Apoptosis during goitre involution - the role of Bcl-2

Area of Science:

• Endocrinology
• Cell Biology
• Histology

Background:

• Goitrogenesis, characterized by thyroid hyperplasia and hypertrophy, necessitates tissue remodeling and angiogenesis.
• Thyroid involution requires removal of excess thyroid volume and further remodeling, potentially involving apoptosis.

Purpose of the Study:

• To investigate the role and mechanisms of apoptosis during the involution of goiter in a rat model.
• To analyze changes in Bcl-2 expression and apoptotic cell levels in the thyroid during goitrogenesis and involution.

Main Methods:

• Male Fisher rats were subjected to a goitrogenic regimen for 14 days, followed by withdrawal and a normal diet to induce involution.
• Thyroid weights were measured, and apoptosis was assessed using in situ end-labeling for DNA fragmentation and immunohistochemistry for Bcl-2 and apoptosis-specific protein.
• Changes were evaluated during goitrogenesis and at various time points during the involution phase.

Main Results:

• Goitrogenic regimen caused a fourfold increase in thyroid weight; involution led to significant weight reduction between days 2 and 4.
• Bcl-2 immunoreactivity, initially high, decreased significantly at 2 days of involution before returning to high levels.
• Apoptosis, indicated by DNA fragmentation, increased during goitrogenesis and peaked at 2 days of involution, primarily in stromal and vascular tissues.

Conclusions:

• Thyroid involution is associated with a rapid downregulation of Bcl-2 expression.
• Increased apoptosis, particularly within the stromal compartment, plays a crucial role in thyroid volume reduction during involution.
• These findings elucidate the cellular mechanisms governing thyroid remodeling post-goitrogenesis.