Follicular development and expression of nuclear respiratory factor-1 and peroxisome proliferator-activated receptor γ coactivator-1 alpha in ovaries of fetal and neonatal doelings.
In livestock, the ovarian reserve of follicles is established during the fetal stage. However, at least two-thirds of the oocytes present in the reserve die because of apoptosis before birth. Notably, mitochondria have been reported to play a crucial role in the fate (life/death) of oocytes. In this study, mitochondrial regulators nuclear respiratory factor-1 (NRF-1) and PPAR γ coactivator-1 alpha (PGC-1α) were examined during this period of follicle development to investigate their effects on follicular development and apoptosis. Fetal and neonatal Capra haimen were used, ranging in age from 60 d postcoitum (dpc) to 30 d postpartum (dpp). Our data demonstrated that egg nests were the earliest recognizable gamete cells in ovaries of fetal and neonatal doelings. Proportions of egg nests decreased from 92.68 to 25.08% whereas single follicles increased from 7.32 to 74.92% between 60 and 120 dpc. Subsequently, between 90 and 120 dpc, the proportion of primordial follicles increased from 9.98 to 61.56% (P < 0.01). However, it did not change between 1 and 30 dpp (P = 0.12). The proportion of primary follicles increased from 1.23 to 37.93% between 90 dpc to 1 dpp (P = 0.01) but did not change between 1 and 30 dpp (P = 0.11). Meanwhile, proportions of secondary and tertiary follicles increased in an age-dependent manner. In addition, results of this study suggested that NRF-1 and PGC-1α proteins are mainly localized in germ cells of egg nests, cytoplasm of oocytes, and granulosa cells of follicles ranging from primordial to tertiary follicles. The transcript abundance of NRF-1 mRNA was up-regulated in 60-dpc-old ovaries compared with 1-dpp-old ovaries (P < 0.05), but the PGC-1α mRNA expression pattern did not change (P = 0.05). Nevertheless, the number of terminal deoxynucleotidyltransferase UTP nick-end labeling (TUNEL) positive cells and caspase-3 activity in 60-dpc-old ovaries was less than those in 1-dpp-old ovaries (P < 0.01, P = 0.01). In conclusion, our results demonstrate that the key stage of primordial follicle formation is between 90 and 120 dpc in Capra haimen. Also, this study suggests that NRF-1 and PGC-1α might have roles in cell apoptosis during ovarian development of fetal and neonatal Capra haimen. These results improve our understanding of apoptotic mechanisms in oogenesis and folliculogenesis.
Center of Embryo Engineering and Technology, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
Z
Z
Zhou
Y
Y
Wan
Y
Y
Zhang
Z
Z
Wang
R
R
Jia
Y
Y
Fan
H
H
Nie
S
S
Ying
P
P
Huang
F
F
Wang
D000818:Animals; D000831:Animals, Newborn; D053148:Caspase 3; D005260:Female; D005333:Fetus / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006041:Goats / Q000254:growth & development* / Q000502:physiology; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D051266:Nuclear Respiratory Factor 1 / Q000235:genetics / Q000378:metabolism*; D010053:Ovary / Q000254:growth & development*; D010063:Ovum / Q000502:physiology; D060888:Real-Time Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D006360:Heat-Shock Proteins; D051266:Nuclear Respiratory Factor 1; D014157:Transcription Factors; D053148:Caspase 3