laboratory of Manipulation of Oocyte and Preantral Follicles (LAMOFOPA), State University of Ceará, Fortaleza, CE, Brazil. Electronic address: jrf.lamofopapapers@gmail.com.
authors.forename: J R
authors.initials: JR
authors.lastname: Figueiredo
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D054885:Cumulus Cells / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D059471:In Vitro Oocyte Maturation Techniques / Q000662:veterinary*; D009865:Oocytes / Q000502:physiology*; D006080:Ovarian Follicle / Q000502:physiology*; D013312:Stress, Physiological
keywords: Bovine; Heat stress; In vitro culture; Oocyte; Preantral follicle