Background Histological Lesions in Aged African Green Monkeys (Chlorocebus sabaeus) From St. Kitts

The Caribbean African Green Monkey (Chlorocebus sabaeus) (AGM) represents a valuable nonhuman primate model for the study of age-related pathology, with an average lifespan of over 20 years. We describe histological background and common lesions in 44 aged AGMs, >15 years, 20 males and 24 females, 26 colony-born and 18 wild-caught from a primate research facility. The most frequent cardiovascular lesion was myocardial fibrosis (54.5%), characterized by multifocal myocardial fibrosis, cardiomyocyte degeneration/necrosis, lipofuscin accumulation, and frequent concurrent vascular hyalinization affecting small to medium-sized arteries across multiple organs. Chronic kidney disease was highly prevalent, marked by lymphoplasmacytic infiltration, interstitial and glomerular fibrosis, tubular degeneration, mineralization, and calcium oxalate crystal deposition; unique renal findings included intratubular iron concretions with foreign body reactions. Hepatic lesions were dominated by lymphoplasmacytic infiltration and widespread hemosiderosis, indicating systemic iron overload. In the respiratory system, silica-laden macrophages (SLM) were the most common finding, alongside diverse forms of pneumonia and occasional cryptogenic organizing pneumonia. Additional aging-related changes included adrenal nodular hyperplasia, uterine pregnancy-associated vascular remodeling (PAVR) (uterine hyaline deposits), and Sarcocystis infection in skeletal muscle. This retrospective, descriptive study provides initial data on age-related background histopathology in the aged AGM.