Freshly isolated adult rat hepatocytes exhibit a flat, extended morphology when cultured on dried rat tail collagen in the presence of growth factors; they actively synthesize DNA and express high levels of cytoskeletal mRNAs and proteins (actin, tubulin, cytokeratins, vinculin, alpha-actinin, and desmoplakin), while exhibiting low levels of liver-specific mRNAs (albumin, alpha 1-inhibitor III, and alpha 1-antitrypsin) and limited synthesis and secretion of albumin. Hepatocytes cultured on hydrated gel matrix from the Engelbreth-Holm-Swarm (EHS) mouse tumor form small spherical aggregates and exhibit low DNA, cytoskeletal mRNA, and protein synthesis, while at the same time exhibiting elevated liver-specific mRNAs and albumin production; these cells, therefore, more nearly conform to the program of gene expression seen within the normal animal. Hepatocytes on hydrated rat tail collagen resemble those on dry collagen when cultured at low density, but at high density they form compact trabecular aggregates, synthesize negligible amounts of DNA, and maintain a pattern of gene expression resembling that of hepatocytes seeded on the EHS matrix. If cell morphology is compact, as on EHS or on hydrated rat tail collagen when densely populated, DNA synthesis and expression of cytoskeletal genes are low, while liver-specific mRNAs are abundant. When cells are extended the opposite is the case. Without the growth supplement DNA synthesis is low throughout but gene expression is little affected. These studies point to the importance of cell-cell and cell-matrix interactions in determining the differentiated phenotype of hepatocytes, and they reveal an inverse relationship between cytoskeletal and liver-specific protein expression.
[1]
L. Johnson,et al.
Regulation of histone mRNA production and stability in serum-stimulated mouse 3T6 fibroblasts
,
1983,
Molecular and cellular biology.
[2]
D. Capco,et al.
Cytoplasmic and nuclear architecture in cells and tissue: form, functions, and mode of assembly.
,
1982,
Cold Spring Harbor symposia on quantitative biology.
[3]
A. Ben-Ze'ev,et al.
Regulation of actin mRNA levels and translation responds to changes in cell configuration
,
1983,
Molecular and cellular biology.
[4]
J. Darnell,et al.
Posttranscriptional modulation of gene expression in cultured rat hepatocytes
,
1984,
Molecular and cellular biology.