Development of ultrastructural abnormalities in the thymic stellate epithelial cells of weanling mice subjected to severe food intake restriction

Abstract

The purpose of the present study was to delineate the sequence of events whereby previously identified ultrastructural abnormalities develop within the thymic epithelium in severe weanling protein-energy malnutrition. Male and female CBA/J mice were subjected to wasting food intake restriction for 3, 6 or 9 days beginning at 23 days of age. Stellate thymic epithelial cells (TEC) were examined by transmission electron microscopy. TEC of restricted (R) mice were compared only to the corresponding cells of ad libitum-fed controls (C) of the same chronological age. Within 3 days cortical TEC of R mice exhibited vacuolar abnormalities consistent with initiation of impairment in hormone secreting activity, whereas medullary TEC exhibited increased number of transfer vesicles suggestive of an initial activation of secretory activity. Cytoplasmic lipid droplets appeared within cortical TEC of R mice at 3 days, and droplet size and numbers subsequently increased in parallel with the progression of thymic involution. By 9 days R mice exhibited many lipid-laden cortical and medullary TEC devoid of a vacuolar system, and all evidence of activated secretory activity within the medullary TEC was gone. Thymic epithelial hormone secretion is acutely sensitive to the stress of PEM, but the nature of the initial response to this condition differs qualitatively among the various types of TEC.