Effect of Tunicamycin on Glycosaminoglycans and Laminins in Embryonic and Postnatal Thymic Tissues.

Objective: To compare histological and molecular alterations in the embryonic and neonatal thymi following exposure to tunicamycin.

Study design: Mouse embryos at gestational days 17 (n = 7) and 18 (n = 7) and newborn animals at post-natal days 1 (n = 5) and 3 (n = 5) were divided into two groups: control and tunicamycin-treated. Combined Alcian blue and Periodic acid-Schiff sequences immunohistochemistry and immunoblotting were performed to determine glycosaminoglycan (GAG) accumulation and laminin expression in control and tunicamycin-treated embryonic and postnatal thymi. The apoptotic effect of tunicamycin was evaluated by TUNEL assay.

Results: In the control group acidic GAGs first appeared in medullary cells at postnatal day 3, whereas treatment with tunicamycin promoted the accumulation of acidic GAGs in all treated groups as of embryonic day 17. However, tunicamycin slightly decreased the laminin expression, and the number of apoptotic cells was considerably increased after tunicamycin treatment.

Conclusion: Results suggest that carboxylated and acidic GAGs are two presumptive candidates to establish the thymic microenvironment during the late fetal development and postnatal periods of mice and that tunicamycin would be implicated in this establishment by increasing the acidic GAG accumulation and by reducing the laminin expression and the thymic stromal cell population.