Histological characterization of major internal organs in infant common marmosets (Callithrix jacchus)

The common marmoset (Callithrix jacchus) is a widely used nonhuman primate model in biomedical research. However, access to infant tissues is limited, and descriptive histological information for early postnatal organ development is needed. We examined a qualitative, descriptive histological overview of five major organs (liver, kidney, spleen, lung and heart) in infant (0-3 weeks) and adult (>12 months) marmosets using hematoxylin and eosin, Ki67 immunohistochemistry, Alcian blue-periodic acid-Schiff, and Sirius red staining. The examined infant livers showed multilayered hepatocyte cords, higher nuclear-to-cytoplasmic ratios, and extramedullary hematopoiesis, and the adult livers exhibited organized hepatic plates and mature stromal structures. The infant kidneys demonstrated active nephrogenesis with immature nephrons, showing progressively more mature glomerular morphology in adults. The spleen displayed small and poorly developed white pulp in infants but fewer, larger, and distinct white pulp structures in adults. The lungs showed thick interalveolarsepta and irregular airspaces during the early postnatal stages, with progressive septal thinning and expanded airspaces in maturity. The infant hearts exhibited loosely packed cardiomyocytes and developing valves, with the adult hearts showing hypertrophied, striated myocardium and compact collagenous valve structures. This study provides descriptive histological information for interpreting developmental features in infant marmosets and supports the use of these data in developmental primate pathology.