The effect of calorie restriction on the presence of apoptotic ovarian cells in normal wild type mice and low-plasma-IGF-1 Laron dwarf mice

Abstract

Background: It is known that caloric restriction extends lifespan and can minimize age-related dysfunction of the reproductive system. We became interested in how caloric restriction influences apoptosis, which is a crucial process that maintains ovarian cell homeostasis.

Methods: We examined ovarian cells in: 2.5-year-old wild type mice on caloric restriction (CR) or fed ad libitum (AL) and Laron dwarf mice (GHR-KO) at the same ages on CR or fed AL. Apoptosis was assessed by histochemical analysis on paraffin sections of ovarian tissue.

Results: Morphological and histochemical analysis revealed that CR improved reproductive potential in 2.5-year-old WT littermates and GHR-KO female mice, as indicated by the increased number of ovarian follicles. The level of apoptosis in ovarian tissue was higher in WT mice on a CR diet compared with WT mice on the AL diet. In GHR-KO mice, the level of apoptosis in ovaries was similar for mice on CR and on AL diets and bigger than in WT mice on CR.

Conclusions: Morphological and histochemical analysis revealed a younger biological age of the ovaries in 2-year-old WT littermates and GHR-KO female mice on CR compared with animals fed AL.

Figure 1

Ovaries of WT mice. Ovaries of 2.5-year-old WT mice fed AL (panels A and C) and WT mice on CR (panels B and D). In WT mice on an AL diet (panels A and C), a cyst (asterisk) is visible that shows a positive reaction for apoptosis in a few granulosa cells (black arrow) inside the cyst and in a few stromal cells (yellow arrow) surrounding the cyst (panel C). In WT mice on caloric restriction (panels B and D), single antral follicles (AF), single Graffian follicle, enlarged interstitial tissue (IT), and macrophages (M) are visible. A positive apoptotic reaction is detectable in a few granulosa cells in apical parts (cross section) of Graffian follicle (black arrow, panels B and D). Magnification: panels A and B x40; panels C and D x400. Insert in panel D represents OSE with absence of apoptotic cells. Magnification: x800.

Figure 2

Ovaries of GHR-KO mice. Ovaries of 2.5-year-old GHR-KO mice fed AL (panels A, C, and E) and 2.5- year-old GHR-KO mice on CR (panels B, D, and F). In both groups, primordial (PRF), primary (PF), preantral (PAF), antral (AF) and Graafian (GF) follicles are visible. A positive reaction for apoptosis was detectable in granulosa cells (arrow) and in ovarian surface epithelium (arrowhead) in both groups. Interstitial cells (IT), macrophages (M). Magnification: panels A and B x40; panels C and D x200; panels E and F x400. Insert in panel E represents primordial follicles located under OSE. Magnification: x800. Insert in panel F represents OSE with positive apoptotic reaction. Magnification: x800.