Age-dependent induction of nestin expression in paraventricular and supraoptic nuclei after hypophysectomy

Abstract

This study examined the expression of nestin in the neurohypophyseal system during the development and after hypophysectomy. The potential role of nestin expression in both normal developing and following injury was also studied. In normal non-injured and sham operated animals, the distribution of nestin positive cells changes with ages. At postnatal day 1 (P1) nestin positive cells and fibers present densely in almost all areas of the hypothalamus. In adult animals, nestin posive cells and fibers are restricted to a narrow area, including the walls of the third ventricle and median eminence (ME). Following hypophysectomy in developing (P14) rats, the expression of nestin slightly increases in both the supraoptic nucleus (SON) and the paraventricular nucleus (PVN). The nestin positive cells display appearance of stellate-shaped astrocytes. In contrast, following hypophysectomy in adult rats, the expression of nestin significantly increases. Strongly immonostained nestin positive cells are observed in SON by 1 week, peak at 2 weeks, and persist for at lease 4 weeks post-injury. These nestin positive cells are glialike cells that exhibit elongated processes, morphologically compatible with radial glia. Moreover, some nestin positive cells are also detected in the posterior part of paraventricular nucleus (PVN) which display appearance of stellate-shaped astrocytes. There is no obvious increase of nestin immunoreactivity in both the walls of the third ventricle and ME in both P14 and adult animals following hypophysectomy as compared with the corresponding sham operated controls. The age- and region-dependent alterations of nestin immunoreactivity in response to the hypophysectomy in hypothalamoneurohypophyseal system may be critical in modulating neural repair and regeneration after hypophysectomy.