Variation of immunocytochemical expression of transforming growth factor (TGF)-beta in hepatocytes in culture and liver slices.
Transforming growth factor beta (TGF-beta) is a major member of a cytokine family with pluripotent biological activity. In the liver, TGF-beta has pathophysiological significance with respect to hepatic fibrogenesis, regulation of liver cell growth, tumor development, and induction of hepatocellular apoptosis. We show that the expression of immunocytochemically detectable TGF-beta in cultured hepatocytes is strongly dependent on culture conditions and cellular microenvironment. Hepatocytes in situ and freshly isolated cells are TGF-beta negative. In contrast, hepatocytes in incubated liver slices are stained with a patch-like pattern, whereas parenchymal cells cultured as a monolayer exhibit strong diffuse positive immunostaining for TGF-beta within 2 h after seeding. The intensity of immunocytochemical staining is dependent on culture substrata, major expression being observed in cells maintained on glass or plastic surfaces. When collagen type-I and type-IV, or EHS-matrix are used as substrata, TGF-beta is absent or only weakly immunocytochemically apparent in cultured hepatocytes, irrespective of the culture medium used. The positive immunocytochemical expression of TGF-beta in hepatocytes arises neither by transcriptional and translational pathways nor by disturbed intracellular calcium homeostasis. However, calcium-dependent proteinases, such as calpain-I and -II, might be involved in the immunochemical presentation of intracellular TGF-beta, because respective calpain inhibitors strongly reduce the appearance of TGF-beta in cultured parenchymal liver cells. Thus, hepatocytes are a major cellular source of (latent) TGF-beta in liver, as becomes evident during culture.
Gressner
A M
AM
Department of Clinical Chemistry and Central Laboratory, Philipps University, Baldingerstrasse, D-35033 Marburg, Germany. gressner@mailer.uni-marburg.de
Wulbrand
U
U
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002154:Calpain / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D018920:Coculture Techniques; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D007150:Immunohistochemistry; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D011500:Protein Synthesis Inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D013194:Staining and Labeling; D014107:Tosyllysine Chloromethyl Ketone / Q000494:pharmacology; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D007476:Ionophores; D011500:Protein Synthesis Inhibitors; D016212:Transforming Growth Factor beta; D003609:Dactinomycin; D014107:Tosyllysine Chloromethyl Ketone; D000001:Calcimycin; D014108:Tosylphenylalanyl Chloromethyl Ketone; D015759:Ionomycin; D003513:Cycloheximide; D002154:Calpain