OBJECTIVETo investigate the possibility of marrow derived multipotent adult progenitor cells (MAPCs) differentiating into hepatocytes by co-culturing with human hepatocyte line L02, and to evaluate the potential use of MAPCs in tissue-engineering either experimentally or clinically.

METHODS(1) Co-culturing without cell-to-cell contact: MAPCs and L02 hepatocytes were spread on coverslips separately (both with a cell density of 1x10(5)/ml), and then they were put in a culture dish (10 cm). The expressions of Alb, AFP, CK18, and CK19 in MAPCs were detected by immunocytochemistry at different time points. A separate culture of L02 hepatocytes served as a positive control and a separate culture of MAPCs served as a negative control. (2) Co-culturing with cell-to-cell contact: MAPCs labeled with CFSE were mixed with L02 hepatocytes (both with a cell density of 1x10(4)/ml), and then the mixed cells were seeded on specific dishes for detection by laser scanning confocal microscope (LSCM). Five days later, the cells were double-stained with SABC-Cy3. The expressions of Alb, AFP, CK18 in MAPCs were observed under LSCM. Similarly, separately cultured L02 hepatocytes served as a positive control and separately cultured MAPCs served as a negative control.

RESULTS(1) Results of co-culturing without cell-to-cell contact: On the first day, the MAPCs expressed a high level of AFP. Then AFP expression tapered daily and there was hardly any expression of AFP on day 7. The expression of Alb was very weak on day 1, but increased significantly by day 3, reached its peak on day 5, and still maintained a high level on day 7. The initial expression of CK18 appeared on day 5 and reached a higher level on day 7. The expression of CK19 was always negative. The positive control cells had a high expression of Alb and CK18, while there was a weak expression of AFP and a negative expression of CK19. The negative control cells had no expressions for the four markers. (2) Results of co-culturing with cell-to-cell contact: On day 5, there were three colors of fluorescence under LSCM: yellow cells were MAPCs differentiating into hepatocytes; green cells were undifferentiated MAPCs; red cells were L02 hepatocytes. The result showed that Alb and CK18 were expressed in many cells and AFP appeared in only a few cells.

CONCLUSIONHuman MAPCs can be induced to differentiate into mature hepatocyte-like cells by co-culturing with L02 hepatocytes, either with or without cell-to-cell contact, but the former way may be more effective.