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

Unraveling the role of MiR-181 in skin fibrosis pathogenesis by targeting NUDT21

Systemic sclerosis (SSc) is a life-threatening autoimmune disease characterized by widespread fibrosis in the skin and several internal organs. Nudix Hydrolase 21 (NUDT2 or CFIm25) downregulation in fibroblasts is known to play detrimental roles in both skin and lung fibrosis. This study aims to investigate the upstream mechanisms that lead to NUDT21 repression in skin fibrosis. We identified transforming growth factor β (TGFβ1) as the primary cytokine that downregulated NUDT21 in normal skin fibroblasts. In the bleomycin-induced dermal fibrosis model, consistent with the peak activation of TGFβ1 at the late fibrotic stage, NUDT21 was downregulated at this stage, and delayed NUDT21 knockdown during this fibrotic phase led to enhanced fibrotic response to bleomycin. Further investigation suggested TGFβ downregulated NUDT21 through microRNA (miRNA) 181a and 181b induction. Both miR-181a and miR-181b were elevated in bleomycin-induced skin fibrosis in mice and primary fibroblasts isolated from SSc patients, and they directly targeted NUDT21 and led to its downregulation in skin fibroblasts. Functional studies demonstrated that miR-181a and miR-181b inhibitors attenuated bleomycin-induced skin fibrosis in mice in association with decreased NUDT21 expression, while miR-181a and miR-181b mimics promoted bleomycin-induced fibrosis. Overall, these findings suggest a novel role for miR-181a/b in SSc pathogenesis by repressing NUDT21 expression.

Hypertrophic Ligamentum Flavum in Lumbar Spine Stenosis Is Associated With the Increased Expression of Secreted Protein Acidic and Rich in Cysteine

STUDY DESIGN

Basic research.

OBJECTIVES

Secreted protein acidic and rich in cysteine (SPARC) is a critical pro-fibrotic mediator. This study aims to characterize the role of SPARC in hypertrophic ligamentum flavum (LF) and fibrosis.

METHODS

Hypertrophic LF samples were obtained from 8 patients with L4/5 lumbar spinal stenosis (LSS) during the decompressive laminectomy. Non-hypertrophic LF from age- and sex-matched 8 patients with L4/5 lumbar disc herniation was selected as control. An in vitro model of fibrosis in human LF cells was established by interleukin 6 (IL-6) to assess SPARC expression.

RESULTS

Hypertrophic LF samples had higher fibrosis scores than control samples by Masson's trichrome staining (3.6 vs. 1.3, P < .001). Hypertrophic LF samples had significantly more positive staining for collagen and SPARC. Collagen III (Col3), α smooth muscle actin (α-SMA), and SPARC mRNA expression levels were significantly higher in hypertrophic LF samples than in control samples by qPCR. SPARC expression and fibrotic and inflammatory makers (collagen I, Col3, IL-6, interleukin 1β) were significantly upregulated in IL-6 stimulation of normal LF in vitro.

CONCLUSION

SPARC was detected in human LF and significantly upregulated in the clinical samples of hypertrophic LF compared to their normal counterparts. We also demonstrated an increased level of SPARC in an in vitro fibrosis model of LF. Thus, SPARC could be a crucial biomarker for the pathogenesis of hypertrophic LF and a therapeutic target for LSS.

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.

The unique pancreatic stellate cell gene expression signatures are associated with the progression from acute to chronic pancreatitis

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Early recognition of chronic pancreatitis (CP) is still lacking. In the setting of CP injury, activated pancreatic stellate cell (PSC) is the central mediator of pancreatic fibrosis. We systematically define highly and uniquely expressed PSC genes and show that these genes are enriched in pancreatic diseases.

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Unresolved or recurrent injury causes dysregulation of biological process following AP, which would cause CP. We demonstrated subset genes that may be associated with the progression from AP to CP. Furthermore, SPARC was identified as a candidate marker for the disease progression.

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Increased expression of SPARC and canonical PSC genes were verified during AP recovery, especially in recurrent AP mice models.

Chronic pancreatitis (CP) is characterized by irreversible fibro-inflammatory changes induced by pancreatic stellate cell (PSC). Unresolved or recurrent injury causes dysregulation of biological process following AP, which would cause CP. Here, we systematically identify genes whose expressions are unique to PSC by comparing transcriptome profiles among total pancreas, pancreatic stellate, acinar, islet and immune cells. We then identified candidate genes and correlated them with the pancreatic disease continuum by performing intersection analysis among total PSC and activated PSC genes, and genes persistently differentially expressed during acute pancreatitis (AP) recovery. Last, we examined the association between candidate genes and AP, and substantiated their potential as biomarkers in experimental AP and recurrent AP (RAP) models. A total of 68 genes were identified as highly and uniquely expressed in PSC. The PSC signatures were highly enriched with extracellular matrix remodeling genes and were significantly enriched in AP pancreas compared to healthy control tissues. Among PSC signature genes that comprised a fibrotic phenotype, 10 were persistently differentially expressed during AP recovery. SPARC was determined as a candidate marker for the pancreatic disease continuum, which was not only persistently differentially expressed even five days after AP injury, but also highly expressed in two clinical datasets of CP. Sparc was also validated as highly elevated in RAP compared to AP mice. This work highlights the unique transcriptional profiles of PSC. These PSC signatures’ expression may help to identify patients with high risk of AP progression to CP.

Extracellular SPARC cooperates with TGF-β signalling to induce pro-fibrotic activation of systemic sclerosis patient dermal fibroblasts

OBJECTIVES

SSc is an autoimmune disease characterized by inflammation, vascular injury and excessive fibrosis in multiple organs. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular glycoprotein that regulates processes involved in SSc pathology, such as inflammation and fibrosis. In vivo and in vitro studies have implicated SPARC in SSc, but it is unclear if the pro-fibrotic effects of SPARC on fibroblasts are a result of intracellular signalling or fibroblast interactions with extracellular SPARC hampering further development of SPARC as a potential therapeutic target. This study aimed to analyse the potential role of exogenous SPARC as a regulator of fibrosis in SSc.

METHODS

Dermal fibroblasts from both healthy controls and SSc patients were stimulated with SPARC alone or in combination with TGF-β1, in the absence or presence of a TGF receptor 1 inhibitor. mRNA and protein expression of extracellular matrix components and other fibrosis-related mediators were measured by quantitative PCR and western blot.

RESULTS

Exogenous SPARC induced mRNA and protein expression of collagen I, collagen IV, fibronectin 1, TGF-β and SPARC by dermal fibroblasts from SSc patients, but not from healthy controls. Importantly, exogenous SPARC induced the activation of the tyrosine kinase SMAD2 and pro-fibrotic gene expression induced by SPARC in SSc fibroblasts was abrogated by inhibition of TGF-β signalling.

CONCLUSION

These results indicate that exogenous SPARC is an important pro-fibrotic mediator contributing to the pathology driving SSc but in a TGF-β dependent manner. Therefore, SPARC could be a promising therapeutic target for reducing fibrosis in SSc patients, even in late states of the disease.

Downregulation of CFIm25 amplifies dermal fibrosis through alternative polyadenylation

This study implicates the key regulator of alternative polyadenylation, CFIm25 in dermal fibrosis and in systemic sclerosis (scleroderma) pathogenesis. CFIm25 downregulation promotes the expression of profibrotic factors, exaggerates bleomycin-induced skin fibrosis, while CFIm25 restoration attenuates skin fibrosis.

Systemic sclerosis (SSc; scleroderma) is a multisystem fibrotic disease. The mammalian cleavage factor I 25-kD subunit (CFIm25; encoded by NUDT21) is a key regulator of alternative polyadenylation, and its depletion causes predominantly 3′UTR shortening through loss of stimulation of distal polyadenylation sites. A shortened 3′UTR will often lack microRNA target sites, resulting in increased mRNA translation due to evasion of microRNA-mediated repression. Herein, we report that CFlm25 is downregulated in SSc skin, primary dermal fibroblasts, and two murine models of dermal fibrosis. Knockdown of CFIm25 in normal skin fibroblasts is sufficient to promote the 3′UTR shortening of key TGFβ-regulated fibrotic genes and enhance their protein expression. Moreover, several of these fibrotic transcripts show 3′UTR shortening in SSc skin. Finally, mice with CFIm25 deletion in fibroblasts show exaggerated skin fibrosis upon bleomycin treatment, and CFIm25 restoration attenuates bleomycin-induced skin fibrosis. Overall, our data link this novel RNA-processing mechanism to dermal fibrosis and SSc pathogenesis.

Emerging Roles of Matricellular Proteins in Systemic Sclerosis

Systemic sclerosis is a rare chronic heterogenous disease that involves inflammation and vasculopathy, and converges in end-stage development of multisystem tissue fibrosis. The loss of tight spatial distribution and temporal expression of proteins in the extracellular matrix (ECM) leads to progressive organ stiffening, which is a hallmark of fibrotic disease. A group of nonstructural matrix proteins, known as matricellular proteins (MCPs) are implicated in dysregulated processes that drive fibrosis such as ECM remodeling and various cellular behaviors. Accordingly, MCPs have been described in the context of fibrosis in sclerosis (SSc) as predictive disease biomarkers and regulators of ECM synthesis, with promising therapeutic potential. In this present review, an informative summary of major MCPs is presented highlighting their clear correlations to SSc- fibrosis.

The extracellular matrix as a multitasking player in disease

Extracellular matrices (ECMs) are highly specialized and dynamic three-dimensional (3D) scaffolds into which cells reside in tissues. ECM is composed of a variety of fibrillar components, such as collagens, fibronectin, and elastin, and non-fibrillar molecules as proteoglycans, hyaluronan, and glycoproteins including matricellular proteins. These macromolecular components are interconnected forming complex networks that actively communicate with cells through binding to cell surface receptors and/or matrix effectors. ECMs exert diverse roles, either providing tissues with structural integrity and mechanical properties essential for tissue functions or regulating cell phenotype and functions to maintain tissue homeostasis. ECM molecular composition and structure vary among tissues, and is markedly modified during normal tissue repair as well as during the progression of various diseases. Actually, abnormal ECM remodeling occurring in pathologic circumstances drives disease progression by regulating cell-matrix interactions. The importance of matrix molecules to normal tissue functions is also highlighted by mutations in matrix genes that give rise to genetic disorders with diverse clinical phenotypes. In this review, we present critical and emerging issues related to matrix assembly in tissues and the multitasking roles for ECM in diseases such as osteoarthritis, fibrosis, cancer, and genetic diseases. The mechanisms underlying the various matrix-based diseases are also discussed. Research focused on the highly dynamic 3D ECM networks will help to discover matrix-related causative abnormalities of diseases as well as novel diagnostic tools and therapeutic targets.

In Systemic Sclerosis, a Unique Long Non Coding RNA Regulates Genes and Pathways Involved in the Three Main Features of the Disease (Vasculopathy, Fibrosis and Autoimmunity) and in Carcinogenesis

Systemic sclerosis (SSc) is an autoimmune disease characterized by three main features: vasculopathy, immune system dysregulation and fibrosis. Long non-coding RNAs (lncRNAs) may play a role in the pathogenesis of autoimmune diseases and a comprehensive analysis of lncRNAs expression in SSc is still lacking. We profiled 542,500 transcripts in peripheral blood mononuclear cells (PBMCs) from 20 SSc patients and 20 healthy donors using Clariom D arrays, confirming the results by Reverse Transcription Polymerase-chain reaction (RT-PCR). A total of 837 coding-genes were modulated in SSc patients, whereas only one lncRNA, heterogeneous nuclear ribonucleoprotein U processed transcript (ncRNA00201), was significantly downregulated. This transcript regulates tumor proliferation and its gene target hnRNPC (Heterogeneous nuclear ribonucleoproteins C) encodes for a SSc-associated auto-antigen. NcRNA00201 targeted micro RNAs (miRNAs) regulating the most highly connected genes in the Protein-Protein interaction (PPI) network of the SSc transcriptome. A total of 26 of these miRNAs targeted genes involved in pathways connected to the three main features of SSc and to cancer development including Epidermal growth factor (EGF) receptor, ErbB1 downstream, Sphingosine 1 phosphate receptor 1 (S1P1), Activin receptor-like kinase 1 (ALK1), Endothelins, Ras homolog family member A (RhoA), Class I Phosphoinositide 3-kinase (PI3K), mammalian target of rapamycin (mTOR), p38 mitogen-activated protein kinase (MAPK), Ras-related C3 botulinum toxin substrate 1 (RAC1), Transforming growth factor (TGF)-beta receptor, Myeloid differentiation primary response 88 (MyD88) and Toll-like receptors (TLRs) pathways. In SSc, the identification of a unique deregulated lncRNA that regulates genes involved in the three main features of the disease and in tumor-associated pathways, provides insight in disease pathogenesis and opens avenues for the design of novel therapeutic strategies.

Design and in vitro release study of siRNA loaded Layer by Layer nanoparticles with sustained gene silencing effect

OBJECTIVES

Clinical translation of siRNA therapeutics has been severely limited due to the lack of stable and sustained siRNA delivery systems. Furthermore, when nanocarrier systems with siRNA are administered systemically to treat diseases, insufficient doses reach the target tissue. Here we report the successful development of a new nanocarrier system for the management of fibrosis.

METHODS

The new carrier has a hydroxyapatite core, with alternating layers of siRNA and a cationic peptide. The siRNA used here targets secreted protein acidic and rich in cysteine (SPARC), a key matricellular protein involved in the regulation of collagen fibrillogenesis and assembly. We have also used FRET studies to elucidate the fate of the particles inside cells, including the mechanistic details of layer-by-layer detachment.

RESULTS

In vitro studies using murine conjunctiva fibroblasts show sustained release over 2 weeks, and that such released siRNA sustained SPARC knockdown without affecting cell growth, and maintained siRNA presence in the cells for at least two weeks with a single-dose treatment. Release studies of siRNA from particles in vitro gave insight on how the particles delivered prolonged gene-silencing effects.

CONCLUSION

A single treatment of the layer-by-layer nanoparticle designed can achieve sustained gene silencing over 2 weeks. Localized delivery of stabilized siRNA with sustained-release capabilities opens the door for many other applications of siRNA-based gene regulation.

Targeted therapy for the post-operative conjunctiva: SPARC silencing reduces collagen deposition

BACKGROUND

To develop targeted antifibrotic therapy for glaucoma filtration surgery; this study determines the effectiveness of small interfering RNA (siRNA) to reduce in vivo secreted protein acidic and rich in cysteine (SPARC) expression using the mouse model of conjunctival scarring.

METHODS

Experimental surgery was performed as described for the mouse model of conjunctival scarring. Scrambled (siScram) or Sparc (siSparc) siRNAs, loaded on layer-by-layer (LbL) nanoparticles, were injected into the conjunctiva immediately after surgery. Expression of Sparc, Col1a1, Fn1 and Mmp14 was measured by real-time PCR and immunoblotting on days 7 and 14 postsurgery. Live imaging of the operated eyes was performed using slit lamp, anterior segment-optical coherence tomography and confocal microscopy. Tissue pathology was evaluated by histochemical and immunofluorescent analyses of operated conjunctival cryosections. Tissue apoptosis was quantitated by annexin V assay. RESULTS : siSparc, delivered via expanded LbL nanoparticles, significantly inhibited Sparc transcription in both day 7 (2.04-fold) and day 14 (1.39-fold) treated tissues. Sparc suppression on day 7 was associated with a significant reduction of Col1a1 (2.52-fold), Fn1 (2.89-fold) and Mmp14 (2.23-fold) mRNAs. At the protein level, both SPARC and collagen 1A1 (COL1A1) were significantly reduced at both time points with siSparc treatment. Nanoparticles were visualised within cell-like structures by confocal microscopy, while overt tissue response or apoptosis was not observed. CONCLUSIONS : SPARC targeted therapy effectively reduced both SPARC and collagen production in the operated mouse conjunctiva. This proof-of-concept study suggests that targeted treatment of fibrosis in glaucoma surgery is safe and feasible, with the potential to extend to a range of potential genes associated with fibrosis.

Insights into the key roles of epigenetics in matrix macromolecules-associated wound healing

Extracellular matrix (ECM) is a dynamic network of macromolecules, playing a regulatory role in cell functions, tissue regeneration and remodeling. Wound healing is a tissue repair process necessary for the maintenance of the functionality of tissues and organs. This highly orchestrated process is divided into four temporally overlapping phases, including hemostasis, inflammation, proliferation and tissue remodeling. The dynamic interplay between ECM and resident cells exerts its critical role in many aspects of wound healing, including cell proliferation, migration, differentiation, survival, matrix degradation and biosynthesis. Several epigenetic regulatory factors, such as the endogenous non-coding microRNAs (miRNAs), are the drivers of the wound healing response. microRNAs have pivotal roles in regulating ECM composition during wound healing and dermal regeneration. Their expression is associated with the distinct phases of wound healing and they serve as target biomarkers and targets for systematic regulation of wound repair. In this article we critically present the importance of epigenetics with particular emphasis on miRNAs regulating ECM components (i.e. glycoproteins, proteoglycans and matrix proteases) that are key players in wound healing. The clinical relevance of miRNA targeting as well as the delivery strategies designed for clinical applications are also presented and discussed.

Gene Profiling in Patients with Systemic Sclerosis Reveals the Presence of Oncogenic Gene Signatures

Systemic sclerosis (SSc) is a rare connective tissue disease characterized by three pathogenetic hallmarks: vasculopathy, dysregulation of the immune system, and fibrosis. A particular feature of SSc is the increased frequency of some types of malignancies, namely breast, lung, and hematological malignancies. Moreover, SSc may also be a paraneoplastic disease, again indicating a strong link between cancer and scleroderma. The reason of this association is still unknown; therefore, we aimed at investigating whether particular genetic or epigenetic factors may play a role in promoting cancer development in patients with SSc and whether some features are shared by the two conditions. We therefore performed a gene expression profiling of peripheral blood mononuclear cells (PBMCs) derived from patients with limited and diffuse SSc, showing that the various classes of genes potentially linked to the pathogenesis of SSc (such as apoptosis, endothelial cell activation, extracellular matrix remodeling, immune response, and inflammation) include genes that directly participate in the development of malignancies or that are involved in pathways known to be associated with carcinogenesis. The transcriptional analysis was then complemented by a complex network analysis of modulated genes which further confirmed the presence of signaling pathways associated with carcinogenesis. Since epigenetic mechanisms, such as microRNAs (miRNAs), are believed to play a central role in the pathogenesis of SSc, we also evaluated whether specific cancer-related miRNAs could be deregulated in the serum of SSc patients. We focused our attention on miRNAs already found upregulated in SSc such as miR-21-5p, miR-92a-3p, and on miR-155-5p, miR 126-3p and miR-16-5p known to be deregulated in malignancies associated to SSc, i.e., breast, lung, and hematological malignancies. miR-21-5p, miR-92a-3p, miR-155-5p, and miR-16-5p expression was significantly higher in SSc sera compared to healthy controls. Our findings indicate the presence of modulated genes and miRNAs that can play a predisposing role in the development of malignancies in SSc and are important for a better risk stratification of patients and for the identification of a better individualized precision medicine strategy.

The 'SPARC' of life: Analysis of the role of osteonectin/SPARC in pancreatic cancer (Review)

Pancreatic ductal adenocarcinoma (PDAC) is one of the most clinically challenging cancers to manage. An estimated 48,960 people will be diagnosed with pancreatic cancer in 2015, of that population, 94% are projected to perish within 5 years. These dismal survival rates can be attributed, in part, to an advanced diagnosis occurring in 80% of cases. The heterogeneous and dynamic microenvironment of pancreatic cancer, and the lack of both specific risk factors and efficacious screening tools contribute to the challenge of diagnosing pancreatic cancer in its early stages. These clinical challenges have directed research into the unique characteristics that define PDAC. Recently, there has been an increased focus on the interaction of tumor cells with their microenvironment in the hope of identifying new therapeutic targets. One of the most promising avenues in this new vein of research is targeting protein communication between the cancer cells and the extracellular matrix. The secreted protein acidic and rich in cysteine (SPARC) is one such extracellular matrix protein that has shown potential as a therapeutic target due to its influence on PDAC invasion and metastasis. In this review, we discuss the complex interaction of SPARC with PDAC cells and its potential to guide treatment and eventually improve the survival of patients diagnosed with this devastating disease.

Extracellular Matrix and Dermal Fibroblast Function in the Healing Wound

Significance: Fibroblasts play a critical role in normal wound healing. Various extracellular matrix (ECM) components, including collagens, fibrin, fibronectin, proteoglycans, glycosaminoglycans, and matricellular proteins, can be considered potent protagonists of fibroblast survival, migration, and metabolism. Recent Advances: Advances in tissue culture, tissue engineering, and ex vivo models have made the examination and precise measurements of ECM components in wound healing possible. Likewise, the development of specific transgenic animal models has created the opportunity to characterize the role of various ECM molecules in healing wounds. In addition, the recent characterization of new ECM molecules, including matricellular proteins, dermatopontin, and FACIT collagens (Fibril-Associated Collagens with Interrupted Triple helices), further demonstrates our cursory knowledge of the ECM in coordinated wound healing. Critical Issues: The manipulation and augmentation of ECM components in the healing wound is emerging in patient care, as demonstrated by the use of acellular dermal matrices, tissue scaffolds, and wound dressings or topical products bearing ECM proteins such as collagen, hyaluronan (HA), or elastin. Once thought of as neutral structural proteins, these molecules are now known to directly influence many aspects of cellular wound healing. Future Directions: The role that ECM molecules, such as CCN2, osteopontin, and secreted protein, acidic and rich in cysteine, play in signaling homing of fibroblast progenitor cells to sites of injury invites future research as we continue investigating the heterotopic origin of certain populations of fibroblasts in a healing wound. Likewise, research into differently sized fragments of the same polymeric ECM molecule is warranted as we learn that fragments of molecules such as HA and tenascin-C can have opposing effects on dermal fibroblasts.

Mesenchymal Stem Cell-Like Properties of Orbital Fibroblasts in Graves' Orbitopathy

PURPOSE

Graves' orbitopathy (GO) is a sight-threatening autoimmune disorder causing extraocular muscle fibrosis, upper lid retraction and eye bulging due to orbital fat expansion. These clinical features are mediated by aspects of orbital fibroblasts differentiation, including adipogenesis and fibrosis. Our previous work suggested that this dual phenotype might be a manifestation of mixed cell populations, partially linked to the expression of mesenchymal stem cell (MSC) marker CD90. Thus, we set out to determine whether GO orbital fibroblasts displayed MSC properties.

METHODS

Control and GO orbital fibroblasts previously characterized for CD90 and CD45 expression were analyzed by flow cytometry for classical MSC positive (CD73, CD105) and negative (CD14, CD19, HLA-DR, and CD34) markers. Graves' orbitopathy fibroblasts were tested further for their ability to undergo lineage specific differentiation following standard protocols.

RESULTS

Control and GO fibroblasts strongly expressed CD73 and CD105, with a higher percentage of positive cells and stronger expression levels in GO. Neither cell type expresses CD14, CD19, and HLA-DR. Protein CD34 was expressed at low levels by 45% to 70% of the cells, with its expression significantly lower in GO cells. Graves' orbitopathy fibroblasts displayed features of osteogenesis (calcium deposits, and osteocalcin [BGLAP] and osteonectin [SPARC] expression), chondrogenesis (glycosaminoglycan production; SOX9 and aggrecan [ACAN] expression), myogenesis (α-smooth muscle actin expression), and neurogenesis (β-III tubulin expression) upon differentiation.

CONCLUSIONS

Our findings suggest that orbital fibroblasts contain a population of cells that fulfil the criteria defining MSC. This subpopulation may be increased in GO, possibly underlying the complex differentiation phenotype of the disease.

Secreted Protein Acidic and Rich in Cysteine in Ocular Tissue

Secreted protein acidic and rich in cysteine (SPARC), also known as osteonectin or BM-40, is the prototypical matricellular protein. Matricellular proteins are nonstructural secreted proteins that provide an integration between cells and their surrounding extracellular matrix (ECM). Regulation of the ECM is important in maintaining the physiologic function of tissues. Elevated levels of SPARC have been identified in a variety of diseases involving pathologic tissue remodeling, such as hepatic fibrosis, systemic sclerosis, and certain carcinomas. Within the eye, SPARC has been identified in the trabecular meshwork, lens, and retina. Studies have begun to show the role of SPARC in these tissues and its possible role, specifically in primary open-angle glaucoma, cataracts, and proliferative vitreoretinopathy. SPARC may, therefore, be a therapeutic target in the treatment of certain ocular diseases. Further investigation into the mechanism of action of SPARC will be necessary in the development of SPARC-targeted therapy.

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.

Matricellular proteins in the trabecular meshwork: review and update

Abstract Primary open-angle glaucoma (POAG) is a leading cause of blindness worldwide, and intraocular pressure (IOP) is an important modifiable risk factor. IOP is a function of aqueous humor production and aqueous humor outflow, and it is thought that prolonged IOP elevation leads to optic nerve damage over time. Within the trabecular meshwork (TM), the eye's primary drainage system for aqueous humor, matricellular proteins generally allow cells to modulate their attachments with and alter the characteristics of their surrounding extracellular matrix (ECM). It is now well established that ECM turnover in the TM affects outflow facility, and matricellular proteins are emerging as significant players in IOP regulation. The formalized study of matricellular proteins in TM has gained increased attention. Secreted protein acidic and rich in cysteine (SPARC), myocilin, connective tissue growth factor (CTGF), and thrombospondin-1 and -2 (TSP-1 and -2) have been localized to the TM, and a growing body of evidence suggests that these matricellular proteins play an important role in IOP regulation and possibly the pathophysiology of POAG. As evidence continues to emerge, these proteins are now seen as potential therapeutic targets. Further study is warranted to assess their utility in treating glaucoma in humans.

Acupuncture-based modalities: novel alternative approaches in the treatment of gastrointestinal dysmotility in patients with systemic sclerosis

BACKGROUND

The gastrointestinal (GI) dysmotility of systemic sclerosis (SSc, scleroderma) patients requires careful evaluation and intervention. The lack of effective prokinetic drugs motivate researchers to search for alternative treatments.

OBJECTIVES

We present an overview of the pathophysiology of SSc GI dysmotility and the advances in its management, with particular focus on acupuncture-related modalities and innovative therapies.

DATA SOURCES

Original research articles were identified based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline methodology. We have searched the MEDLINE database using Medical Subject Heading (MeSH) for all English and non-English articles with an English abstract from 2005 to October 2012.

RESULTS

Only four original articles of various study designs were found studying Complementary and Alternative Medicine (CAM) therapies for SSc patients. Despite the small patient study numbers, CAM treatments, acupressure, and transcutaneous electroacupuncture, showed self-reported and physiologic evidence of improvement of GI functioning and/or symptoms in SSc patients.

CONCLUSIONS

CAM therapies include experimental modalities with the potential to offer relief of symptoms from GI dysmotility. Larger studies are needed to investigate their optimal use in patient subsets to tailor therapies to patient needs.

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 oppositely regulates inflammation and fibrosis in bleomycin-induced lung damage

Fibrosis results from inflammatory tissue damage and impaired regeneration. In the context of bleomycin-induced pulmonary fibrosis, we demonstrated that the matricellular protein termed secreted protein acidic and rich in cysteine (SPARC) distinctly regulates inflammation and collagen deposition, depending on its cellular origin. Reciprocal Sparc(-/-) and wild-type (WT) bone marrow chimeras revealed that SPARC expression in host fibroblasts is required and sufficient to induce collagen fibrosis in a proper inflammatory environment. Accordingly, Sparc(-/-) >WT chimeras showed exacerbated inflammation and fibrosis due to the inability of Sparc(-/-) macrophages to down-regulate tumor necrosis factor production because of impaired responses to tumor growth factor-β. Hence, the use of bone marrow cells expressing a dominant-negative form of tumor growth factor-β receptor type II under the monocyte-specific CD68 promoter, as a decoy, phenocopied Sparc(-/-) donor chimeras. Our results point to an unexpected dual role of SPARC in oppositely influencing the outcome of fibrosis.

Extracellular remodelling during oncogenic Ras-induced epithelial-mesenchymal transition facilitates MDCK cell migration

Epithelial-mesenchymal transition (EMT) describes a process whereby immotile epithelial cells escape structural constraints imposed by cellular architecture and acquire a phenotype characteristic of migratory mesenchymal cells. Implicated in carcinoma progression and metastasis, EMT has been the focus of several recent proteomics-based studies aimed at identifying new molecular players. To gain insights into extracellular mediators associated with EMT, we conducted an extensive proteomic analysis of the secretome from MDCK cells following oncogenic Ras-induced EMT (21D1 cells). Using Orbitrap technology and a label-free quantitative approach, differential expression of several secreted modulators were revealed. Proteomic findings were further substantiated by mRNA transcript expression analysis with 71% concordance. MDCK cells undergoing Ras-induced EMT remodel the extracellular matrix (ECM) via diminished expression of basement membrane constituents (collagen type IV and laminin 5), up-regulation of extracellular proteases (MMP-1, kallikreins -6 and -7), and increased production and secretion of ECM constituents (SPARC, collagen type I, fibulins -1 and -3, biglycan, and decorin). Collectively, these findings suggest that hierarchical regulation of a subset of extracellular effectors may coordinate a biological response during EMT that enhances cell motility. Transient silencing of MMP-1 in 21D1 cells via siRNA-mediated knockdown attenuated cell migration. Many of the secretome proteins identified broaden our understanding of the EMT process.

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 deficiency results in improved surgical survival in a novel mouse model of glaucoma filtration surgery

Glaucoma is a disease frequently associated with elevated intraocular pressure that can be alleviated by filtration surgery. However, the post-operative subconjunctival scarring response which blocks filtration efficiency is a major hurdle to the achievement of long-term surgical success. Current application of anti-proliferatives to modulate the scarring response is not ideal as these often give rise to sight-threatening complications. SPARC (secreted protein, acidic and rich in cysteine) is a matricellular protein involved in extracellular matrix (ECM) production and organization. In this study, we investigated post-operative surgical wound survival in an experimental glaucoma filtration model in SPARC-null mice. Loss of SPARC resulted in a marked (87.5%) surgical wound survival rate compared to 0% in wild-type (WT) counterparts. The larger SPARC-null wounds implied that aqueous filtration through the subconjunctival space was more efficient in comparison to WT wounds. The pronounced increase in both surgical survival and filtration efficiency was associated with a less collagenous ECM, smaller collagen fibril diameter, and a loosely-organized subconjunctival matrix in the SPARC-null wounds. In contrast, WT wounds exhibited a densely packed collagenous ECM with no evidence of filtration capacity. Immunolocalization assays confirmed the accumulation of ECM proteins in the WT but not in the SPARC-null wounds. The observations in vivo were corroborated by complementary data performed on WT and SPARC-null conjunctival fibroblasts in vitro. These findings indicate that depletion of SPARC bestows an inherent change in post-operative ECM remodeling to favor wound maintenance. The evidence presented in this report is strongly supportive for the targeting of SPARC to increase the success of glaucoma filtration surgery.

The role of SPARC in extracellular matrix assembly

SPARC is a collagen-binding matricellular protein. Expression of SPARC in adult tissues is frequently associated with excessive deposition of collagen and SPARC-null mice fail to generate a robust fibrotic response to a variety of stimuli. This review summarizes recent advancements in the characterization of the binding of SPARC to collagens and describes the results of studies that implicate a function for SPARC in the regulation of the assembly of basal lamina and fibrillar collagen in the ECM. Potential cellular mechanisms that underlie SPARC activity in ECM deposition are also explored.

Inflammation-dependent expression of SPARC during development of chronic pancreatitis in WBN/Kob rats and a microarray gene expression analysis

The pathophysiology of human chronic pancreatitis is not well understood and difficult to follow on a molecular basis. Therefore, we used a rat model [Wistar-Bonn/Kobori (WBN/Kob)] that exhibits spontaneous chronic inflammation and fibrosis in the pancreas. Using microarrays we compared gene expression patterns in the pancreas during development of inflammation and fibrosis of WBN/Kob rats with age-matched healthy Wistar rats. The extracellular matrix protein SPARC (secreted protein, acidic, and rich in cysteines) and other transcripts of inflammatory genes were quantified by real-time PCR, and some were localized by immunohistochemistry. When pancreatic inflammation becomes obvious at the age of 16 wk, several hundred genes are increased between 3- and 50-fold in WBN/Kob rats compared with healthy Wistar rats. Proteins produced by acinar cells and characteristic for inflammation, e.g., pancreatitis-associated protein, are highly upregulated. Other proteins, derived from infiltrating inflammatory cells and from activated stellate cells (fibrosis) such as collagens and fibronectins are also significantly upregulated. SPARC was localized to acinar cells where it increased in the vicinity of inflammatory foci. However, acinar expression of SPARC was lost during destruction of acinar cells. In human pancreatic specimens with chronic pancreatitis, SPARC exhibited a similar expression profile. During chronic inflammation and fibrosis in the WBN/Kob rat, inflammatory genes, growth factors, and structural genes exhibit a high increase of expression. A temporal profile including pre- and postinflammatory phases indicates a concurrent activation of inflammatory and fibrotic changes. Inflammation dependent expression of SPARC appears to be lost during acinar-to-duct metaplasia both in rat and human pancreas.

Matricellular proteins in the trabecular meshwork

The trabecular meshwork is one of the primary tissues of interest in the normal regulation and dysregulation of intraocular pressure (IOP) that is a causative risk factor for primary open-angle glaucoma. Matricellular proteins generally function to allow cells to modulate their attachments with and alter the characteristics of their surrounding extracellular matrix (ECM). In non-ocular tissues, matricellular proteins generally increase fibrosis. Since ECM turnover is very important to the outflow facility, matricellular proteins may have a significant role in the regulation of IOP. The formalized study of matricellular proteins in trabecular meshwork is in its infancy. SPARC, thrombospondins-1 and -2, and tenascins-C and -X, and osteopontin have been localized to varying areas within the trabecular meshwork. Preliminary evidence indicates that SPARC and thrombospondin-1 play a role in the regulation of IOP and possibly the pathophysiology of glaucoma. These data show promise that matricellular proteins are involved in IOP dysregulation and are potential therapeutic targets. Further study is needed to clarify these roles.

Recombinant mouse SPARC promotes parietal endoderm differentiation and cardiomyogenesis in embryoid bodies

In the absence of leukemia inhibitory factor, murine embryonic stem cells cultured in vitro spontaneously aggregate to from three-dimensional embryoid bodies that differentiate to produce hematopoietic, endothelial, muscle, and neuronal cell lineages in a manner recapitulating the events of early embryogenesis. Cardiomyogenesis in embryoid bodies was recently demonstrated to be promoted by PYS-2-derived native SPARC (secreted protein, acidic and rich in cysteine), whose expression is upregulated in parietal endoderm at the onset of the epithelial to mesenchymal transition. Here, we confirm the stimulatory effects of mouse SPARC on cardiomyogenesis using a recombinant baculovirus-produced protein (rmSPARC). Embryoid bodies cultured in the presence of glycosylated rmSPARC, or an unglycosylated peptide spanning the C-terminal EF-hand domain, developed greater numbers of beating cardiomyocytes than did time-matched controls, with enhanced expression of cardiac marker genes including Nkx2.5, Troponin, BMP-2, and MHCα. Histochemical analysis revealed an expansion of the peripheral endoderm, with thicker layers of extracellular matrix (ECM) material observed atop underlying cells. Embryoid bodies treated with SPARC also displayed increased adherence to polystyrene culture dishes, with enhanced expression of ECM mRNAs including collagen IVα3, collagen IVα5, and laminin α1. These results indicate that, in addition to the promotion of cardiomyogenesis, SPARC may also help regulate the molecular composition and organization of ECM secreted by the mesenchymal parietal endoderm.

Gene expression profiling in limb-girdle muscular dystrophy 2A

Limb-girdle muscular dystrophy type 2A (LGMD2A) is a recessive genetic disorder caused by mutations in calpain 3 (CAPN3). Calpain 3 plays different roles in muscular cells, but little is known about its functions or in vivo substrates. The aim of this study was to identify the genes showing an altered expression in LGMD2A patients and the possible pathways they are implicated in. Ten muscle samples from LGMD2A patients with in which molecular diagnosis was ascertained were investigated using array technology to analyze gene expression profiling as compared to ten normal muscle samples. Upregulated genes were mostly those related to extracellular matrix (different collagens), cell adhesion (fibronectin), muscle development (myosins and melusin) and signal transduction. It is therefore suggested that different proteins located or participating in the costameric region are implicated in processes regulated by calpain 3 during skeletal muscle development. Genes participating in the ubiquitin proteasome degradation pathway were found to be deregulated in LGMD2A patients, suggesting that regulation of this pathway may be under the control of calpain 3 activity. As frizzled-related protein (FRZB) is upregulated in LGMD2A muscle samples, it could be hypothesized that beta-catenin regulation is also altered at the Wnt signaling pathway, leading to an incorrect myogenesis. Conversely, expression of most transcription factor genes was downregulated (MYC, FOS and EGR1). Finally, the upregulation of IL-32 and immunoglobulin genes may induce the eosinophil chemoattraction explaining the inflammatory findings observed in presymptomatic stages. The obtained results try to shed some light on identification of novel therapeutic targets for limb-girdle muscular dystrophies.

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.

Genetic basis for systemic sclerosis

Among the connective tissue diseases, systemic sclerosis is an orphan disease in which diffuse connective tissue alterations lead to multi-organ involvement. Environmental factors implicated in triggering this multifactorial disease include crystalline silica, chlorine solvents, welding vapors, and various other solvents. Clustering within families indicates a role for genetic factors. Although concordance for the disease among identical twins is low, concordance for autoantibodies associated with systemic sclerosis and for fibroblast gene expression profiles is higher. Because multiplex families are rare, association and candidate gene strategies are the most appropriate methods for investigating the genetics of systemic sclerosis. The most consistent data relate to the involvement of fibrosis genes, most notably the TGF-beta regulation pathway, secreted protein acid and rich in cysteine (SPARC) genes, and the fibrillin-1 gene (FBN1). Several variants of genes for cytokines or their receptors may be involved. Data on the vasculopathy characteristic of systemic sclerosis are somewhat conflicting. Investigations into the genetics of systemic sclerosis may shed light on the complex pathophysiology of this disease, help to identify factors that predict organ involvement, and suggest new treatment strategies.

SPARC Regulates Processing of Procollagen I and Collagen Fibrillogenesis in Dermal Fibroblasts

A characterization of the factors that control collagen fibril formation is critical for an understanding of tissue organization and the mechanisms that lead to fibrosis. SPARC (secreted protein acidic and rich in cysteine) is a counter-adhesive protein that binds collagens. Herein we show that collagen fibrils in SPARC-null skin from mice 1 month of age were inefficient in fibril aggregation and accumulated in the diameter range of 60-70 nm, a proposed intermediate in collagen fibril growth. In vitro, procollagen I produced by SPARC-null dermal fibroblasts demonstrated an initial preferential association with cell layers, in comparison to that produced by wild-type fibroblasts. However, the collagen I produced by SPARC-null cells was not efficiently incorporated into detergent-insoluble fractions. Coincident with an initial increase in cell association, greater amounts of total collagen I were present as processed forms in SPARC-null versus wild-type cells. Addition of recombinant SPARC reversed collagen I association with cell layers and decreased the processing of procollagen I in SPARC-null cells. Although collagen fibers formed on the surface of SPARC-null fibroblasts earlier than those on wild-type cells, fibers on SPARC-null fibroblasts did not persist. We conclude that SPARC mediates the association of procollagen I with cells, as well as its processing and incorporation into the extracellular matrix.

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.