Limbo-corneal stem cells: News and therapeutic applications

Stem cells are those poorly differentiated bodily cells capable of self-renewing and differentiating into specialized cells in the human body. They can be found in all self-renewing tissues like epithelia. It is well known that in corneal epithelium stem cells are housed in the limbal region, more concentrated in the upper and lower corneal limbus. Some of the markers that have been used to identify them are: p63, ABCG2, C/EBPd, Bmi1, Notch1, K19, vimentin, among others. Currently, research has been made on the use of limbal stem cells to treat conditions that involve their deficiency, such as: chemical or thermal damage to the ocular surface, Stevens-Johnson syndrome, and aniridia. To culture stem cells it is necessary to take a 1-2 mm2 biopsy from the sclerocorneal limbus which can be directly seeded or previously treated with trypsin and dispase to create a cell suspension. Feeder layers have been used as scaffold based on 3T3 fibroblasts, amniotic membrane, matrigel extracellular matrix, collagen, thermosensible gelation polymers, and anterior lens capsule. Culture media also vary, being the following the most used: Dulbecco's modified Eagle medium, Ham F12, MCDB151, EpiLife medium, PCT, etc. Various substrates have been studied to transport stem cells to the ocular surface. Amniotic membrane has been the most used to date, but others such as contact lenses, fibrin gels, and thermosensible biopolymers have also been reported.