Small interfering RNA inhibition of SPARC attenuates the profibrotic effect of transforming growth factor ?1 in cultured normal human fibroblasts

Sustained intra-cellular siRNA release from Poly(hypenCapswithspaceRetainColl1rginine) multilayered nanoparticles for prolonged gene silencing

BACKGROUND

Sustained siRNA release from nanocarriers is difficult to achieve inside the cell after entry: typically, all nanocarriers exhibit burst release of the cargo into the cytoplasm.

RESEARCH DESIGN AND METHODS

Layer by layer (LbL) nanoparticles (NPs) can be constructed so that they escape endosomes intact, and subsequently exhibit sustained release of the cargo. Our work quantifies intra-cellular siRNA release from multilayered NPs, evaluates mechanism behind the sustained release, and optimizes the duration of release.

RESULTS

Intra-cellular studies showed that nanoparticles developed with 4 layers of polyL-arginine, alternated with 3 layers of siRNA layers was able to elicit effective and prolonged SPARC knockdown activity over 21 days with a single dose treatment. For the first time, we have quantified the amounts of released siRNA in the cytoplasm and the amount of siRNA remaining inside the nanoparticles at each timepoint. Furthermore, we have correlated the amount of released siRNA within cells by LbL NPs to the cellular knockdown efficiency of multilayered delivery system.

CONCLUSIONS

This methodology may provide an excellent screening tool for assessing the duration of gene silencing by various nanocarrier formulations.

Decellularized heart extracellular matrix alleviates activation of hiPSC-derived cardiac fibroblasts

Human induced pluripotent stem cell derived cardiac fibroblasts (hiPSC-CFs) play a critical role in modeling human cardiovascular diseases in vitro. However, current culture substrates used for hiPSC-CF differentiation and expansion, such as Matrigel and tissue culture plastic (TCPs), are tissue mismatched and may provide pathogenic cues. Here, we report that hiPSC-CFs differentiated on Matrigel and expanded on tissue culture plastic (M-TCP-iCFs) exhibit transcriptomic hallmarks of activated fibroblasts limiting their translational potential. To alleviate pathogenic activation of hiPSC-CFs, we utilized decellularized extracellular matrix derived from porcine heart extracellular matrix (HEM) to provide a biomimetic substrate for improving hiPSC-CF phenotypes. We show that hiPSC-CFs differentiated and expanded on HEM (HEM-iCFs) exhibited reduced expression of hallmark activated fibroblast markers versus M-TCP-iCFs while retaining their cardiac fibroblast phenotype. HEM-iCFs also maintained a reduction in expression of hallmark genes associated with pathogenic fibroblasts when seeded onto TCPs. Further, HEM-iCFs more homogenously integrated into an hiPSC-derived cardiac organoid model, resulting in improved cardiomyocyte sarcomere development. In conclusion, HEM provides an improved substrate for the differentiation and propagation of hiPSC-CFs for disease modeling.

The role of SPARC (secreted protein acidic and rich in cysteine) in the pathogenesis of obesity, type 2 diabetes, and non-alcoholic fatty liver disease

Secreted protein acidic and rich in cysteine (SPARC) is an extracellular matrix glycoprotein with pleiotropic functions, which is expressed in adipose, hepatic, muscular, and pancreatic tissue. Particularly, several studies demonstrated that SPARC is an important player in the context of obesity, diabetes, and fatty liver disease including advanced hepatic fibrosis and hepatocellular carcinoma. Evidence in murine and human samples indicates that SPARC is involved in adipogenesis, cellular metabolism, extracellular matrix modulation, glucose and lipid metabolism, among others. Furthermore, studies in SPARC knockout mouse model showed that SPARC contributes to adipose tissue formation, non-alcoholic fatty liver disease (NAFLD), and diabetes. Hence, SPARC may represent a novel and interesting target protein for future therapeutic interventions or a biomarker of disease progression. This review summarizes the role of SPARC in the pathophysiology of obesity, and extensively revised SPARC functions in physiological and pathological adipose tissue deposition, muscle metabolism, liver, and diabetes-related pathways.

SPARC Is Highly Expressed in Young Skin and Promotes Extracellular Matrix Integrity in Fibroblasts via the TGF-β Signaling Pathway

The matricellular secreted protein acidic and rich in cysteine (SPARC; also known as osteonectin), is involved in the regulation of extracellular matrix (ECM) synthesis, cell-ECM interactions, and bone mineralization. We found decreased SPARC expression in aged skin. Incubating foreskin fibroblasts with recombinant human SPARC led to increased type I collagen production and decreased matrix metalloproteinase-1 (MMP-1) secretion at the protein and mRNA levels. In a three-dimensional culture of foreskin fibroblasts mimicking the dermis, SPARC significantly increased the synthesis of type I collagen and decreased its degradation. In addition, SPARC also induced receptor-regulated SMAD (R-SMAD) phosphorylation. An inhibitor of transforming growth factor-beta (TGF-β) receptor type 1 reversed the SPARC-induced increase in type I collagen and decrease in MMP-1, and decreased SPARC-induced R-SMAD phosphorylation. Transcriptome analysis revealed that SPARC modulated expression of genes involved in ECM synthesis and regulation in fibroblasts. RT-qPCR confirmed that a subset of differentially expressed genes is induced by SPARC. These results indicated that SPARC enhanced ECM integrity by activating the TGF-β signaling pathway in fibroblasts. We inferred that the decline in SPARC expression in aged skin contributes to process of skin aging by negatively affecting ECM integrity in fibroblasts.

Positive-charge tuned gelatin hydrogel-siSPARC injectable for siRNA anti-scarring therapy in post glaucoma filtration surgery

Small interfering RNA (siRNA) therapy is a promising epigenetic silencing strategy. However, its widespread adoption has been severely impeded by its ineffective delivery into the cellular environment. Here, a biocompatible injectable gelatin-based hydrogel with positive-charge tuned surface charge is presented as an effective platform for siRNA protection and delivery. We demonstrate a two-step synthesis of a gelatin-tyramine (Gtn-Tyr) hydrogel with simultaneous charge tunability and crosslinking ability. We discuss how different physiochemical properties of the hydrogel interact with siSPARC (siRNA for secreted protein, acidic and rich in cysteine), and study the positive-charge tuned gelatin hydrogel as an effective delivery platform for siSPARC in anti-fibrotic treatment. Through in vitro studies using mouse tenon fibroblasts, the positive-charge tuned Gtn-Tyr hydrogel shows sustained siSPARC cellular internalization and effective SPARC silencing with excellent biocompatibility. Similarly, the same hydrogel platform delivering siSPARC in an in vivo assessment employing a rabbit model shows an effective reduction in subconjunctival scarring in post glaucoma filtration surgery, and is non-cytotoxic compared to a commonly used anti-scarring agent, mitomycin-C. Overall, the current siRNA delivery strategy involving the positive-charge tuned gelatin hydrogel shows effective delivery of gene silencing siSPARC for anti-fibrotic treatment. The current charge tunable hydrogel delivery system is simple to fabricate and highly scalable. We believe this delivery platform has strong translational potential for effective siRNA delivery and epigenetic silencing therapy.

Immunomodulatory Role of the Extracellular Matrix Within the Liver Disease Microenvironment

Chronic liver disease when accompanied by underlying fibrosis, is characterized by an accumulation of extracellular matrix (ECM) proteins and chronic inflammation. Although traditionally considered as a passive and largely architectural structure, the ECM is now being recognized as a source of potent damage-associated molecular pattern (DAMP)s with immune-active peptides and domains. In parallel, the ECM anchors a range of cytokines, chemokines and growth factors, all of which are capable of modulating immune responses. A growing body of evidence shows that ECM proteins themselves are capable of modulating immunity either directly via ligation with immune cell receptors including integrins and TLRs, or indirectly through release of immunoactive molecules such as cytokines which are stored within the ECM structure. Notably, ECM deposition and remodeling during injury and fibrosis can result in release or formation of ECM-DAMPs within the tissue, which can promote local inflammatory immune response and chemotactic immune cell recruitment and inflammation. It is well described that the ECM and immune response are interlinked and mutually participate in driving fibrosis, although their precise interactions in the context of chronic liver disease are poorly understood. This review aims to describe the known pro-/anti-inflammatory and fibrogenic properties of ECM proteins and DAMPs, with particular reference to the immunomodulatory properties of the ECM in the context of chronic liver disease. Finally, we discuss the importance of developing novel biotechnological platforms based on decellularized ECM-scaffolds, which provide opportunities to directly explore liver ECM-immune cell interactions in greater detail.

Polymorphisms in SPARC and coal workers' pneumoconiosis risk in a Chinese population

Background

The SPARC is a crucial matricellular protein and may influence the course of various diseases like tumor metastasis and fibrosis. In the present study, we investigated the association between the potential functional polymorphisms in SPARC and coal workers' pneumoconiosis (CWP) risk in a Chinese population.

Methods

Five potentially functional polymorphisms (rs1059279, rs1059829, rs1053411, rs2304052 and rs4958281) in SPARC were genotyped and analyzed in a case-control study including 697 CWP cases and 694 controls. The genotyping was used by the TaqMan method with the ABI 7900HT Real Time PCR system.

Results

Our results revealed that three SNPs (rs1059279, rs1059829, rs1053411) were significantly associated with increased risk of CWP under an additive model (OR = 1.35, 95%CI = 1.06–1.71, P = 0.015 for rs1059279; OR = 1.20, 95%CI = 1.03–1.39, P = 0.021 for rs1059829; OR = 1.31, 95%CI = 1.03–1.65, P = 0.025 for rs1053411). In the stratification analysis, significant associations were observed between each of these three SNPs and patients with 0–20 pack-years of smoking (OR = 1.73, 95%CI = 1.21–2.45 for rs1059279; OR = 1.48, 95%CI = 1.07–2.05 for rs105982; OR = 1.58, 95%CI = 1.13–2.22 for rs1053411). Furthermore, the association between rs1059279 and CWP risk remained significant among subjects with over 27 years of exposure (OR = 1.27, 95%CI = 1.03–1.56, P = 0.023). In the combined analysis of these five polymorphisms, individuals with multiple risk alleles had a higher risk of CWP (Ptrend = 0.015).

Conclusion

Our results indicate that three functional SPARC SNPs are associated with an increased risk of CWP in a Chinese population. Further functional research and validation studies with diverse populations are warranted to confirm our findings.

Dissection of the mechanism of traditional Chinese medical prescription-Yiqihuoxue formula as an effective anti-fibrotic treatment for systemic sclerosis

Background

Systemic sclerosis (SSc) is a connective tissue fibrotic disease for which there is no effective treatment. Traditional Chinese Medicine (TCM), such as the Yiqihuoxue formula used in Shanghai TCM-integrated Hospital, has shown the efficacy of anti-fibrosis in clinical applications. This study was aiming to dissect the anti-fibrotic mechanism of Yiqihuoxue treatment for SSc.

Methods

Bleomycin-induced mice and SSc dermal fibroblasts were treated with Yiqihuoxue decoction; NIH-3T3 fibroblasts were exposed to exogenous TGF-β1, and then cultured with or without Yiqihuoxue decoction. Luciferase reporter gene assay was used to determine the activity of Smad binding element (SBE). Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to examine the mRNA levels of extracellular matrix (ECM) genes. The protein levels of type I collagen, Smad3 and phosphorylated-Smad3 (p-Smad3) were detected by western blotting. Student’s t-tests were used to determine the significance of the results.

Results

Bleomycin-induced mice, SSc dermal fibroblasts and TGF-β1-induced NIH/3T3 fibroblasts showed higher levels of ECM gene transcriptions and collagen production. In addition, the phosphorylation level of Smad3 and activity of SBE were significantly increased after exogenous TGF-β1 induction. Whereas, Yiqihuoxue treatment could obviously attenuate fibrosis in bleomycin-induced mice, down regulate ECM gene expressions and collagen production in SSc dermal fibroblasts and TGF-β1-induced NIH/3T3 fibroblasts. Furthermore, the aberrantly high phosphorylation level of Smad3 and activity of SBE in the TGF-β1-induced NIH/3T3 fibroblasts were also dramatically decreased by Yiqihuoxue treatment.

Conclusions

Yiqihuoxue treatment could effectively reduce collagen production via down-regulating the phosphorylation of Smad3 and then the activity of SBE, which are involved in the TGF-β pathway and constitutively activated in the progression of SSc.

Secreted protein acidic and rich in cysteine (SPARC) is upregulated by transforming growth factor (TGF)-β and is required for TGF-β-induced hydrogen peroxide production in fibroblasts

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a poorly understood progressive disease characterized by the recurrent damage of alveolar epithelial cells as well as inappropriate expansion and activation of fibroblasts resulting in pronounced extracellular matrix (ECM) deposition. Although recent studies have indicated the involvement of secreted protein acidic and rich in cysteine (SPARC), a matricellular protein regulating ECM deposition, in the pathogenesis of fibrosis, factors regulating SPARC expression or roles of SPARC in fibrosis have not been fully elucidated.

RESULTS

Among the profibrotic factors examined in cultured fibroblasts, we showed that SPARC expression was upregulated mainly by transforming growth factor (TGF)-β. We also showed that expression of SPARC in the lung was upregulated in the murine bleomycin-induced pulmonary fibrosis model, which was inhibited by TGF-β receptor I inhibitor. Knockdown of SPARC in fibroblasts using siRNA or treatment with the antioxidant N-acetylcysteine attenuated epithelial cell injury induced by TGF-β-activated fibroblasts in a coculture system. We also demonstrated that SPARC was required for hydrogen peroxide (H2O2) production in fibroblasts treated with TGF-β. Furthermore, TGF-β activated integrin-linked kinase (ILK), which was inhibited by SPARC siRNA. Knockdown of ILK attenuated extracellular H2O2 generation in TGF-β-stimulated fibroblasts. Our results indicated that SPARC is upregulated by TGF-β and is required for TGF-β-induced H2O2 production via activation of ILK, and this H2O2 production from fibroblasts is capable of causing epithelial cell injury.

CONCLUSIONS

The results presented in this study suggest that SPARC plays a role in epithelial damage in the IPF lung via enhanced H2O2 production from fibroblasts activated by TGF-β. Therefore, SPARC inhibition may prevent epithelial injury in IPF lung and represent a potential therapeutic approach for IPF.

Prospective potency of TGF-β1 on maintenance and regeneration of periodontal tissue

Periodontal ligament (PDL) tissue, central in the periodontium, plays crucial roles in sustaining tooth in the bone socket. Irreparable damages of this tissue provoke tooth loss, causing a decreased quality of life. The question arises as to how PDL tissue is maintained or how the lost PDL tissue can be regenerated. Stem cells included in PDL tissue (PDLSCs) are widely accepted to have the potential to maintain or regenerate the periodontium, but PDLSCs are very few in number. In recent studies, undifferentiated clonal human PDL cell lines were developed to elucidate the applicable potentials of PDLSCs for the periodontal regenerative medicine based on cell-based tissue engineering. In addition, it has been suggested that transforming growth factor-beta 1 is an eligible factor for the maintenance and regeneration of PDL tissue.

The Function of SPARC as a Mediator of Fibrosis

Fibrosis is a common end-point of a number of different diseases such as hypertension, diabetes, liver cirrhosis, and those associated with chronic inflammation. Fibrosis is characterized by excessive deposition of extracellular matrix that interferes with normal tissue architecture and function. Increased expression of secreted protein acidic and rich in cysteine (SPARC) in fibrotic tissues has been reported in numerous studies. SPARC is a 43 kDa collagen-binding protein secreted from several different cell types into the extracellular matrix and has been shown to be anti-proliferative and counter-adhesive in vitro. SPARC is a matricellular protein; meaning SPARC is secreted into the extracellular space but does not serve a structural function. Instead, SPARC modulates interactions between cells and the surrounding extracellular matrix. In animal models of fibrotic disease and in human fibrotic tissues, elevated expression of SPARC has been reported in many tissues including heart, lungs, kidneys, liver, dermis, intestine, and eyes. In this review, we will summarize current studies that have examined the expression and functional importance of SPARC in various animal models of fibrosis and in human tissues. Although cellular mechanisms of SPARC in fibrosis remain to be fully elucidated, the studies summarized here provide impetus to further explore the efficacy of SPARC as a potential target for reducing fibrosis.

Attenuation of expression of extracellular matrix genes with siRNAs to Sparc and Ctgf in skin fibroblasts of CTGF transgenic mice

Transgenic mice that over-express connective tissue growth factor (CTGF) in fibroblasts under the control of an enhancer/promoter element of the Col1a2 gene (Col1a2-CTGF) recapitulate multiorgan fibrosis similar to fibrosis observed in Scleroderma (SSc). In this study we investigate the regulation of secreted protein acidic and rich in cysteine (Sparc) and Ctgf siRNAs on the expression of several extracellular matrix components in the fibroblasts derived from Col1a2-CTGF transgenic mice. Three fibroblast lines were obtained from each of wide type C57BL/6 and CTGF transgenic C57BL/6, and were transfected with Sparc siRNA or Ctgf siRNA. Real-time quantitative RT-PCR and Western blotting were used to examine the transcription and protein levels of type I collagen, CTGF and SPARC. Student's t-tests were used to determine the significance of the results. Our results showed that Col1a2 and Ctgf increased expression at both transcriptional and translational levels in the fibroblasts from the Col1a2-CTGF transgenic mice compared with those in the fibroblasts from their normal wild-type littermate. The treatment with Sparc siRNA or Ctgf siRNA attenuated the mRNA and/or protein expression of the Col1a2, Ctgf and Sparc in these fibroblasts. Sparc and Ctgf siRNAs also showed a reciprocal inhibition at transcript levels. Therefore, our results indicated that both SPARC and CTGF appeared to be involved in the same biological pathway, and they have the potential to serve as a therapeutic target for fibrotic diseases such as SSc.

SPARC downregulation attenuates the profibrogenic response of hepatic stellate cells induced by TGF-β1 and PDGF

Liver fibrosis is an active process that involves changes in cell-cell and cell-extracellular matrix (ECM) interaction. Secreted protein, acidic and rich in cysteine (SPARC) is an ECM protein with many biological functions that is overexpressed in cirrhotic livers and upregulated in activated hepatic stellate cells (aHSCs). We have recently shown that SPARC downregulation ameliorates liver fibrosis in vivo. To uncover the cellular mechanisms involved, we have specifically knocked down SPARC in two aHSC lines [the CFSC-2G (rat) and the LX-2 (human)] and in primary cultured rat aHSCs. Transient downregulation of SPARC in hepatic stellate cells (HSCs) did not affect their proliferation and had only minor effects on apoptosis. However, SPARC knockdown increased HSC adhesion to fibronectin and significantly decreased their migration toward PDFG-BB and TGF-β(1). Interestingly, TGF-β(1) secretion by HSCs was reduced following SPARC small interfering RNA (siRNA) treatment, and preincubation with TGF-β(1) restored the migratory capacity of SPARC siRNA-treated cells through mechanisms partially independent from TGF-β(1)-mediated induction of SPARC expression; thus SPARC knockdown seems to exert its effects on HSCs partially through modulation of TGF-β(1) expression levels. Importantly, collagen-I mRNA expression was reduced in SPARC siRNA-transfected HSCs. Consistent with previous results, SPARC knockdown in aHSCs was associated with altered F-actin expression patterns and deregulation of key ECM and cell adhesion molecules, i.e., downregulation of N-cadherin and upregulation of E-cadherin. Our data together suggest that the upregulation of SPARC previously reported for aHSCs partially mediates profibrogenic activities of TGF-β(1) and PDGF-BB and identify SPARC as a potential therapeutic target for liver fibrosis.

Toll-like receptor 3 upregulation by type I interferon in healthy and scleroderma dermal fibroblasts

Introduction

Increased levels of genes in the type I interferon (IFN) pathway have been observed in patients with systemic sclerosis (SSc), or scleroderma. How type I IFN regulates the dermal fibroblast and its participation in the development of dermal fibrosis is not known. We hypothesized that one mechanism by which type I IFN may contribute to dermal fibrosis is through upregulation of specific Toll-like receptors (TLRs) on dermal fibroblasts. Therefore, we investigated the regulation of TLR expression on dermal fibroblasts by IFN.

Methods

The expression of TLRs was assessed in cultured dermal fibroblasts from control and SSc patients stimulated with IFNα2. The ability of IFNα2 to regulate TLR-induced interleukin (IL)-6 and CC chemokine ligand 2 production was also assessed. Immunohistochemical analyses were performed to determine whether TLR3 was expressed in skin biopsies in the bleomycin-induced skin fibrosis model and in patients with SSc.

Results

IFNα2 increased TLR3 expression on human dermal fibroblasts, which resulted in enhanced TLR3-induced IL-6 production. SSc fibroblasts have an augmented TLR3 response to IFNα2 relative to control fibroblasts. Pretreatment of fibroblasts with transforming growth factor (TGF)-β increased TLR3 induction by IFNα2, but coincubation of TGF-β did not alter TLR3 induction by IFN. Furthermore, IFNα2 inhibits but does not completely block the induction of connective tissue growth factor and collagen expression by TGF-βin fibroblasts. TLR3 expression was observed in dermal fibroblasts and inflammatory cells from skin biopsies from patients with SSc as well as in the bleomycin-induced skin fibrosis model.

Conclusions

Type I IFNs can increase the inflammatory potential of dermal fibroblasts through the upregulation of TLR3.

LPS induces greater bone and PDL loss in SPARC-null mice

Individuals with periodontal disease have increased risk of tooth loss, particularly in cases with associated loss of alveolar bone and periodontal ligament (PDL). Current treatments do not predictably regenerate damaged PDL. Collagen I is the primary component of bone and PDL extracellular matrix. SPARC/Osteonectin (SP/ON) is implicated in the regulation of collagen content in healthy PDL. In this study, periodontal disease was induced by injections of lipopolysaccharide (LPS) from Aggregatibacter actinomycetemcomitans in wild-type (WT) and SP/ON-null C57/Bl6 mice. A 20-µg quantity of LPS was injected between the first and second molars 3 times a week for 4 weeks, whereas PBS control was injected into the contralateral maxilla. LPS injection resulted in a significant decrease in bone volume fraction in both genotypes; however, significantly greater bone loss was detected in SP/ON-null maxilla. SP/ON-null PDL exhibited more extensive degradation of connective tissue in the gingival tissues. Although total cell numbers in the PDL of SP/ON-null were not different from those in WT, the inflammatory infiltrate was reduced in SP/ON-null PDL. Histology of collagen fibers revealed marked reductions in collagen volume fraction and in thick collagen volume fraction in the PDL of SP/ON-null mice. SP/ON protects collagen content in PDL and in alveolar bone in experimental periodontal disease.

The role of CTGF in the diabetic rat retina and its relationship with VEGF and TGF-β(2) , elucidated by treatment with CTGFsiRNA

PURPOSE

 The critical association of connective tissue growth factor (CTGF) with diabetic retinopathy (DR) remains to be clarified. We detected alterations in the gene and protein expression of CTGF and related cytokines, including vascular endothelial growth factor (VEGF) and transforming growth factor-β(2) (TGF-β(2) ), and their response to small interfering RNA (siRNA) targeting the CTGF (CTGFsiRNA) in the retina of diabetic rats. The relationships between CTGF, VEGF and TGF-β(2) levels, as well as the degree of apoptosis in the diabetic retina, were also investigated.

METHODS

  Diabetes was induced in rats by the β-cell toxin streptozotocin (STZ). Retinas were obtained from control and diabetic rats and similar animals treated with CTGFsiRNA by intravitreal injection. mRNA level and protein expression of CTGF, VEGF and TGF-β(2) were measured by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, and located by immunohistochemistry. Retinal apoptosis was detected by TUNEL staining.

RESULTS

The levels of CTGF, VEGF and TGF-β(2) and the number of TUNEL-positive nuclei were significantly higher in diabetic retinas than in control retinas (p<0.01). The level of CTGF rose at 8weeks, earlier than levels of VEGF and TGF-β(2) , which rose at 12weeks after the onset of diabetes. The difference was significant (p<0.05). siRNA-mediated inhibition of CTGF mRNA inhibited retinal VEGF and TGF-β(2) and also resulted in a significant decrease in apoptosis. Significant correlations were found between CTGF and VEGF (p=0.009), CTGF and TGF-β(2) (p=0.01), and apoptosis and these three cytokines (p<0.01) in the rat retina early in diabetes.

CONCLUSIONS

These results suggest that the diabetes-mediated increase in CTGF upregulates VEGF and TGF-β(2) expression and induces apoptosis in the retina. This elevation may be inhibited by treatment with CTGFsiRNA. Connective tissue growth factor may serve as a potential target for the prevention and treatment of DR.

CTGFsiRNA ameliorates retinal cells apoptosis in streptozotocin-induced diabetic rats

AIM

To detect the effect of connective tissue growth factor (CTGF) on the apoptosis in the diabetic retina with small interfering RNAs (siRNA) targeting CTGF.

METHODS

A total of 60 rats were divided into 6 groups including control group, diabetic 4, 8, 12, 16 weeks groups, and interference group. Diabetic rats were induced by intraperitoneal streptozotocin (STZ). Retinas were obtained from control, diabetic rats and diabetic rats of interference group treated by intravitreal injection of CTGFsiRNA to suppress the expression of CTGF mRNA. Retinal cells apoptosis was detected by Tunnel staining and mRNA expression of CTGF was analyzed by RT-PCR.

RESULTS

The levels of CTGF and the apoptosis in the retinas of diabetic rats were significantly higher than those in the controls. Apoptosis occurred at 4 weeks after a diabetic model being set up, became serious with the diabetes developing, while CTGF elevated at 8 weeks. The apoptosis cell counts increased to 25.8cells/mm(2) at 24weeks of diabetes. SiRNA-mediated inhibition of CTGF mRNA resulted in a significant decrease in apoptosis. Significant correlations were found between CTGF and apoptosis in the retina.

CONCLUSION

It was suggested that CTGF might be involved in retinal cells apoptosis which is a characteristic of early diabetic retina. SiRNA targeting CTGF seems to have the advantage of ameliorating retinal cells apoptosis.

Attenuation of fibrosis in vitro and in vivo with SPARC siRNA

Introduction

SPARC is a matricellular protein, which, along with other extracellular matrix components including collagens, is commonly over-expressed in fibrotic diseases. The purpose of this study was to examine whether inhibition of SPARC can regulate collagen expression in vitro and in vivo, and subsequently attenuate fibrotic stimulation by bleomycin in mouse skin and lungs.

Methods

In in vitro studies, skin fibroblasts obtained from a Tgfbr1 knock-in mouse (TBR1^CA; Cre-ER) were transfected with SPARC siRNA. Gene and protein expressions of the Col1a2 and the Ctgf were examined by real-time RT-PCR and Western blotting, respectively. In in vivo studies, C57BL/6 mice were induced for skin and lung fibrosis by bleomycin and followed by SPARC siRNA treatment through subcutaneous injection and intratracheal instillation, respectively. The pathological changes of skin and lungs were assessed by hematoxylin and eosin and Masson's trichrome stains. The expression changes of collagen in the tissues were assessed by real-time RT-PCR and non-crosslinked fibrillar collagen content assays.

Results

SPARC siRNA significantly reduced gene and protein expression of collagen type 1 in fibroblasts obtained from the TBR1^CA; Cre-ER mouse that was induced for constitutively active TGF-β receptor I. Skin and lung fibrosis induced by bleomycin was markedly reduced by treatment with SPARC siRNA. The anti-fibrotic effect of SPARC siRNA in vivo was accompanied by an inhibition of Ctgf expression in these same tissues.

Conclusions

Specific inhibition of SPARC effectively reduced fibrotic changes in vitro and in vivo. SPARC inhibition may represent a potential therapeutic approach to fibrotic diseases.

SPARC suppresses apoptosis of idiopathic pulmonary fibrosis fibroblasts through constitutive activation of beta-catenin

Idiopathic pulmonary fibrosis (IPF) is a poorly understood progressive disease characterized by the accumulation of scar tissue in the lung interstitium. A hallmark of the disease is areas of injury to type II alveolar epithelial cells with attendant accumulation of fibroblasts in areas called fibroblastic foci. In an effort to better characterize the lung fibroblast phenotype in IPF patients, we isolated fibroblasts from patients with IPF and looked for activation of signaling proteins, which could help explain the exaggerated fibrogenic response in IPF. We found that IPF fibroblasts constitutively expressed increased basal levels of SPARC, plasminogen activator inhibitor-1 (PAI-1), and active beta-catenin compared with control cells. Control of basal PAI-1 expression in IPF fibroblasts was regulated by SPARC-mediated activation of Akt, leading to inhibition of glycogen synthase kinase-3beta and activation of beta-catenin. Additionally, IPF fibroblasts (but not control fibroblasts) were resistant to plasminogen-induced apoptosis and were sensitized to plasminogen-mediated apoptosis by inhibition of SPARC or beta-catenin. These findings uncover a newly discovered regulatory pathway in IPF fibroblasts that is characterized by elevated SPARC, giving rise to activated beta-catenin, which regulates expression of downstream genes, such as PAI-1, and confers an apoptosis-resistant phenotype. Disruption of this pathway may represent a novel therapeutic target in IPF.

Lack of host SPARC enhances vascular function and tumor spread in an orthotopic murine model of pancreatic carcinoma

Utilizing subcutaneous tumor models, we previously validated SPARC (secreted protein acidic and rich in cysteine) as a key component of the stromal response, where it regulated tumor size, angiogenesis and extracellular matrix deposition. In the present study, we demonstrate that pancreatic tumors grown orthotopically in Sparc-null (Sparc(-/-)) mice are more metastatic than tumors grown in wild-type (Sparc(+/+)) littermates. Tumors grown in Sparc(-/-) mice display reduced deposition of fibrillar collagens I and III, basement membrane collagen IV and the collagen-associated proteoglycan decorin. In addition, microvessel density and pericyte recruitment are reduced in tumors grown in the absence of host SPARC. However, tumors from Sparc(-/-) mice display increased permeability and perfusion, and a subsequent decrease in hypoxia. Finally, we found that tumors grown in the absence of host SPARC exhibit an increase in alternatively activated macrophages. These results suggest that increased tumor burden in the absence of host SPARC is a consequence of reduced collagen deposition, a disrupted vascular basement membrane, enhanced vascular function and an immune-tolerant, pro-metastatic microenvironment.

Adenovirus-mediated inhibition of SPARC attenuates liver fibrosis in rats

BACKGROUND

The interaction between fibrogenic cells and extracellular matrix plays a role in liver fibrosis, yet the mechanisms are largely unknown. Secreted protein, acidic and rich in cysteine (SPARC) is a matricellular glycoprotein that is expressed by hepatic stellate cells and is overexpressed in fibrotic livers. We investigated the in vivo role of SPARC in experimentally induced liver fibrosis in rats.

METHODS

A recombinant adenovirus carrying antisense SPARC was constructed (AdasSPARC). Advanced liver fibrosis was induced in Sprague-Dawley rats by prolonged intraperitoneal administration of thioacetamide. Animals received injections of AdasSPARC or Ad beta gal (control adenovirus) via the tail vein and directly into the liver 1 week after the first dose. The pathological changes in liver tissues and indices of fibrosis were assessed at eight weeks. Expression of SPARC, transforming growth factor (TGF)-beta and alpha-smooth muscle actin were evaluated by quantitative real-time polymerase chain reaction, western blotting, enzyme-linked immunosorbent assay and immunohistochemistry.

RESULTS

Hepatic SPARC expression significantly increased during the development of liver fibrosis. AdasSPARC markedly attenuated the development of hepatic fibrosis in rats treated with thiocetamide, as assessed by decreased collagen deposition, lower hepatic content of hydroxyproline and less advanced morphometric stage of fibrosis. AdasSPARC treatment reduced inflammatory activity (Knodell score) and suppressed transdifferentiation of hepatic stellate cell to the myofibroblasts like phenotype in vivo. Furthermore, in vitro inhibition of SPARC on hepatic stellate cells decreases the production of TGF-beta.

CONCLUSIONS

This is the first study to demonstrate that knockdown of hepatic SPARC expression ameliorates thioacetamide-induced liver fibrosis in rats with chronic liver injury. SPARC is a potential target for gene therapy in liver fibrosis.

The role of the matricellular protein SPARC in the dynamic interaction between the tumor and the host

Tumor growth is essentially the result of an evolving cross-talk between malignant and surrounding stromal cells (fibroblasts, endothelial cells and inflammatory cells). This heterogeneous mass of extracellular matrix and intermingled cells interact through cell-cell and cell-matrix contacts. Malignant cells also secrete soluble proteins that reach neighbor stromal cells, forcing them to provide the soil on which they will grow and metastasize. Different studies including expression array analysis identified the matricellular protein SPARC as a marker of poor prognosis in different cancer types. Further evidence demonstrated that high SPARC levels are often associated with the most aggressive and highly metastatic tumors. Here we describe the most recent evidence that links SPARC with human cancer progression, the controversy regarding its role in certain human cancers and the physiological processes in which SPARC is involved: epithelial-mesenchymal transition, immune surveillance and angiogenesis. Its relevance as a potential target in cancer therapy is also discussed.

The role of the matricellular protein SPARC in the dynamic interaction between the tumor and the host

Tumor growth is essentially the result of an evolving cross-talk between malignant and surrounding stromal cells (fibroblasts, endothelial cells and inflammatory cells). This heterogeneous mass of extracellular matrix and intermingled cells interact through cell-cell and cell-matrix contacts. Malignant cells also secrete soluble proteins that reach neighbor stromal cells, forcing them to provide the soil on which they will grow and metastasize. Different studies including expression array analysis identified the matricellular protein SPARC as a marker of poor prognosis in different cancer types. Further evidence demonstrated that high SPARC levels are often associated with the most aggressive and highly metastatic tumors. Here we describe the most recent evidence that links SPARC with human cancer progression, the controversy regarding its role in certain human cancers and the physiological processes in which SPARC is involved: epithelial-mesenchymal transition, immune surveillance and angiogenesis. Its relevance as a potential target in cancer therapy is also discussed.

Genetics and genomic studies in scleroderma (systemic sclerosis)

It currently is believed that scleroderma is a complex polygenic disease that occurs in genetically predisposed individuals who have encountered specific environment exposures and/or other stochastic factors. The nature of these genetic determinants and how they interact with environmental factors are areas of active investigation. This article discusses the evidence that supports a strong genetic link to scleroderma. These studies implicate potential pathogenetic mechanisms involved in scleroderma, which, it is hoped, may translate into clinical utility, including determination of disease risk, diagnosis, prognosis, and novel therapeutics.

SPARC, an upstream regulator of connective tissue growth factor in response to transforming growth factor beta stimulation

OBJECTIVE

To differentiate the effects of inhibition of specific small interfering RNA (siRNA) of SPARC (secreted protein, acidic and rich in cysteine) and siRNA of connective tissue growth factor (CTGF) in cultured human fibroblasts, and to identify potential interrelationships between SPARC and CTGF.

METHODS

Fibroblasts from skin biopsy specimens of 2 normal individuals were transfected with siRNA of SPARC and siRNA of CTGF. The fibroblasts were stimulated with or without transforming growth factor beta1 (TGFbeta1) and examined by real-time quantitative reverse transcription-polymerase chain reaction to determine the transcription levels of several extracellular matrix genes.

RESULTS

After exogenous TGFbeta1 stimulation, both SPARC siRNA and CTGF siRNA showed a protective role against overexpression of collagen genes. Following TGFbeta1 stimulation, SPARC siRNA-transfected fibroblasts showed a greater reduction in expression of the collagen genes compared with CTGF siRNA-transfected fibroblasts, as well as a significantly decreased expression of CTGF (P < 0.05). Using linear structure equations to quantitatively model a genetic network based on expression levels of each gene, a positive regulatory role of SPARC on CTGF, COL1A2, COL3A1, COL11A1, and TIMP3 was observed. However, the regulatory role of CTGF on SPARC appeared to be negative and very small, while the positive regulatory effects of CTGF on COL1A2, COL3A1, COL11A1, and TIMP3 were less than those of SPARC.

CONCLUSION

The results of this quantitative comparison support the hypothesis that in these cultured fibroblasts, the regulatory effects of SPARC on some major extracellular matrix structural components are greater than those of CTGF. In addition, SPARC appears to regulate CTGF in a predominantly positive manner, while CTGF may act as a negative feedback control on SPARC following TGFbeta stimulation.

Myofibroblasts and hyalinized collagen as markers of skin disease in systemic sclerosis

OBJECTIVE

To investigate the correlation between the degree of dermal fibrosis and myofibroblast infiltration using clinical assessments of skin thickness and hardness in systemic sclerosis (SSc).

METHODS

Eleven patients with diffuse SSc and 10 healthy controls were evaluated using the modified Rodnan skin thickness score and durometry (hardness measurement). Biopsy samples were obtained from the dorsal mid-forearm in all subjects at the baseline visit and again 6-12 months later in patients with SSc. Five of the patients with SSc received treatment with cyclophosphamide (CYC) in the interval between skin biopsies. Biopsy sections were assessed for myofibroblast and hyalinized collagen content by 2 blinded observers.

RESULTS

Myofibroblast and hyalinized collagen scores each correlated with the forearm skin score (r = 0.83, P < 0.0001 and r = 0.78, P < 0.0001, respectively) and with the forearm durometry score (r = 0.72, P < 0.0004 and r = 0.69, P < 0.0008, respectively). The change in the dermal hyalinized collagen score correlated with the change in the forearm durometry score (r = 0.74, P < 0.0213). The myofibroblast score decreased in all 5 patients who received CYC and increased in those receiving non-CYC treatments (P < 0.01 for the difference).

CONCLUSION

Myofibroblasts play an important role in the pathogenesis of fibrosis, and our data imply that quantification of myofibroblasts and hyalinized collagen in skin may be a useful outcome measure in clinical studies of SSc.

Gene expression in fibroadenomas of the rat mammary gland in contrast to spontaneous adenocarcinomas and normal mammary gland

Fibroadenomas are considered a benign lesion in rodent carcinogenicity studies. However, the entity adenocarcinoma arising in fibroadenoma does exist and in humans there is evidence of certain forms of fibroadenomas to confer greater risk of subsequent breast cancer. In this study, we aim to elucidate the molecular features of both spontaneous fibroadenomas and adenocarcinomas. The gene expression of the two tumour types is examined and compared to mammary gland in the same developmental state and examined for similarities which might indicate common molecular pathways. In the present study no similarities were discovered. We conclude that in the tumours examined here, no progression to adenocarcinoma is likely. Further studies are needed, examining a greater number of tumours and including cases of adenocarcinoma arising in fibroadenoma.

Scleroderma: it has been a long hard journey

Progress in the understanding of the aetiopathogenesis of scleroderma (systemic sclerosis) has been painfully slow and this has greatly impeded the application of specific disease modifying treatments. This article provides a brief historical overview of scleroderma (including the important Australian contribution of Dr Alfred Barnett and colleagues--see accompanying article in this issue on pages 513-18), highlights some recent pathogenic developments and summarises some exciting new therapies. Cautious optimism can now be offered to scleroderma sufferers.

Attenuation of collagen production with small interfering RNA of SPARC in cultured fibroblasts from the skin of patients with scleroderma

OBJECTIVE

Recently, it was observed that SPARC (secreted protein, acidic and rich in cysteine) is overexpressed in the fibroblasts of skin biopsy specimens obtained from patients with systemic sclerosis (SSc; scleroderma), and that specific inhibition of SPARC expression in normal human fibroblasts attenuated the profibrotic effect of transforming growth factor beta (TGFbeta). The purpose of this study was to examine whether inhibition of SPARC with small interfering RNA (siRNA) can be used to ameliorate the overproduction of major extracellular matrix components in SSc fibroblasts.

METHODS

Fibroblasts obtained from biopsy specimens of the unaffected skin of 3 patients with diffuse SSc and 3 age- and sex-matched healthy controls were cultured and transfected with SPARC siRNA. Before and after transfection, real-time quantitative reverse transcription-polymerase chain reaction, immunostaining, and Western blotting were used to examine the transcription and/or protein levels of SPARC, connective tissue growth factor (CTGF), type I collagen, type II collagen, TGFbeta receptor 1 (TGFbetaR1), and Smad3. Student's paired t-tests were used to determine the significance of the results.

RESULTS

SSc fibroblasts showed overexpression of SPARC, COL1A2, COL3A1, and CTGF, which is consistent with an activated fibroblast phenotype. Upon inhibition of SPARC with siRNA, these activated SSc fibroblasts showed decreased gene expression of COL1A2, COL3A1, and CTGF (43%, 54%, and 58%, respectively). In addition, the overproduction of type I collagen protein in SSc fibroblasts was inhibited and was shown to parallel levels of SPARC expression. In contrast, the expression of TGFBR1 and Smad3 did not change significantly nor was the level of phosphorylation of Smad3 reduced upon SPARC siRNA silencing in unstimulated cultured SSc fibroblasts.

CONCLUSION

Overproduction of collagens in SSc skin fibroblasts can be attenuated through SPARC silencing. This inhibition may be associated either with direct interaction between SPARC and collagens or with inhibition of CTGF, which is a downstream effector of TGFbeta signaling. However, SPARC silencing in SSc fibroblasts appears not to be associated with TGFBR1- and Smad3-dependent processes. Application of SPARC silencing represents a potential therapeutic approach to SSc.

Tweaking microtubules to treat scleroderma

van Laar and Huizinga discuss a new study of a mouse model of scleroderma, which showed that stabilizing microtubules with paclitaxel led to reduced fibrosis.