Fibroblasts feeder niche and Flt3 Ligand as a novel inducer of plasmacytoid dendritic cells development in vitro

Plasmacytoid dendritic cell (pDC), plays central role in antiviral immunity. The aimof this study was to assess the
effect of Flt3 ligand (FL) alone or with L929 fibroblast feeder or L929 conditioned media on differentiation of
mouse bone marrow (BM) cells into pDC in vitro.Murine BMcells were cultured with FL or with L929 or conditioned
media for 9 days. The differentiated cells were analyzed using flow cytometry for PDCA-1, B220 and
CXCR4. The relative expression of Stat3, CXCR4, CXCR7, IFN-β, TGF-β and Runx2 in differentiated cells determined
by real time PCR. The development of pDC showed up to 19% increase after co-culture of BM cells with fibroblast
feeder. Upregulation of Stat3, Runx2 and CXCR4 due to the presence of fibroblast feeder with FL in
culture results in improved pDC development. Furthermore, 30% L929 supernatant along with Flt3 ligand was
able to derive pDC up to 8.9% in comparison with FL alone, which was 6.6% in vitro. Thus, for the first time we
introduced L929 fibroblast feeder as a niche producer of M-CSF and probably other growth factors and
chemokines, which promotes the development of pDC in vitro along with FL, similar to in vivo niche.