Polyclonal origin of hormone-producing cell populations evaluated as a direct in situ demonstration in EGFP/BALB/C...

We report the first demonstration of the embryonal patch patterns of endocrine organs and the polyclonality of hormone-producing cell populations using chimeric mice produced by aggregation of C57BL/6-Tg(CAG-EGFP)C14-Y01-FM131Osb transgenic mice and BALB/C mice. Confocal laser scanning microscopy (CLSM) analysis for enhanced green fluorescent protein (EGFP) and immunohistochemistry with anti-EGFP antibody revealed that all endocrine organs of chimeric mice had a mosaic appearance of EGFP-positive patches and EGFP-negative patches. The patches composed of EGFP-positive cells were distinctive in their size and shape. The pituitary patches were large and irregular, representing a geographical pattern. In contrast, parathyroid, pancreatic islet, and adrenal medulla patches were small and demarcated, representing an island-like pattern. Thyroid follicles and adrenal cortex cords showed a mixture of monophenotypia and polyphenotypia, indicating polyclonal embryonic origin. Furthermore, we studied the tissue clonality of hormone-producing cell populations in the pituitary, thyroid, and pancreatic islets using a combination method of CLSM for EGFP and immunohistochemistry for hormones. All the pituitary cell populations of GH, prolactin, TSH, FSH, LH, and ACTH, the calcitonin-producing cell population in the thyroid, and the insulin- and glucagon-producing cell populations in pancreatic islets had mosaic patterns in EGFP expression in the chimeric mice, suggesting polyclonal embryonic origin. In conclusion, the different patch patterns of the endocrine organs could contribute to the understanding of embryonic development and organization of endocrine organs. Furthermore, we clearly demonstrate that all hormone-producing cell populations are of polyclonal embryonic origin, derived from more than two progenitor cells.