Cell & Stem Cell Research

Neurogenesis from endogenous neural stem cells might contribute to functional recovery after brain injury. In this regard, the current study is focused on understanding the axonal injury induced neurogenesis at the supraependymal region of the third ventricle in rat using light and electron microscopy. The floor of the infundibulum is lined by a non-ciliated ependyma. Presence of supraependymal cells (SEC) and supraependymal nerve fibers (SEN) that are immersed in the cerebrospinal fluid is a prominent feature of the ventricular floor. In this study retrograde neuronal tracers, fast blue and fluorogold were used to understand the origin of SEN. For monitoring contralateral collateral sprouting and the changes in the SEC following unilateral cervical sympathectomy, sixteen Wistar rats weighing 150-200g were divided into four groups. Group I was used as normal control, group II and III for unilateral and bilateral cervical sympathectomy respectively and group IV as sham control. Fourteen days after the experiment, the ventricular floor was studied. For microscopic analysis, the animals were perfused under anesthesia transcardially with 3% glutaraldehyde and the brains were dissected out and processed. The SEN consist of a mixture of cholinergic, serotonergic and peptidergic nerve fibers. Retrograde tracer analysis showed that at least some of the SEN could originate from the superior cervical ganglia. Fourteen days after unilateral cervical sympathectomy, there was a profound increase in the number of SEN and supraependymal neurons of the infundibular floor. From these studies, it can be concluded that SEC of the third ventricular floor represent another neural stem cell niche that are induced to proliferate and differentiate following axotomy of the SEN.