Cell cycle stage of donor cells significantly influences the cloning efficiency during SCNT. Donor cells in G1/G0 stage have better capability to undergo nuclear reprogramming following transfer to an unfertilized oocyte. The lack of availability of cells synchronized at G1/G0 stage is one of the major factors limiting cloning efficiency in buffalo. The aim of this study was to compare the efficacy of various methods for cell cycle synchronization of buffalo fetal ?broblast cells for SCNT. Cells isolated from fetus, 2 to 3 months old, were cultured in DMEM + 10% FBS. The primary culture was sub-cultured 8 to 10 times. For cell cycle synchronization, the cells were cultured to 1) 60 to 70% confluence (controls), 2) 60 to 70% confluence followed by serum starvation (DMEM + 0.5% FBS) for 24 h (serum starved), 3), full confluence followed by culture for additional 3 to 5 days (full confluent), 4) full confluence followed by serum starvation (DMEM + 0.5% FBS) for 24 h (full confluent+serum starved) and 5) 60 to 70% confluence followed by treatment with roscovitine (10, 20, or 30 μM) for 24 h. The synchronization efficiency was examined by propidium iodide staining followed by analysis of DNA content using flow cytometry and the data were analysed by 1-way ANOVA followed by Fisher’s l.s.d. test after arcsine transformation. The percentage of cells in G0/G1 phase of cell cycle was significantly higher (P < 0.05) in the full confluent+serum starved and roscovitine treated (20 or 30 μM) groups than that in the full confluent group and that treated with 10 μM roscovitine which, in turn, was higher (P < 0.05) than that in the serum starved and control groups. These results suggest that buffalo fetal fibroblast cells can be synchronized by roscovitine treatment or by serum starvation of fully confluent cell cultures to obtain a high proportion of cells in G0/G1 stage for SCNT.

Table 1.  Buffalo skin fibroblast cells at various stages following different treatments for cell cycle synchronization