Factors Determining the Efficiency of Porcine Somatic Cell Nuclear Transfer: Data Analysis with Over 200,000 Reconstructed Embryos

Data analysis in somatic cell nuclear transfer (SCNT) research is usually limited to several hundreds or thousands of reconstructed embryos. Here, we report mass results obtained with an established and consistent porcine SCNT system (handmade cloning [HMC]). During the experimental period, 228,230 reconstructed embryos and 82,969 blastocysts were produced. After being transferred into 656 recipients, 1070 piglets were obtained. First, the effects of different types of donor cells, including fetal fibroblasts (FFs), adult fibroblasts (AFs), adult preadipocytes (APs), and adult blood mesenchymal (BM) cells, were investigated on the further in vitro and in vivo development. Compared to adult donor cells (AFs, APs, BM cells, respectively), FF cells resulted in a lower blastocyst/reconstructed embryo rate (30.38% vs. 37.94%, 34.65%, and 34.87%, respectively), but a higher overall efficiency on the number of piglets born alive per total blastocysts transferred (1.50% vs. 0.86%, 1.03%, and 0.91%, respectively) and a lower rate of developmental abnormalities (10.87% vs. 56.57%, 24.39%, and 51.85%, respectively). Second, recloning was performed with cloned adult fibroblasts (CAFs) and cloned fetal fibroblasts (CFFs). When CAFs were used as the nuclear donor, fewer developmental abnormalities and higher overall efficiency were observed compared to AFs (56.57% vs. 28.13% and 0.86% vs. 1.59%, respectively). However, CFFs had an opposite effect on these parameters when compared with CAFs (94.12% vs. 10.87% and 0.31% vs. 1.50%, respectively). Third, effects of genetic modification on the efficiency of SCNT were investigated with transgenic fetal fibroblasts (TFFs) and gene knockout fetal fibroblasts (KOFFs). Genetic modification of FFs increased developmental abnormalities (38.96% and 25.24% vs. 10.87% for KOFFs, TFFs, and FFs, respectively). KOFFs resulted in lower overall efficiency compared to TFFs and FFs (0.68% vs. 1.62% and 1.50%, respectively). In conclusion, this is the first report of large-scale analysis of porcine cell nuclear transfer that provides important data for potential industrialization of HMC technology.