Tonsils contain pluripotent MSCs. (A) Differentiation of T-MSCs. After a 14- to 28-day culture in appropriate differentiation media, T-MSCs were stained with Oil-red O (left), Alizarin red (middle), and Alcian blue (right) to reveal the presence of adipocyte-specific lipid vacuoles, osteoblast-specific calcium deposits, and chondrocyte-specific proteoglycans, respectively. Cells were examined using an Olympus IX71 inverted microscope (Olympus, Tokyo, Japan) equipped with a 40 ×/0.60 NA objective, and digital images were acquired using an Olympus Camedia C-5060 camera. (B) Induction of an extracellular meshwork. T-MSCs were stained for fibronectin and transglutaminase (TG) after 7 days of culture with or without stimulation with TNF/LT. Bar represents 20 μm. (C) Growth of BL2 cell line. BL2 was cultured for 3 days in low serum concentration alone, or with confluent clonal T-MSC, pretreated or not with TNF/LT for 7 days. Proliferation was assessed by tritiated thymidine (3H-TdR) incorporation determined in sixplicate culture wells. Stromal cells cultured alone always showed tritiated thymidine incorporation less than 500 cpm. Data are expressed as percentages of thymidine incorporation by BL2 cells cultured in the presence of clonal T-MSCs (pretreated or not with TNF/LT) with respect to BL2 cells alone (assigned to 100%). Bars represent mean values ± SD from 6 independent experiments. *Mean value is statistically significantly different from that obtained without stromal cells (P<.05). **Mean value is statistically significantly different from that obtained with untreated T-MSC (P<.05).
