Fig 2: Establishment of a sandwich ELISA for detecting L59 LAP-DPs. a Schematic diagram of the ELISA for L59 LAP-DPs. In the ELISA, L59 LAP-DPs are first captured by coated L59 antibodies (Ab) and then sandwiched by biotin-conjugated anti-LAP antibodies (aLAP-Ab), which form a complex with strep-AP. For detection, an enzyme substrate is added and absorbance at 405 nm was measured. b, c Incubation time- and PLK concentration-dependent increases in the absorbance of the samples containing LAP incubated with PLK. The LAP (final 25 nM) was digested with 12.5 nM (open triangle), 25 nM (open reverse triangle), and 50 nM (open square) PLK, or without PLK (open circle) for 0–90 min, and then the samples were diluted by 1/50 and subjected to the L59 LAP-DP ELISA (b). Also, 25 nM rhLAP was digested with 50 nM PLK (open square) or PLN (cross mark), or PLK in the presence of 5 µM camostat mesilate (open diamond) (c). All data were presented as mean ± SD from two different experiments ?*p-value <0.05, **p-value <0.01, ***p-value<0.001 obtained comparing to corresponding control values

Fig 3: L59 LAP-DP levels in the culture media of TWNT-4 treated with SB431542. The (a) as well as (b) were measured after a 72-h treatment of TWNT-4 with 20 µM SB431542 (SB). Data are mean ± SD (N = 3). Representative results from two different experiments with similar results are shown ***p-value <0.001

Fig 4: Plasma concentrations of L59 LAP-DPs in BDL mice. a Plasma concentrations of L59 LAP-DPs, as well as hepatic HDP contents in BDL mice, were measured at the indicated post-operative days (POD). b The expression of aSMA protein in liver tissues was examined by Western blotting. Expression levels were semi-quantitated using NIH imageJ. A set of experiments was performed using two to four mice in each group. Representative results from two different experiments with similar results are shown *p-value <0.05, **p-value <0.01, ***p-value <0.001 obtained comparing to sham

Fig 5: Correlation among L59 LAP-DPs and active TGF-ß in the culture medium, and intracellular signal transduction. a, c The ×9CAGA-Luc-transformed CCL64 cells were cultured in PLK-added CM derived from HEK293T cells overexpressing hLTGF-ß1. After 6 h, the levels of active TGF-ß1 and L59 LAP-DPs were determined by respective ELISAs (a), and the extent of TGF-ß signaling was measured by luciferase activity in CCL64 cells (c). b, d The scatterplots between the levels of L59 LAP-DPs and active TGF-ß shown in a (b) and between increases in L59 LAP-DP levels and increases in luminescence from the values obtained compared to basal levels in the absence of PLK shown in c (d). A significant positive correlation was seen (b) *p-value <0.05, ***p-value <0.001 obtained comparing to 0