OBJECTIVETo investigate the suitable transfection condition of human epidermal cells (hECs) with human epidermal growth factor (EGF) gene by adenovirus vector (Ad-hEGF) and its effects on the biological characteristics of hECs.

METHODShECs were isolated from deprecated human fresh prepuce tissue of circumcision by enzyme digestion method and then sub-cultured. hECs of the third passage were used in the following experiments. (1) Cells were divided into non-transfection group and 5, 20, 50, 100, 150, and 200 fold transfection groups according to the random number table (the same grouping method below), with 3 wells in each group. Cells in non-transfection group were not transfected with Ad-hEGF gene, while cells in the latter six groups were transfected with Ad-hEGF gene in multiplicities of infection (MOI) of 5, 20, 50, 100, 150, and 200 respectively. The morphology of the cells was observed with inverted phase contrast microscope, and expression of green fluorescent protein of the cells was observed with inverted fluorescence microscope at transfection hour (TH) 24, 48, and 72. (2) Another three batches of cells were collected, grouped, and treated as above, respectively. Then the transfection rate of Ad-hEGF gene was detected by flow cytometer (n=3), the mass concentration of EGF in culture supernatant of cells was detected by enzyme-linked immunosorbent assay (n=6), and the proliferation activity of cells was detected by cell counting kit 8 (CCK8) and microplate reader (n=6) at TH 24, 48, and 72, respectively. (3) Cells were collected and divided into non-transfection group and transfection group, with 6 wells in each group. Cells in non-transfection group were cultured with culture supernatant of cells without transfection, while cells in transfection group were cultured with culture supernatant of cells which were transfected with Ad-hEGF gene in the optimum MOI (50). CCK8 and microplate reader were used to measure the biological activity of EGF secreted by cells on culture day 1, 3, and 5. (4) Cells were collected and divided into non-transfection group and transfection group, with 12 wells in each group. Cells in non-transfection group were not transfected with Ad-hEGF gene, while cells in transfection group were transfected with Ad-hEGF gene in the optimum MOI (50). The expression levels of cytokeratin 14 (CK14) and CK19 of cells were measured by immunofluorescence staining at TH 24. (5) Cells were collected, grouped, and treated as in (4), with 6 wells in each group. At post scratch hour (PSH) 0 (immediately after scratch), 12, 24, and 48, the migration distance of cells was observed and measured with inverted phase contrast microscope. Data were processed with analysis of variance of factorial design, analysis of variance for repeated measurement, and LSD test.

RESULTS(1) At TH 24 and 48, morphology of cells in each transfection group and non-transfection group were similar. Compared with that in non-transfection group, the cell debris increased significantly in 200 fold transfection group at TH 72. At TH 24, 48, and 72, the expression of green fluorescent protein was not seen in cells of non-transfection group, whereas it increased in cells of transfection group over transfection time. (2) The transfection rate of Ad-hEGF gene of cells in each transfection group increased gradually over transfection time. At TH 72, the transfection rates of Ad-hEGF gene of cells in 50-200 fold transfection groups were all above 90%, while the transfection rates of Ad-hEGF gene of cells in non-transfection group, 5, and 20 fold transfection groups were (0.51±0.20)%, (62.44±6.23)%, and (75.00±5.43)% respectively, which were obviously lower than the rate in 50 fold transfection group [(93.12±2.55)%, with P values below 0.01]. The mass concentration of EGF in culture supernatant of cells in each transfection group increased gradually over transfection time. At TH 72, the mass concentration of EGF in culture supernatant of cells in 50 fold transfection group was obviously higher than that in each of the other groups (with P values below 0.01). The proliferation activity of cells in each group at TH 24 and 48 was similar (with P values above 0.05). At TH 72, the proliferation activity of cells in 200 fold transfection group was obviously lower than that in other groups (with P values below 0.05). (3) On culture day 1, the biological activity of EGF secreted by cells in two groups was similar (P>0.05). On culture day 3 and 5, the biological activity of EGF secreted by cells in transfection group were obviously higher than that in non-transfection group (with P values below 0.01). (4) At TH 24, the expression levels of CK14 and CK19 of cells in transfection group were higher than those in non-transfection group. (5) The width of scratch in two groups was nearly the same at PSH 0. At PSH 12-48, the migration distance of cells in transfection group was obviously longer than that in non-transfection group (with P values below 0.01).

CONCLUSIONSThe suitable range of MOI of hECs transfected with Ad-hEGF gene is 50-150, and 50 is the optimum. hECs transfected with Ad-hEGF gene with MOI 50 can effectively express the EGF gene and keep its good abilities of proliferation, differentiation, and migration, as well.