Stem cells are the ‘basic cells’ of our body. They are specialised cells that can divide and replace other (non-stem) cells when they are lost. Stem cells can be found in embryos as well as adult tissues, but they have slightly different properties.
These cells migrate to injured areas within the body and get transplanted and transform themselves into new tissue cells that replace the damaged ones. Stem cells have the capacity to multiply and renew themselves almost indefinitely.
Limbal stem cell corneal transplantation
Stem/progenitor cells located in different regions of the eye are capable of differentiating, enabling cell re-population and tissue regeneration. At present, limbal epithelial stem transplantation is the sole ocular cell-based therapy being implemented into clinical practice.
Limbal stem cell corneal transplantation surgically replaces critical stem cells at the limbus (the area where the conjunctiva meets the cornea). Host stem cells normally reside in this area. Transplantation is done when the host stem cells have been too severely damaged to recover from disease or injury.
Conditions such as severe chemical burns, Stevens-Johnson syndrome, ocular cicatricial pemphigoid, neuroparalytic keratopathy, radiation keratopathy and severe contact lens overwear, may cause persistent non-healing corneal epithelial defects (defect of the cells that normally cover the surface of the cornea). These defects result from failure of these stem cells to produce sufficient epithelial cells to repopulate the cornea. If untreated, persistent non-healing corneal epithelial defects are vulnerable to infection, which can lead to scarring, perforation, or both.
Under these circumstances, a corneal transplant, which replaces only the central cornea and not the limbus, is insufficient; stem cells are needed to produce new cells that repopulate the cornea, restoring the regenerative capacity of the ocular surface. Corneal limbal stem cells can be transplanted from the patient’s healthy eye or from a cadaveric donor eye. Limbal stem cells along with amniotic membrane transplant have been a revolution in ophthalmology in recent times, for some of these dreaded diseases.
Stem cell therapy may help in some of the retinal diseases like hereditary macular degeneration and age related macular degeneration (AMD). Retinal stem cell therapy aims to inject stem cells into the eye, where they can turn into photoreceptor cells and thereby replace the cells that have been lost due to retinal diseases like age related macular degeneration (AMD) and retinitis pigmentosa.
Stem cell transplant may provide a promising new avenue for optic nerve damage in diseases like glaucoma and optic neuropathies. These studies are in experimental phase. .