CORNEAL EPITHELIUM

NCRM’s work on Corneal Epithelium:

Though the cornea has three well defined components, until recently, even for a partial damage of the cornea i.e damage of one of the three components, the whole cornea was transplanted.

 The junction between the Cornea and the Sclera is called the Limbus and in this Limbus, the Corneal Epithelial Limbal stem cells are present. These stem cells when needed multiply and repair the damages of the corneal epithelial cell layer. When there is a damage to this Limbus itself (Eg stevens-johnson syndrome) or when the repairing capacity of the Limbal stem cells are overcome by the disease process (Eg. persistent corneal ulcer), damage to the corneal epithelium results in opacity affecting the vision.

Recently, Cultivated Limbal Stem Cell transplantation has been used in the treatment of Limbal Stem Cell deficiency.
 The substrate used for the development of Ocular surface tissue-equivalents include human amniotic membrane (HAM), collagen gel and fibrin glue, of which HAM is currently the most commonly used substrate for ocular surface transplantation  However the issue of allogenic biological materials associated with the risk of transmission of infections and allograft rejection. In addition, many of the substrates lack the mechanical properties that allow easy handling and suturing as well as prolonged endurance after transplantation.

Nishida et al showed that tissue-engineered cell sheets from autologous oral mucosal epithelium may serve as effective substitutes for allografts of Limbal tissue in the reconstruction of the corneal and Limbal surfaces. In their study four patients were treated with autologous mucosal epithelium whose corneal transparency was restored and postoperative visual acuity improved remarkably, with no serious complications. First, in vivo oral mucosal epithelium expresses keratin 3, which is also expressed by the corneal epithelium but not by the epidermis. Second, the Excision of a small piece of oral mucosal tissue from the patient is relatively easy, resulting in wound healing within several days without incident or scarring. Third, the transparent carrier free sheets of tissue-engineered epithelial cells fabricated from oral mucosal epithelial cells were similar to the transparency of corneal epithelial-cell sheets originating from Limbal Stem Cells. Autologous oral mucosal epitheliums are effective for reconstructing the ocular surface and restoring vision in patients with bilateral total stem cell deficiencies.

NCRM’S work: 
NCRM developed a new method of ocular surface reconstruction by using Nano Polymers as a substitute for Stroma which supports the epithelial growth. Nano Polymers supported the proliferation of epithelial cells in culture and the cells were viable. Limbal Stem Cell markers were expressed and corneal phenotype suggesting that Nano Polymers retains the stemness of the cultured cells.  Such Nano polymers overcomes problem related to the use of allogenic tissue and biological substrate. These Nano Polymers could be custom fabricated to suit each condition and could provide a ready supply of materials for clinical use and avoid poor mechanical strength and risk of immunologic rejection. Nano Polymers are non-toxic and biodegradable with adequate tensile strength.  

NCRM also evaluated the efficacy of autologous expanded corneal epithelial cell transplants derived from harvested Limbal biopsy cultured on a Mebiol Gel  for the management of unilateral Limbal Stem Cell deficiency (LSCD) Corneal Limbal biopsies from 12 rabbits were cultured on a Mebiol Gel. Cells harvested after three weeks were transplanted to induced Limbal stem cell deficient rabbit eyes. Reparative surgery was a total success in seven rabbits, partial success in two and failure in three eyes. Histology of the seven successful rabbits’ eyes showed successful growth of corneal epithelium. Immunohistochemistry and RT-PCR showed the corneal phenotype and stem cell associated markers in the Limbus of the seven successful eyes, which indicates the homing of the cultured cells into the Limbus suggesting that the transplantation of autologous Limbal epithelial cells grown in Nano Polymer may restore a nearly normal ocular epithelial surface in eyes with unilateral LSCD.