Mesenchymal stem cells inhibit microglia proliferation through contact-dependent cell cycle modulation. BV2 and Mesenchymal stem cells (MSC) were cultured at a 1:0.2 ratio and stimulated with 1 μg/ml lipopolysaccharide (LPS) after overnight incubation. Cells were harvested 48 hours post-LPS stimulation and cell cycle was analysed by propidium iodide staining. Separation of BV2 and MSC populations on flow cytometry was enabled by CD45 staining (see Additional file 3: Figure S3). Histograms show distribution of (a) BV2 cells and (b) MSC from direct co-culture across G0/G1, S and G2/M phases of cell cycle at 48 hours after LPS stimulation and/or co-culture. Values are expressed as mean ± standard deviation of percentage of cells from three independent experiments. (a) *P < 0.01, versus BV2 cells; #P < 0.01, versus BV2 +μlPS. (b) *P < 0.001, versus MSC; #P < 0.001, versus MSC +μlPS.