Endocrine Abstracts

Our initial studies suggested that plurihormonal cells are constantly found in early embryonic stages of human pituitary but are very rare later.

Aim: A quantitative evaluation and morphological characterization of these plurihormonal cells.

Methods: Pituitaries from therapeutically aborted human fetuses of 8–24 weeks, gestational age were fixed (with ethical permission) by immersion in 4% buffered formaldehyde. One-μm-thick sections of LRGold-embedded tissue and 12-μm-thick cryostat sections were incubated for immunocytochemical labeling with anti-rat GH and anti-human FSH or anti-LH primary antibodies. Primary antibodies were located with either fluorescein- or Texas red-linked secondary antibodies. Confocal microscopy was to analyze the sections. All possible combinations of primary antibodies, produced in mouse, rabbit and monkey were tested, and secondary antibodies coupled to FITC, Texas red or rhodamine, biotinylated or not. Cell density counting, digital densitometric analysis, gray level measurement, and 3D digital analysis were performed.

Results: The density of plurihormonal cells (GH with both or either FSH and LH) is maximal at 15–16 weeks (2.87±1.96 cells per microscopic field) and decreases toward 20–24 weeks (0.14±0.55) (mean±S.D.) (P<0.005). Colocalisation with GH at the early stage (8–10 weeks) was detected in 15–20% of the gonadotropin-immunoreactive cells. 3D digital analysis and gray levels confirmed specific patterns of colocalisation.

The plurihormonal cells showed occasionally cytoplasmic extensions and bridges suggesting a polyhedral lattice. High magnification of colocalising cells showed distinct immunoreactive spots for the gonadotropins and GH, suggesting that subcellular colocalisation was rarely complete. In 8–10 weeks pituitary the colocalizing cells were adjacent to peripheral blood vessels.

Conclusion: These data show that colocalisation/coexistence of GH with FSH/LH occurs in pituitary cells early during normal human ontogenesis but decreases markedly up to 20 weeks gestation. We suggest that these might be progenitor cells. The potential for colocalisation could be reactivated in adulthood during tumoral transformation.