Apoptosis in thyroid tissue from patients with Hashimoto's thyroiditis

Area of Science:

• Endocrinology
• Immunology
• Cell Biology

Background:

• Autoimmune thyroiditis, specifically Hashimoto's thyroiditis, is characterized by chronic inflammation and gradual destruction of thyroid tissue.
• The precise mechanisms driving thyroid follicular cell loss in Hashimoto's thyroiditis are not fully understood, particularly the role of programmed cell death.

Purpose of the Study:

• To investigate the presence and extent of apoptosis in thyroid follicular epithelial cells within Hashimoto's thyroiditis tissue.
• To correlate the incidence of apoptosis with histological features of autoimmune thyroiditis.

Main Methods:

• Analysis of 17 thyroid tissue specimens from patients with Hashimoto's thyroiditis.
• Staining for fragmented DNA to detect apoptotic cells.
• Electron microscopy to identify cellular morphological changes consistent with apoptosis.
• Quantitative assessment of DNA fragmentation in relation to proximity to lymphoid infiltrates and fibrosis.

Main Results:

• Widespread positive staining for fragmented DNA was observed in follicular epithelial cells, particularly those in atrophic follicles adjacent to mononuclear cell infiltration and fibrosis.
• The percentage of follicular epithelial cells with DNA fragmentation decreased with increasing distance from lymphoid cell aggregates, ranging from 30-80%.
• Electron microscopy confirmed the presence of epithelial cells exhibiting nuclear condensation and shrinkage, consistent with apoptotic morphology, correlating well with DNA fragmentation findings.

Conclusions:

• Apoptosis is a significant contributor to thyroid follicular epithelial cell death in Hashimoto's thyroiditis.
• The spatial distribution of apoptosis suggests a link between immune cell infiltration and the induction of programmed cell death in thyroid tissue.
• These findings highlight apoptosis as a critical mechanism underlying tissue injury in autoimmune thyroid disease.