Nuclear transfer using clonal lines of porcine fetal fibroblasts with different sizes and population doubling rates.

The aim of the present study was to examine the development of pig embryos produced by somatic cell nuclear transfer (NT) using the clonal lines of fetal fibroblasts with different population doublings (PD) per day and sizes. Clonal lines were established by plating fetal fibroblasts from a Day 35 pig fetus into 96-well clusters, one cell to each well. Four clonal lines (L1-L4) were selected for NT according to their PD per day (1.1 +/- 0.2 to 0.8 +/- 0.2) and mean cell size (15.1 +/- 2.0 to 20.1 +/- 2.9). Donor cells were transferred into enucleated oocytes, fused and activated simultaneously with electrical stimuli (two pulses of 125 V mm(-1) for 30 micros) and cultured for 6 days. The proportion of embryos that developed to the blastocyst stage in the L3 (19.6%) and L4 (25.3%) lines, which had a lower PD per day and larger cell size, were significantly higher (P < 0.05) than that of the L2 line (10.6%), which had a higher PD per day and the smallest cell size. The proportion of embryos developing to the blastocyst stage in the L1 line (17.3%), which had the highest PD per day and smaller cell size, was significantly lower (P < 0.05) than that of the L4 line. These results suggest that clonal lines with larger sized cell populations in mean and lower PD per day have a greater in vitro developmental potential following NT.