Capillary angiogenesis and degeneration in bovine ovarian antral follicles

Abstract

Angiogenesis and capillary degeneration are both evident during ovarian follicle growth. However, the characteristics and distribution of thecal capillary proliferative and degenerative structures have not been fully defined. Indeed, the role of thecal microvasculature changes in follicular atresia is still a matter of debate. The present study examined the distribution of thecal capillary changes occurring during follicular growth and related the changes to capillary morphology (by scanning electron microscopy, SEM, on bovine ovarian corrosion casts) with the incidence of capillary apoptosis (TdT-mediated dUTP nick end-labelling, TUNEL) and follicular status (as confirmed by follicular fluid steroid concentrations). SEM demonstrated well-perfused vascular plexuses of small to large antral follicles with structural and functional changes to capillaries. Angiogenesis was evident mainly in the apical part of the inner capillary layer of medium follicles and the middle or basal part of the inner capillary layer of dominant follicles that exhibited high oestradiol:progesterone ratios. Degenerative capillaries were observed mainly in the outer vascular layers of small follicles, and in the inner and outer vascular layers of medium antral follicles. Although apoptotic structures were present only in the outer capillaries of the theca interna of morphologically healthy antral follicles, atretic follicles showed apoptotic structures in both the outer and inner thecal capillary layers. These results show that angiogenesis increases during bovine follicular growth and occurs unevenly in different inner theca regions of the follicles. The differential angiogenic and degenerative response of theca interna capillaries may reflect differences in the microenvironment of the follicles, which in turn determine the fate of the follicles (continued growth versus atresia).

Follicular blood flow, antrum growth and angiogenic mediators in mares from ovulation to deviation

“…The increased percent of color blood flow area without antrum of the selected next dominant till completed its deviation compared to the other subordinates from day 6 (3 days before deviation) till day 12 agreed with the differential blood flow velocities between dominant and subordinates that was observed 2 days earlier than diameter deviation and the continued increase of velocity in dominant and the beginning of decrease in subordinate was referred to the reduced blood velocity or vascularity in the developing subordinate follicle due to the reduced proliferation of endothelial cells in follicle capillaries and reduced theca vascularity that were early events in follicle atresia in cattle (Jiang et al, 2003) and sheep (Jablonka-Sharif et al, 1994). In mares of this study, the increased percent of blood flow vascularization area without antrum started 3 to 4 days before deviation of both diameter and area.…”

Changes in the glucose-6-phosphate dehydrogenase activity in granulosa cells during follicular atresia in ewes

“…G6PD as a supplier of NADPH is indispensable for replenishing GSH in oxidative stress conditions of diverse cells (Leopold & Loscalzo 2000, Filosa et al 2003, Jiang et al 2003. The over-expression of G6PD protects against H 2 O 2 -induced cellular death through GSH production (Salvemini et al 1999) and, by contrast, the deficiency of G6PD increases susceptibility to oxidative stress and apoptosis (Pandolfil et al 1995, Filosa et al 2003, Jiang et al 2003.…”

“…The over-expression of G6PD protects against H 2 O 2 -induced cellular death through GSH production (Salvemini et al 1999) and, by contrast, the deficiency of G6PD increases susceptibility to oxidative stress and apoptosis (Pandolfil et al 1995, Filosa et al 2003, Jiang et al 2003. This indicates that cells with high G6PD activity respond efficiently to NADPH requirements for maintaining cellular redox states, antioxidant systems, and cell survival.…”

“…In this context, glucose-6-phosphate dehydrogenase (G6PD) has been proposed as a cell enzyme aiding in survival against oxidative stress by generating NADPH required for GSH regeneration (Leopold & Loscalzo 2000, Filosa et al 2003, Jiang et al 2003, Díaz-Flores et al 2006. G6PD activity increases in growing cells and prevents cell death during oxidative stress (Tian et al 1998(Tian et al , 1999; hence, its inhibition brings about a drop in NADPH levels, a decrease in cell growth (Endo et al 1993), and an exacerbation of damage caused by free radicals (Filosa et al 2003).…”

Overlerde Anjiyogenezi Etkileyen Faktörler

“…Yapılan bazı çalışmalar anjiyogenezin, ovulasyonun meydana gelmesi için gerekli fonksiyonel adaptasyon olan vazodilatasyonu takiben oluşabildiği gibi teka tabakasının endokrin fonksiyonunun gelişimi ile de meydana gelebileceğini göstermektedir 17 . Bu yüzden, foliküler gelişim sürecinde teka hücre anjiyogenezinin önemli ölçüde etkili olduğuna dair kanıtlar bulunmaktadır 18 .…”