Attenuated liver fibrogenesis in SPARC (Secreted Protein, Acidic and Rich in Cysteine)-deficient mice.

ATORRASAGASTI C; AQUINO JB; KIPPES NESTOR; MALVICINI M; ALANIZ L; GARCIA M; PICCIONI F; BAYO FINA J; BATALLER R; PODHAJCER O; MAZZOLINI G

San Fransico

Congreso; 62 ND Annual Meeting of the American Association for the study of liver diseases; 2011

Introduction: Liver cirrhosis is characterized by the accumulation of extracellular matrix (ECM) that leads to disorganization of the parenchymal architecture and the subsequent liver failure. Secreted protein acidic and rich in cysteine (SPARC) is a 43-kDa ECM glycoprotein involved in many biological processes including cell adhesion, wound healing, differentiation and proliferation. It is upregulated in cirrhosis, mainly in hepatic stellate cells (HSC), although its role in the development of liver fibrosis remains unknown. We have previously observed that the administration of an adenovirus that encodes a SPARC antisense mRNA (AdasSPARC) in a rat model (Camino et al 2006) results in attenuation of liver fibrosis and decrease the number of activated HSC. The aim of this study was to investigate the development of fibrosis on SPARC null mice. Methods: Two in vivo models of liver fibrosis, based on TAA chronic intoxication and bile duct ligation (BDL), were developed on SPARC wild-type (SPARC+/+) and knock-out (SPARC-/-) mice. Additionally, SPARC expression levels in human liver samples were analyzed by qPCR. Fibrosis was assessed by Sirius Red and hyaluronan-binding stainings, and the maturation state of collagen fibers was analyzed using polarized light. Necroinflammatory activity was evaluated by Knodell score. Activated HSC were assessed by α-SMA immunohistochemistry. Pro-fibrogenic genes and inflammatory cytokines were measured by qPCR and/or ELISA. Results: SPARC was overexpressed in fibrotic livers of mouse and human. In SPARC-/- mice the development of hepatic fibrosis was markedly attenuated and a reduction in the inflammatory and fibrosis degree was observed. Consistently, collagen deposits (Sirius red stained positive area: 4.37±0.85 vs 2.06±0.23, WT vs. SPARC-/-, respectively), mRNA collagen expression levels (6.48±0.95 vs 3.31±0.64, WT vs. SPARC-/-, respectively) and hyaluronan accumulation were decreased in SPARC-/- mice when compared to WT mice. In addition, a reduction in the number of activated myofibroblasts was observed (positive α-SMA area: 0.45±0.02 vs. 0.11±0.01, WT vs. SPARC-/-, respectively). Moreover, TGF-β1 expression levels were also down-regulated in the liver (3.34±0.25 vs 2.2±0.19; WT vs. SPARC-/-, respectively) as well as in the serum of TAA-treated knock-out animals when compared to treated wild-type counterparts (936±83 vs. 489±59 pg/ml, WT vs. SPARC-/-, respectively). Conclusions: SPARC plays a significant role in liver fibrogenesis. Interventions to inhibit SPARC expression are suggested as promising approaches for liver fibrosis treatment.