Immunocytochemical characterisation of rabbit and mouse embryonic fibroblasts

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.