Tissue remodelling in the adrenal gland

Area of Science:

• Endocrinology
• Cell Biology
• Histology

Background:

• Adrenal gland adaptation involves complex functional and structural regulation.
• Classical theories on adrenal zonation (migrational, zonal, transformation field) attempt to explain structure, proliferation, and cell death.
• Recent data necessitate a re-evaluation of these theories in light of apoptosis and cell renewal.

Purpose of the Study:

• To revisit classical theories of adrenal zonation using updated data on cell death and renewal.
• To investigate the role of programmed cell death (apoptosis) in adrenal gland homeostasis and zonation.
• To explore the regulatory mechanisms of apoptosis and proliferation within different adrenal zones.

Main Methods:

• Immunoreactivity for FAS (CD 95), an apoptosis-inducing receptor.
• In situ end labeling of fragmented DNA.
• Ultrastructural analyses.
• Assessment of angiotensin II receptor subtypes.
• Analysis of proto-oncogene expression (c-jun, c-fos, jun-B, c-myc).
• Detection of proliferation markers (proliferating cell nuclear antigen, Ki-67).
• Evaluation of class II major histocompatibility complex expression.

Main Results:

• Programmed cell death (apoptosis) occurs throughout the entire adrenal gland.
• Angiotensin II receptor subtypes modulate tissue homeostasis through proliferative and antiproliferative effects.
• Proto-oncogenes regulate cell cycle and apoptosis; adrenocorticotropin influences these via specific proto-oncogenes.
• Proliferation markers are found in zones of expected cell senescence.
• Class II MHC expression facilitates immune system communication and may trigger Fas/Fas-ligand-mediated regression.

Conclusions:

• New data reconcile classical theories of adrenal zonation.
• Apoptosis is a physiological process with differential regulation across adrenal zones.
• Investigating apoptosis mechanisms can elucidate fundamental principles of adrenal zonation.