Fig. 4.

Hepatocyte growth factor (HGF) and TGF-β1 signaling in microfluidic hepatocyte cultures. A: HGF ELISA demonstrates higher levels of this hepato-inductive signal in three-dimensional (3-D) small-volume cultures (3S) compared with small-volume microfluidic (2S) and 3-D large-volume (3L) cultures. Statistical significance determined by Mann–Whitney test. B: TGF-β1 ELISA demonstrating higher levels of this hepato-disruptive signal observed in 3L and 2S cultures where hepatic phenotype was decaying more rapidly. Lowest TGF-β1 levels were observed in 3S cultures where HGF was highest and hepatic phenotype was best maintained. Statistical significance determined by Welch’s t test. C: inhibitor of TGF-β signaling (A83-01, 5 μM) was added into cell culture media on daily basis. This resulted in maintenance of high albumin levels (measured by ELISA) over the course of 28 days. Statistical significance determined by Mann–Whitney test. *P < 0.05.