Culture & characterisation of limbal epithelial cells & oral mucosal cells.

Background & objectives: Sources of autologous tissue that can functionally replace the corneal epithelium have been considered as an alternative to allogenous limbal transplants for limbal stem cells deficiency (LSCD). The aim of the present study was to compare the characterization of oral mucosa with limbal epithelial cells by markers using reverse transcriptase polymerase chain reaction (RT-PCR). Methods: Experiments were performed using oral tissue (n=6) obtained from patients who underwent oral mucosal graft for LSCD. Confluent cultures of limbus and oral mucosa epithelial cells were characterized by the pututative stem cell markers using RT-PCR. The morphological characteristics of cultivated epithelial cells were analyzed by haematoxylin and eosin staining and phase contrast microscopy. Results: Confluent sheets of epithelial cells were seen at the end of 14th day resembling the morphological features of limbal epithelia. RT–PCR analysis showed that cultured oral epithelial cells expressed markers such as ABCG2, p63, delta Np63, isoforms of p63, Keratin 3 (K3), membrane protein – Mucin (MUC 1, 4 and 16) and Antimicrobial Peptide - AMP (Human β Defensin – hBD 1, 2 and 3). Interpretation & conclusions: Oral epithelial cultures have morphological features resembling corneal and limbal epithelial cells by expressing similar marker genes. Thus, feasibility of clinical use of oral epithelial cells need be evaluated for allogenous limbal transplants.

Tear ascorbic acid levels and the total antioxidant status in contact lens wearers: A pilot study.

Aims: The tear ascorbate owing to its high concentration, functions as an effective antioxidant against the oxidative damage of cornea. Contact lens wearers (CLW) are prone to oxidative stress due to the lens-induced hypoxic conditions. A pilot study was done to compare the tear ascorbic acid level and the total antioxidant capacity give as in normal and CLW. Materials and Methods: In this study 21 CLW (Mean age 23 ± 3 years; M-2, F-19), who were daily wear users, with duration of wear not more than four years, along with age-matched 28 controls (Mean age 28 ± 3; M-15, F-13) were recruited in the study for collection of reflex tears using Schirmer's strip. Ascorbic acid in tears was determined using high-performance liquid chromatography (HPLC), total antioxidant capacity (TAC) and total protein assay by spectrophotometric analysis. Results: CLW showed no significant change in the tear ascorbic acid levels (0.4 ± 0.26 mM) compared to the control subjects (0.61 ± 0.59 mM). The amount of ascorbic acid in tears did not correlate with the TAC or the total protein of the tears. The mean TAC in CLW was 0.69 ± 0.16 mM, with a total protein of 1.35 ± 0.46 mg/ml while in controls it was 0.7 ± 0.18 mM and 1.21 ± 0.47 mg/ml respectively. Conclusions: Soft contact lens wear did not show any significant change in tear ascorbic acid, TAC and total protein levels compared to controls.

Putative stem cell markers in limbal epithelial cells cultured on intact & denuded human amniotic membrane.

BACKGROUND & OBJECTIVES: The ocular surface is an ideal region to study the epithelial stem cell (SC) biology because of the unique spatial arrangement of stem cells and transient amplifying cells. A major challenge in corneal SC biology is the ability to identify SC in vitro and in situ, and one of the major controversies in the field relates to reliable SC markers. This study was carried out to evaluate and compare the expression of the stem cell associated marker: ABCG2, keratinocyte stem cell marker: p63 and corneal differentiation markers: Cnx43 and K3/K12 on limbal explants cultured on human amniotic membrane (HAM) with intact epithelium and HAM denuded of its epithelium. METHODS: Human limbal biopsies obtained from the cadaveric donor eyes were used in this study. The cells were cultured over the HAM with intact and denuded epithelium. Reverse transcriptase PCR, immunohistochemistry, Western blotting for ABCG2, P63, Cnx43 and K3/K12 were done. RESULTS: The limbal epithelial cells cultured over intact HAM expressed the stem cell associated markers (ABCG2, p63) and showed reduced expression of the differentiation markers (Cnx43 and K3/K12) when compared to limbal epithelial cells cultured over denuded HAM, which expressed more differentiation markers at the end of three weeks. BrdU label retaining cells were observed in the limbal epithelial cells cultured over HAM with epihelium only. INTERPRETATION & CONCLUSIONS: Our results showed that the intact HAM supported the growth of limbal epithelial cells expressing stem cell associated markers, and allowing little differentiation of the limbal cells to cornea phenotype. Further studies are needed to understand the properties of the amniotic epithelium that retains the stemness in the cultured limbal stem cells.