Age-related changes in ovarian morphology from birth to menopause in the Japanese monkey,Macaca fuscata fuscata

Abstract

Age-related changes in ovarian morphology were studied in female Japanese monkeys,Macaca fuscata fuscata. A total of 47 nonlactating females of various ages ranging from new-born to >28 yr old were used. Ovarian size increased during the first decade of life, reached a plateau at around 10 yr. This was followed by a gradual decline throughout the remaining life span. The ovarian cortex of new-born animals consisted of numerous clusters of mitotic primordial germ cells. Such mitotic germ cells were observed even in the ovary of 28-day-old animal, but were not found in any animal after 1.5 yr of age. Numbers of primordial follicles decreased exponentially with the advance of age, and only a few primordial follicles were observed after about 16 yr of age. The numbers of primary and tertiary follicles increased from ages 4 to 16 yr, with a peak at 8 to 10 yr, and then decreased gradually. Developing tertiary follicles were observed as early as 1.5 yr of age. About 40% of tertiary follicles were atretic follicles throughout life, and their size was similar to that of developing tertiary follicles. Corpora lutea or corpora albicantia were found in ovaries more than 4 yr old. Remnants of corpora lutea and corpora albicantia, together with thick-walled blood vessels and fibrosis, became apparent in ovaries after 16 yr, and were observed characteristically in ovaries over 26 yr of age. There was no significant difference in the number or in the size of tertiary follicles between the breeding and nonbreeding seasons.