Distribution of Cytochrome P450‐side Chain Cleavage in the Theca Interna Layers of Bovine Small Antral and Cystic Follicles

Abstract

Cystic follicle is anovulatory follicular structure that is caused by an endocrine imbalance. The activity of cytochrome P450-side chain cleavage (P450scc) is essential for the initiation of steroidogenesis in the follicle. The present study was designed to compare the frequency of cells containing P450scc between healthy and atretic small antral follicles, and among several types (I, II and III, classified based on the presence of granulosa layer) of cystic follicles. Paraffin sections of healthy (2-5 mm in diameter), atretic (2-5 mm) and cystic follicles (>25 mm) were immunohistochemically stained with rabbit polyclonal antibody to bovine P450scc. The P450scc-positive cells were counted in four different regions of the follicles from the apical to the basal side. In small antral follicles and cystic follicles, P450scc-positive cells were localized in the theca interna layers but not granulosa layers. The P450scc-positive cell populations decreased in the late atretic follicles compared with the early and advanced atretic follicles at all the regions of follicle. Type III cystic follicles showed significantly lower frequencies of P450scc-positive cells than those in the types I and II cystic follicles. These results suggest that in both small and cystic follicles in cows, total loss of granulosa cells may be associated with the reduction of frequency of P450scc-positive cells in theca interna layer.

Cholesterol Side-Chain Cleavage Cytochrome P450 and 3β-Hydroxysteroid Dehydrogenase Expression and the Concentrations of Steroid Hormones in the Follicular Fluids of Different Phenotypes of Healthy and Atretic Bovine Ovarian Follicles1

“…Granulosa cell expression of the steroidogenic enzymes SCC and 3␤-HSD occurred when healthy bovine follicles reached 10 mm in diameter. This is consistent with the previous findings of no detectable SCC in granulosa cells in 2-5-mm follicles [25] and of increased 3␤-HSD mRNA expression in granulosa cells from follicles of increasing size [26]. However, previous studies have detected mRNA for SCC in granulosa cells of follicles [27,28] far smaller in diameter than when the SCC protein was first detected here.…”

Expression of steroidogenic enzymes in porcine polycystic ovaries.

“…The positive reaction for P450 scc and P450 arom was also observed in both granulosa and theca interna layers of small follicles (with exception of the presence of P450 scc in granulosa cells of the CON group) in all animals, but the intensity of immunolabelling to P450 scc in theca interna cells, and to P450 arom in granulosa cells was stronger after DXM treatment. Similar localization of P450 scc was described earlier in the follicular structures from polycystic ovaries of women [6], whereas in cows the P450 scc reaction was presented only in the theca interna cells of cysts [8]. However, the higher intensity of the immunoreaction for P450 scc in the theca interna layer of cysts and follicles is in line with Jakimiuk et al [36] earlier study where they have found an increase in the P450 scc mRNA expression in the theca interna cells of follicles in the women with COD.…”

“…It has previously been reported that alterations in the content of steroid hormones in the cystic ovaries of women [5,6], rat [7] and cow [8] was accompanied by changes in the expression and cellular distribution pattern of cholesterol side-chain cleavage cytochrome (P450 scc ), 3β-hydroxysteroid dehydrogenase (3β-HSD), 17,20-lyase, 20α-HSD and/or aromatase cytochrome (P450 arom ). Furthermore, our pilot study showed that dexamethasone (DXM) injections in gilts from day 16 of the first studied estrous cycle until day 9 of the second studied cycle, lead to changes in the of P450 scc , 3β-HSD and P450 arom protein expression, as well as in the content of progesterone (P 4 ), androgens and estrogens in ovarian structures [9].…”

Deficient Proliferation and Apoptosis in the Granulosa and Theca Interna Cells of the Bovine Cystic Follicle

“…Follicular cysts are reportedly caused by an endocrine imbalance in the hypothalamo-hypophyseal-gonadal axis [2][3][4]. Inappropriate productions of LH, steroid hormones and steroid synthesizing enzymes have been observed in cows with cystic follicles [3][4][5][6][7][8][9][10]. Delay of follicle regression after ovulation disorder is alternative cause of cysts [4] because a preovulatory follicle that cannot be ovulated will not grow further if it regresses immediately; therefore, no cystic follicle will be formed.…”