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Myofibroblasts are the major source of extracellular matrix components that accumulate during tissue fibrosis, and hepatic stellate cells (HSCs) are believed to be the major source of myofibroblasts in the liver. To date, robust systems to genetically manipulate these cells have not been developed. We report that Cre under control of the promoter of Pdgfrb (Pdgfrb-Cre) inactivates loxP-flanked genes in mouse HSCs with high efficiency. We used this system to delete the gene encoding α(v) integrin subunit because various α(v)-containing integrins have been suggested as central mediators of fibrosis in multiple organs. Such depletion protected mice from carbon tetrachloride-induced hepatic fibrosis, whereas global loss of β₃, β₅ or β₆ integrins or conditional loss of β₈ integrins in HSCs did not. We also found that Pdgfrb-Cre effectively targeted myofibroblasts in multiple organs, and depletion of the α(v) integrin subunit using this system was protective in other models of organ fibrosis, including pulmonary and renal fibrosis. Pharmacological blockade of α(v)-containing integrins by a small molecule (CWHM 12) attenuated both liver and lung fibrosis, including in a therapeutic manner. These data identify a core pathway that regulates fibrosis and suggest that pharmacological targeting of all α(v) integrins may have clinical utility in the treatment of patients with a broad range of fibrotic diseases.

Author(s): L E Reynolds [1, 5]; F J Conti [1, 5]; M Lucas [3]; R Grose [2]; S Robinson [1]; M Stone [1]; G Saunders [1]; C Dickson [2]; R [...]

Myofibroblasts are the major source of extracellular matrix components that accumulate during tissue fibrosis, and hepatic stellate cells (HSCs) are believed to be the major source of myofibroblasts in the liver. To date, robust systems to genetically manipulate these cells have not been developed. We report that Cre under control of the promoter of Pdgfrb (Pdgfrb-Cre) inactivates loxP-flanked genes in mouse HSCs with high efficiency. We used this system to delete the gene encoding αv integrin subunit because various αv-containing integrins have been suggested as central mediators of fibrosis in multiple organs. Such depletion protected mice from carbon tetrachloride-induced hepatic fibrosis, whereas global loss of β3, β5 or β6 integrins or conditional loss of β8 integrins in HSCs did not. We also found that Pdgfrb-Cre effectively targeted myofibroblasts in multiple organs, and depletion of the αv integrin subunit using this system was protective in other models of organ fibrosis, including pulmonary and renal fibrosis. Pharmacological blockade of αv-containing integrins by a small molecule (CWHM 12) attenuated both liver and lung fibrosis, including in a therapeutic manner. These data identify a core pathway that regulates fibrosis and suggest that pharmacological targeting of all αv integrins may have clinical utility in the treatment of patients with a broad range of fibrotic diseases. [ABSTRACT FROM AUTHOR]

The upregulation of TGF-ß1 and integrin expression during wound healing has implicated these molecules in this process, but their precise regulation and roles remain unclear. Here we report that, notably, mice lackingß3-integrins show enhanced wound healing with re-epithelialization complete several days earlier than in wild-type mice. We show that this effect is the result of an increase in TGF-ß1 and enhanced dermal fibroblast infiltration into wounds ofß3-null mice. Specifically,ß3-integrin deficiency is associated with elevated TGF-ßreceptor I and receptor II expression, reduced Smad3 levels, sustained Smad2 and Smad4 nuclear localization and enhanced TGF-ß1-mediated dermal fibroblast migration. These data indicate thatavß3-integrin can suppress TGF-ß1-mediated signaling, thereby controlling the rate of wound healing, and highlight a new mechanism for TGF-ß1 regulation byß3-integrins. [ABSTRACT FROM AUTHOR]