TY - JOUR
T1 - Increased stiffness of the rat liver precedes matrix deposition
T2 - Implications for fibrosis
AU - Georges, Penelope C.
AU - Hui, Jia Ji
AU - Gombos, Zoltan
AU - McCormick, Margaret E.
AU - Wang, Andrew Y.
AU - Uemura, Masayuki
AU - Mick, Rosemarie
AU - Janmey, Paul A.
AU - Furth, Emma E.
AU - Wells, Rebecca G.
PY - 2007/12
Y1 - 2007/12
N2 - Liver fibrosis, the response to chronic liver injury, results from the activation of mesenchymal cells to fibrogenic myofibroblasts. We have recently shown that two key myofibroblast precursor populations, hepatic stellate cells and portal fibroblasts, undergo activation in culture in response to increasing substrate stiffness. We therefore hypothesized that alterations in liver stiffness precede myofibroblast activation and fibrosis in vivo as well. To test this hypothesis, we induced fibrosis in rats by twice weekly injections of carbon tetrachloride (CCl4) and then killed the animals at various time points ranging from 3 to 70 days after the initiation of injury. The shear storage modulus of the whole liver was measured on fresh tissue; fixed and frozen tissue from the same livers was used to quantify fibrosis. We observed that liver stiffness increased immediately and continued to increase, leveling out by day 28. Fibrosis, measured histologically by trichrome staining as well as by quantitative sirius red staining, increased with time, although these increases were delayed relative to changes in stiffness. There was no direct correlation between stiffness and fibrosis at early or late time points. Treatment of a second cohort of rats with the lysyl oxidase inhibitor, β-aminopropionitrile (BAPN), partially prevented early increases in liver stiffness. We concluded that increases in liver stiffness precede fibrosis and potentially myofibroblast activation. Liver stiffness appears to result from matrix cross-linking and possibly other unknown variables in addition to matrix quantity. We suggest that increased liver stiffness may play an important role in initiating the early stages of fibrosis.
AB - Liver fibrosis, the response to chronic liver injury, results from the activation of mesenchymal cells to fibrogenic myofibroblasts. We have recently shown that two key myofibroblast precursor populations, hepatic stellate cells and portal fibroblasts, undergo activation in culture in response to increasing substrate stiffness. We therefore hypothesized that alterations in liver stiffness precede myofibroblast activation and fibrosis in vivo as well. To test this hypothesis, we induced fibrosis in rats by twice weekly injections of carbon tetrachloride (CCl4) and then killed the animals at various time points ranging from 3 to 70 days after the initiation of injury. The shear storage modulus of the whole liver was measured on fresh tissue; fixed and frozen tissue from the same livers was used to quantify fibrosis. We observed that liver stiffness increased immediately and continued to increase, leveling out by day 28. Fibrosis, measured histologically by trichrome staining as well as by quantitative sirius red staining, increased with time, although these increases were delayed relative to changes in stiffness. There was no direct correlation between stiffness and fibrosis at early or late time points. Treatment of a second cohort of rats with the lysyl oxidase inhibitor, β-aminopropionitrile (BAPN), partially prevented early increases in liver stiffness. We concluded that increases in liver stiffness precede fibrosis and potentially myofibroblast activation. Liver stiffness appears to result from matrix cross-linking and possibly other unknown variables in addition to matrix quantity. We suggest that increased liver stiffness may play an important role in initiating the early stages of fibrosis.
KW - Hepatic stellate cells
KW - Lysyl oxidase
KW - Myofibroblast
KW - Reticulin
KW - Shear storage modulus
UR - http://www.scopus.com/inward/record.url?scp=37149050014&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=37149050014&partnerID=8YFLogxK
U2 - 10.1152/ajpgi.00032.2007
DO - 10.1152/ajpgi.00032.2007
M3 - Article
C2 - 17932231
AN - SCOPUS:37149050014
SN - 0193-1857
VL - 293
SP - G1147-G1154
JO - American Journal of Physiology - Gastrointestinal and Liver Physiology
JF - American Journal of Physiology - Gastrointestinal and Liver Physiology
IS - 6
ER -