Cultivated Limbal Epithelial Transplant

Introduction

In recent years, research in Limbal epithelial transplantation have undergone revolutionary advances and resulted in substantial benefits to patients suffering from limbal stem cell deficiency (LSCD). The goal in LSCD management is to restore the limbal microenvironment and to regain a corneal epithelial phenotype by transplantation of limbal stem cells.

LSCD can be caused by primary causes such as Aniridia, multiple endocrine deficiency, congenital erythrokeratodermia or secondary causes such as chemical injuries, contact lens wear, inflammatory eye diseases (Stevens-Johnson syndrome, ocular cicatricial pemphigoid), neurotrophic keratitis, radiation, surgery, or topical antimetabolites (5-fluorouracil, Mitomycin C). LSCD is diagnosed on the basis of history and clinical findings, which include loss of limbal anatomy, corneal conjunctivalization, persistent epithelial defects, and scar formation. ^, The diagnosis is confirmed by impression cytology, illustrating the presence of goblet cells, increased cytokeratin 19 (CK19) expression, and reduced CK3/12 expression. More recently CK7, mucin1, and mucin5AC have been reported as more specific than CK19 for diagnostic purposes. In vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (OCT) are newer techniques that assist in diagnosing and quantifying LSCD and guiding therapeutic management.

History

Management of LSCD remains a challenge even after several advances in the field in the last 20–30 years. The earliest treatments for limbal stem cell transplantations included keratolimbal lamellar allograft (KLAL), conjunctival-limbal autografts (CLAU), and living-related conjunctival-limbal allografts (LR-CLAL), all of which required large sections of limbal donor tissue.

Advances in cell culture techniques have led to the use of cultured epithelial transplantation as an alternative procedure for the treatment of LSCD. In 1989, Kenyon and Tseng were the first to show that LSCD could be reversed by transplantation of healthy limbal tissue. Pellegrini 1997 first showed that smaller amounts of donor limbal epithelium could be cocultured with 3T3 fibroblasts and then this cultivated expanded limbal epithelium could be transplanted successfully in patients with unilateral LSCD (auto-cultivated limbal epithelial transplantation [CLET]). In 2004, Nakamura et al. reported that cultured oral mucosal epithelium on human amniotic membrane (HAM) could be used to successfully treat patients with LSCD. Finally, in 2012, Sangwan et al. showed that the direct transplantation of small amounts of autologous donor limbal epithelium could be used to successfully treat unilateral LSCD.

Origin of Cells

Both autologous and allogeneic sources of limbal epithelial stem cells have been used in clinical trials. Autologous cells are preferred, as they have no risk of immunoreactivity and require no systemic immunosuppression, but this is not possible in cases of bilateral disease.