Efficient Cultivation Conditions for Human Limbal Epithelial Cells

To compare the stem niche in different culture conditions of limbal epithelial cells, the suspended human limbal epithelial cells (HLECs) were seeded on the 3T3-pretreated plates and the other suspended cells were plated on amniotic membranes (AMs) which were either cryo-preserved or freeze-dried. All were cultured for 10 to 12 days. Reverse transcription-polymerase chain reaction (RT-PCR) for ATP-binding casette, subfamily G, member 2 (ABCG2), p63, cytokeratin 12, and connexin 43 were performed in cultivated HLECs and their expression levels were compared. The mRNA expression of all markers examined showed no statistically significant differences between the cells on cryo-preserved and on freeze-dried AM. The expression of p63 and cytokeratin 12 in cultivated cells on AMs were significantly lower than those in 3T3-cocultured cells on RT-PCR and immunofluorescent staining. Cultivated HLECs on AMs showed reduced proliferation and differentiation while maintaining stem-property regardless of the preservative method of AM.

Isolation of Putative Corneal Epithelial Stem Cells from Cultured Limbal Tissue

PURPOSE: To investigate methods of isolating putative corneal epithelial stem cells from cultured limbal tissue. METHODS: Three extraction techniques were compared to identify an efficient method of obtaining a large number of viable corneal epithelial stem cells from the limbus. Limbal tissues were extracted by incubation at 37 degrees C or 4 degrees C for 1 or 16 hours, respectively, with 1.2U/ml dispase/trypsin or by treatment with 0.05% trypsin and 0.01% ethyldiaminetetraacetic acid (EDTA) at 37 degrees C in single procedure. Collected cells were cultured on NIH/3T3-seeded plates, and colony forming efficiency (CFE) was evaluated. Fluorescence activated cell sorting (FACS) was performed with a Coulter EPICS 753 after incubation with Hoechst 33342 and propidium iodide (PI). Hoechst negative cells were obtained using gates exhibiting low Hoechst blue with a 424/44 nm BP filter. Gated cells of each fraction were re-cultured to assess the capability of colony formation. RESULTS: The mean numbers of viable cells obtained from treatment with dispase and trypsin was 3x10(4) cell/ml and 8.06x10(5) cell/ml at 37 degrees C and 4 degrees C incubations; the number increased to 1.21x10(6) cell/ml with a trypsin/EDTA treatment (p<0.05). CFE was 9.67+/-2.13% and 6.63+/-2.35% in rabbit and human cells, respectively. Likewise, the Hoechst negative fraction was 3.61+/-0.42% and 5.21+/-4.91% in rabbit and human cells, respectively. The sorted Hoechst negative cells were cultured through four passages, forming small round colonies. In rabbit cells, the CFEs of Hoechst negative and positive fractions after FACS, were 12.67+/-2.24% and 1.17+/-6.13%, respectively (p<0.05). CONCLUSIONS: Putative corneal epithelial stem cells were efficiently isolated from limbal tissue using a trypsin/EDTA extraction and FACS. This technique may be very useful in tissue engineered stem cell therapy.

Isolation of Putative Limbal Epithelial Stem Cells by Fluorescein Activated Cell Sorting

PURPOSE: To analyze the isolating pattern of slow cycling cells as putative limbal epithelial stem cells (PLESCs) using Hoechst exclusive cell sorting. METHODS: Rabbits were injected with 5-bromo-2-deoxyuridine (Brd U) 1 month prior to be sacrificed. After obtaining limbal tissues, fluorescence-activated cells were sorted on a Coulter EPICS 753 after they had been incubated with Hoechst 33342 and propidium iodide. Two different methods were applied to sort PLESCs. Side-population(Sp) cells were obtained using gates with dichroic mirror to detect low Hoechst blue and red after verapamil was treated. Hoechst negative cells were obtained using gates exhibiting low Hoechst blue with a 424/44 BP filter. Brd U-retaining cells were counted and their sizes were evaluated in each gated sample to compare isolating pattern of PLESCs in each method. RESULTS: The percentages of Sp cells and of the Hoechst negative fraction were 0.96 +/- 0.79% and 16.01 +/- 13.60%, respectively(p=0.021). Homogeneity and density of the small cells were higher in Hoechst negative fraction than in Sp cells. The percentage of Brd U-retaining cells was 47.36 +/- 10.34% and 47.14 +/- 14.94% in Sp cells and Hoechst negative fraction, respectively(p>0.05), and they were 10 times higher than in non-Sp and Hoechst positive fraction(p=0.000). CONCLUSIONS: Hoechst negative exclusion without verapamil more efficiently isolated PLESCs than Sp did.