الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Stem cells and their possible therapeutic applications currently constitute an extremely active area of research with the potential to revolutionize medical practice. Despite the apparently recent foundation of the field, its origin dates back to the second half of the 19th century, for many years’ stem cells remained ambiguous and theoretical entities till the end of last century. Stem cells are present in all self-regeneration tissue and have unique characteristics thatenable them to control cell replacement during homeostasis and tissuerepair. The ocular surface is made up of two distinct types of epithelial cells,Although anatomicallycontinuous with each other at the corneoscleral limbus,constituting the conjunctival and corneal epithelia. These epithlia arestratified, sequamous and non-keratinized. The evidence for the basal limbal location of corneal epithelialstem cellsmostly in the palisades of Vogtcomes from almost 40 years ofboth clinical observations and basic science research and more localization for different cells in regenerative limbal stem cells pathway done byusing a highly powerful combination of LCM and RNA sequencing. The cellular microenvironment is very importantin maintaining the stemness of limbal cells. This is known as the stem cell niche. These stem cells is responsible for constant and unending supply of cornealepithelial cells throughout life, thus maintaining a stable and uniformly transparent refractive corneal surface. Limbal stem cell deficiency is a disease in which the stem cell functions of the limbus and its barrier function fails due to cells loss or dysfunction. Patients with limbal stem cell deficiency were unable to maintain a stable cornea resulting in conjunctival invasion, vascularization and persistent epithelial defect. Diagnosis of LSCD is often clinical. Significantadvances have been made to develop non-invasive tests to objectively diagnose LSCD, including In vivo laser scanning confocal microscopy (IVCM) and impression cytology. Regenerative medicine for the cornea provides a novel treatment strategy for patients with corneal diseases instead of conventional keratoplasty, by using different surgical techniques in limbal stem cell transplantation including limbal auto graft, living relative conjunctival allograft, keratolimbal allograft, the adjunctive use of amniotic membrane and ex-vivo expanded transplantation. Stem cells can be expanded successfully in vitro using different types of culture media and various carriers.Alternate sources of autologous epithelial cells have been studied in order to avoid the need for systemic immunosuppression in patients with severe bilateral LSC deficiency, including oral mucosal epithelial cells, mesenchymal stem cells, immature dental pulp stem cells and hair follicle stem cells. The management of ocular surface disorders using Tissue engineering technology in limbal stem cell transplantation has benefited from major breakthroughs in recent years. Advances in microsurgical techniques and understanding of the role of limbal stem cells have led to great improvements in both visual acuity and quality of life for these patients.