Figure 4.

Profile of isolated hepatocytes exposed to hypoxia and normoxia. Hepatocytes isolated from C57BL/6 mice express and secrete lysyl oxidase (LOX) in response to hypoxia, resulting in more active collagen cross-linking. (A) Results of reverse-transcriptase polymerase chain reaction demonstrating that expression of LOX messenger RNA from hepatocytes exposed to hypoxia for 24 h is increased (5.9 times normoxia value; *P = 0.046). (B) Results of Western blot showing that LOX is secreted into culture media by hepatocytes exposed to hypoxia for 24 h. (C) Confocal reflection microscopy images of collagen matrices incorporating fixed amounts of concentrated culture media from cells exposed to 16% O₂ (left panel), 1% O₂ (middle panel), and 1% O₂ plus β-aminopropionitrile (BAPN), a LOX inhibitor (right panel). A denser network of precipitated, cross-linked collagen fibers is seen in hypoxia without BAPN. (D) Mean pixel density of collagen from images obtained during the collagen cross-linking experiment in C. P < 0.001 in all group comparisons.