Ependyma
| Ependyma | |
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| Section of central canal of medulla spinalis, showing ependymal and neuroglial cells. | |
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| Photomicrograph of hematoxylin stained section of normal ependymal cells at 400x magnification. Human autopsy tissue | |
| Gray's | subject #189 829 |
| MeSH | Ependyma |
| Code | TA A14.1.00.022 |
Ependyma is the thin epithelial membrane lining the ventricular system of the brain and the spinal cord. Ependyma is one of the four types of neuroglia in the central nervous system. It is involved in the production of cerebrospinal fluid (CSF).
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[edit] Ependymal Cells
The ependyma is made up of ependymal cells. These are the epithelial cells that line the CSF-filled ventricles in the brain and the central canal of the spinal cord. The cells are ciliated simple cuboidal epithelium. Their apical surfaces are covered in a layer of cilia, which circulate CSF around the central nervous system. Their apical surfaces are also covered with microvilli, which absorb CSF. Ependymal cells are a type of Glial cell and are also CSF producing cells. Within the brain's ventricles, a population of modified ependymal cells and capillaries together form a system called the choroid plexus, which produces the CSF.
Tight junctions, zonae occludentes, between ependymal cells control fluid release across the epithelium. This release allows free exchange between CSF and nervous tissue of brain and spinal cord. This is why sampling of CSF (e.g. through a "spinal tap") gives one window to CNS.
[edit] Pathology
Ependymoma is a tumor of the ependymal cells.
[edit] Stem cells
Jonas Frisén and his colleagues at the Karolinska Institute in Stockholm provided evidence that ependymal cells act as reservoir cells in the forebrain, which can be activated after stroke and as in vivo and in vitro stem cells in the spinal cord.[1] [2] One study observed that ependymal cells from the lining of the lateral ventricle might be a source for cells which can be transplanted into the cochlea to reverse hearing loss.[3]
[edit] Ependyma and Neurodegeneration
In 2004, Dr. Milan Radojicic proposed the ependymal stem cell niche disruption hypothesis highlighting the role of local ischemia, cerebrospinal fluid dynamics and cytotoxic factors in disrupting the ependymal stromal epithelium, along with periependymal stem/progenitor cells, thereby tipping the balance between injury and self-repair (i.e., neurogenesis and gliogenesis) in the central nervous system toward further degeneration over time.
[edit] See also
- Ependymin, glycoprotein isolated from the ependyma
[edit] References
- ^ Johansson CB, Momma S, Clarke DL, Risling M, Lendahl U, Frisen J (1999). "Identification of a neural stem cell in the adult mammalian central nervous system". Cell 96 (1): 25–34. doi:10.1016/S0092-8674(00)80956-3. PMID 9989494.
- ^ Carlén M, Meletis K, Göritz C, Darsalia V, Evergren E, Tanigaki K, Amendola M, Barnabé-Heider F, Yeung MS, Naldini L, Honjo T, Kokaia Z, Shupliakov O, Cassidy RM, Lindvall O, Frisén J. (2009). "Forebrain ependymal cells are Notch-dependent and generate neuroblasts and astrocytes after stroke.". Nature Neuroscience 12 (3): 259–267. doi:10.1038/nn.2268. PMID 19234458.
- ^ "Brain cell hope for hearing loss". BBC News. 2008-12-09. http://news.bbc.co.uk/2/hi/health/7770665.stm. Retrieved 2008-12-09.
[edit] External links
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