46 EFFICIENT TRANSFECTION OF PLASMID DNA INTO CELLS FOR USE AS NUCLEAR DONORS

Abstract

Somatic cell nuclear transfer (SCNT) has the potential to significantly improve the production of valuable livestock that produce recombinant proteins, such as pharmaceutical proteins for human disease or biomaterials for medical use. The success of this potential depends on efficient and optimized protocols for introducing exogenous DNA into cells. In this study, we compared two methods of transfection, Effectene (Qiagen, Inc., Valencia, CA, USA) and electroporation. Plasmid DNA (pEGFF-N1, Clontech, Seoul, Korea) was transfected into fetal fibroblasts (FFB), cumulus cells (CUC), and adult ear skin cells (ESC). Transfection efficiency, chromosome normality, gene expression, and apoptosis were assessed. Cells cultured in α-modified Eagle's medium (α-MEM; BioWhittaker, Walkersville, MD, USA) + 10% FBS were transfected with pEGFP-N1. For electroporation, cells (5 × 10⁶ cells/mL) were mixed in 300 μL perrim buffer (75% Cytosalts with 120 mM KCl, 0.15 mM CaCl₂, 10 mM K₂HPO₄, 5 mM MgCl₂, and 25% α-MEM) + 15 μg pEGFP-N1, and subjected to two pulses of 0.38 kV and 400 μF delivered by Gene Pulser (Bio-Rad; BMS, Ltd., Seoul, South Korea). For Effectene transfection, the procedure suggested by the manufacture was followed. Transfected cells were selected with 600 μg/mL G418 (Gibco; KDR Biotech Co., Ltd., Seoul, South Korea) and cultured at 39°C, 5% CO₂ in air. Assessments of EGFP transfected cells by green fluorescence was carried out under an inverted epifluorescence microscope (Nicon, Kanagawa, Japan) equipped with a filter for FITC (excitation maximum = 488 nm; emission maximum = 507 nm). Differences among the groups were analyzed using one-way ANOVA after arc-sine transformation of proportional data. Most cells (>80%) in confluence were at G0/G1 phase, and transfection of the gene into all three cell types did not affect the incidence of chromosomal abnormality or change morphology. In addition, the rates of apoptosis assessed by TUNEL did not differ in all three cell types by either method of transfection at different cell passages. However, the efficiency of gene transfection into FFB by Effectene reagent (14.2 ± 1.7%) was significantly (P < 0.05) higher than that by electroporation (5.1 ± 1.0%). Among the three type cells, the efficiency of gene transfection by Effectene and electroporation of FFB (14.2 ± 1.7 and 5.1 ± 1.0%, respectively) was significantly (P < 0.05) higher than those of CUC and ESC (9.4 ± 1.5 and 3.3 ± 0.8; 8.8 ± 0.7 and 2.1 ± 0.4%, respectively). In conclusion, although there were no differences in the alteration of chromosomes, cell morphology, and apoptosis among three cell types transfected with or without plasmid DNA, FFB is the most effective cell type to be transfected. Effectene is superior to other currently available methods for introducing plasmid DNA into a variety of cells. The high level of transfection achieved by Effectene will encourage its use as a tool for producing transgenic embryos and animals by SCNT.

This work was supported by High Technology Development Project for Agriculture and Forestry Korea, MAF-SGRP, 300012-05-3-SB010.