Spontaneous Reproductive Tract Lesions in Aged Captive Chimpanzees

Abstract

Chimpanzees (Pan troglodytes) have served as an important model for studies of reproductive diseases and aging-related disorders in humans. However, limited information is available about spontaneously occurring reproductive tract lesions in aging chimpanzees. In this article, the authors present histopathologic descriptions of lesions identified in the reproductive tract, including the mammary gland, of 33 female and 34 male aged chimpanzees from 3 captive populations. The most common findings in female chimpanzees were ovarian atrophy, uterine leiomyoma, adenomyosis, and endometrial atrophy. The most common findings in male chimpanzees were seminiferous tubule degeneration and lymphocytic infiltrates in the prostate gland. Other less common lesions included an ovarian granulosa cell tumor, cystic endometrial hyperplasia, an endometrial polyp, uterine artery hypertrophy and mineralization, atrophic vaginitis, mammary gland inflammation, prostatic epithelial hyperplasia, dilated seminal vesicles, a sperm granuloma, and lymphocytic infiltrates in the epididymis. The findings in this study closely mimic changes described in the reproductive tract of aged humans, with the exception of a lack of malignant changes observed in the mammary gland and prostate gland.

Keywords: biological aging; chimpanzee; female; genital organs; leiomyoma; male; mammary glands; pathology; uterine.

Figures 1–3. Ovarian atrophy, chimpanzee. Hematoxylin and eosin (HE). Figure 1. 45-year-old. There is an absence of primordial follicles within the cortex. Figure 2. 42-year-old. Remaining primordial follicles are situated in clusters within the ovarian cortex. Figure 3. 44-year-old. Frequent vessels within the ovary exhibit wall thickening and hyalinization. Figure 4. Follicular cyst, ovary, chimpanzee, 43 years old. A cyst is present within the ovarian cortex. HE. Figure 5. Ovary, chimpanzee, 47 years old. There are multifocal clusters of hemosiderophages and free hemosiderin within the ovarian cortex. HE. Figures 6 and 7. Granulosa cell tumor, ovary, chimpanzee, 41 years old. HE. Figure 6. Neoplastic cells are arranged in nests and often form rosette-like structures that surround eosinophilic hyaline material (Call-Exner bodies). Figure 7. Polygonal to columnar cells have variably distinct cell borders and a moderate amount of vacuolated pale eosinophilic cytoplasm. Figures 8 and 9. Leiomyoma, uterus, chimpanzee, 47 years old. HE. Figure 8. The neoplasm in the endometrium is composed of interlacing bundles of smooth muscle cells. Figure 9. Neoplastic cells are characterized by an elongate nucleus with coarsely stippled chromatin and an elongated, spindyloid, eosinophilic cell body. Figures 10 and 11. Leiomyoma, uterus, chimpanzee, 41 years old. Figure 10. Osseous metaplasia is present in this leiomyoma, surrounded by necrotic tissue at the center of the mass. Hematoxylin and eosin (HE). Figure 11. A large cervical leiomyoma protrudes into the vagina and led to heavy bleeding. Figure 12. Adenomyosis, uterus, chimpanzee, 43 years old. Clusters of endometrial glands and surrounding stroma within the myometrium. HE. Figure 13. Endometrial atrophy, uterus, chimpanzee, 44 years old. Atrophic endometrium with fluid-filled, dilated, and irregularly oriented glands. HE. Figure 14. Arterial hypertrophy and mineralization, uterus, chimpanzee, 41 years old. Uterine artery with thickened and mineralized arterial wall. HE. Figures 15 and 16. Testicular atrophy, chimpanzee, 47 years old. HE. Figure 15. There is variable loss of the seminiferous tubular epithelium and spermatids with some sclerotic tubules. Figure 16. There is diffuse atrophy of the seminiferous tubular epithelium with no sperm present, sclerosis of the tubules, and fibrosis of the interstitium but with preservation of some of the interstitial cells. HE. Figure 17. Lymphocytic infiltrates, prostate gland, chimpanzee, 37 years old. There is periglandular lymphocytic infiltration, neutrophils within glands, and periglandular fibrosis. HE. Figure 18. Prostatic glandular epithelial hyperplasia, chimpanzee, 37 years old. There is multifocal hyperplasia of basaloid cells. HE.

Figures 1–3. Ovarian atrophy, chimpanzee. Hematoxylin and eosin (HE). Figure 1. 45-year-old. There is an absence of primordial follicles within the cortex. Figure 2. 42-year-old. Remaining primordial follicles are situated in clusters within the ovarian cortex. Figure 3. 44-year-old. Frequent vessels within the ovary exhibit wall thickening and hyalinization. Figure 4. Follicular cyst, ovary, chimpanzee, 43 years old. A cyst is present within the ovarian cortex. HE. Figure 5. Ovary, chimpanzee, 47 years old. There are multifocal clusters of hemosiderophages and free hemosiderin within the ovarian cortex. HE. Figures 6 and 7. Granulosa cell tumor, ovary, chimpanzee, 41 years old. HE. Figure 6. Neoplastic cells are arranged in nests and often form rosette-like structures that surround eosinophilic hyaline material (Call-Exner bodies). Figure 7. Polygonal to columnar cells have variably distinct cell borders and a moderate amount of vacuolated pale eosinophilic cytoplasm. Figures 8 and 9. Leiomyoma, uterus, chimpanzee, 47 years old. HE. Figure 8. The neoplasm in the endometrium is composed of interlacing bundles of smooth muscle cells. Figure 9. Neoplastic cells are characterized by an elongate nucleus with coarsely stippled chromatin and an elongated, spindyloid, eosinophilic cell body. Figures 10 and 11. Leiomyoma, uterus, chimpanzee, 41 years old. Figure 10. Osseous metaplasia is present in this leiomyoma, surrounded by necrotic tissue at the center of the mass. Hematoxylin and eosin (HE). Figure 11. A large cervical leiomyoma protrudes into the vagina and led to heavy bleeding. Figure 12. Adenomyosis, uterus, chimpanzee, 43 years old. Clusters of endometrial glands and surrounding stroma within the myometrium. HE. Figure 13. Endometrial atrophy, uterus, chimpanzee, 44 years old. Atrophic endometrium with fluid-filled, dilated, and irregularly oriented glands. HE. Figure 14. Arterial hypertrophy and mineralization, uterus, chimpanzee, 41 years old. Uterine artery with thickened and mineralized arterial wall. HE. Figures 15 and 16. Testicular atrophy, chimpanzee, 47 years old. HE. Figure 15. There is variable loss of the seminiferous tubular epithelium and spermatids with some sclerotic tubules. Figure 16. There is diffuse atrophy of the seminiferous tubular epithelium with no sperm present, sclerosis of the tubules, and fibrosis of the interstitium but with preservation of some of the interstitial cells. HE. Figure 17. Lymphocytic infiltrates, prostate gland, chimpanzee, 37 years old. There is periglandular lymphocytic infiltration, neutrophils within glands, and periglandular fibrosis. HE. Figure 18. Prostatic glandular epithelial hyperplasia, chimpanzee, 37 years old. There is multifocal hyperplasia of basaloid cells. HE.