title: Hepatocyte dynamics in a three-dimensional rotating bioreactor.
abstract: OBJECTIVE
  The use of an artificial liver system with extracorporeal circulation or a three-dimensional bioreactor perfused with liquid culture medium inevitably exposes hepatocytes to fluid mechanical stress (MS). The expression of liver-specific hepatocyte functions seems to be modulated by the magnitude of MS. Nonetheless, few studies have focused on the direct effects of MS on hepatocytes. We subjected hepatocytes to MS using an MS loading device and investigated the effects on the cytoskeleton and hepatocyte dynamics inside three-dimensional scaffolds by monitoring the changes in actin fiber, one of the components of the cytoskeleton. We also assessed the influence of MS on specific hepatocyte functions.
  
  
  METHODS
  We subjected hepatocytes to MS by a rotating radial flow bioreactor (RRFB) and examined the effects by comparing the MS-loaded culture cells with cells cultured under stationary conditions without MS loading. The hepatocytes (1 x 10(6)/cm(3)) were seeded on gauze without collagen coating and examined to determine morphological changes after 60 h incubation. Actin filaments in samples from the MS-loaded hepatocyte culture were stained by fluorescein isothiocyanate-labeled phalloidin.
  
  
  RESULTS
  Hepatocyte aggregation was observed in the MS-loaded culture, but not in the unloaded stationary culture. Better albumin products were observed in the MS-loaded group than in the stationary culture group at all measurement points. Actin filaments extended toward the scaffold after the start of MS loading incubation and polymerized around the hepatocytes. The hepatocyte aggregation eventually advanced to the formation of spheroids.
  
  
  CONCLUSIONS
  These results suggest that MS-induced polymerization of actin filaments stimulate hepatocyte aggregation and thereby improve hepatocyte-specific function.
authors.affiliation: Department of Surgery, Saitama Medical School, Saitama, Japan. miyazawa@saitama-med.ac.jp
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Miyazawa
authors.forename: Takahiro
authors.initials: T
authors.lastname: Torii
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Toshimitsu
authors.forename: Katsuya
authors.initials: K
authors.lastname: Okada
authors.forename: Isamu
authors.initials: I
authors.lastname: Koyama
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000418:Albumins / Q000378:metabolism; D000818:Animals; D019149:Bioreactors; D002449:Cell Aggregation; D018929:Cell Culture Techniques / Q000295:instrumentation*; D002478:Cells, Cultured; D022781:Hepatocytes / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D012399:Rotation; D018874:Spheroids, Cellular; D013314:Stress, Mechanical
chemical_list: D000418:Albumins