By using indirect immunofluorescence we demonstrated the localisation of ex
tracellular matrix (ECM) proteins (laminin - LAM, collagen IV - COL IV, fib
ronectin - FN) and the basic Fibroblast growth factor (bFGF) in rabbit and
mouse primary embryonic fibroblasts (PEF). Proliferating mitotically arrest
ed PEF (by mitomycin C) were compared in both species. The stability of pro
tein expression was ascertained during the first five successive passages.
In addition, STO cells (i.e. permanent line of irradiated mouse fibroblasts
) were similarly analysed. Rabbit PEF showed very high extracellular staini
ng for FN and a negligible cytoplasmic positivity for LAM and COL IV A tota
lly reversed staining pattern for ECM proteins was found in mouse PEF. A de
nse cytoplasmic granulation (concentrated around the nucleus) was revealed
for LAM and COL TV and almost no reaction for FN. The staining patterns wer
e very stable at the culture conditions we applied. They were maintained du
ring the first five successive passages in proliferating as well as non-pro
liferating mouse and rabbit PEF and were independent of cell concentration
(individually dispersed cells versus cells in a confluent layer). STO cells
showed the same staining for ECM proteins as the mouse PEF, thus confirmin
g their origin from the same animal species. Light granular staining for bF
GF was found in the cytoplasm of proliferating and mitotically arrested rab
bit and mouse PEF and STO cells. The differences in expression of ECM prote
ins between the rabbit and mouse PEF, as well as the synthesis of bFGF, sho
uld be taken into consideration when these cells are used in vitro as a fee
der layer for various cells (e.g. embryonic stem cells). (C) Inra/Elsevier,
Paris.