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Proliferation and differentiation of pituitary corticotrophs during the fetal and postnatal period: a quantitative
Y Taniguchi1, R Kominami, S Yasutaka
1Department of Anatomy, Kanazawa Medical University, Ishikawa, Japan. yuh-tani@kanazawa-med.ac.jp
Insights
Pituitary corticotroph development involves both new cell differentiation and existing cell proliferation. This study tracks the origins of these crucial hormone-producing cells in developing rats.
Area of Science:
- Endocrinology
- Developmental Biology
- Cell Biology
Background:
- Pituitary corticotrophs are vital for stress response.
- Understanding their development is key to pituitary function.
Purpose of the Study:
- To investigate the proliferation and differentiation of pituitary corticotrophs during rat development.
- To determine the origins of new corticotrophs.
Main Methods:
- Administered bromodeoxyuridine (BrdU) to pregnant rats and pups.
- Immunostained pituitary sections for BrdU and adrenocorticotropic hormone (ACTH).
- Quantified proliferating cells, corticotrophs, and double-labeled cells.
Main Results:
- Corticotrophs first appeared in fetuses at 15.5 days.
- Proliferating cells were abundant throughout development.
- Double-labeled cells (proliferating and corticotrophs) emerged by 17.5 days, increasing significantly by 19.5 days.
Conclusions:
- Early corticotroph development relies on differentiation from undifferentiated cells.
- Later fetal and early postnatal development involves proliferation of existing corticotrophs.
- A fraction of proliferating cells differentiate into corticotrophs when needed.
Abstract:
To study the proliferation and differentiation of pituitary corticotrophs, we administered bromodeoxyuridine (BrdU) to pregnant rats at 15.5-21.5 days of gestation and to rat pups at 3, 7, and 28 days after birth. The pituitary sections of fetuses and pups were consecutively immunostained with anti-BrdU and anti-adrenocorticotropic hormone (ACTH) to detect proliferating cells and corticotrophs, respectively. The number of cells labeled with BrdU, ACTH, or both were counted. The diameters of their nuclei and the volume of the pituitary were measured. The BrdU-positive cells were around 76,000-96,000/mm3 during the period studied. The corticotrophs were first detected in the fetus at 15.5 days and they increased during the fetal and postnatal periods. The double-labeled cells were first detected in the 17.5-day fetus. They increased markedly at 19.5 days and comprised about one-quarter of the corticotrophs that increased in 24 h at this stage. These results indicate that: (1) at 15.5-18.5 days the corticotrophs were derived almost exclusively from undifferentiated cells; (2) during the later fetal and early postnatal periods, the proliferation of existing corticotrophs contributed, at least in part, to their increase; (3) about 1/20 of proliferating cells differentiated to corticotrophs when their increase was required.