Potential role of tanycyte-derived neurogenesis in Alzheimer's disease

Tanycytes, specialized ependymal cells located in the hypothalamus, play a crucial role in the generation of new neurons that contribute to the neural circuits responsible for regulating the systemic energy balance. The precise coordination of the gene networks controlling neurogenesis in naive and mature tanycytes is essential for maintaining homeostasis in adulthood. However, our understanding of the molecular mechanisms and signaling pathways that govern the proliferation and differentiation of tanycytes into neurons remains limited. This article aims to review the recent advancements in research into the mechanisms and functions of tanycyte-derived neurogenesis. Studies employing lineage-tracing techniques have revealed that the neurogenesis specifically originating from tanycytes in the hypothalamus has a compensatory role in neuronal loss and helps maintain energy homeostasis during metabolic diseases. Intriguingly,metabolic disorders are considered early biomarkers of Alzheimer's disease. Furthermore,the neurogenic potential of tanycytes and the state of newborn neurons derived from tanycytes heavily depend on the maintenance of mild microenvironments, which may be disrupted in Alzheimer's disease due to the impaired blood–brain barrier function.However, the specific alterations and regulatory mechanisms governing tanycyte-derived neurogenesis in Alzheimer's disease remain unclear. Accumulating evidence suggests that tanycyte-derived neurogenesis might be impaired in Alzheimer's disease, exacerbating neurodegeneration. Confirming this hypothesis, however, poses a challenge because of the lack of long-term tracing and nucleus-specific analyses of newborn neurons in the hypothalamus of patients with Alzheimer's disease. Further research into the molecular mechanisms underlying tanycyte-derived neurogenesis holds promise for identifying small molecules capable of restoring tanycyte proliferation in neurodegenerative diseases. This line of investigation could provide valuable insights into potential therapeutic strategies for Alzheimer's disease and related conditions.

Neural progenitor cells but not astrocytes respond distally to thoracic spinal cord injury in rat models

Traumatic spinal cord injury （SCI） is a detrimental condition that causes loss of sensory and motor function in an individual. Many complex secondary injury cascades occur after SCI and they offer great potential for therapeutic targeting. In this study, we investigated the response of endogenous neural progenitor cells, astrocytes, and microglia to a localized thoracic SCI throughout the neuroaxis. Twenty-five adult female Sprague-Dawley rats underwent mild-contusion thoracic SCI （n = 9）, sham surgery （n = 8）, or no surgery （n = 8）. Spinal cord and brain tissues were fixed and cut at six regions of the neuroaxis. Immunohistochem- istry showed increased reactivity of neural progenitor cell marker nestin in the central canal at all levels of the spinal cord. Increased reactivity of astrocyte-specific marker glial fibrillary acidic protein was found only at the lesion epicenter. The number of activated microglia was significantly increased at the lesion site, and activated microglia extended to the lumbar enlargement. Phagocytic microglia and macrophages were significantly increased only at the lesion site. There were no changes in nestin, glial fibrillary acidic protein, microglia and macrophage response in the third ventricle of rats subjected to mild-contusion thoracic SCI compared to the sham surgery or no surgery. These findings indicate that neural progenitor cells, astrocytes and microglia respond differently to a localized SCI, presumably due to differences in inflammatory signaling. These different cellular responses may have implications in the way that neural progenitor cells can be manipulated for neuroregeneration after SCI. This needs to be further investigated.

Adult brain neural stem cells: technological and translational advances

Understanding the role of adult neural stem cells in maintaining specific brain function is a rapidly expanding research field. Recent technological advances to culture and trace neural stem cells, such as stem cell isolation and expansion and inducible transgenic lineage tracing mouse models, have enabled more in-depth studies into the mechanisms governing neural stem cell homeostasis and pathophysiology in the adult brain. In this review we will briefly discuss the types and locations of adult neural stem cells in the mammalian brain, recent developments in tools used to study these cells, and the translational implications.

Fabrication and characterisation of random and aligned electrospun scaffolds to investigate hypothalamic stem/progenitor cell behaviour

Tanycytes are stem/progenitor cells that reside in the hypothalamus of the adult vertebrate brain.Tanycytes can be cultured as free-floating neurospheres in vitro but tend to spontaneously differentiate over time.Here we asked whether morphological cues provided by engineered polymer scaffolds can modify spontaneous differentiation.Tanycyte-derived neurospheres were cultured on electrospun scaffolds,prepared with either random or aligned fiber morphologies.Cells dispersed widely on the scaffolds,and-on aligned scaffolds-were highly organized,orientated parallel to the fibers.Immunocytochemical analysis showed that cells cultured on aligned scaffolds showed significantly greater expression of the neural stem/progenitor cell marker,NrCAM and reduced expres-sion of differentiated cell markers in comparison to those cultured on random scaffolds.Together this shows that tanycytes respond to local engineered cues,and that a morphologically constrained environment can better main-tain tanycytes as stem cells.The aligned scaffold culture system provides a powerful tool to better investigate this novel stem/progenitor cell population.

Two Cases of Spinal Tanycytic Ependymoma Associated with Neurofibromatosis Type 2

INTRODUCTION Tanycytic ependymoma is a rare subtype of the World Health Organization Grade il ependymoma most commonly found in the cervical and thoracic segments of the spinal cord. Spinal tumors in neurofibromatosis type 2 （NF-2） can be intramedullary, extramedullary, or associated with the nerve roots, and there may be multiple tumors at multiple locations in the spine.