Retrovirus-mediated gene transfer is one of the most commonly used methods
to deliver, integrate, and express the gene of interest because the retrovi
rus can insert the desired gene into the chromosome of the target cells wit
h high stability. However, to deliver the gene successfully, the retrovirus
requires active division to integrate reversely transcribed DNA into the c
hromosome of target cells. In this study, we focused on the effect of cell-
cell contact inhibition on the efficiency of retroviral transduction with t
wo anchorage-dependent cell lines: NIH 3T3 and 293 cells. These two cell li
nes have very different cell morphologies and growth patterns on surfaces.
Human embryonic kidney epithelial 293 cells tend to stick together after di
viding, while NIH 3T3 cells migrate to occupy available surface and spread.
Experimental data indicate that the abatement of the transduction rate of
293 cells was initiated in the early stage of the culture, whereas effect o
f contact inhibition of NIH 3T3 cells on the transduction rate became domin
ating at the end of the culture period. Experimental results were also quan
titatively illustrated by plotting normalized multiplicity of infection (MO
I) versus normalized cell density. According to the outcomes, cell inoculat
ion density plays an important role in optimizing the retroviral transducti
on rate. The optimal time of retroviral transduction should be confined to
the accelerating growth phase for 293 cells and at the exponential growth p
hase for NIH 3T3 cells. The implication drawn from this study is that conta
ct inhibition effect on retroviral transduction should be taken into accoun
t for large-scale gene transfer systems such as the microcarrier bioreactor
.