Lack of the Matricellular Protein SPARC (Secreted Protein, Acidic and Rich in Cysteine) Attenuates Liver Fibrogenesis in Mice

Catalina Atorrasagasti,Laura Alaniz,Néstor Kippes,Esteban J Fiore,Guillermo Mazzolini,Elizabeth Guruceaga,Ramón Bataller,Juan Bayo,Mariana Garcia,Fernando Corrales,Jorge B Aquino,Flavia Piccioni,Mariana Malvicini,Estanislao Peixoto,Osvaldo Podhajcer

doi:10.1371/journal.pone.0054962

Abstract

IntroductionSecreted Protein, Acidic and Rich in Cysteine (SPARC) is a matricellular protein involved in many biological processes and found over-expressed in cirrhotic livers. By mean of a genetic approach we herein provide evidence from different in vivo liver disease models suggesting a profibrogenic role for SPARC.MethodsTwo in vivo models of liver fibrosis, based on TAA administration and bile duct ligation, were developed on SPARC wild-type (SPARC+/+) and knock-out (SPARC−/−) mice. Hepatic SPARC expression was analyzed by qPCR. Fibrosis was assessed by Sirius Red staining, and the maturation state of collagen fibers was analyzed using polarized light. Necroinflammatory activity was evaluated by applying the Knodell score and liver inflammatory infiltration was characterized by immunohistochemistry. Hepatic stellate cell activation was assessed by α-SMA immunohistochemistry. In addition, pro-fibrogenic genes and inflammatory cytokines were measured by qPCR and/or ELISA. Liver gene expression profile was analyzed in SPARC−/− and SPARC+/+ mice using Affymetrix Mouse Gene ST 1.0 array.ResultsSPARC expression was found induced in fibrotic livers of mouse and human. SPARC−/− mice showed a reduction in the degree of inflammation, mainly CD4+ cells, and fibrosis. Consistently, collagen deposits and mRNA expression levels were decreased in SPARC−/− mice when compared to SPARC+/+ mice; in addition, MMP-2 expression was increased in SPARC−/− mice. A reduction in the number of activated myofibroblasts was observed. Moreover, TGF-β1 expression levels were down-regulated in the liver as well as in the serum of TAA-treated knock-out animals. Ingenuity Pathway Analysis (IPA) analysis suggested several gene networks which might involve protective mechanisms of SPARC deficiency against liver fibrogenesis and a better established machinery to repair DNA and detoxify from external chemical stimuli.ConclusionsOverall our data suggest that SPARC plays a significant role in liver fibrogenesis. Interventions to inhibit SPARC expression are suggested as promising approaches for liver fibrosis treatment.

Highlights

Secreted Protein, Acidic and Rich in Cysteine (SPARC) is a matricellular protein involved in many biological processes and found over-expressed in cirrhotic livers
These findings suggest that SPARC may have a prominent role in liver fibrogenesis; we have recently demonstrated that a forced transitory reduction in SPARC expression levels by an adenovirus encoding an antisense specific for SPARC mRNA (AdasSPARC) attenuates fibrosis development in an in vivo experimental rat model [5]
To address whether SPARC expression levels may change during liver fibrogenesis, samples were processed for qPCR studies

Summary

Introduction

Secreted Protein, Acidic and Rich in Cysteine (SPARC) is a matricellular protein involved in many biological processes and found over-expressed in cirrhotic livers. SPARC was found overexpressed in activated hepatic stellate (HSCs) and in endothelial cells [6,7]. These findings suggest that SPARC may have a prominent role in liver fibrogenesis; we have recently demonstrated that a forced transitory reduction in SPARC expression levels by an adenovirus encoding an antisense specific for SPARC mRNA (AdasSPARC) attenuates fibrosis development in an in vivo experimental rat model [5]

Methods

Results

Conclusion