Histology of the Ovary of the Laying Hen (Gallus domesticus)

Abstract

Abstract:The laying hen (Gallus domesticus) is a robust animal model for epithelial ovarian cancer. The use of animal models is critical in identifying early disease markers and developing and testing chemotherapies. We describe the microscopic characteristics of the normally functioning laying hen ovary and proximal oviduct to establish baselines from which lesions associated with ovarian cancer can be more readily identified. Ovaries and oviducts were collected from 18-month-old laying hens (n = 18) and fixed in 10% neutral buffered formalin. Hematoxylin-and eosin-stained sections were examined by light microscopy. Both post-ovulatory follicular regression and atresia of small follicles produce remnant clusters of vacuolated cells with no histological evidence that scar tissue persists. Infiltrates of heterophils are associated with atresia of small follicles, a relationship not previously documented in laying hen ovaries. Because these tissues can be mistaken for cancerous lesions, we present a detailed histological description of remnant Wolffian tissues in the laying hen ovary. Immunohistochemical staining for pancytokeratin produced a positive response in ovarian surface epithelium and staining for vimentin produced a positive response in granulosa cells of follicles. Epithelial cells lining glands of the remnant epoöphoron had a positive response to both pancytokeratin and vimentin, a result also observed in women.

Chicken Is a Useful Model to Investigate the Role of Adipokines in Metabolic and Reproductive Diseases

“…Physiologically, only the largest preovulatory follicle ovulates every 26–28 h. The characteristics of ovarian asymmetry and preovulatory follicle hierarchy are generally believed to be at least in part reflections of weight reduction for flight [ 57 ]. In ad libitum (free access to food) fed hens, the ovarian follicular hierarchy is disorganised by multiple ovulations resulting in fertility deficiency and ovarian cancer [ 58 , 59 ]. As in mammals, steroidogenesis in preovulatory follicles occurs within multiple layers of the theca.…”

Germ cell dynamics during nest breakdown and formation of the primordial follicle pool in the domestic turkey (Meleagris gallopavo)

“…This seems to suggest that within the first 3 wk posthatch, some primordial follicles are growing or have been selected to grow while others have not. We know that this occurs in mature birds as ovaries possess follicles at all stages of development, even unrecruited primordial follicles ( Apperson et al., 2017 ). To our knowledge, this is the first evidence to suggest that certain follicles in ovaries 1 to 3 wk posthatch are being selected to grow over others, potentially meaning that the follicle hierarchy is already being established.…”

Confirmation of ovarian follicles in an enantiornithine (Aves) from the Jehol biota using soft tissue analyses

“…Therefore, it is also possible that organic remnants from the original spherical yolk and/or the inner perivitelline membrane are preserved, but extensive further analyses (using different methods such as immunohistochemistry or spectroscopy) are required to confirm this. Additionally, the most external tissue covering preovulatory follicles in extant birds is made of pancytokeratin 18 , a hydrophobic protein with a high potential for fossilization 52 . We propose that this hydrophobic molecule may have acted as a barrier and also facilitated the exceptional preservation of follicles.…”

“…If the purported follicles are indeed remnants of a PFM, they should present the same histological characteristics as the homologous tissues forming the PFM in the ovaries of extant, reproductively active birds. The PFM (or theca) surrounds the yolk-filled oocytes and links them to the ovarian medulla 18 . The three main components of a PFM are collagen fibers, smooth muscle fibers, and blood vessels 18 – 21 .…”

“…The PFM (or theca) surrounds the yolk-filled oocytes and links them to the ovarian medulla 18 . The three main components of a PFM are collagen fibers, smooth muscle fibers, and blood vessels 18 – 21 . On the other hand, the tissues forming seeds (or any type of plant material) are completely different and their cells possess a distinct cell wall absent in all animal cells 22 .…”