A rat study on the PTEN expression in ovarian tissue in PCOS and folliculogenesis

Abstract

The objective of this investigation was to examine alterations in PTEN expression within ovarian tissue in a rat model of polycystic ovary syndrome (PCOS). The analysis also encompassed the examination of PTEN alterations in the ovarian tissue throughout the process of folliculogenesis in rats with normal ovulatory cycles. The study involved 12 adult female Sprague‒Dawley rats randomly assigned to the letrozole-induced polycystic ovary syndrome (PCOS) group as part of an animal-based research endeavour. The sections derived from the ovaries were subjected to immunohistochemical staining for PTEN. The evaluation of PTEN staining levels in ovarian tissues was conducted using electron microscopy. Follicle counts, as well as hormonal and biochemical analyses (serum luteinising hormone (LH), follicle-stimulating hormone (FSH), anti-Müllerian hormone (AMH), testosterone, oestradiol levels and serum glucose, triglyceride, HDL and LDL-cholesterol levels), were conducted to provide evidence of the manifestation of polycystic ovary syndrome (PCOS) in rats. The number of primordial and Graafian follicles in the PCOS group decreased significantly, and the number of primary, secondary and antral follicles increased significantly. PTEN expression was found to be significantly higher in the PCOS group than in the control group in the primordial follicle oocyte cytoplasm, primordial follicle granulosa cells, primary follicle oocyte cytoplasm, primary follicle granulosa cells, antral follicle oocyte cytoplasm, antral follicle granulosa cells, and corpus luteum (p = 0.007, p = 0.001, p = 0.001, p = 0.001, p = 0.001, p = 0.002, and p = 0.018, respectively). In the non-PCOS group, a time-dependent comparison of the amount of oocyte cytoplasm and PTEN staining in granulosa cells of the oocytes at different stages of development was performed. While the follicles were developing from the primordial follicle to the primary and antral follicle, the amount of PTEN staining in the oocyte cytoplasm decreased, whereas the PTEN activity in the granulosa cells increased as the oocyte developed (p = 0.001 and p = 0.001, respectively). The current investigation demonstrated changes in PTEN expression in ovarian tissue throughout the course of normal folliculogenesis, as well as in instances of disrupted folliculogenesis, with a focus on rats with PCOS.

Figure 1

IHC staining with PTEN primary antibody of ovarian tissues in the control group; Primordial follicles (red arrows), the multilaminar primary follicle (MPF), oocyte cytoplasm (white arrows), corpus luteum (CL), stroma (white star) (× 100). (Ia) Primordial follicles (red arrows) (× 400). Strong PTEN involvement was observed in the oocyte cytoplasm of the primordial follicle, and weak involvement in the granulosa cell cytoplasm surrounding the follicle. A moderate uptake was observed in the granulosa cell cytoplasm of the primary follicle growing in the surrounding area. Corpus Luteum involvement was moderate.

Figure 2

IHC staining with PTEN primary antibody of ovarian tissues in the control group; Primordial follicles (red arrows), the unilaminar primary follicle (UPF), the antral follicle (AF), corpus luteum (CL), stroma (white star) (× 100). (IIa) Unilaminar primary follicle (UPF) (× 400). PTEN involvement was strong in the oocyte cytoplasm of the primordial follicle, weak in the granulosa cell cytoplasm of the primordial follicle, and strong in the granulosa cells of the secondary and antral follicles. PTEN immune reactivity was moderate in the granulosa cells of the unilaminar primary follicle.

Figure 3

In the ovarian tissue of the control group stained with PTEN primary antibody; primordial Follicle (), Multilaminar Primary Follicle (MPF), Antral Follicle (AF), Oocyte Cytoplasm (), Corpus Luteum (CL), Stroma () (DAP—Hematoxylin × 100). (IIIa) Primordialfolicula (), Multilaminar Primer Follicle (MPF), Oocyte Cytoplasm () (DAP—Hematoxylin × 400). (IIIb) Primordial Follicle- Primary Follicle Transition () Unilaminar Primary Follicle (UPF) (DAP—Hematoxylin × 400). PTEN immunoreactivity was strong in the oocyte cytoplasm of the primordial follicle, weak in the granulosa cells surrounding the oocyte, and varying from weak to moderate in the oocyte cytoplasm of the cubic granulosa cells. PTEN involvement was moderate in the surrounding unilaminar primary follicle granulosa cells and moderate to strong in the multilaminar primary and antral follicle granulosa cells. In the corpus luteum, PTEN immunoreactivity was moderate.

Figure 4

IHC staining with PTEN primary antibody of ovarian tissues in the PCOS group; Antral follicle (AF), Graaf follicle (GF), corpus luteum (CL), Cyst (C), stroma (white star) (× 100). (Iva) Antral follicle (AF), Graaf follicle (GF), oocyte cytoplasm (white arrows), granulosa cells (black arrows), Cyst(C), stroma (white star) (× 400). Moderate PTEN involvement was observed in the oocyte cytoplasm of the antral and Graafian follicles and strong PTEN involvement was observed in the granulosa cells surrounding the oocytes in the PCOS group. Once more, strong PTEN immunoreactivity was observed in both cystic structures and the Corpus Luteum.

Figure 5

IHC staining with PTEN primary antibody of ovarian tissues in the PCOS group; Antral follicle (AF), antrum (A), cyst (C), stroma (white star) (× 100). (Va) Antral follicle (AF), the unilaminar primary follicle (UPF) (× 400). (Vb) Antral follicle (AF), granulosa cells (black arrows), Cyst(C), stroma (star) (× 400). Moderate PTEN involvement was observed in the oocyte cytoplasm of the antral follicle in the PCOS group, whereas strong PTEN involvement was observed in the granulosa cells surrounding the oocyte. Additionally, strong PTEN immunoreactivity was observed in both cystic structures and the Corpus Luteum. PTEN involvement in primordial and primary follicles was quite strong.