Spatial and temporal changes in follicle distribution in the human ovarian cortex

Area of Science:

• Reproductive biology
• Human embryology
• Ovarian histology

Background:

• Follicle distribution is crucial for understanding ovarian reserve and reproductive potential.
• The spatial organization of follicles in the human ovarian cortex changes throughout a woman's reproductive lifespan.
• Previous research has not fully elucidated the age-related evolution of follicle distribution patterns.

Purpose of the Study:

• To investigate how follicle distribution evolves in the human ovarian cortex between the ages of 20 and 35 years.
• To analyze the spatial patterns of primordial and transitory follicles in relation to age.
• To explore potential mechanisms driving follicle distribution.

Main Methods:

• Quantitative histological assessment of human ovarian cortex tissue fragments.
• Recording two-dimensional coordinates of follicles within samples.
• Analysis of spatial statistical methods to determine follicle distribution patterns.
• Inclusion of samples from 14 women aged 20-35 years undergoing fertility preservation.

Main Results:

• Primordial and transitory follicles exhibit a clustered distribution in the ovarian cortex (average cluster radius ~270 µm).
• Follicle density declines with age, while the distance between neighboring follicles increases.
• Cluster radius decreases with age, but the degree of clustering tends to increase.
• Follicles at different developmental stages are typically found in separate clusters.

Conclusions:

• Primordial and transitory follicles are organized in distinct clusters within the human ovarian cortex.
• Spatio-temporal simulations suggest interfollicular signals may promote clustered distribution and reduce follicle loss.
• Clinical assessment of ovarian reserve should consider a woman's age due to age-related changes in follicle distribution and clustering.