Objective: 

Maternal thyroid hormone deficiency can impair proper brain development in fetus. We aimed to explore whether neuroepithelial and mesenchymal tissue transplantation into hippocampal regions of offspring of hypothyroidic rat dams could result in successful engraftment or not, and if successful, could allograft transplantation improve cognitive performance or not.

Methods: 

Five pregnant Wistar albino rats received 10 mg/kg/day propylthiouracil via drinking water throughout pregnancy. Offspring were grown until 75 days and at this time they were divided into transplantation and sham groups. Neuroepithelial stem cell with adjacent mesenchymal tissue obtained from mesencephalic neural plate and adjacent ventral mesenchyme of 10.5-days-old embryo of pregnant rats was stereotaxically injected into hippocampus of transplantation group animals. Sham group was stereotaxically injured with a Hamilton syringe but not implanted with embryo tissue. Three weeks after transplantation (at postnatal 95th day) all rats were tested on Morris water maze and probe test for cognitive functions. After the test for cognitive functions all rats were sacrified and whole brain was examined immunohistochemically, for glial fibrillary acidic protein (GFAP) and vimentin, markers of astrocyte maturation. For all the immunohistochemical procedures, areas adjacent to the engraftment implated regions served as negative controls.

Results: 

Brain sections of transplanted animals showed marked increase of vimentin and GFAP expression in areas of stem cell implantation, implying successful engraftment. Cognitive performance of transplanted animals on Morris water maze and the probe trial was significantly better than sham controls.

Conclusions: 

Mesencephalic neural plate cells with adjacent mesenchymal tissue can successfully be implanted to cognitively impaired animals and this may help cognitive recovery of animals.