Methods: The synthesis of the basement membrane (BM) proteins entactin, laminin, and collagen type TV and of the extracellular matrix (ECM) proteins tenascin and fibronectin with or without TGF-beta 1 - stimulation was analyzed by immunostaining, immunoprecipitation of endogenously labeled proteins and Northern blot analysis of total RNA extracted from freshly isolated or cultured SECs from rat or guinea pig livers. Furthermore, SECs were isolated from acutely and chronically CCl4-damaged rat livers and were analyzed for matrix protein expression.

Results: SECs were adherent 24 h after isolation and formed confluent monolayers on day 4 of primary culture. Specific immunoprecipitates and specific transcripts for the BM proteins entactin, laminin, and collagen type IV and for ECM proteins tenascin and fibronectin were detectable in freshly isolated or cultured SECs. The synthesis of all tested BM proteins and ECM proteins was stimulated at least 3-fold by TGF-PL. In SECs isolated after CCl4-induced acute and chronic liver damage, increased levels of matrix protein transcripts were detectable.

Conclusions: The stimulation of the synthesis of all BM-proteins by TGF-beta 1 in vitro and the accumulation of ECM transcripts in SECs isolated from CCl4-treated livers, suggests that SECs are involved in the formation of a basement membrane during the "capillarization" of the sinusoids during liver disease.