ACTA VETERINARIA ET ZOOTECHNICA SINICA ›› 2017, Vol. 48 ›› Issue (10): 1863-1870.doi: 10.11843/j.issn.0366-6964.2017.10.009

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Study on Histology and Patterns of Follicular Atresia during Ovarian Development in Pig

LIANG Xue-chao, JIANG Ming, LUO Yu-ru, ZHANG Wei-min*, QING Su-zhu*   

  1. College of Veterinary Medicine, Northwest A&F University, Yangling 712100, China
  • Received:2017-04-24 Online:2017-10-23 Published:2017-10-23

Abstract:

The study aimed to analyze the histological structures at different ages of postnatal porcine ovary and rules of follicular atresia during ovarian development. Three pig ovary samples from 3,40,50,60,72,86,95 and 165 postnatal days were collected, respectively, and these samples were examined by using common paraffin sectioning method,HE staining and terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) technology. The results showed that the histological development process of pig ovary was divided into 3 periods:proliferation of oogonia, slow growth of follicles and rapid growth of follicles. Proliferation of oogonia period was characterized by the proliferation of oogonia. In slow growth of follicles period, the number of primordial follicles gradually declined with ages, while the number and the volume of primary follicles evidently increased. In rapid growth of follicles period, both the number and the volume of growing follicles continued to increase, and the number reached its maximum at 86 postnatal days. Tertiary follicles were first observed in ovary at 72 postnatal days, and nearly mature follicles appeared at 95 postnatal days, respectively. In all 3 periods, the phenomenon of follicular atresia could be observed both in oogonia and follicles. Eespecially, the atresia in primordial follicles were the most significant. TUNEL staining showed that, in proliferation of oogonia period, the atresia of a great number of primordial follicles and primary follicles could be observed, which were mainly caused by apoptosis on follicular oocytes. In slow growth of follicles period, phenomenon of atresia occured in all kinds of growing follicles. Primary follicular atresia was mainly caused by apoptosis on oocyte, some of them were caused by the apoptosis both on oocytes and follicular cells. Secondary follicular atresia was mainly due to apoptosis of layers of the granular cells. In rapid growth of follicles period, with the rapid growth of follicles, the phenomenon of atresia occured in all kinds of follicles became more evident. The atresia in tertiary follicles and secondary follicles were mainly caused by the apoptosis of granulosa cells.

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