ABSTRACT
BACKGROUND: Corneal epithelial stem cells, also known as limbal stem cells, are distributed in the basal layer of limbal epithelium. It is extremely difficult to deal with limbal stem cell deficiency or dysfunction that is caused by severe thermal burn, chemical burn, and chronic inflammation of ocular surface. At present, in vitro culture of corneal epithelial stem cells using tissue engineering technology followed by clinical transplantation is a new and effective therapeutic direction. OBJECTIVE: To explore the feasibility of serum-free culture of human corneal epithelial stem cells in vitro using modified explant culture method. METHODS: The remaining donor corneal tissues after keratoplasty (less than 8 mm in diameter) were obtained from Henan Eye Bank, and the outer and middle limbus were dissected under surgical microscope. Two culture methods were used to culture human corneal epithelial stem cells. In the conventional explant culture group, the limbal tissues were adhered to the dish with the epithelium being upward, then Keratinocyte-serum free medium (K-SFM) was added into dishes, followed by incubation at 37 °C in a 5% CO2 incubator. In the modified explant culture group, limbal tissues were dissected to immerse in the K-SFM culture medium and incubated at 37 °C in the 5% CO2 incubator for 12 hours. The limbal tissues were then adhered to the dish with the epithelium being downward. The day whenever the cells from the limbal tissues adhered to the dish was marked as the 1st day of culture, and changes in cell morphology and growth were recorded by phase contrast microscopy every day. Immunofluorescent staining was used to detect the expression of K3 and p63 in primary cells on the 5th, 10th and 14th day of the modified explant culture. RESULTS AND CONCLUSION: The mean early stage of growth in the modified explant culture group was shorter than that of the conventional explant culture group (P < 0.05), and the mean growth rate of the modified explant culture group was higher than that of the conventional explant culture group (P < 0.05). In the modified explant culture group, cells had a good growth state, and many cells with small size gathered together on the 10th day of culture. On the 14th day, cell clones were formed, and the cells in the clone showed uniform morphology. On the 5th day, K3 highly expressed, while p63 lowly expressed in primary cells. On the 10th day, both of K3 and p63 had an increased expression. On the 14th day, there was no significant increase in the K3 expression, but the expression of p63 increased significantly. In the in vitro serum-free culture condition, the modified explant culture could significantly promote the growth of corneal epithelial stem cells, and expand corneal epithelial stem cells in vitro, which could provide sufficient seed cells for enriching corneal epithelial stem cells and constructing human limbal multilayered epithelial sheets.
ABSTRACT
BACKGROUND:There are two types of epithelial stem cells in the ocular surface tissue:corneal epithelial stem cells and conjunctival epithelial stem cells. The corneal epithelial stem cells play an important role in renewal of corneal epithelial cells and maintenance of corneal transparency. OBJECTIVE:To study the location of corneal epithelial stem cells using laser in vivo confocal microscopy and immunofluorescent staining. METHODS:Patients with unilateral limbal stem celldeficiency who went to Henan Eye Institute from September 2009 to September 2012 were enrol ed in this study. Bilateral eyes were scanned by laser in vivo confocal microscopy, and the healthy eye was imaged as a control. The central cornea and limbus were scanned and images were recorded for statistical analysis. The eye bal s were obtained from Henan Eye Bank, China. Central cornea and limbus were dissected and embedded in the OCT compound for frozen section and the proper thickness of the section was 5-7μm. Immunofluorescent staining was used to detect the expression of p63, ABCG2, K3 and Connexin 43 in the epithelial layers of central cornea and limbus. RESULTS AND CONCLUSION:Twenty-four patients diagnosed with unilateral limbal stem celldeficiency were recruited. Under confocal microscopy, in the affected eyes, the typical morphology of conjunctival epithelial cells and goblet cells was detected instead of corneal epithelial cells;in the limbus, a great amount of fiber scarring tissue was detected instead of Vogt palisade, rete pegs and pigment cells. Immunofluorescent staining showed the expression of p63, ABCG2 was mainly in the basal layer of limbal epithelium, especial y in the outer and middle parts, but the expression of p63 and ABCG2 was not detected in the epithelial celllayers of central cornea. K3 and Connexin43 were not expressed in suprabasal layers of limbal epithelium, but in central cornea, they were expressed highly in the whole epithelial celllayers. Laser in vivo confocal microscopy and immunofluorescent staining showed the corneal epithelial stem cells were located in the basal layer of outer and middle limbal epithelium, mainly in Vogt palisade and rete pegs.