Distribution of the Basement Membrane Components in the Rat Thyroid Gland during the pre - and postnatal Period

Kim, Hye Sook; Jung, Mi Jin; Hwang, Young Il; Jang, Ga Yong

Abstract

It is well known that the spatial patterns of basement membrane[BM] components show a close correlation with the morphogenetic process in developing organs during pre- and postnatal period. But little is known about the chronological changes in BM components during the development of thyroid gland. To investigate the correlation of the distribution of BM components with the development of the thyroid gland, immunohistochemical localization of the BM components was performed, using rat fetuses[from 15 to 21 days of gestation] and pups[from 1 to 14 days]. According to the histological features with H.E. staining, prenatal development[El5-21] of the rat thyroid could be divided into 3 representative stages : 1] Undifferentiated primordium of thyroid epithelia, forming cell cords or cell nests [until El5 day]. 2] An intervening stage of cell proliferation with the pattern of lobulation[El6-17 days]. 3] Stage of maturing follicles[El8-21 days]. It could be concluded that differentiation of the thyroid follicle are terminated during the prenatal period and growth in size and number occurs during the first two weeks after birth. By the immunohistochemical localization of laminin[LM], fibronectin[FN], type IV collagen[CIV], the basement membranes investing thyroid follicles could be clearly delineated at 15 days of gestation. Reactivity for LN and CIV associated with BM increased with advancing development, while that of FH was apparently weakened during the 2 weeks after birth. On the other hand immunoreactivity for CIV in the same age group increased, compared to that of previous swage of development. These results indicate that BM components were expressed in distinct spatial patterns with advancing development of thyroid gland. Based on these observations, it could be concluded that these BM components are important determinants in epithelial growth and differentiation during thyroid development.