Z Gastroenterol 2008; 46 - P1_17
DOI: 10.1055/s-2008-1037473

The absence of latent transforming growth factor-beta binding protein–1 (LTBP–1) inhibits TGF-beta secretion

F Drews 1, C Conrad 1, AM Gressner 1, R Weiskirchen 1
  • 1Institute of Clinical Chemistry and Pathobiochemistry, University Hospital of The RWTH Aachen, Aachen

Aims: Latent transforming growth factor (TGF)-β binding proteins (LTBPs) play important roles in the secretion and activation of TGF-β, which is a key factor in wound healing and fibrosis. TGF-β is synthesized as latent high-molecular weight complex, composed of TGF-β, a part of the TGF-β precursor, and the latent TGF-β binding protein. LTBP for itself is an ingredient of the extracellular matrix, targets TGF-β thither, and participates in the activation of free TGF-β. We have previously shown that mice lacking LTBP–1 are less prone to hepatic fibrogenesis [1]. To understand the underlying mechanisms, we here examined the capability of embryonic cells from wildtype and LTBP–1 knockout mice to secrete active TGF-β.

Methods: Embryonic fibroblasts were isolated from wildtype, heterozygous and also LTBP–1 knockout mice and cultivated for a few passages. The amount of active TGF-β in the medium was measured in a luciferase reporter assay with a TGF-β responsive promoter. Therefore, conditioned media of cultured fibroblasts were activated by a pH shift and finally added to mink lung epithelial cells (MLEC) [2]. The cells were harvested, and the luciferase activity was measured and normalized to the protein concentration.

Results: The level of biologically active TGF-β was distinctly higher in supernatants taken from wildtype cells than in medium of LTBP–1 knockout cells. Heterozygous cells behaved in between although cells from different animals demonstrated a certain variance. The observed effects were further influenced by cellular density during culturing of fibroblasts.

Conclusions: The lack of LTBP–1 obviously inhibits the cellular release of TGF-β and its bioavailability illustrating the relevant function of LTBP–1 in this process. This data also emphasise previous findings that LTBP–1 knockout mice are less susceptible to hepatic fibrogenesis.

Literatur: [1] Drews F, Knöbel S, Moser M, Muhlack KG, Mohren S, Stoll C, Bosio A, Gressner AM, Weiskirchen R (2007) BBA Mol. Cell Res., in press. [2] Abe M, Harpel JG, Meth CN, Nunes I, Loskutoff DJ, Rifkin DB (1994) Anal. Biochem. 216, 276-284.

LTBP-1 - TGF-beta bioavailability - TGF-beta signalling - knockout