MICROFABRICATION OF HEPATOCYTE FIBROBLAST COCULTURES - ROLE OF HOMOTYPIC CELL-INTERACTIONS/

Cell-cell interactions are important in embryogenesis, in adult physio logy and pathophysiology of many disease processes. Co-cultivation of parenchymal and mesenchymal cells has been widely utilized as a paradi gm for the study of cell-cell interactions in vitro. In addition, co-c ultures of two cell types provide highly functional tissue constructs for use in therapeutic or investigational applications. The inherent c omplexity of such co-cultures creates difficulty in characterization o f cell-cell interactions and their effects on function. In the present study, we utilize conventional ''randomly distributed'' co-cultures o f primary rat hepatocytes and murine 3T3-J2 fibroblasts to investigate the role of increasing fibroblast density on hepatic function. In add ition, we utilize microfabrication techniques to localize both cell po pulations in patterned configurations on rigid substrates. This techni que allowed the isolation of fibroblast number as an independent varia ble in hepatic function. Notably, homotypic hepatocyte interactions we re held constant by utilization of similar hepatocyte patterns in all conditions, and the heterotypic interface (region of contact between c ell populations) was also held constant. Co-cultures were probed for s ynthetic and metabolic markers of liver-specific function. The data su ggest that fibroblast number plays a role in modulation of hepatocellu lar response through homotypic fibroblast interactions. The response t o changes in fibroblast number are distinct from those attributed to i ncreased contact between hepatocytes and fibroblasts. This approach wi ll allow further elucidation of the complex interplay between two cell types as they form a functional model tissue in vitro or as they inte ract in vivo to form a functional organ.