Ovarian transcriptome associated with reproductive senescence in the long-living Ames dwarf mice

Abstract

The aim of the current work was to evaluate the ovarian follicle reserve and the ovarian transcriptome in Ames dwarf (df/df) mice. The results suggest a delayed ovarian aging in df/df mice compared to normal (N) mice. Although a high number of genes were differentially expressed during aging of N mice, only a small fraction of these changed with aging in df/df mice. These alterations involved more than 500 categorized biological processes. The majority of these biological processes, including inflammatory/immune responses, were up-regulated with aging in N mice, while old df/df mice were characterized by down-regulation of these same processes in comparison to age matched N mice. However, biological processes related to DNA damage and repairing were commonly down-regulated with aging in both genotypes. In conclusion, delayed ovarian aging in long-living df/df mice was associated with reduced expression of genes related to the inflammatory and immune responses.

Keywords: GH; IGF; Ovarian aging; Transcriptome; mRNA.

Figure 1

Number of primordial, primary, secondary and tertiary follicles in the ovaries of 12 mo-old Ames dwarf (df/df) and Normal (N) mice. Differences at P<0.05 were considered as significant.

Figure 2

Detailed histological images of each follicle stage (primordial, primary, secondary, and tertiary) and whole ovarian sections for Ames dwarf and Normal mice. The diameter of oocytes enclosed in primordial follicles was smaller in Ames dwarf than Normal mice. No further histological differences were observed between genotypes. O – oocyte, ON – oocyte nuclei, GC – granulosa cells, TC - theca cells, A – antrum, CL – corpus luteum, TF – tertiary follicle.

Figure 3

Principal components analysis of the 500 most variable ovarian expressed mRNAs Ames dwarf (n=9; Young – DY dark blue; Old – DO light blue) and Normal mice (n=10; Young – NY dark green; Old – NO light green) (Panel A). Unsupervised hierarchical clustering of expression levels for the top 200 most expressed genes in ovaries of df/df (n=9; Young – DY and Old – DO) and N mice (n=10; Young – NY and Old – NO) (Panel B).

Figure 4

Number of differentially expressed genes (DEGs) between Ames dwarf (df/df) mice with aging (22 vs 6 mo; A), and between aged (22 mo old) and young (6 mo old) df/df and Normal (N) mice (B). Number of regulated gene ontology (GO) biological process (BP) terms between df/df mice with aging (22 vs 6 mo; C), and between aged (22 mo old) and young (6 mo old) df/df and N mice (D).

Figure 5

Schematic representation of the regulated set of genes between old Normal (N) and young N mice (22 vs 6 mo) and between Ames dwarf (df/df) and N mice at old age (22 mo. IGF-I – insulin-like growth factor type I, IGFR – insulin-like growth factor receptor, TLR – toll like receptor, IRAK - IL-1 Receptor-Associated Kinases, NFκB – nuclear factor kappa B, IκB – inhibitor of κB, TNF – tumor necrosis factor alpha, IL-1β – interleukin 1 beta, PI3K - phosphatidylinositide 3-kinase, AKT – protein kinase B, PKA – protein kinase B, CYCB2 – cyclin B2, CDK1 - cyclin-dependent kinase 1, TGFβR – transforming growth factor beta receptor. Orange arrows indicate genes changed with age in Normal (N) mice and blue arrows indicate genes changed in old (22 mo) df/df compared to old N mice.