ABSTRACT
BACKGROUND:Co-culture technique makes different kinds of ceils cultured in the same system.The trans-differentiation from osteoblasts to adipocytes is usually analyzed under the action of adipogenesis inducers in vitro,but the cellular interactions in vivo are neglected.OBJECTIVE:To investigate the trans-differentiation from osteoblasts to adipocytes in indirect co-culture using Transwell system.METHODS:Mouse preadipocytes 3t3-l1 were induced to adipocytes.There were three groups:group A:mature adipocytes in the lower chamber of Transwell system;group B:mouse osteoblasts MC3T3-E1 in the upper chamber of Transwell system according to a ratio of 1:4 (MC3T3-E1:3t3-l1);group C:mouse osteoblasts MC3T3-E1 alone.At 7,14,and 21 days the cell morphology was observed under inverted phase contrast microscope,the relative level of triglyceride,expression of peroxisome proliferator-activated recoptor y2 in each group were detected,and red oil O staining and alizarin red staining were performed.The cell proliferation inhibition rate in the groups B and C were detected at 0,24 and 36 hours.RESULTS AND CONCLUSION:At 2 weeks after culture,spindle-shaped 3t3-l1 coils changed into round,the light and round lipid droplets in the cytoplasm were increased and were reserved after identified by oil red O staining.In the group B,the cells presented with spindle shape with no transparent lipid droplets after 7-day co-culture until black granules and small round lipid droplets appeared on day 14;and the cells changed from spindle shape to oval or round,and larger lipid droplets were found on day 21.Alizarin red staining results:the staining region in the group B was on a decline with time,while the group C showed no significant changes at each time point and all appeared with large staining region.Oil red O staining results:the staining region in the group B increased gradually in a time-dependant manner,while the group C was negative for oil red O staining and showed no significant changes at different time points.The relative level of triacylglycerol in the group B was increased with time,and there was significant difference between groups A and B (P ＜0.05),and the group C showed no significant differences (P ＞ 0.05).The coll proliferation inhibiting rate in the group B was increased with time,which showed significant difference from the group C (P ＜ 0.05).The expression level of peroxisome proliferator-activated recoptor y2 in the group B was on a rise with time,which had significant difference compared with the groups A and C (P ＜ 0.05).These results indicate that the trans-differentiation from osteoblasts to adipocytes appears in the Transwell system,and metabolic products and cytokines of adipocytes obviously inhibit the proliferation of osteoblasts,but all above conclusions need to be studied in depth.