The Function of SPARC as a Mediator of Fibrosis

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.

Wound Modulations in Glaucoma Surgery: A Systematic Review

Excessive fibrosis and resultant poor control of intraocular pressure (IOP) reduce the efficacy of glaucoma surgeries. Historically, corticosteroids and anti-fibrotic agents, such as mitomycin C (MMC) and 5-fluorouracil (5-FU), have been used to mitigate post-surgical fibrosis, but these have unpredictable outcomes. Therefore, there is a need to develop novel treatments which provide increased effectiveness and specificity. This review aims to provide insight into the pathophysiology behind wound healing in glaucoma surgery, as well as the current and promising future wound healing agents that are less toxic and may provide better IOP control.

Gingival proteomics reveals the role of TGF beta and YAP/TAZ signaling in Raine syndrome fibrosis

Raine syndrome (RNS) is a rare autosomal recessive osteosclerotic dysplasia. RNS is caused by loss-of-function disease-causative variants of the FAM20C gene that encodes a kinase that phosphorylates most of the secreted proteins found in the body fluids and extracellular matrix. The most common RNS clinical features are generalized osteosclerosis, facial dysmorphism, intracerebral calcifications and respiratory defects. In non-lethal RNS forms, oral traits include a well-studied hypoplastic amelogenesis imperfecta (AI) and a much less characterized gingival phenotype. We used immunomorphological, biochemical, and siRNA approaches to analyze gingival tissues and primary cultures of gingival fibroblasts of two unrelated, previously reported RNS patients. We showed that fibrosis, pathological gingival calcifications and increased expression of various profibrotic and pro-osteogenic proteins such as POSTN, SPARC and VIM were common findings. Proteomic analysis of differentially expressed proteins demonstrated that proteins involved in extracellular matrix (ECM) regulation and related to the TGFβ/SMAD signaling pathway were increased. Functional analyses confirmed the upregulation of TGFβ/SMAD signaling and subsequently uncovered the involvement of two closely related transcription cofactors important in fibrogenesis, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ). Knocking down of FAM20C confirmed the TGFβ-YAP/TAZ interplay indicating that a profibrotic loop enabled gingival fibrosis in RNS patients. In summary, our in vivo and in vitro data provide a detailed description of the RNS gingival phenotype. They show that gingival fibrosis and calcifications are associated with, and most likely caused by excessed ECM production and disorganization. They furthermore uncover the contribution of increased TGFβ-YAP/TAZ signaling in the pathogenesis of the gingival fibrosis.

Effect of Sparc knockout on the extracellular matrix of mouse periodontal ligament cells

The periodontal ligament (PDL) is a critical component in maintaining tooth stability. It is composed of cells and an extracellular matrix (ECM), each with unique roles in tissue function and homeostasis. Secreted protein acidic and rich in cysteine (SPARC), a calcium-binding matricellular glycoprotein, plays a crucial role in regulating ECM assembly and turnover, alongside facilitating cellular-ECM interactions. In the present study, mass spectrometry-based proteomics was used to assess the impacts of Sparc-knockout (KO) on PDL-derived cells. Results demonstrated that Sparc-KO significantly reduces ECM production and alters its composition with increased levels of type I collagen. Despite this increase in Sparc-KO, type I collagen was not likely to be effectively integrated into the fibrils due to collagen cross-linking impairment. Furthermore, the pathway and process enrichment analyses suggested that SPARC plays a protective role against ECM degradation by antagonistically interacting with cell-surface collagen receptors. These findings provide detailed insights into the multifaceted role of SPARC in ECM organization, including its impact on ECM production, collagen regulation, and interactions with various cellular compartments. A better understanding of these complex mechanisms is crucial for comprehending the causes of periodontal disease and tissue regeneration, where precise control of ECM organization is necessary.

Overexpression of ameloblastin in secretory ameloblasts results in demarcated, hypomineralized opacities in enamel

Introduction: Developmental defects of the enamel manifest before tooth eruption and include amelogenesis imperfecta, a rare disease of underlying gene mutations, and molar-incisor hypomineralization (MIH), a prevalent disease in children originating from environmental and epigenetic factors. MIH enamel presents as the abnormal enamel marked by loss of translucency, demarcation between the healthy and affected enamel, and reduced mineral content. The pathophysiology of opaque, demarcated enamel lesions is not understood; however, the retention of enamel proteins in the matrix has been suggested. Ameloblastin (Ambn) is an enamel protein of the secreted calcium-binding phosphoproteins (SCPPs) critical for enamel formation. When the Ambn gene is mutated or deleted, teeth are affected by hypoplastic amelogenesis imperfecta. Methods: In this study, enamel formation in mice was analyzed when transgenic Ambn was overexpressed from the amelogenin promoter encoding full-length Ambn. Ambn was under- and overexpressed at six increasing concentrations in separate mouse lines. Results: Mice overexpressing Ambn displayed opaque enamel at low concentrations and demarcated lesions at high concentrations. The severity of enamel lesions increased starting from the inner enamel close to the dentino-enamel junction (DEJ) to span the entire width of the enamel layer in demarcated areas. Associated with the opaque enamel were 17-kDa Ambn cleavage products, a prolonged secretory stage, and a thin basement membrane in the maturation stage. Ambn accumulations found in the innermost enamel close to the DEJ and the mineralization front correlated with reduced mineral content. Demarcated enamel lesions were associated with Ambn species of 17 kDa and higher, prolonged secretory and transition stages, a thin basement membrane, and shortened maturation stages. Hypomineralized opacities were delineated against the surrounding mineralized enamel and adjacent to ameloblasts detached from the enamel surface. Inefficient Ambn cleavage, loss of contact between ameloblasts, and the altered basement membrane curtailed the endocytic activity; thus, enamel proteins remained unresorbed in the matrix. Ameloblasts have the ability to distinguish between Ambn concentration and Ambn cleavage products through finely tuned feedback mechanisms. The under- or overexpression of Ambn in murine secretory ameloblasts results in either hypoplastic amelogenesis imperfecta or hypomineralization with opaque or sharply demarcated boundaries of lesions, similar to MIH.

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.

Suppression of SPARC Ameliorates Ovalbumin-induced Airway Remodeling via TGFβ1/Smad2 in Chronic Asthma

PURPOSE

Airway remodeling is a critical feature of asthma. Secreted protein acidic and rich in cysteine (SPARC), which plays a cardinal role in regulating cell-matrix interactions, has been implicated in various fibrotic diseases. However, the effect of SPARC in asthma remains unknown.

METHODS

We studied the expression of SPARC in human bronchial epithelial cells and serum of asthmatics as well as in the lung tissues of chronic asthma mice. The role of SPARC was examined by using a Lentivirus-mediated SPARC knockdown method in the ovalbumin (OVA)-induced asthma mice. The biological processes regulated by SPARC were identified using RNA sequencing. The function of SPARC in the remodeling process induced by transforming growth factor β1 (TGFβ1) was conducted by using SPARC small interfering RNA (siRNA) or recombinant human SPARC protein in 16HBE cells.

RESULTS

We observed that SPARC was up-regulated in human bronchial epithelia of asthmatics and the asthmatic mice. The levels of serum SPARC in asthmatics were also elevated and negatively correlated with the forced expiratory volume in one second (FEV1) to forced vital capacity ratio (FVC) (r = -0.485, P < 0.01) and FEV1 (%predicted) (r = -0.425, P = 0.001). In the chronic asthmatic mice, Lentivirus-mediated SPARC knockdown significantly decreased airway remodeling and airway hyper-responsiveness. According to gene set enrichment analysis, negatively enriched pathways found in the OVA + short hairpin-SPARC group included ECM organization and collagen formation. In the lung function studies, knockdown of SPARC by siRNA reduced the expression of remodeling-associated biomarkers, cell migration, and contraction by blocking the TGFβ1/Smad2 pathway. Addition of human recombinant SPARC protein promoted the TGFβ1-induced remodeling process, cell migration, and contraction in 16HBE cells via the TGFβ1/Smad2 pathway.

CONCLUSIONS

Our studies provided evidence for the involvement of SPARC in the airway remodeling of asthma via the TGFβ1/Smad2 pathway.

Polyenylphosphatidylcholine as bioactive excipient in tablets for the treatment of liver fibrosis

Liver fibrosis is a condition characterized by the accumulation of extracellular matrix (ECM) arising from the myofibroblastic transdifferentiation of hepatic stellate cells (HSCs) occurring as the natural response to liver damage. To date, no pharmacological treatments have been specifically approved for liver fibrosis. We recently reported a beneficial effect of polyenylphosphatidylcholines (PPCs)-rich formulations in reverting fibrogenic features of HSCs. However, unsaturated phospholipids' properties pose a constant challenge to the development of tablets as preferred patient-centric dosage form. Profiting from the advantageous physical properties of the PPCs-rich Soluthin® S 80 M, we developed a tablet formulation incorporating 70% w/w of this bioactive lipid. Tablets were characterized via X-ray powder diffraction, thermogravimetry, and Raman confocal imaging, and passed the major compendial requirements. To mimic physiological absorption after oral intake, phospholipids extracted from tablets were reconstituted as protein-free chylomicron (PFC)-like emulsions and tested on the fibrogenic human HSC line LX-2 and on primary cirrhotic rat hepatic stellate cells (PRHSC). Lipids extracted from tablets and reconstituted in buffer or as PFC-like emulsions exerted the same antifibrotic effect on both activated LX-2 and PRHSCs as observed with plain S 80 M liposomes, showing that the manufacturing process did not interfere with the bioactivity of PPCs.

Glaucoma: Novel antifibrotic therapeutics for the trabecular meshwork

Glaucoma is a chronic and progressive neurodegenerative disease characterized by the loss of retinal ganglion cells and visual field defects, and currently affects around 1% of the world's population. Elevated intraocular pressure (IOP) is the best-known modifiable risk factor and a key therapeutic target in hypertensive glaucoma. The trabecular meshwork (TM) is the main site of aqueous humor outflow resistance and therefore a critical regulator of IOP. Fibrosis, a reparative process characterized by the excessive deposition of extracellular matrix components and contractile myofibroblasts, can impair TM function and contribute to the pathogenesis of primary open-angle glaucoma (POAG) as well as the failure of minimally invasive glaucoma surgery (MIGS) devices. This paper provides a detailed overview of the current anti-fibrotic therapeutics targeting the TM in glaucoma, along with their anti-fibrotic mechanisms, efficacy as well as the current research progress from pre-clinical to clinical studies.

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.

Omics Overview of the SPARC Gene in Mesothelioma

The SPARC gene plays multiple roles in extracellular matrix synthesis and cell shaping, associated with tumor cell migration, invasion, and metastasis. The SPARC gene is also involved in the epithelial-mesenchymal transition (EMT) process, which is a critical phenomenon leading to a more aggressive cancer cell phenotype. SPARC gene overexpression has shown to be associated with poor survival in the mesothelioma (MESO) cohort from the TCGA database, indicating that this gene may be a powerful prognostic factor in MESO. Its overexpression is correlated with the immunosuppressive tumor microenvironment. Here, we summarize the omics advances of the SPARC gene, including the summary of SPARC gene expression associated with prognosis in pancancer and MESO, the immunosuppressive microenvironment, and cancer cell stemness. In addition, SPARC might be targeted by microRNAs. Notably, despite the controversial functions on angiogenesis, SPARC may directly or indirectly contribute to tumor angiogenesis in MESO. In conclusion, SPARC is involved in tumor invasion, metastasis, immunosuppression, cancer cell stemness, and tumor angiogenesis, eventually impacting patient survival. Strategies targeting this gene may provide novel therapeutic approaches to the treatment of MESO.

Safety, Pharmacokinetics, and Antifibrotic Activity of CC-90001 (BMS-986360), a c-Jun N-Terminal Kinase Inhibitor, in Pulmonary Fibrosis

Approved treatments for idiopathic pulmonary fibrosis have tolerability concerns and limited efficacy. CC-90001, a c-Jun N-terminal kinase inhibitor, is under investigation as a therapy for fibrotic diseases. A Phase 1b safety, pharmacokinetics, and pharmacodynamics study of oral CC-90001 (100, 200, or 400 mg) administered once daily for 12 weeks was conducted in patients with pulmonary fibrosis (NCT02510937). Sixteen patients with a mean age of 68 years were studied. The most common treatment-emergent adverse events were nausea and headache; all events were of mild or moderate intensity. Pharmacokinetic profiles were similar between the patients in this trial and healthy adults in previous studies. Forced vital capacity increased in the 200- and 400-mg cohorts from baseline to Week 12, and dose-dependent reductions in fibrosis biomarkers were observed. Antifibrotic activity of CC-90001 was also evaluated in vitro in transforming growth factor beta 1 (TGF-β1)-stimulated cells. CC-90001 reduced in vitro profibrotic gene expression in both lung epithelial cells and fibroblasts, supporting a potential direct antifibrotic action of c-Jun N-terminal kinase inhibition in either or both cell types. Overall, CC-90001 was generally safe and well tolerated, and treatment was associated with forced vital capacity improvement and reductions in profibrotic biomarkers.

SPARC-YAP/TAZ inhibition prevents the fibroblasts-myofibroblast transformation

BACKGROUND

Fibrotic scar is a severe side effect of trabeculectomy, resulting in unsatisfactory outcomes for glaucoma surgery. Accumulating evidence showed human Tenon's fibroblasts (HTFs) play an important role in fibrosis formation. We previously reported that the aqueous level of secreted protein acidic and rich in cysteine (SPARC) was higher in the patients with primary angle closure glaucoma, which was associated with the failure of trabeculectomy. In this study, the potential effect and mechanism of SPARC in promoting fibrosis were explored by using HTFs.

METHODS

HTFs were employed in this study and examined under a phase-contrast microscope. Cell viability was determined by CCK-8. The expressions of SPARC-YAP/TAZ signaling and the fibrosis-related markers were examined with reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), Western blot, and immunofluorescence, subcellular fractionation was conducted to further determined the variation of YAP and phosphorylated YAP. The differential gene expressions were analyzed with RNA sequencing (RNAseq), followed by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses.

RESULTS

Exogenous SPARC induced HTFs-myofibroblast transformation, as evidenced by the increased expression of α-SMA, collagen I and fibronectin in both protein and mRNA levels. SPARC knockdown decreased the expressions of the above genes in TGF-β2-treated HTFs. KEGG analysis showed that the Hippo signaling pathway was mostly enriched. SPARC treatment increased the expressions of YAP, TAZ, CTGF and CYR61 as well as enhanced YAP translocation from cytoplasm to nucleus, and decreased the phosphorylation of YAP and LAST1/2, which was reversed by SPARC knockdown. Knockdown of YAP1 decreased the fibrosis-related markers, such as α-SMA, collagen I and Fibronectin, in SPARC-treated HTFs.

CONCLUSIONS

SPARC induced HTFs-myofibroblast transformation via activating YAP/TAZ signaling. Targeting SPARC-YAP/TAZ axis in HTFs might provide a novel strategy for inhibiting fibrosis formation after trabeculectomy.

Plasma SPARC Elevation in Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage

Matricellular proteins have been implicated in pathologies after subarachnoid hemorrhage (SAH). To find a new therapeutic molecular target, the present study aimed to clarify the relationships between serially measured plasma levels of a matricellular protein, secreted protein acidic and rich in cysteine (SPARC), and delayed cerebral ischemia (DCI) in 117 consecutive aneurysmal SAH patients with admission World Federation of Neurological Surgeons (WFNS) grades I-III. DCI developed in 25 patients with higher incidences of past history of hypertension and dyslipidemia, preoperative WFNS grade III, modified Fisher grade 4, spinal drainage, and angiographic vasospasm. Plasma SPARC levels were increased after SAH, and significantly higher in patients with than without DCI at days 7-9, and in patients with VASOGRADE-Yellow compared with VASOGRADE-Green at days 1-3 and 7-9. However, there were no relationships between plasma SPARC levels and angiographic vasospasm. Receiver-operating characteristic curves differentiating DCI from no DCI determined the cut-off value of plasma SPARC ≥ 82.1 ng/ml at days 7 - 9 (sensitivity, 0.800; specificity, 0.533; and area under the curve, 0.708), which was found to be an independent determinant of DCI development in multivariate analyses. This is the first study to show that SPARC is upregulated in peripheral blood after SAH, and that SPARC may be involved in the development of DCI without angiographic vasospasm in a clinical setting.

Ectonucleoside triphosphate diphosphohydrolase-1 (CD39) impacts TGF-β1 responses: insights into cardiac fibrosis and function following myocardial infarction

Extracellular purine nucleotides and nucleosides released from activated or injured cells influence multiple aspects of cardiac physiology and pathophysiology. Ectonucleoside triphosphate diphosphohydrolase-1 (ENTPD1; CD39) hydrolyzes released nucleotides and thereby regulates the magnitude and duration of purinergic signaling. However, the impact of CD39 activity on post-myocardial infarction (MI) remodeling is incompletely understood. We measured the levels and activity of ectonucleotidases in human left ventricular samples from control and ischemic cardiomyopathy (ICM) hearts and examined the impact of ablation of Cd39 expression on post-myocardial infarction remodeling in mice. We found that human CD39 levels and activity are significantly decreased in ICM hearts (n = 5) compared with control hearts (n = 5). In mice null for Cd39, cardiac function and remodeling are significantly compromised in Cd39-/- mice following myocardial infarction. Fibrotic markers including plasminogen activator inhibitor-1 (PAI-1) expression, fibrin deposition, α-smooth muscle actin (αSMA), and collagen expression are increased in Cd39-/- hearts. Importantly, we found that transforming growth factor β1 (TGF-β1) stimulates ATP release and induces Cd39 expression and activity on cardiac fibroblasts, constituting an autocrine regulatory pathway not previously appreciated. Absence of CD39 activity on cardiac fibroblasts exacerbates TGF-β1 profibrotic responses. Treatment with exogenous ectonucleotidase rescues this profibrotic response in Cd39-/- fibroblasts. Together, these data demonstrate that CD39 has important interactions with TGF-β1-stimulated autocrine purinergic signaling in cardiac fibroblasts and dictates outcomes of cardiac remodeling following myocardial infarction. Our results reveal that ENTPD1 (CD39) regulates TGF-β1-mediated fibroblast activation and limits adverse cardiac remodeling following myocardial infarction.NEW & NOTEWORTHY We show that CD39 is a critical modulator of TGF-β1-mediated fibroblast activation and cardiac remodeling following myocardial infarction via modulation of nucleotide signaling. TGF-β1-induced CD39 expression generates a negative feedback loop that attenuates cardiac fibroblast activation. In the absence of CD39 activity, collagen deposition is increased, elastin expression is decreased, and diastolic dysfunction is worsened. Treatment with ecto-apyrase attenuates the TGF-β1-induced profibrotic cardiac fibroblast phenotype, revealing a novel approach to combat post-myocardial infarction cardiac fibrosis.

Matricellular proteins in cutaneous wound healing

Cutaneous wound healing is a complex process that encompasses alterations in all aspects of the skin including the extracellular matrix (ECM). ECM consist of large structural proteins such as collagens and elastin as well as smaller proteins with mainly regulative properties called matricellular proteins. Matricellular proteins bind to structural proteins and their functions include but are not limited to interaction with cell surface receptors, cytokines, or protease and evoking a cellular response. The signaling initiated by matricellular proteins modulates differentiation and proliferation of cells having an impact on the tissue regeneration. In this review we give an overview of the matricellular proteins that have been found to be involved in cutaneous wound healing and summarize the information known to date about their functions in this process.

Tracking matricellular protein SPARC in extracellular vesicles as a non-destructive method to evaluate lipid-based antifibrotic treatments

Uncovering the complex cellular mechanisms underlying hepatic fibrogenesis could expedite the development of effective treatments and noninvasive diagnosis for liver fibrosis. The biochemical complexity of extracellular vesicles (EVs) and their role in intercellular communication make them an attractive tool to look for biomarkers as potential alternative to liver biopsies. We developed a solid set of methods to isolate and characterize EVs from differently treated human hepatic stellate cell (HSC) line LX-2, and we investigated their biological effect onto naïve LX-2, proving that EVs do play an active role in fibrogenesis. We mined our proteomic data for EV-associated proteins whose expression correlated with HSC treatment, choosing the matricellular protein SPARC as proof-of-concept for the feasibility of fluorescence nanoparticle-tracking analysis to determine an EV-based HSCs’ fibrogenic phenotype. We thus used EVs to directly evaluate the efficacy of treatment with S80, a polyenylphosphatidylcholines-rich lipid, finding that S80 reduces the relative presence of SPARC-positive EVs. Here we correlated the cellular response to lipid-based antifibrotic treatment to the relative presence of a candidate protein marker associated with the released EVs. Along with providing insights into polyenylphosphatidylcholines treatments, our findings pave the way for precise and less invasive diagnostic analyses of hepatic fibrogenesis.

A method is developed to isolate and characterize extracellular vesicles (EVs) from human hepatic stellate cells and proteomics reveals that the matricellular protein SPARC may be used as an EV marker after lipid-based antifibrotic treatment.

β-catenin cancer-enhancing genomic regions axis is involved in the development of fibrolamellar hepatocellular carcinoma

Fibrolamellar hepatocellular carcinoma (FLC) is a disease that occurs in children and young adults. The development of FLC is associated with creation of a fusion oncoprotein DNAJB1-PKAc kinase, which activates multiple cancer-associated pathways. The aim of this study was to examine the role of human genomic regions, called cancer-enhancing genomic regions or aggressive liver cancer domains (CEGRs/ALCDs), in the development of FLC. Previous studies revealed that CEGRs/ALCDs are located in multiple oncogenes and cancer-associated genes, regularly silenced in normal tissues. Using the regulatory element locus intersection (RELI) algorithm, we searched a large compendium of chromatin immunoprecipitation-sequencing (ChIP) data sets and found that CEGRs/ALCDs contain regulatory elements in several human cancers outside of pediatric hepatic neoplasms. The RELI algorithm further identified components of the β-catenin-TCF7L2/TCF4 pathway, which interacts with CEGRs/ALCDs in several human cancers. Particularly, the RELI algorithm found interactions of transcription factors and chromatin remodelers with many genes that are activated in patients with FLC. We found that these FLC-specific genes contain CEGRs/ALCDs, and that the driver of FLC, fusion oncoprotein DNAJB1-PKAc, phosphorylates β-catenin at Ser675, resulting in an increase of β-catenin-TCF7L2/TCF4 complexes. These complexes increase a large family of CEGR/ALCD-dependent collagens and oncogenes. The DNAJB1-PKAc-β-catenin-CEGR/ALCD pathway is preserved in lung metastasis. The inhibition of β-catenin in FLC organoids inhibited the expression of CEGRs/ALCDs-dependent collagens and oncogenes, preventing the formation of the organoid's structure. Conclusion: This study provides a rationale for the development of β-catenin-based therapy for patients with FLC.

Colon stroma mediates an inflammation-driven fibroblastic response controlling matrix remodeling and healing

Chronic inflammation is often associated with the development of tissue fibrosis, but how mesenchymal cell responses dictate pathological fibrosis versus resolution and healing remains unclear. Defining stromal heterogeneity and identifying molecular circuits driving extracellular matrix deposition and remodeling stands to illuminate the relationship between inflammation, fibrosis, and healing. We performed single-cell RNA-sequencing of colon-derived stromal cells and identified distinct classes of fibroblasts with gene signatures that are differentially regulated by chronic inflammation, including IL-11-producing inflammatory fibroblasts. We further identify a transcriptional program associated with trans-differentiation of mucosa-associated fibroblasts and define a functional gene signature associated with matrix deposition and remodeling in the inflamed colon. Our analysis supports a critical role for the metalloprotease Adamdec1 at the interface between tissue remodeling and healing during colitis, demonstrating its requirement for colon epithelial integrity. These findings provide mechanistic insight into how inflammation perturbs stromal cell behaviors to drive fibroblastic responses controlling mucosal matrix remodeling and healing.

SPARC knockdown attenuated TGF-β1-induced fibrotic effects through Smad2/3 pathways in human pterygium fibroblasts

PURPOSE

Secreted protein acidic and rich in cysteine (SPARC), a matricellular glycoprotein, has been found to regulate processes involved in fibrotic diseases. The aim of this study was to investigate the anti-fibrotic effects of SPARC in primary human pterygium fibroblasts (HPFs) and elucidate the underlying mechanisms.

METHODS

The expression of SPARC in HPFs was knocked down by RNA interference-based approach. Subsequently, we examined the expression of profibrotic markers induced by transforming growth factor-β1 (TGF-β1), including type 1 collagen (COL1), α-smooth muscle actin (α-SMA), and fibronectin (FN). The changes in signaling pathways and matrix metalloproteinases (MMPs) were also detected by western blotting. The cellular migration ability, proliferation ability, apoptosis, and contractile phenotype were detected using the wound healing assay, Cell Counting Kit-8 assay, flow cytometry, and collagen gel contraction assay, respectively. The interaction between SPARC and TGF-β RII was detected by Co-IP RESULTS: Silencing of SPARC inhibited the basal and TGF-β1-induced expression of COL1, α-SMA, and FN in HPFs, and suppressed the expression of p-Smad2, p-Smad3, Smad4 and MMP2, MMP9. The downregulation of SPARC also attenuated the cell migration and contractile phenotype of HPFs. SPARC could bind to TGF-βRII under TGF-β1 treatment. However, knockdown of SPARC did not affect the proliferation and apoptosis of HPFs.

CONCLUSION

SPARC knockdown attenuated the fibrotic effect induced by TGF-β1 at least in part by inactivating the Smad2/3 pathways in HPFs. Therefore, SPARC may be a promising therapeutic target for the treatment of pterygium.

miR‑29a‑3p regulates the epithelial‑mesenchymal transition via the SPARC/ERK signaling pathway in human bronchial epithelial cells

Neutrophilic asthma (NA) is a subtype of asthma that responds poorly to corticosteroid treatment. In certain diseases, microRNA (miR)‑29a‑3p is considered to be a key regulatory molecule for remodeling of the extracellular matrix. However, the effect of miR‑29a‑3p on airway remodeling is unknown. The present study aimed to investigate the role of miR‑29a‑3p in NA. A mouse model of NA was established and these animals were compared to normal controls. Both groups of mice were subjected to lung function tests and histopathological analysis. Human bronchial epithelial cells (16HBE) were grown in culture and incubated with secreted protein acidic rich in cysteine (SPARC) and a miR‑29a‑3p mimic. The expression of miR‑29a‑3p, SPARC and epithelial‑mesenchymal transition (EMT)‑related markers were measured using reverse transcription‑quantitative PCR and western blotting. Luciferase reporter assay was performed to identify the direct regulatory relationship between miR‑29a‑3p and SPARC. miR‑29a‑3p expression was significantly decreased, while SPARC expression was increased in the NA mouse model with a phenotype of EMT. Overexpression of SPARC downregulated the expression of E‑cadherin, while it increased the expression of vimentin in 16HBE cells. miR‑29a‑3p administration reversed the SPARC‑induced effects on E‑cadherin and vimentin expression. Luciferase assays confirmed that SPARC was the target gene for miR‑29a‑3p. Furthermore, SPARC overexpression increased the protein expression of phosphorylated (p)‑ERK, while transfection with miR‑29a‑3p mimics significantly inhibited this increase. The data suggested that EMT in the NA mouse model was associated with decreased levels of miR‑29a‑3p and elevated SPARC. Furthermore, SPARC could induce the formation of EMT in 16HBE cells in vitro and this was directly targeted by miR‑29a‑3p and mediated by p‑ERK, suggesting that miR‑29a‑3p may participate in the airway remodeling of NA.

SPARC inhibition accelerates NAFLD-associated hepatocellular carcinoma development by dysregulating hepatic lipid metabolism

BACKGROUND AND AIMS

Non-alcoholic fatty liver (NAFLD) and its more serious form non-alcoholic steatohepatitis increase risk of hepatocellular carcinoma (HCC). Lipid metabolic alterations and its role in HCC development remain unclear. SPARC (Secreted Protein, Acidic and Rich in Cysteine) is involved in lipid metabolism, NAFLD and diabetes, but the effects on hepatic lipid metabolism and HCC development is unknown. The aim of this study was to evaluate the role of SPARC in HCC development in the context of NAFLD.

METHODS

Primary hepatocyte cultures from knockout (SPARC^-/- ) or wild-type (SPARC^+/+ ) mice, and HepG2 cells were used to assess the effects of free fatty acids on lipid accumulation, expression of lipogenic genes and de novo triglyceride (TG) synthesis. A NAFLD-HCC model was stabilized on SPARC^-/- or SPARC^+/+ mice. Correlations among SPARC, lipid metabolism-related gene expression patterns and clinical prognosis were studied using HCC gene expression dataset.

RESULTS

SPARC^-/- mice increases hepatic lipid deposits over time. Hepatocytes from SPARC^-/- mice or inhibition of SPARC by an antisense adenovirus in HepG2 cells resulted in increased TG deposit, expression of lipid-related genes and nuclear translocation of SREBP1c. Human HCC database analysis revealed that SPARC negatively correlated with genes involved in lipid metabolism, and with poor survival. In NAFLD-HCC murine model, the absence of SPARC accelerates HCC development. RNA-seq study revealed that pathways related to lipid metabolism, cellular detoxification and proliferation were upregulated in SPARC^-/- tumour-bearing mice.

CONCLUSIONS

The absence of SPARC is associated with an altered hepatic lipid metabolism, and an accelerated NAFLD-related HCC development.

SPARC regulation of PMN clearance protects from pristane-induced lupus and rheumatoid arthritis

The secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein with unexpected immunosuppressive function in myeloid cells. We investigated the role of SPARC in autoimmunity using the pristane-induced model of lupus that, in mice, mimics human systemic lupus erythematosus (SLE). Sparc -/- mice developed earlier and more severe renal disease, multi-organ parenchymal damage, and arthritis than the wild-type counterpart. Sparc +/- heterozygous mice showed an intermediate phenotype suggesting Sparc gene dosage in autoimmune-related events. Mechanistically, reduced Sparc expression in neutrophils blocks their clearance by macrophages, through defective delivery of don't-eat-me signals. Dying Sparc -/- neutrophils that escape macrophage scavenging become source of autoantigens for dendritic cell presentation and are a direct stimulation for γδT cells. Gene profile analysis of knee synovial biopsies from SLE-associated arthritis showed an inverse correlation between SPARC and key autoimmune genes. These results point to SPARC down-regulation as a leading event characterizing SLE and rheumatoid arthritis pathogenesis.

Cross your heart? Collagen cross-links in cardiac health and disease

Extracellular matrix (ECM) remodeling occurs in response to various cardiac insults including infarction, pressure overload and dilated myopathies. Each type of remodeling necessitates distinct types of ECM turnover and deposition yet an increase in myocardial fibrillar collagen content is appreciated as a contributing feature to cardiac dysfunction in each of these pathologies. In addition, aging, is also associated with increases in cardiac collagen content. The importance of characterizing differences in ECM composition and processes used by cardiac fibroblasts in the assembly of fibrotic collagen accumulation is critical for the design of strategies to reduce and ultimately regress cardiac fibrosis. Collagen cross-linking is one factor that influences collagen deposition and insolubility with direct implications for tissue properties such as stiffness. In this review, three different types of collagen cross-links shown to be important in cardiac fibrosis will be discussed; those catalyzed by lysyl oxidases, those catalyzed by transglutaminases, and those that result from non-enzymatic modification by the addition of advanced glycation end products. Insight into cellular mechanisms that govern collagen cross-linking in the myocardium will provide novel pathways for exploring new treatments to treat diseases associated with cardiac fibrosis.

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.

Targeting FSTL1 for Multiple Fibrotic and Systemic Autoimmune Diseases

Follistatin-like 1 (FSTL1) is a matricellular protein that is upregulated during development and disease, including idiopathic pulmonary fibrosis (IPF), keloid, and arthritis. The profibrotic and pro-inflammatory roles of FSTL1 have been intensively studied during the last several years, as well as in this report. We screened and identified epitope-specific monoclonal neutralizing antibodies (nAbs) to functionally block FSTL1. FSTL1 nAbs attenuated bleomycin-induced pulmonary and dermal fibrosis in vivo and transforming growth factor (TGF)-β1-induced dermal fibrosis ex vivo in human skin. In addition, FSTL1 nAbs significantly reduced existing lung fibrosis and skin fibrosis in experimental models. FSTL1 nAbs exerted their potent antifibrotic effects via reduced TGF-β1 responsiveness and subsequent myofibroblast activation and extracellular matrix production. We also observed that FSTL1 nAbs attenuated the severity of collagen-induced arthritis in mice, which was accompanied by reduced inflammatory responses in vitro. Our findings suggest that FSTL1 nAbs are a promising new therapeutic strategy for the treatment of multiple organ fibrosis and systemic autoimmune diseases.

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.

Secreted protein acidic and rich in cysteine (SPARC) regulates thermogenesis in white and brown adipocytes

SPARC, also known as osteonectin, is well known for its physiological roles in bone formation and tissue remodeling, as well as in cancer pathology; however, evidence regarding its function in adipocytes is lacking. The present study explored the physiological role of SPARC in cultured 3T3-L1 white and HIB1B brown adipocytes of murine cell lines. Treatment of recombinant SPARC upregulated the fat browning marker proteins and genes in white adipocytes and activated brown adipocytes. Conversely, knockdown of Sparc markedly reduced these genes and proteins in both cell lines. In addition, recombinant SPARC inhibited expression of adipogenic and lipogenic proteins but elevated lipolytic and fatty acid oxidation proteins. Furthermore, in silico analysis revealed that SPARC directly interacted and regulated VEGF in adipocytes. In conclusion, SPARC acts as a regulatory protein in both white and brown adipocytes by controlling thermogenesis and is thus regarded as a possible therapeutic target for treatment of obesity.

A phenome-wide association study (PheWAS) in the Population Architecture using Genomics and Epidemiology (PAGE) study reveals potential pleiotropy in African Americans

We performed a hypothesis-generating phenome-wide association study (PheWAS) to identify and characterize cross-phenotype associations, where one SNP is associated with two or more phenotypes, between thousands of genetic variants assayed on the Metabochip and hundreds of phenotypes in 5,897 African Americans as part of the Population Architecture using Genomics and Epidemiology (PAGE) I study. The PAGE I study was a National Human Genome Research Institute-funded collaboration of four study sites accessing diverse epidemiologic studies genotyped on the Metabochip, a custom genotyping chip that has dense coverage of regions in the genome previously associated with cardio-metabolic traits and outcomes in mostly European-descent populations. Here we focus on identifying novel phenome-genome relationships, where SNPs are associated with more than one phenotype. To do this, we performed a PheWAS, testing each SNP on the Metabochip for an association with up to 273 phenotypes in the participating PAGE I study sites. We identified 133 putative pleiotropic variants, defined as SNPs associated at an empirically derived p-value threshold of p<0.01 in two or more PAGE study sites for two or more phenotype classes. We further annotated these PheWAS-identified variants using publicly available functional data and local genetic ancestry. Amongst our novel findings is SPARC rs4958487, associated with increased glucose levels and hypertension. SPARC has been implicated in the pathogenesis of diabetes and is also known to have a potential role in fibrosis, a common consequence of multiple conditions including hypertension. The SPARC example and others highlight the potential that PheWAS approaches have in improving our understanding of complex disease architecture by identifying novel relationships between genetic variants and an array of common human phenotypes.

Metabolic Syndrome, Brain Insulin Resistance, and Alzheimer's Disease: Thioredoxin Interacting Protein (TXNIP) and Inflammasome as Core Amplifiers

Empirical evidence indicates a strong association between insulin resistance and pathological alterations related to Alzheimer's disease (AD) in different cerebral regions. While cerebral insulin resistance is not essentially parallel with systemic metabolic derangements, type 2 diabetes mellitus (T2DM) has been established as a risk factor for AD. The circulating "toxic metabolites" emerging in metabolic syndrome may engage several biochemical pathways to promote oxidative stress and neuroinflammation leading to impair insulin function in the brain or "type 3 diabetes". Thioredoxin-interacting protein (TXNIP) as an intracellular amplifier of oxidative stress and inflammasome activation may presumably mediate central insulin resistance. Emerging data including those from our recent studies has demonstrated a sharp TXNIP upregulation in stroke, aging and AD and well underlining the significance of this hypothesis. With the main interest to illustrate TXNIP place in type 3 diabetes, the present review primarily briefs the potential mechanisms contributing to cerebral insulin resistance in a metabolically deranged environment. Then with a particular focus on plausible TXNIP functions to drive and associate with AD pathology, we present the most recent evidence supporting TXNIP as a promising therapeutic target in AD as an age-associated dementia.

Structural and functional study of FK domain of Fstl1

Fstl1 is a TGF-β superfamily binding protein which involved in many pathological processes. The function of Fstl1 has been widely elucidated, but its structural characterization has not been explored. Here we solved the high-resolution crystal structure of FK domain of murine Fstl1, analyzed its unique characteristics, and investigated its contribution to the function of full-length Fstl1. We found that Fstl1-FK forms a stable dimer in both solution and crystal, which suggest that this protein may function as a dimer during its interaction with TGF-β, a molecule known to form dimer during activation process. We also found this FK domain is indispensable for the proper function of Fstl1 during the transduction of TGF-β signaling. These observations provide important insights into the understanding of Fstl1 and may facilitate the exploration of this molecule in clinical study.

Activated Fibroblast Program Orchestrates Tumor Initiation and Progression; Molecular Mechanisms and the Associated Therapeutic Strategies

: Neoplastic epithelial cells coexist in carcinomas with various non-neoplastic stromal cells, together creating the tumor microenvironment. There is a growing interest in the cross-talk between tumor cells and stromal fibroblasts referred to as carcinoma-associated fibroblasts (CAFs), which are frequently present in human carcinomas. CAF populations extracted from different human carcinomas have been shown to possess the ability to influence the hallmarks of cancer. Indeed, several mechanisms underlying CAF-promoted tumorigenesis are elucidated. Activated fibroblasts in CAFs are characterized as alpha-smooth muscle actin-positive myofibroblasts and actin-negative fibroblasts, both of which are competent to support tumor growth and progression. There are, however, heterogeneous CAF populations presumably due to the diverse sources of their progenitors in the tumor-associated stroma. Thus, molecular markers allowing identification of bona fide CAF populations with tumor-promoting traits remain under investigation. CAFs and myofibroblasts in wound healing and fibrosis share biological properties and support epithelial cell growth, not only by remodeling the extracellular matrix, but also by producing numerous growth factors and inflammatory cytokines. Notably, accumulating evidence strongly suggests that anti-fibrosis agents suppress tumor development and progression. In this review, we highlight important tumor-promoting roles of CAFs based on their analogies with wound-derived myofibroblasts and discuss the potential therapeutic strategy targeting CAFs.

The Influence of the Extracellular Matrix in Inflammation: Findings from the SPARC-Null Mouse

Matricellular proteins are secreted proteins that, among other functions, can contribute to extracellular matrix (ECM) assembly including modulation of cell:ECM interactions. Recent discoveries have indicated a fundamental role for the ECM in the regulation of inflammatory responses including cell extravasation and recruitment, immune cell differentiation, polarization, activation, and retention in tissues. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular collagen-binding protein implicated in fibrillar collagen assembly in the ECM of connective tissue as well as in basal lamina organization. Functions of SPARC in modulating cell adhesion events are also reported. Studies of phenotypic responses observed in SPARC-null mice to a variety of injury models have yielded interesting insight into the functional importance of SPARC production and aberrations in ECM structure that occur in the absence of SPARC that influence immune cell behavior and inflammatory pathways. In this review, we will discuss several examples from different tissues in which SPARC-null mice exhibited an inflammatory response distinct from those of SPARC expressing mice and provide insight into novel ECM-dependent mechanisms that influence these responses. Anat Rec, 2019. © 2019 Wiley Periodicals, Inc.

Stemness and Regenerative Potential of Corneal Stromal Stem Cells and Their Secretome After Long-Term Storage: Implications for Ocular Regeneration

Purpose

To assess the stemness and regenerative potential of cryopreserved corneal stromal stem cells (cryo-CSSCs) after long-term storage. We also used the secretome from these cells to observe the effect on wound-healing capacity of corneal fibroblasts and on the expression of fibrotic markers during wound healing.

Methods

CSSCs were obtained from three donors and stored in liquid nitrogen for approximately 10 years. Post thaw, cryo-CSSCs were characterized for stemness using phenotypic and genotypic markers along with colony-forming efficiency and three-dimensional spheroid formation. Multilineage differentiation was observed by differentiation into osteocytes, adipocytes, neural cells, and keratocytes. Secretome was harvested by culturing cryo-CSSCs in log phase. Wound-healing capacity was observed by live-cell time-lapse microscopy. Statistical analysis was done using 1-way ANOVA and Tukey posttest.

Results

CSSCs displayed good viability post thaw and showed >90% expression of stem cell markers CD90, CD73, CD105, STRO1, and CD166. cryo-CSSCs also expressed stem cell genes OCT4, KLF4, and ABCG2, and could also form colonies and three-dimensional spheroids. Multipotency assessment showed that all three cryo-CSSCs could differentiate into osteocytes, adipocytes, neural cells, as shown by β-III tubulin and neurofilament antibody staining and corneal keratocytes as observed by staining for Kera C, J19, and collagen V antibodies. The secretome derived from these three populations could promote the wound healing of corneal fibroblasts and reduce the expression of fibrotic markers SPARC and fibronectin.

Conclusions

CSSCs maintained their stemness and multipotency after long-term storage, and secretome derived from these cells can be of paramount importance for corneal regeneration and prevention of fibrosis.

ISSLS Prize in Basic science 2019: Physical activity attenuates fibrotic alterations to the multifidus muscle associated with intervertebral disc degeneration

PURPOSE

Chronic low back pain causes structural remodelling and inflammation in the multifidus muscle. Collagen expression is increased in the multifidus of humans with lumbar disc degeneration. However, the extent and mechanisms underlying the increased fibrotic activity in the multifidus are unknown. Physical activity reduces local inflammation that precedes multifidus fibrosis during intervertebral disc degeneration (IDD), but its effect on amelioration of fibrosis is unknown. This study aimed to assess the development of fibrosis and its underlying genetic network during IDD and the impact of physical activity.

METHODS

Wild-type and SPARC-null mice were either sedentary or housed with a running wheel, to allow voluntary physical activity. At 12 months of age, IDD was assessed with MRI, and multifidus muscle samples were harvested from L2 to L6. In SPARC-null mice, the L1/2 and L3/4 discs had low and high levels of IDD, respectively. Thus, multifidus samples from L2 and L4 were allocated to low- and high-IDD groups compared to assess the effects of IDD and physical activity on connective tissue and fibrotic genes.

RESULTS

High IDD was associated with greater connective tissue thickness and dysregulation of collagen-III, fibronectin, CTGF, substance P, TIMP1 and TIMP2 in the multifidus muscle. Physical activity attenuated the IDD-dependent increased connective tissue thickness and reduced the expression of collagen-I, fibronectin, CTGF, substance P, MMP2 and TIMP2 in SPARC-null animals and wild-type mice. Collagen-III and TIMP1 were only reduced in wild-type animals.

CONCLUSIONS

These data reveal the fibrotic networks that promote fibrosis in the multifidus muscle during chronic IDD. Furthermore, physical activity is shown to reduce fibrosis and regulate the fibrotic gene network. These slides can be retrieved under Electronic Supplementary Material.

Pulmonary immunity and extracellular matrix interactions

The lung harbors a complex immune system composed of both innate and adaptive immune cells. Recognition of infection and injury by receptors on lung innate immune cells is crucial for generation of antigen-specific responses by adaptive immune cells. The extracellular matrix of the lung, comprising the interstitium and basement membrane, plays a key role in the regulation of these immune systems. The matrix consists of several hundred assembled proteins that interact to form a bioactive scaffold. This template, modified by enzymes, acts to facilitate cell function and differentiation and changes dynamically with age and lung disease. Herein, we explore relationships between innate and adaptive immunity and the lung extracellular matrix. We discuss the interactions between extracellular matrix proteins, including glycosaminoglycans, with prominent effects on innate immune signaling effectors such as toll-like receptors. We describe the relationship of extracellular matrix proteins with adaptive immunity and leukocyte migration to sites of injury within the lung. Further study of these interactions will lead to greater knowledge of the role of matrix biology in lung immunity. The development of novel therapies for acute and chronic lung disease is dependent on a comprehensive understanding of these complex matrix-immunity interactions.

A fragment of SPARC reflecting increased collagen affinity shows pathological relevance in lung cancer - implications of a new collagen chaperone function of SPARC

The matricellular protein SPARC (secreted proteome acidic and rich in cysteine) is known to bind collagens and regulate fibrillogenesis. Cleavage of SPARC at a single peptide bond, increases the affinity for collagens up to 20-fold. To investigate if this specific cleavage has pathological relevance in fibrotic disorders, we developed a competitive ELISA targeting the generated neo-epitope on the released fragment and quantified it in serum from patients with lung cancer, idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD) and healthy subjects. Furthermore, the ability of SPARC to protect fibrillar collagens from proteolytic degradation was investigated in vitro, potentially adding a new collagen chaperone function to SPARC. The fragment was significantly elevated in lung cancer patients when compared to healthy subjects measured in a discovery cohort (p = 0.0005) and a validation cohort (p < 0.0001). No significant difference was observed for IPF and COPD patients compared to healthy subjects. When recombinant SPARC was incubated with type I or type III collagen and matrix metalloproteinase-9, collagen degradation was completely inhibited. Together, these data suggest that cleavage of SPARC at a specific site, which modulates collagen binding, is a physiological mechanism increased during pathogenesis of lung cancer. Furthermore, inhibition of fibrillar collagen degradation by SPARC adds a new chaperone function to SPARC which may play additional roles in the contribution to increased collagen deposition leading to a pro-fibrotic and tumorigenic environment.

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.

SPARC preserves endothelial glycocalyx integrity, and protects against adverse cardiac inflammation and injury during viral myocarditis

Myocardial damage as a consequence of cardiotropic viruses leads to a broad variety of clinical presentations and is still a complicated condition to diagnose and treat. Whereas the extracellular matrix protein Secreted Protein Acidic and Rich in Cysteine or SPARC has been implicated in hypertensive and ischemic heart disease by modulating collagen production and cross-linking, its role in cardiac inflammation and endothelial function is yet unknown. Absence of SPARC in mice resulted in increased cardiac inflammation and mortality, and reduced cardiac systolic function upon coxsackievirus-B3 induced myocarditis. Intra-vital microscopic imaging of the microvasculature of the cremaster muscle combined with electron microscopic imaging of the microvasculature of the cardiac muscle uncovered the significance of SPARC in maintaining endothelial glycocalyx integrity and subsequent barrier properties to stop inflammation. Moreover, systemic administration of recombinant SPARC restored the endothelial glycocalyx and consequently reversed the increase in inflammation and mortality observed in SPARC KO mice in response to viral exposure. Reducing the glycocalyx in vivo by systemic administration of hyaluronidase, an enzyme that degrades the endothelial glycocalyx, mimicked the barrier defects found in SPARC KO mice, which could be restored by subsequent administration of recombinant SPARC. In conclusion, the secreted glycoprotein SPARC protects against adverse cardiac inflammation and mortality by improving the glycocalyx function and resulting endothelial barrier function during viral myocarditis.

SPARC expression is associated with hepatic injury in rodents and humans with non-alcoholic fatty liver disease

Mechanisms that control progression from simple steatosis to steato-hepatitis and fibrosis in patients with non-alcoholic fatty liver disease (NAFLD) are unknown. SPARC, a secreted matricellular protein, is over-expressed in the liver under chronic injury. Contribution of SPARC accumulation to disease severity is largely unknown in NAFLD. We assessed the hypothesis that SPARC is increased in livers with more necrosis and inflammation and could be associated with more fibrosis. qrt-PCR, immunohistochemistry, and ELISA were employed to localize and quantify changes in SPARC in 62 morbidly obese patients with NAFLD/NASH and in a mouse model of diet-induced-NASH. Results were correlated with the severity of NAFLD/NASH. In obese patients 2 subgroups were identified with either high SPARC expression (n = 16) or low SPARC expression (n = 46) in the liver, with a cutoff of 1.2 fold expression. High expression of SPARC paralleled hepatocellular damage and increased mRNA expression of pro-fibrogenic factors in the liver. In line with these findings, in the NASH animal model SPARC knockout mice were protected from inflammatory injury, and showed less inflammation and fibrosis. Hepatic SPARC expression is associated with liver injury and fibrogenic processes in NAFLD. SPARC has potential as preventive or therapeutic target in NAFLD patients.

Production and purification of recombinant human SPARC

The matricellular protein SPARC (secreted protein acidic and rich in cysteine, also known as osteonectin or as BM-40) is a collagen-binding protein with a capacity to induce cell rounding and influence proliferation in cultured cells. In mice that do not express SPARC, fibrillar collagen is reduced in some adult tissues; notably, a reduction in fibrosis is reported in response to fibrotic stimuli in lungs, heart, skin, liver, and in the eye. Recently, mutations in the gene encoding SPARC were found in patients afflicted with osteogenesis imperfecta. Thus, SPARC appears to be a critical mediator of collagen deposition and assembly in tissues. A useful tool for assessing the function of SPARC in ECM assembly is a source of purified recombinant SPARC. Outlined in this chapter is a brief discussion of different strategies for generating recombinant SPARC and an experimental strategy for producing and purifying human recombinant SPARC driven by baculoviral expression in insect cells.

The Roles of Matricellular Proteins in Oncogenic Virus-Induced Cancers and Their Potential Utilities as Therapeutic Targets

Matricellular proteins differ from other classical extracellular matrix proteins; for instance, they are transiently expressed as soluble proteins rather than being constitutively expressed in pathological conditions, such as acute viral infections. Accumulating studies have revealed that matricellular proteins, including osteopontin and tenascin-C, both of which interact with integrin heterodimers, are involved in inflammatory diseases, autoimmune disorders, and cancers. The concentrations of these matricellular proteins are elevated in the plasma of patients with certain types of cancers, indicating that they play important roles in oncogenesis. Chronic viral infections are associated with certain cancers, which are distinct from non-viral cancers. Viral oncogenes play critical roles in the development and progression of such cancers. It is vital to investigate the mechanisms of tumorigenesis and, particularly, the mechanism by which viral proteins induce tumor progression. Viral proteins have been shown to influence not only the viral-infected cancer cells, but also the stromal cells and matricellular proteins that constitute the extracellular matrix that surrounds tumor tissues. In this review, we summarize the recent progress on the involvement of matricellular proteins in oncogenic virus-induced cancers to elucidate the mechanism of oncogenesis and consider the possible role of matricellular proteins as therapeutic targets in virus-induced cancers.

A holistic approach to dissecting SPARC family protein complexity reveals FSTL-1 as an inhibitor of pancreatic cancer cell growth

SPARC is a matricellular protein that is involved in both pancreatic cancer and diabetes. It belongs to a wider family of proteins that share structural and functional similarities. Relatively little is known about this extended family, but evidence of regulatory interactions suggests the importance of a holistic approach to their study. We show that Hevin, SPOCKs, and SMOCs are strongly expressed within islets, ducts, and blood vessels, suggesting important roles for these proteins in the normal pancreas, while FSTL-1 expression is localised to the stromal compartment reminiscent of SPARC. In direct contrast to SPARC, however, FSTL-1 expression is reduced in pancreatic cancer. Consistent with this, FSTL-1 inhibited pancreatic cancer cell proliferation. The complexity of SPARC family proteins is further revealed by the detection of multiple cell-type specific isoforms that arise due to a combination of post-translational modification and alternative splicing. Identification of splice variants lacking a signal peptide suggests the existence of novel intracellular isoforms. This study underlines the importance of addressing the complexity of the SPARC family and provides a new framework to explain their controversial and contradictory effects. We also demonstrate for the first time that FSTL-1 suppresses pancreatic cancer cell growth.

SPARC/osteonectin in mineralized tissue

Secreted protein acidic and rich in cysteine (SPARC/osteonectin/BM40) is one of the most abundant non-collagenous protein expressed in mineralized tissues. This review will focus on elucidating functional roles of SPARC in bone formation building upon results from non-mineralized cells and tissues, the phenotype of SPARC-null bones, and recent discoveries of human diseases with either dysregulated expression of SPARC or mutations in the gene encoding SPARC that give rise to bone pathologies. The capacity of SPARC to influence pathways involved in extracellular matrix assembly such as procollagen processing and collagen fibril formation as well as the capacity to influence osteoblast differentiation and osteoclast activity will be addressed. In addition, the potential for SPARC to regulate cross-linking of extracellular matrix proteins by members of the transglutaminase family of enzymes is explored. Elucidating defined biological functions of SPARC in terms of bone formation and turnover are critical. Further insight into specific cellular mechanisms involved in the formation and homeostasis of mineralized tissues will lead to a better understanding of disease progression.

SPARC-Dependent Cardiomyopathy in Drosophila

Supplemental Digital Content is available in the text.

Background—

The Drosophila heart is an important model for studying the genetics underpinning mammalian cardiac function. The system comprises contractile cardiomyocytes, adjacent to which are pairs of highly endocytic pericardial nephrocytes that modulate cardiac function by uncharacterized mechanisms. Identifying these mechanisms and the molecules involved is important because they may be relevant to human cardiac physiology.

Methods and Results—

This work aimed to identify circulating cardiomodulatory factors of potential relevance to humans using the Drosophila nephrocyte–cardiomyocyte system. A Kruppel-like factor 15 (dKlf15) loss-of-function strategy was used to ablate nephrocytes and then heart function and the hemolymph proteome were analyzed. Ablation of nephrocytes led to a severe cardiomyopathy characterized by a lengthening of diastolic interval. Rendering adult nephrocytes dysfunctional by disrupting their endocytic function or temporally conditional knockdown of dKlf15 led to a similar cardiomyopathy. Proteomics revealed that nephrocytes regulate the circulating levels of many secreted proteins, the most notable of which was the evolutionarily conserved matricellular protein Secreted Protein Acidic and Rich in Cysteine (SPARC), a protein involved in mammalian cardiac function. Finally, reducing SPARC gene dosage ameliorated the cardiomyopathy that developed in the absence of nephrocytes.

Conclusions—

The data implicate SPARC in the noncell autonomous control of cardiac function in Drosophila and suggest that modulation of SPARC gene expression may ameliorate cardiac dysfunction in humans.