Tanycyte proliferation and migration through the sonic hedgehog pathway restores hypothalamic function after ischemic injury.

Abstract

Tanycytes, a distinct type of glial cell within the hypothalamus, will be investigated in this study to elucidate the intrinsic mechanisms by which they facilitate the restoration of hypothalamic function. We injected endothelin 1 (ET-1) into the third ventricle to establish an ischemic hypothalamic injury model. Nestin CreER^T2 and Rosa26R-CAG:tdTomato mice were crossbred, and viral tracing was used to label and track tanycytes. Functional changes in these cells were observed with calcium imaging. Alterations in tanycytes were assessed with single-cell and transcriptomic sequencing analyses. The involvement of specific pathways was confirmed via intraperitoneal injection of N-acetyl cysteine (NAC) and cycloheximide. Following ischemic injury to the hypothalamus in mice, acute weight loss and impaired activity of Agrp neurons were observed, both of which recovered within 7 days. The fate of tanycytes was traced in Nestin-CreER^T2: Rosa26R-CAG:Tdtomato mice to confirm their proliferation and migration after hypothalamic injury. Calcium imaging indicated that these proliferating and migrating cells participated in signal transduction, thereby reconstructing the regulatory network of tanycytes. The analysis of single-cell data on postnatal days 8 and 45 identified CDK1 as a marker of proliferative tanycytes. The roles of ROS and the Shh pathway in the proliferation and migration of tanycytes were validated via the intraperitoneal injection of NAC and cycloheximide inhibitors. After inducing ischemic injury to the arcuate nucleus of the hypothalamus, Agrp neuronal activity declined, accompanied by ROS fluctuations within tanycytes. Activation of the Shh pathway prompts the transition of tanycytes from a quiescent state to a proliferative state, thereby leading to their migration to the arcuate nucleus. This process re-establishes the regulatory network of tanycytes and restores metabolic balance. This finding may provide an important target for promoting the recovery of hypothalamic function.