SPARC-null mice exhibit accelerated cutaneous wound closure

Downregulation of SPARC Expression Enhances the Fusion of BeWo Choriocarcinoma Cells

Syncytiotrophoblasts, which are formed by the fusion of villous cytotrophoblasts, play an essential role in maintaining a successful pregnancy. Secreted protein acidic and rich in cysteine (SPARC) is a non-structural Ca2+-binding extracellular matrix glycoprotein involved in tissue remodeling and cell proliferation, differentiation, and migration. Previous studies have revealed that SPARC is expressed in villous and extravillous cytotrophoblasts in the first trimester and that RNA interference targeted at SPARC significantly inhibited invasion of human extravillous trophoblast HTR8/SVneo cells. However, the involvement of SPARC in cytotrophoblast fusion remains unknown. This study aimed to investigate the role of SPARC in cytotrophoblast fusion, using the BeWo choriocarcinoma cell line as a model of villous cytotrophoblasts. Immunohistochemical analysis was conducted to assess SPARC expression in normal human placentas using placental tissues obtained during the first and third trimesters of pregnancy. We investigated the effects of SPARC knockdown on trophoblast differentiation markers and cell fusion in BeWo cells using small interfering RNA. Immunohistochemical analysis revealed that SPARC expression was high in the early gestational chorionic villi and low in the late gestational chorionic villi. SPARC knockdown increased the expressions of human chorionic gonadotropin and Ovo-like transcriptional repressor 1; however, glial cells missing transcription factor 1, syncytin-1, and syncytin-2 showed no significant changes. The assessment revealed that SPARC knockdown significantly enhanced cell fusion compared to the non-silencing control. Our data suggest that SPARC plays a vital role in regulating trophoblast fusion and differentiation during placental development.

Establishing a Dexamethasone Treatment Regimen To Alleviate Sulfur Mustard-Induced Corneal Injuries in a Rabbit Model

Sulfur mustard (SM) is an ominous chemical warfare agent. Eyes are extremely susceptible to SM toxicity; injuries include inflammation, fibrosis, neovascularization (NV), and vision impairment/blindness, depending on the exposure dosage. Effective countermeasures against ocular SM toxicity remain elusive and are warranted during conflicts/terrorist activities and accidental exposures. We previously determined that dexamethasone (DEX) effectively counters corneal nitrogen mustard toxicity and that the 2-hour postexposure therapeutic window is most beneficial. Here, the efficacy of two DEX dosing frequencies [i.e., every 8 or 12 hours (initiated, as previously established, 2 hours after exposure)] until 28 days after SM exposure was assessed. Furthermore, sustained effects of DEX treatments were observed up to day 56 after SM exposure. Corneal clinical assessments (thickness, opacity, ulceration, and NV) were performed at the day 14, 28, 42, and 56 post-SM exposure time points. Histopathological assessments of corneal injuries (corneal thickness, epithelial degradation, epithelial-stromal separation, inflammatory cell, and blood vessel counts) using H&E staining and molecular assessments (COX-2, MMP-9, VEGF, and SPARC expressions) were performed at days 28, 42, and 56 after SM exposure. Statistical significance was assessed using two-way ANOVA, with Holm-Sidak post hoc pairwise multiple comparisons; significance was established if P < 0.05 (data represented as the mean ± S.E.M.). DEX administration every 8 hours was more potent than every 12 hours in reversing ocular SM injury, with the most pronounced effects observed at days 28 and 42 after SM exposure. These comprehensive results are novel and provide a comprehensive DEX treatment regimen (therapeutic-window and dosing-frequency) for counteracting SM-induced corneal injuries. SIGNIFICANCE STATEMENT: The study aims to establish a dexamethasone (DEX) treatment regimen by comparing the efficacy of DEX administration at 12 versus 8 hours initiated 2 hours after exposure. DEX administration every 8 hours was more effective in reversing sulfur mustard (SM)-induced corneal injuries. SM injury reversal during DEX administration (initial 28 days after exposure) and sustained [further 28 days after cessation of DEX administration (i.e., up to 56 days after exposure)] effects were assessed using clinical, pathophysiological, and molecular biomarkers.

Matricellular Proteins in the Homeostasis, Regeneration, and Aging of Skin

Matricellular proteins are secreted extracellular proteins that bear no primary structural functions but play crucial roles in tissue remodeling during development, homeostasis, and aging. Despite their low expression after birth, matricellular proteins within skin compartments support the structural function of many extracellular matrix proteins, such as collagens. In this review, we summarize the function of matricellular proteins in skin stem cell niches that influence stem cells' fate and self-renewal ability. In the epidermal stem cell niche, fibulin 7 promotes epidermal stem cells' heterogeneity and fitness into old age, and the transforming growth factor-β-induced protein ig-h3 (TGFBI)-enhances epidermal stem cell growth and wound healing. In the hair follicle stem cell niche, matricellular proteins such as periostin, tenascin C, SPARC, fibulin 1, CCN2, and R-Spondin 2 and 3 modulate stem cell activity during the hair cycle and may stabilize arrector pili muscle attachment to the hair follicle during piloerections (goosebumps). In skin wound healing, matricellular proteins are upregulated, and their functions have been examined in various gain-and-loss-of-function studies. However, much remains unknown concerning whether these proteins modulate skin stem cell behavior, plasticity, or cell-cell communications during wound healing and aging, leaving a new avenue for future studies.

Single-cell analysis reveals distinct functional heterogeneity of CD34+ cells in anagen wound and diabetic wound

Wound healing is a complex biological process involving multiple cell types with their critical functions. The diabetic wounds show delayed wound healing, while the anagen wounds display accelerated wound closure. However, the mechanisms underlying the effect of cellular heterogeneity on wound healing are still unclear. CD34⁺ cells exhibit high heterogeneity in wound skins and improve wound healing. Herein, we investigated the phenotypic and functional heterogeneity of CD34⁺ cells in normal, anagen, and diabetic wounds. We obtained CD34 lineage tracing mice, constructed distinct wound models, collected CD34⁺ cells from wound edges, and performed single-cell RNA sequencing. We identified 10 cell clusters and 6 cell types of CD34⁺ cells, including endothelial cells, fibroblasts, keratinocytes, neutrophils, macrophages, and T cells. 5 subclusters were defined as fibroblasts. The CD34⁺ fibroblasts C2 highly expressed papillary fibroblastic markers took up the largest proportion in anagen wounds and were associated with inflammation and extracellular matrix. Increased CD34⁺ endothelial cells, fibroblasts C4, and neutrophils as well as decreased fibroblasts C1 were discovered in diabetic wounds. We also filtered out differentially expressed genes (DEGs) of each cell cluster in anagen wounds and diabetic wounds. Functional enrichment analysis was performed on these DEGs to figure out the enriched pathways and items for each cell cluster. Pseudotime analysis of CD34⁺ fibroblasts was next carried out indicating fibroblast C4 mainly with low differentiation. Our results have important implications for understanding CD34⁺ cell type-specific roles in anagen and diabetic wounds, provide the possible mechanisms of wound healing from a new perspective, and uncover potential therapeutic approaches to treating wounds.

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.

Research models of sulfur mustard- and nitrogen mustard-induced ocular injuries and potential therapeutics

Sulfur mustard (SM) is a notorious, bifunctional alkylating vesicant that was first used in warfare during World War I in 1917 and since then has been deployed in numerous skirmishes with its most recent documented use being during the Middle Eastern conflicts. Apart from its use in combat and terrorist activities, continual threat of accidental exposure from old stockpiles and improperly discarded munitions is ever present, especially to the innocent and unassuming civilian populations. SM can cause devastating injuries, depending on the dosage of SM exposure, route of exposure, as well as the physiological conditions of the individuals exposed. The most common routes of exposure are ocular, dermal, and exposure to the lungs and respiratory tissues through inhalation. Eyes are the most susceptible organ to SM-induced toxicities owing to their high moisture content and rapidly dividing cells. Additionally, ocular injury causes the most expeditious disablement of individuals even upon whole-body exposures. Therefore, it is imperative to understand the mechanisms underlying SM-induced ocular toxicity and design therapeutic interventions to prevent/mitigate ocular injuries. Ocular SM exposure may cause a wide range of symptoms such as inflammation, lacrimation, itching, dryness, photophobia, edema of the cornea/sclera/retina/iris, conjunctivitis, degradation of the corneal layer, fusion of two or more ocular layers, neovascularization, fibrosis, and temporary or permanent structural damage to one or more ocular layers. These symptoms may lead to vision impairments, resulting in partial or complete blindness that may be permanent. The highly toxic and exceedingly notorious nature of SM makes it a highly regulated chemical, requiring very expensive licensing, security, and safety requirements; thus, the more easily accessible analogue, nitrogen mustard (NM) that mimics SM-induced toxicity and injuries is employed in plethora of studies conducted in different animal models and culture systems. This review provides a comprehensive account of the injuries and symptoms that occur upon ocular SM exposures in human patients as well as studies in animal (in vivo, ex vivo) and cell (in vitro) models of SM and NM ocular exposures. Special emphasis has been laid on highlighting the strengths and lacunae in the research as well as the possible unexplored avenues of mechanisms underlying mustard-induced ocular injury that can be explored in future research endeavors. Furthermore, development of therapeutic interventions and targets of interest in the ocular system exposed to SM and NM, based on studies in human patients as well as in vivo, ex vivo, and in vitro models has been discussed in great depth, providing a valuable knowledge database to delineate pathways associated with vesicant-induced toxicity, and strategies/diagnostic tools against SM-induced toxicity.

Thrombospondin-1 Signaling Through the Calreticulin/LDL Receptor Related Protein 1 Axis: Functions and Possible Roles in Glaucoma

Thrombospondin-1 (TSP-1) is a matricellular extracellular matrix protein. Matricellular proteins are components of the extracellular matrix (ECM) that regulate key cellular functions and impact ECM organization, but which lack direct primary structural roles in the ECM. TSP-1 expression is upregulated in response to injury, hypoxia, growth factor stimulation, inflammation, glucose, and by reactive oxygen species. Relevant to glaucoma, TSP-1 is also a mechanosensitive molecule upregulated by mechanical stretch. TSP-1 expression is increased in ocular remodeling in glaucoma in both the trabecular meshwork and in the optic nerve head. The exact roles of TSP-1 in glaucoma remain to be defined, however. It plays important roles in cell behavior and in ECM remodeling during wound healing, fibrosis, angiogenesis, and in tumorigenesis and metastasis. At the cellular level, TSP-1 can modulate cell adhesion and migration, protease activity, growth factor activity, anoikis resistance, apoptosis, and collagen secretion and matrix assembly and cross-linking. These multiple functions and macromolecular and receptor interactions have been ascribed to specific domains of the TSP-1 molecule. In this review, we will focus on the cell regulatory activities of the TSP-1 N-terminal domain (NTD) sequence that binds to cell surface calreticulin (Calr) and which regulates cell functions via signaling through Calr complexed with LDL receptor related protein 1 (LRP1). We will describe TSP-1 actions mediated through the Calr/LRP1 complex in regulating focal adhesion disassembly and cytoskeletal reorganization, cell motility, anoikis resistance, and induction of collagen secretion and matrix deposition. Finally, we will consider the relevance of these TSP-1 functions to the pathologic remodeling of the ECM in glaucoma.

Topical heparin as an effective and safe treatment for patients with capecitabine-induced hand-foot syndrome: results of a phase IIA trial supported by proteomic profiling of skin biopsies

Background:

Hand-foot syndrome (HFS) is a common adverse reaction associated with capecitabine chemotherapy that significantly affects the quality of life of patients. This study evaluates the safety and effectiveness of a topical heparin (TH) treatment on the clinical manifestations and anatomopathological alterations of capecitabine-induced HFS. In addition, we performed proteome profiling of skin biopsies obtained from patients with HFS at baseline and after heparin treatment.

Methods:

Patients with grade ⩽ 2 HFS associated with capecitabine were included in this study. The primary end point was the effectiveness of TH in reducing HFS of any grade. Clinical improvement was evaluated by clinicians, and an improvement was perceived by patients who performed a weekly visual analog scale questionnaire. Secondary end points included a comparative histological analysis and protein expression in skin biopsies at baseline and after 3 weeks of HT treatment. Proteomic profiling was carried out using quantitative isobaric labelling and subsequently validated by a T-array.

Results:

Twenty-one patients were included in the study. The median TH treatment time was 7.6 weeks (range = 3.6–41.6 weeks), and the median response time was 3.01 weeks (95% CI = 2.15–3.97). At the end of treatment, 19 of 21 patients (90.48%) responded to treatment with a decrease in one or more grades of HFS. None of the patients experienced adverse effects related to TH usage, nor did they suspend chemotherapy treatment. The main findings observed in skin biopsies after treatment were a decrease in hyperkeratosis and lymphocytic infiltrates. The proteomic analysis showed altered expression of 34 proteins that were mainly related to wound healing, cell growth, and the immune response.

Conclusion:

Based on our results, topical heparin is an effective and safe treatment for clinical manifestations of HFS, probably due to the restauration of skin homeostasis after heparin treatment, as supported by our proteomics-derived data.

Trial registration:

EudraCT 2009-018171-13

Secreted protein acidic and rich in cysteine (SPARC) and a disintegrin and metalloproteinase with thrombospondin type 1 motif (ADAMTS1) increments by the renin-angiotensin system induce renal fibrosis in deoxycorticosterone acetate-salt hypertensive rats

Secreted protein acidic and rich in cysteine (SPARC), an extracellular matrix (ECM) protein, was recently shown to induce collagen deposition through the production of a disintegrin and metalloproteinase with thrombospondin type 1 motif (ADAMTS1) in the aging heart. ADAMTS1 regulates ECM turnover by degrading ECM components, and its excessive activation contributes to various pathological states, including fibrosis. The present study investigated the pathophysiological regulation and role of SPARC and ADAMTS1 in renal fibrosis using uninephrectomized rats treated with deoxycorticosterone acetate (DOCA, 40 mg/kg/week, subcutaneously) and salt (1% in drinking water). The administration of DOCA and salt gradually and significantly elevated systolic blood pressure during the 3-week treatment period, induced proteinuria, decreased creatinine clearance, and increased NADPH oxidase-derived superoxide production, malondialdehyde concentrations, and monocyte chemoattractant protein-1 and osteopontin expression in the kidneys. Glomerulosclerosis, fibrillar collagen deposition, and transforming growth factor-β expression increased in a time-dependent manner, and SPARC and ADAMTS1 expression showed a similar pattern to these changes. The angiotensin II type-1 receptor blocker losartan suppressed the overexpression of SPARC and ADAMTS1, and an in vitro exposure to angiotensin II induced the production of both SPARC and ADAMTS1 in renal fibroblast NRK-49F cells. Knockdown of the SPARC gene with small interfering RNA reduced all forms (the 110-kDa latent and 87- and 65-kDa bioactive forms) of ADAMTS1 expression as well as collagen production. These results suggest that SPARC is induced by the renin-angiotensin system and may be a fibrogenic factor, at least in part, by producing ADAMTS1 in hypertensive renal disease.

Association with Corneal Remodeling Related Genes, ALDH3A1, LOX, and SPARC Genes Variations in Korean Keratoconus Patients

Purpose

To determine whether the cornea remodeling-related genes aldehyde dehydrogenase 3A1 (ALDH3A1), lysyl oxidase (LOX), and secreted protein acidic and rich in cysteine (SPARC) were potential susceptibility candidate genes for keratoconus in Korean patients, we investigated the associations of single nucleotide polymorphisms (SNPs) in these three genes in Korean patients with keratoconus.

Methods

Genomic DNA was extracted from blood samples of unrelated patients with keratoconus and healthy control individuals. For screening of genetic variations, all exons from the entire coding regions of the ALDH3A1, LOX, and SPARC genes were directly sequenced to determine the presence of mutations. Control individuals were selected from the general population without keratoconus.

Results

In this study, we detected nine SNPs in ALDH3A1, four SNPs in LOX, and 18 SNPs in SPARC. rs116992290, IVS3-62c>t, rs116962241, and rs2228100 in ALDH3A1 and rs2956540 and rs1800449 in LOX were significantly different between patient and control groups. In the SPARC gene, the distribution of the *G allele of EX10+225 T>G (p = 0.018; odds ratio, 1.869) was strongly associated with the risk of keratoconus in the Korean population. In haplotype analysis, C-G of rs2956540-rs2288393 in LOX (p = 0.046) and C-C-G and G-G-G of rs60610024-rs2228100-rs57555435 (p = 0.021 and p < 0.001), G-A of IVS3-62 a>g - rs116962241 in ALDH3A1 (p = 0.048) predisposed significantly to keratoconus. After cross-validation consistency and permutation tests, two locus model was the best SNP variations interaction pattern.

Conclusions

Our results suggested that genetic variations in ALDH3A1, LOX, and SPARC genes were associated with a predisposition for keratoconus in Korean individuals. Moreover, variations in ALDH3A1and LOX may serve as strong biomarkers for keratoconus.

Exercise Training of Secreted Protein Acidic and Rich in Cysteine (Sparc) KO Mice Suggests That Exercise-Induced Muscle Phenotype Changes Are SPARC-Dependent

We previously identified secreted protein acidic and rich in cysteine (Sparc) as an exercise-induced gene in young and elderly individuals. Via this animal experiment, we aim to identify selected implications of SPARC mainly within the muscle in the contexts of exercise. Mice were divided into eight groups based on three variables (age, genotype and exercise): Old (O) or young (Y) × Sparc knock-out (KO) or wild-type (WT) × sedentary (Sed) or exercise (Ex). The exercised groups were trained for 12 weeks at the lactate threshold (LT) speed (including 4 weeks of adaptation period) and all mice were sacrificed afterwards. Body and selected tissues were weighed, and lactate levels in different conditions measured. Expression of skeletal muscle (SM) collagen type I alpha 1 chain (COL1A1) and mitochondrially encoded cytochrome c oxidase I (MT-CO1) in addition to SM strength (grip power) were also measured. Ageing increased the body and white adipose tissue (WAT) weights but decreased SM weight percentage (to body weight) and MT-CO1 expression (in WT). Exercise increased SM COL1A1 in WT mice and MT-CO1 expression, as well as weight percentage of the tibialis anterior muscle, and decreased WAT weight (trend). Compared to WT mice, Sparc KO mice had lower body, muscle and WAT weights, with a decrease in SM MT-CO1 and COL1A1 expression with no genotype effect on lactate levels in all our blood lactate measures. Sparc KO effects on body composition, adiposity and metabolic patterns are toward a reduced WAT and body weight, but with a negative metabolic and functional phenotype of SM. Whereas such negative effects on SM are worsened with ageing, they are relatively improved by exercise. Importantly, our data suggest that the exercise-induced changes in the SM phenotype, in terms of increased performance (metabolic, strength and development), including lactate-induced changes, are SPARC-dependent.

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.

Secreted protein acidic and rich in cysteine and bioenergetics: Extracellular matrix, adipocytes remodeling and skeletal muscle metabolism

The extracellular matrix (ECM) remodeling plays important roles in both adipocytes shape/expansion remodeling and the skeletal muscle (SM) metabolism. Secreted protein acidic and rich in cysteine (SPARC) is expressed in divers tissues including adipose tissue (AT) and SM where it impacts a variety of remodeling as well as metabolic functions. SPARC, also known as osteonectin or BM-40, is a glycoprotein associated with the ECM. Numerous researches attempted to elucidate the implications of SPARC in these two key metabolic tissues under different conditions. Whereas SPARC deficiency tends to shape the remodeling of the adipocytes and the fat distribution, this deficiency decreases SM metabolic properties. On the other hand, SPARC seems to be an enhancer of the metabolism and a mediator of the exercise-induced adaptation in the SM and as well as an adipogenesis inhibitor. Some findings about the SPARC effects on AT and SM seem "contradictory" in terms of tissue development and energy profile therefore highlighting the mechanistic role of SPARC in both is a priority. Yet, within this review, we expose selected researches and compare the results. We conclude with explanations to "reconcile" the different observations, hypothesize the feedback and regulatory character of SPARC and put its roles within the energetic and structural maps of both adipocytes and myocytes in homeostasis and in situations such as obesity or exercise. These properties explain the modifications and the remodeling seen in AT and SM undergoing adaptive changes (obesity, exercise, etc.) and represent a starting point for precise therapeutic targeting of SPARC-related pathways is conditions such as obesity, sarcopenia and diabetes.

Pre-eclampsia onset and SPARC: A possible involvement in placenta development

Pre-eclampsia (PE) is a multisystem disorder commonly diagnosed in the latter half of pregnancy and it is a leading cause of intrauterine fetal growth retardation (IUGR). The aim of this study was to investigate the localization and the role of SPARC, secreted protein acidic, and rich in cysteine, in PE and PE-IUGR placentas in comparison with normal placentas. SPARC was mainly expressed in the villous and extravillous cytotrophoblastic cells in first trimester, whereas in PE, PE-IUGR and at term placentas, SPARC immunostaining was visible in both cytotrophoblastic cells and syncytiotrophoblast. SPARC expression significantly decreased in normal placenta from first to third trimester and a further significant reduction was demonstrated in PE and PE-IUGR. The latter downregulation of SPARC depends on hypoxic condition as shown by in vitro models. In conclusion, SPARC can play a pivotal role in PE and PE-IUGR onset and it should be considered as a key molecule for future investigations in such pathologies.

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.

Secreted protein acidic and rich in cysteine functions in colitis via IL17A regulation in mucosal CD4+ T cells

BACKGROUND AND AIM

Secreted protein acidic and rich in cysteine (SPARC) is a matricellular glycol that regulates cell proliferation, tissue repair, and tumorigenesis. Despite evidence linking SPARC to inflammation, the mechanisms are unclear. Accordingly, the role of SPARC in intestinal inflammation was investigated.

METHODS

Colitis was induced in wild-type (WT) and SPARC knockout (KO) mice using trinitrobenzene sulfonic acid (TNBS). Colons were assessed for damage; leukocyte infiltration; Tnf, Ifng, Il17a, and Il10 mRNA expression; and histology. Cytokine profiling of colonic lamina propria mononuclear cells (LPMCs) was performed by flow cytometry. Naïve CD4⁺ T cells were isolated from WT and SPARC KO mouse spleens, and the effect of SPARC on Th17 cell differentiation was examined. Recombination activating gene 1 knockout (RAG1 KO) mice reconstituted with T cells from either WT or SPARC KO mice were investigated.

RESULTS

Trinitrobenzene sulfonic acid exposure significantly reduced bodyweight and increased mucosal inflammation, leukocyte infiltration, and Il17a mRNA expression in WT relative to SPARC KO mice. The percentage of IL17A-producing CD4⁺ T cells among LPMCs from KO mice was lower than that in WT mice when both groups were exposed to TNBS. Th17 cell differentiation was suppressed in cells from SPARC KO mice. In the T cell transfer colitis model, RAG1 KO mice receiving T cells from WT mice were more severely affected than those reconstituted with cells from SPARC KO mice.

CONCLUSIONS

Secreted protein acidic and rich in cysteine accelerates colonic mucosal inflammation via modulation of IL17A-producing CD4⁺ T cells. SPARC is a potential therapeutic target for conditions involving intestinal inflammation.

Extracellular matrix contribution to skin wound re-epithelialization

The ability of skin to act as a barrier is primarily determined by cells that maintain the continuity and integrity of skin and restore it after injury. Cutaneous wound healing in adult mammals is a complex multi-step process that involves overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodeling. Under favorable conditions, epidermal regeneration begins within hours after injury and takes several days until the epithelial surface is intact due to reorganization of the basement membrane. Regeneration relies on numerous signaling cues and on multiple cellular processes that take place both within the epidermis and in other participating tissues. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here we focus on the involvement of the extracellular matrix proteins that impact epidermal regeneration during wound healing.

Transcriptomic responses to wounding: meta-analysis of gene expression microarray data

BACKGROUND

A vast amount of microarray data on transcriptomic response to injury has been collected so far. We designed the analysis in order to identify the genes displaying significant changes in expression after wounding in different organisms and tissues. This meta-analysis is the first study to compare gene expression profiles in response to wounding in as different tissues as heart, liver, skin, bones, and spinal cord, and species, including rat, mouse and human.

RESULTS

We collected available microarray transcriptomic profiles obtained from different tissue injury experiments and selected the genes showing a minimum twofold change in expression in response to wounding in prevailing number of experiments for each of five wound healing stages we distinguished: haemostasis & early inflammation, inflammation, early repair, late repair and remodelling. During the initial phases after wounding, haemostasis & early inflammation and inflammation, the transcriptomic responses showed little consistency between different tissues and experiments. For the later phases, wound repair and remodelling, we identified a number of genes displaying similar transcriptional responses in all examined tissues. As revealed by ontological analyses, activation of certain pathways was rather specific for selected phases of wound healing, such as e.g. responses to vitamin D pronounced during inflammation. Conversely, we observed induction of genes encoding inflammatory agents and extracellular matrix proteins in all wound healing phases. Further, we selected several genes differentially upregulated throughout different stages of wound response, including established factors of wound healing in addition to those previously unreported  in this context such as PTPRC and AQP4.

CONCLUSIONS

We found that transcriptomic responses to wounding showed similar traits in a diverse selection of tissues including skin, muscles, internal organs and nervous system. Notably, we distinguished transcriptional induction of inflammatory genes not only in the initial response to wounding, but also later, during wound repair and tissue remodelling.

Association of the anti-angiogenic factor secreted protein and rich in cysteine (SPARC) with vascular complications among Chinese type 2 diabetic patients in Singapore

AIMS

This study evaluated the association of the anti-angiogenic SPARC with known angiogenesis-associated factors and diabetes-related micro- and macro-vascular complications in a Singapore Chinese cohort with type 2 diabetes (T2DM).

METHODS

Plasma SPARC was measured by immunoassay in 438 T2DM adults (mean age:58±11years).

RESULTS

Higher SPARC levels in subjects stratified by SPARC tertiles displayed decreased pro-angiogenic adiponectin, osteopontin, vascular cell adhesion molecule (VCAM)-1 and matrix metalloproteinase (MMP)-2 concentrations (all p<0.05). The anti-angiogenic pigment epithelium-derived factor (PEDF) level was not statistically different among the SPARC tertiles. Age-adjusted partial correlation revealed significant associations of SPARC with adiponectin, osteopontin, VCAM-1, MMP-2, and PEDF (all p<0.05). Lower SPARC was accompanied by less favorable estimated glomerular filtration rate (eGFR) and carotid-femoral pulse wave velocity (PWV) readings (all p<0.05). Conversely, ankle-brachial index (ABI) reduced with increasing SPARC (p=0.048). The eGFR (B=0.834, p=0.019), PWV (B=-7.925, p=0.009), and ABI (B=-142.160, p=0.010) remained as determinants of SPARC after confounder adjustment. Moreover, individuals in the lowest SPARC tertile had increased odds of aortic stiffness (OR=1.900, 95% CI=1.103-3.274) but reduced odds of peripheral arterial disease (OR=0.400, 95% CI=0.175-0.919). However, SPARC was not independently associated with chronic kidney disease.

CONCLUSIONS

The anti-angiogenic SPARC may be associated with the pathophysiology of diabetes-related macrovascular complications.

Formation of the inner ear during embryonic and larval development of the cichlid fish (Oreochromis mossambicus)

BACKGROUND

The vertebrate inner ear comprises mineralized elements, namely the otoliths (fishes) or the otoconia (mammals). These elements serve vestibular and auditory functions. The formation of otoconia and otoliths is described as a stepwise process, and in fish, it is generally divided into an aggregation of the otolith primordia from precursor particles and then a growth process that continues throughout life.

RESULTS

This study was undertaken to investigate the complex transition between these two steps. Therefore, we investigated the developmental profiles of several inner ear structural and calcium-binding proteins during the complete embryonic and larval development of the cichlid fish Oreochromis mossambicus in parallel with the morphology of inner ear and especially otoliths. We show that the formation of otoliths is a highly regulated temporal and spatial process which takes place throughout embryonic and larval development.

CONCLUSIONS

Based on our data we defined eight phases of otolith differentiation from the primordia to the mature otolith.

Functional Analysis of the Matricellular Protein SPARC with Novel Monoclonal Antibodies

SPARC (osteonectin, BM-40) is a matricellular glycoprotein that is expressed in many embryogenic and adult tissues undergoing remodeling or repair. SPARC modulates cellular interaction with the extracellular matrix (ECM), inhibits cell adhesion and proliferation, and regulates growth factor activity. To explore further the function and activity of this protein in tissue homeostasis, we have developed several monoclonal antibodies (MAbs) that recognize distinct epitopes on SPARC. The MAbs bind to SPARC with high affinity and identify SPARC by ELISA, Western blotting, immunoprecipitation, immunocytochemistry, and/or immunohistochemistry. The MAbs were also characterized in functional assays for potential alteration of SPARC activity. SPARC binds to collagen I and laminin-1 through an epitope defined by MAb 293; this epitope is not involved in the binding of SPARC to collagen III. The other MAbs did not interfere with the binding of SPARC to collagen I or III or laminin-1. Inhibition of the anti-adhesive effect of SPARC on endothelial cells by MAb 236 was also observed. Functional analysis of SPARC in the presence of these novel MAbs now confirms that the activities ascribed to this matricellular protein can be assigned to discrete subdomains.

Increased ADAMTS1 mediates SPARC-dependent collagen deposition in the aging myocardium

Secreted protein acidic and rich in cysteine (SPARC) is a collagen-binding matricellular protein highly expressed during fibrosis. Fibrosis is a prominent component of cardiac aging that reduces myocardial elasticity. Previously, we reported that SPARC deletion attenuated myocardial stiffness and collagen deposition in aged mice. To investigate the mechanisms by which SPARC promotes age-related cardiac fibrosis, we evaluated six groups of mice (n = 5-6/group): young (3-5 mo old), middle-aged (10-12 mo old), and old (18-29 mo old) C57BL/6 wild type (WT) and SPARC-null (Null) mice. Collagen content, determined by picrosirius red staining, increased in an age-dependent manner in WT but not in Null mice. A disintegrin and metalloproteinase with thrombospondin-like motifs 1 (ADAMTS1) increased in middle-aged and old WT compared with young, whereas in Null mice only old animals showed increased ADAMTS1 expression. Versican, a substrate of ADAMTS1, decreased with age only in WT. To assess the mechanisms of SPARC-induced collagen deposition, we stimulated cardiac fibroblasts with SPARC. SPARC treatment increased secretion of collagen I and ADAMTS1 (both the 110-kDa latent and 87-kDa active forms) into the conditioned media as well as the cellular expression of transforming growth factor-β1-induced protein (Tgfbi) and phosphorylated Smad2. An ADAMTS1 blocking antibody suppressed the SPARC-induced collagen I secretion, indicating that SPARC promoted collagen production directly through ADAMTS1 interaction. In conclusion, ADAMTS1 is an important mediator of SPARC-regulated cardiac aging.

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.

Detection of Connexion 26 GENE (GJB2) Mutations in Cases of Congenital Non Syndromic Deafness

Hearing loss is most common form of genetic hearing disorder. Non-syndromic sensory neural autosomal recessive deafness (NSRD) is the most common form of genetic hearing loss. Mutations in GJB2 gene, which encodes the connexin 26 protein, are major cause of NSRD. The aim of this study is directed towards the mutations caused along the connexin 26 gene using blood samples from nonsyndromic deaf children. The study was conducted on 36 congenitally hearing impaired children who visited to our department with complains of hearing loss and reduced speech and whose age was <10 years with no other congenital anomaly. After a thorough history, clinical examination and all audiological and radiological assessment, blood samples are collected and DNA extraction, PCR and sequencing were done for further genetic analysis. Annotated and documented autosomal recessive (pathogenic) mutations were observed in 57 % of NSRD cases. The frequency of pathogenic mutation was commonest for Ins G between nucleotide 30-35 (40 % of cases) followed by Del T at nucleotide 59(20 % of cases).These two common mutations (singly or doubly) were present in 51.4 % of cases. Present study helps to screen the families with hearing impaired children, which will facilitate the development of strategies for diagnosis and treatment of these common genetic disorders.

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.

Lumican deficiency results in cardiomyocyte hypertrophy with altered collagen assembly

The ability of the heart to adapt to increased stress is dependent on the modification of its extracellular matrix (ECM) architecture that is established during postnatal development as cardiomyocytes differentiate, a process that is poorly understood. We hypothesized that the small leucine-rich proteoglycan (SLRP) lumican (LUM), which binds collagen and facilitates collagen assembly in other tissues, may play a critical role in establishing the postnatal murine myocardial ECM. Although previous studies suggest that LUM deficient mice (lum(-/-)) exhibit skin anomalies consistent with Ehlers-Danlos syndrome, lum(-/-) hearts have not been evaluated. These studies show that LUM was immunolocalized to non-cardiomyocytes of the cardiac ventricles and its expression increased throughout development. Lumican deficiency resulted in significant (50%) perinatal death and further examination of the lum(-/-) neonatal hearts revealed an increase in myocardial tissue without a significant increase in cell proliferation. However cardiomyocytes from surviving postnatal day 0 (P0), 1 month (1 mo) and adult (4 mo) lum(-/-) hearts were significantly larger than their wild type (WT) littermates. Immunohistochemistry revealed that the increased cardiomyocyte size in the lum(-/-) hearts correlated with alteration of the cardiomyocyte pericellular ECM components collagenα1(I) and the class I SLRP decorin (DCN). Western blot analysis demonstrated that the ratio of glycosaminoglycan (GAG) decorated DCN to core DCN was reduced in P0 and 1 mo lum(-/-) hearts. There was also a reduction in the β and γ forms of collagenα1(I) in lum(-/-) hearts. While the total insoluble collagen content was significantly reduced, the fibril size was increased in lum(-/-) hearts, indicating that LUM may play a role in collagen fiber stability and lateral fibril assembly. These results suggest that LUM controls cardiomyocyte growth by regulating the pericellular ECM and also indicates that LUM may coordinate multiple factors of collagen assembly in the murine heart. Further investigation into the role of LUM may yield novel therapeutic targets and/or biomarkers for patients with cardiovascular disease.

The Function of Matricellular Proteins in the Lamina Cribrosa and Trabecular Meshwork in Glaucoma

PURPOSE

To review the current literature regarding the role of matricellular proteins in glaucoma, specifically in the lamina cribrosa (LC) region of the optic nerve head (ONH) and the trabecular meshwork (TM).

METHODS

A literature search was performed for published articles describing the expression and function of matricellular proteins such as thrombospondin (TSP), connective tissue growth factor (CTGF), secreted protein acidic and rich in cysteine (SPARC), and periostin in glaucoma.

RESULTS

In glaucoma, there are characteristic extracellular matrix (ECM) changes associated with optic disc cupping in the ONH and subsequent visual field defects. Matricellular proteins are a family of nonstructural secreted glycoproteins, which enable cells to communicate with their surrounding ECM, including CTGF, also known as CCN2, TSPs, SPARC, periostin, osteonectin, and tenascin-C and -X, and other ECM proteins. Such proteins appear to play a role in fibrosis and increased ECM deposition. Importantly, most are widely expressed in tissues particularly in the TM and ONH, and deficiency of TSP1 and SPARC has been shown to lower intraocular pressure in mouse models of glaucoma through enhanced outflow facility.

CONCLUSION

This article highlights the role of matricellular proteins in glaucoma pathology. The potential role of these proteins in glaucoma is emerging as some have an association with the pathophysiology of the TM and LC region and might therefore be potential targets for therapeutic intervention in glaucoma.

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.

Loss of SPARC protects hematopoietic stem cells from chemotherapy toxicity by accelerating their return to quiescence

Around birth, hematopoietic stem cells (HSCs) expanding in the fetal liver migrate to the developing bone marrow (BM) to mature and expand. To identify the molecular processes associated with HSCs located in the 2 different microenvironments, we compared the expression profiles of HSCs present in the liver and BM of perinatal mice. This revealed the higher expression of a cluster of extracellular matrix-related genes in BM HSCs, with secreted protein acidic and rich in cysteine (SPARC) being one of the most significant ones. This extracellular matrix protein has been described to be involved in tissue development, repair, and remodeling, as well as metastasis formation. Here we demonstrate that SPARC-deficient mice display higher resistance to serial treatment with the chemotherapeutic agent 5-fluorouracil (5-FU). Using straight and reverse chimeras, we further show that this protective effect is not due to a role of SPARC in HSCs, but rather is due to its function in the BM niche. Although the kinetics of recovery of the hematopoietic system is normal, HSCs in a SPARC-deficient niche show an accelerated return to quiescence, protecting them from the lethal effects of serial 5-FU treatment. This may become clinically relevant, as SPARC inhibition and its protective effect on HSCs could be used to optimize chemotherapy schemes.

The role of matricellular proteins in glaucoma

Glaucoma is an optic neuropathy affecting approximately 60million people worldwide and is the second most common cause of irreversible blindness. Elevated intraocular pressure (IOP) is the main risk factor for developing glaucoma and is caused by impaired aqueous humor drainage through the trabecular meshwork (TM) and Schlemm's canal (SC). In primary open angle glaucoma (POAG), this elevation in IOP in turn leads to deformation at the optic nerve head (ONH) specifically at the lamina cribrosa (LC) region where there is also a deposition of extracellular matrix (ECM) molecules such as collagen and fibronectin. Matricellular proteins are non-structural secreted glycoproteins that help cells communicate with their surrounding ECM. This family of proteins includes connective tissue growth factor (CTGF), also known as CCN2, thrombospondins (TSPs), secreted protein acidic and rich in cysteine (SPARC), periostin, osteonectin, and Tenascin-C and -X and other ECM proteins. All members appear to play a role in fibrosis and increased ECM deposition. Most are widely expressed in tissues particularly in the TM and ONH and deficiency of TSP1 and SPARC have been shown to lower IOP in mouse models of glaucoma through enhanced outflow facility. The role of these proteins in glaucoma is emerging as some have an association with the pathophysiology of the TM and LC regions and might therefore be potential targets for therapeutic intervention in glaucoma.

The wound healing, chronic fibrosis, and cancer progression triad

For decades tumors have been recognized as "wounds that do not heal." Besides the commonalities that tumors and wounded tissues share, the process of wound healing also portrays similar characteristics with chronic fibrosis. In this review, we suggest a tight interrelationship, which is governed as a concurrence of cellular and microenvironmental reactivity among wound healing, chronic fibrosis, and cancer development/progression (i.e., the WHFC triad). It is clear that the same cell types, as well as soluble and matrix elements that drive wound healing (including regeneration) via distinct signaling pathways, also fuel chronic fibrosis and tumor progression. Hence, here we review the relationship between fibrosis and cancer through the lens of wound healing.

Molecular mechanisms underlying the divergent roles of SPARC in human carcinogenesis

Communication between the cell and its surrounding environment, consisting of proteinaceous (non-living material) and extracellular matrix (ECM), is important for biophysiological and chemical signaling. This signaling results in a range of cellular activities, including cell division, adhesion, differentiation, invasion, migration and angiogenesis. The ECM non-structural secretory glycoprotein called secreted protein, acidic and rich in cysteine (SPARC), plays a significant role in altering cancer cell activity and the tumor's microenvironment (TME). However, the role of SPARC in cancer research has been the subject of controversy. This review mainly focuses on recent advances in understanding the contradictory nature of SPARC in relation to ECM assembly, cancer cell proliferation, adhesion, migration, apoptosis and tumor growth.

Associations among SPARC mRNA expression in adipose tissue, serum SPARC concentration and metabolic parameters in Korean women

OBJECTIVE

Secreted protein acidic and rich in cysteine (SPARC) is expressed in most tissues and is also secreted by adipocytes. The associations of SPARC mRNA expression in visceral adipose tissue (VAT), subcutaneous abdominal adipose tissue (SAT), serum SPARC concentration, and metabolic parameters in Korean women are investigated.

DESIGN AND METHODS

This is a cross-sectional study. Fifty-eight women were recruited, of whom 15 women who underwent bariatric surgery for morbid obesity (BMI mean ± SD: 40.2±5.7 kg/m(2) ), 16 who underwent metabolic surgery for type 2 diabetes (BMI: 28.9±4.5 kg/m(2) ), and, as a control group, 27 who underwent gynecological surgery (BMI: 22.7±2.4 kg/m(2) ). Anthropometric variables, metabolic parameters, SPARC mRNA expression in adipose tissue, and serum SPARC concentration were measured.

RESULTS

In all subjects, SPARC mRNA expression was significantly higher in SAT than in VAT. Serum SPARC concentrations (mean ± SE) in morbidly obese subjects, subjects with type 2 diabetes, and normal weight subjects were 267.3±40.2 ng/mL, 130.4±33.0 ng/mL, and 53.1±2.8 ng/mL, respectively. SPARC mRNA in SAT was significantly correlated with BMI, whereas SPARC mRNA in VAT was significantly correlated with BMI and VAT area. Serum SPARC concentration was significantly correlated with BMI, waist circumference, total adipose tissue area, and SAT area. After BMI adjustment, serum SPARC concentration was significantly correlated with fasting insulin concentration and HOMA-IR score. Multivariate regression analysis showed that BMI and HOMA-IR were independently associated with serum SPARC concentration.

CONCLUSIONS

Serum SPARC concentration is significantly correlated with obesity indices and might be influenced by insulin resistance. These findings suggest that SPARC may contribute to the metabolic dysregulation associated with obesity in humans.

Secreted protein acidic and rich in cysteine (SPARC) exacerbates colonic inflammatory symptoms in dextran sodium sulphate-induced murine colitis

BACKGROUND

Secreted Protein Acidic and Rich in Cysteine (SPARC) is expressed during tissue repair and regulates cellular proliferation, migration and cytokine expression. The aim was to determine if SPARC modifies intestinal inflammation.

METHODS

Wild-type (WT) and SPARC-null (KO) mice received 3% dextran sodium sulphate (DSS) for 7 days. Inflammation was assessed endoscopically, clinically and histologically. IL-1β, IL-4, IL-5, IL-6, IL-10, IL-13, IL-17A, IL-12/IL23p40, TNF-α, IFN-γ, RANTES, MCP-1, MIP-1α, MIP-1β, MIG and TGF-β1 levels were measured by ELISA and cytometric bead array. Inflammatory cells were characterised by CD68, Ly6G, F4/80 and CD11b immunofluorescence staining and regulatory T cells from spleen and mesenteric lymph nodes were assessed by flow cytometry.

RESULTS

KO mice had less weight loss and diarrhoea with less endoscopic and histological inflammation than WT animals. By day 35, all (n = 13) KO animals completely resolved the inflammation compared to 7 of 14 WT mice (p<0.01). Compared to WTs, KO animals at day 7 had less IL1β (p= 0.025) and MIG (p = 0.031) with higher TGFβ1 (p = 0.017) expression and a greater percentage of FoxP3+ regulatory T cells in the spleen and draining lymph nodes of KO animals (p<0.01). KO mice also had fewer CD68+ and F4/80+ macrophages, Ly6G+ neutrophils and CD11b+ cells infiltrating the inflamed colon.

CONCLUSIONS

Compared to WT, SPARC KO mice had less inflammation with fewer inflammatory cells and more regulatory T cells. Together, with increased TGF-β1 levels, this could aid in the more rapid resolution of inflammation and restoration of the intestinal mucosa suggesting that the presence of SPARC increases intestinal inflammation.

Human hair follicle dermal sheath and papilla cells support keratinocyte growth in monolayer coculture

Traditional skin grafting techniques are effective but limited methods of skin replacement. Autologous transplantation of rapidly cultured keratinocytes is successful for epidermal regeneration, but the current gold-standard technique requires mouse fibroblast feeders and serum-rich media, with serum-free systems and dermal fibroblast (DF) feeders performing relatively poorly. Here, we investigated the capacity of human hair follicle dermal cells to act as alternative supports for keratinocyte growth. Dermal papilla (DP) dermal sheath (DS), DF and 3T3 cells were used as inactivated feeder cells for human keratinocyte coculture. Under conditions favouring dermal cells, proliferation of keratinocytes in the presence of either DS or DP cells was significantly enhanced compared with DF cells, at levels comparable to keratinocytes cultured under gold-standard conditions. Secreted protein acidic and rich in cysteine (SPARC) expression increased DS and DP cells relative to DFs; however, further experiments did not demonstrate a role in keratinocyte support.

Exogenous SPARC suppresses proliferation and migration of prostate cancer by interacting with integrin β1

BACKGROUND

The matricellular protein secreted protein acidic and rich in cysteine (SPARC) plays an important role on tumor metastasis and progression in several cancers. However, the roles of SPARC in prostate cancer (PCa) remain unclear.

METHODS

To identify SPARC protein in prostate tissue, immunohistochemical analysis of SPARC was conducted using human prostate tissue microarray. To detect SPARC expression in prostate cancer (LNCaP, DU145, and PC-3) and stromal cells, RT-PCR, western blot analysis, and ELISA was conducted. To reveal the function of exogenous SPARC in PCa cells, AKT phosphorylation was confirmed by western blot analysis after coculture with stromal cells. Proliferation and migration of PCa cells were examined by addition of SPARC. The interaction between SPARC and integrin β1 was confirmed by western blot analysis after immunoprecipitation.

RESULTS

SPARC protein was expressed well in normal tissue compared with PCa tissue. ELISA showed high secreted SPARC protein in normal prostate-derived stromal cell (PrSC) compared with PCa-derived stromal cell (PCaSC) and PCa. PCa cells cocultured with PrSC showed reduced AKT phosphorylation more than with PCaSC. PCa cells cocultured with PrSC whose SPARC was knocked-down restored AKT phosphorylation. Moreover, PCa cells treated with SPARC led to reduced AKT phosphorylation. Immunoprecipitation with SPARC revealed interaction of SPARC and integrin β1 in PCa cells. Inhibited proliferation and migration of PCa cells by SPARC was restored by integrin β1 neutralizing antibody.

CONCLUSIONS

Reduced SPARC secretion from stromal cells might affect PCa progression mediating through limiting AKT phosphorylation after interaction with integrin β1.

Secreted protein acidic and rich in cysteine (SPARC)-null mice exhibit more uniform outflow

PURPOSE

Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein known to regulate extracellular matrix (ECM) in many tissues and is highly expressed in trabecular meshwork (TM). SPARC-null mice have a 15% to 20% decrease in intraocular pressure (IOP) compared to wild-type (WT) mice. We hypothesized that mouse aqueous outflow is segmental, and that transgenic deletion of SPARC causes a more uniform pattern that correlates with IOP and TM morphology.

METHODS

Eyes of C57BL6-SV129 WT and SPARC-null mice were injected with fluorescent microbeads, which were also passively exposed to freshly enucleated eyes. Confocal and electron microscopy were performed. Percentage effective filtration length (PEFL) was calculated as PEFL = FL/TL × 100%, where TL = total length and FL = filtration length. IOP was measured by rebound tonometry.

RESULTS

Passive microbead affinity for WT and SPARC-null ECM did not differ. Segmental flow was observed in the mouse eye. SPARC-null mice had a 23% decrease in IOP. PEFL increased in SPARC-null (70.61 ± 11.36%) versus WT mice (54.68 ± 9.95%, P < 0.005; n = 11 pairs), and PEFL and IOP were negatively correlated (R(2) = 0.72, n = 10 pairs). Morphologically, TM of high-tracer regions had increased separation between beams compared to low-tracer regions. Collagen fibril diameter decreased in SPARC-null (28.272 nm) versus WT tissue (34.961 nm, P < 0.0005; n = 3 pairs).

CONCLUSIONS

Aqueous outflow in mice is segmental. SPARC-null mice demonstrated a more uniform outflow pattern and decreased collagen fibril diameter. Areas of high flow had less compact juxtacanalicular connective tissue ECM, and IOP was inversely correlated with PEFL. Our data show a correlation between morphology, aqueous outflow, and IOP, indicating a modulatory role of SPARC in IOP regulation.

SPARC regulates microgliosis and functional recovery following cortical ischemia

Secreted protein acidic rich in cysteine (SPARC) is a matricellular protein that modulates the activity of growth factors, cytokines, and extracellular matrix to play multiple roles in tissue development and repair, such as cellular adhesion, migration, and proliferation. Throughout the CNS, SPARC is highly localized in mature ramified microglia, but its role in microglia--in development or during response to disease or injury--is not understood. In the postnatal brain, immature amoeboid myeloid precursors only induce SPARC expression after they cease proliferation and migration, and transform into mature, ramified resting microglia. SPARC null/CX3CR1-GFP reporter mice reveal that SPARC regulates the distribution and branching of mature microglia, with significant differences between cortical gray and white matter in both controls and SPARC nulls. Following ischemic and excitotoxic lesion, reactive, hypertrophic microglia rapidly downregulate and release SPARC at the lesion, concomitant with reactive, hypertrophic perilesion astrocytes upregulating SPARC. After photothrombotic stroke in the forelimb sensorimotor cortex, SPARC nulls demonstrate enhanced microgliosis in and around the lesion site, which accompanies significantly enhanced functional recovery by 32 d after lesion. Microglia from SPARC nulls also intrinsically proliferate at a greater rate in vitro--an enhanced effect that can be rescued by the addition of exogenous SPARC. SPARC is thus a novel regulator of microglial proliferation and structure, and, in addition to regulating glioma progression, may play an important role in differently regulating the gray and white matter microglial responses to CNS lesion--and modulating behavioral recovery--after injury.

Loss of SPARC in bladder cancer enhances carcinogenesis and progression

Secreted protein acidic and rich in cysteine (SPARC) has been implicated in multiple aspects of human cancer. However, its role in bladder carcinogenesis and metastasis are unclear,with some studies suggesting it may be a promoter and others arguing the opposite. Using a chemical carcinogenesis model in Sparc-deficient mice and their wild-type littermates, we found that loss of SPARC accelerated the development of urothelial preneoplasia (atypia and dysplasia), neoplasia, and metastasis and was associated with decreased survival. SPARC reduced carcinogen-induced inflammation and accumulation of reactive oxygen species as well as urothelial cell proliferation. Loss of SPARC was associated with an inflammatory phenotype of tumor-associated macrophages and fibroblasts, with concomitant increased activation of urothelial and stromal NF-κB and AP1 in vivo and in vitro. Syngeneic spontaneous and experimental metastasis models revealed that tumor- and stroma-derived SPARC reduced tumor growth and metastasis through inhibition of cancer-associated inflammation and lung colonization. In human bladder tumor tissues, the frequency and intensity of SPARC expression were inversely correlated with disease-specific survival. These results indicate that SPARC is produced by benign and malignant compartments of bladder carcinomas where it functions to suppress bladder carcinogenesis, progression, and metastasis.

A role for estrogen receptor-α and estrogen receptor-β in collagen biosynthesis in mouse skin

Hormonal regulation of the dermal collagenous extracellular matrix plays a key role in maintaining proper tissue homeostasis, however the factors and pathways involved in this process are not fully defined. This study investigated the role of estrogen receptors (ERs) in the regulation of collagen biosynthesis in mice lacking ERα or ERβ. Collagen content was significantly increased in the skin of ΕRα^-/- mice as measured by acetic acid extraction and the hydroxyproline assay and correlated with the decreased levels of MMP-15 and elevated collagen production by ΕRα^-/- fibroblasts. In contrast, collagen content was decreased in the skin of ERβ^-/- mice despite markedly increased collagen production by ERβ^-/- fibroblasts. However, expression of several matrix metalloproteinases (MMPs), including MMP-8 and -15 was significantly elevated suggesting increased degradation of dermal collagen. Furthermore, ERβ^-/- mice were characterized by significantly reduced levels of small leucine proteoglycans (SLRPs), lumican and decorin, leading to the defects in collagen fibrillogenesis and possibly less stable collagen fibrils. ERα^-/- mice also exhibited fibrils with irregular structure and size, which correlated with increased levels of lumican and decorin. Together, these results demonstrate distinct functions of estrogen receptors in the regulation of collagen biosynthesis in mouse skin in vivo.

Matricellular proteins in cardiac adaptation and disease

The term matricellular proteins describes a family of structurally unrelated extracellular macromolecules that, unlike structural matrix proteins, do not play a primary role in tissue architecture, but are induced following injury and modulate cell-cell and cell-matrix interactions. When released to the matrix, matricellular proteins associate with growth factors, cytokines, and other bioactive effectors and bind to cell surface receptors transducing signaling cascades. Matricellular proteins are upregulated in the injured and remodeling heart and play an important role in regulation of inflammatory, reparative, fibrotic and angiogenic pathways. Thrombospondin (TSP)-1, -2, and -4 as well as tenascin-C and -X secreted protein acidic and rich in cysteine (SPARC), osteopontin, periostin, and members of the CCN family (including CCN1 and CCN2/connective tissue growth factor) are involved in a variety of cardiac pathophysiological conditions, including myocardial infarction, cardiac hypertrophy and fibrosis, aging-associated myocardial remodeling, myocarditis, diabetic cardiomyopathy, and valvular disease. This review discusses the properties and characteristics of the matricellular proteins and presents our current knowledge on their role in cardiac adaptation and disease. Understanding the role of matricellular proteins in myocardial pathophysiology and identification of the functional domains responsible for their actions may lead to design of peptides with therapeutic potential for patients with heart disease.

Elevated plasma levels of SPARC in patients with newly diagnosed type 2 diabetes mellitus

OBJECTIVE

Secreted protein acidic and rich in cysteine (SPARC) also known as BM-40 which has been studied in various pathological conditions, has recently been suggested as a key player in the pathology of obesity and type 2 diabetes mellitus (T2DM). However, there are few studies on putative pathophysiologic roles of SPARC in glucose metabolism. The aim of this study was to determine whether plasma SPARC concentrations were altered in subjects with different glucose metabolic conditions and to investigate the affecting factors.

DESIGN AND METHODS

In this study, 54 newly diagnosed T2DM subjects, 53 subjects with impaired glucose regulation (IGR), and 53 normal subjects (body mass index (BMI): 24.98 ± 3.75 vs 24.70 ± 2.78 and 24.53 ± 3.66 kg/m(2), P>0.05) were enrolled. Plasma SPARC levels were measured with an ELISA under overnight fasting conditions. The relationships between plasma SPARC and several metabolic factors, such as BMI, blood lipids, blood glucose, plasma insulin levels, and other factors were also assessed. Results SPARC levels were higher in subjects with T2DM compared with IGR and control subjects (16.74 ± 6.99 vs 14.04 ± 8.03 μg/l, P<0.05 and 16.74 ± 6.99 vs 11.72 ± 4.47 μg/l, P<0.01). However, there was no difference in plasma SPARC levels between IGR subjects and the controls. Plasma SPARC levels correlated positively with BMI, the percentage of fat, triglyceride, fasting plasma insulin, 2 h plasma insulin after a glucose load, and the homeostasis model assessment of insulin resistance in simple regression analysis.

CONCLUSION

The present work indicates a potential link between SPARC and the pathogenesis of T2DM.

Secreted protein acidic and rich in cysteine is a matrix scavenger chaperone

Secreted Protein Acidic and Rich in Cysteine (SPARC) is one of the major non-structural proteins of the extracellular matrix (ECM) in remodeling tissues. The functional significance of SPARC is emphasized by its origin in the first multicellular organisms and its high degree of evolutionary conservation. Although SPARC has been shown to act as a critical modulator of ECM remodeling with profound effects on tissue physiology and architecture, no plausible molecular mechanism of its action has been proposed. In the present study, we demonstrate that SPARC mediates the disassembly and degradation of ECM networks by functioning as a matricellular chaperone. While it has low affinity to its targets inside the cells where the Ca(2+) concentrations are low, high extracellular concentrations of Ca(2+) activate binding to multiple ECM proteins, including collagens. We demonstrated that in vitro, this leads to the inhibition of collagen I fibrillogenesis and disassembly of pre-formed collagen I fibrils by SPARC at high Ca(2+) concentrations. In cell culture, exogenous SPARC was internalized by the fibroblast cells in a time- and concentration-dependent manner. Pulse-chase assay further revealed that internalized SPARC is quickly released outside the cell, demonstrating that SPARC shuttles between the cell and ECM. Fluorescently labeled collagen I, fibronectin, vitronectin, and laminin were co-internalized with SPARC by fibroblasts, and semi-quantitative Western blot showed that SPARC mediates internalization of collagen I. Using a novel 3-dimensional model of fluorescent ECM networks pre-deposited by live fibroblasts, we demonstrated that degradation of ECM depends on the chaperone activity of SPARC. These results indicate that SPARC may represent a new class of scavenger chaperones, which mediate ECM degradation, remodeling and repair by disassembling ECM networks and shuttling ECM proteins into the cell. Further understanding of this mechanism may provide insight into the pathogenesis of matrix-associated disorders and lead to the novel treatment strategies.

SPARC mediates Src-induced disruption of actin cytoskeleton via inactivation of small GTPases Rho-Rac-Cdc42

The matricellular glycoprotein Secreted Protein Acidic and Rich in Cysteine (SPARC) plays an important role in the regulation of cell adhesion and proliferation as well as in tumorigenesis and metastasis. Earlier, we reported that, in addition to its potent anti-angiogenic functions, SPARC also induces apoptosis in medulloblastoma cells, mediated by autophagy. We therefore sought to investigate the underlying molecular mechanism through which SPARC inhibits migration and invasion of Daoy medulloblastoma cells, both in vitro and in vivo. For this study, we used SPARC-overexpressing stable Daoy medulloblastoma cells. SPARC overexpression in Daoy medulloblastoma cells inhibited migration and invasion in vitro. Additionally, SPARC overexpression significantly suppressed the activity of Rho, Rac and Cdc42, which all regulate the actin cytoskeleton. This suppression was accompanied by an increase in the phosphorylation of Src at Tyr-416, which led to a loss of actin stress fibers and focal contacts and a decrease in the phosphorylation level of cofilin. The reduced phosphorylation level of cofilin, which is indicative of receding Rho function, in turn led to inhibition of active Rho A. To confirm the role of SPARC in inhibition of migration and invasion of Daoy medulloblastoma cells, we transfected parental and SPARC-overexpressing Daoy cells with a plasmid vector carrying siRNA against SPARC. Transfection with SPARC siRNA reversed Src-mediated disruption of the cytoskeleton organization as well as dephosphorylation of cofilin and activation of Rho A. Taken together, these results establish SPARC as an effector of Src-induced cytoskeleton disruption in Daoy medulloblastoma cells, which subsequently led to decreased migration and invasion.

Differential Expression of SPARC in Intestinal-type Gastric Cancer Correlates with Tumor Progression and Nodal Spread

AIMS

Nodal spread is the single most important prognostic factor of survival in gastric cancer patients. In this study, genes that were upregulated in the lymph node metastases of gastric cancer were identified and may serve as putative novel therapeutic target.

METHODS

Complementary DNA (cDNA) microarray analysis and quantitative real-time polymerase chain reaction of primary gastric carcinomas and matched lymph node metastasis were carried out. Immunohistochemistry with anti-SPARC antibodies was performed on large tissue sections of 40 cases with primary gastric carcinoma (20 diffuse, 20 intestinal) and the corresponding lymph node metastases, as well as on tissue microarrays of 152 gastric cancer cases.

RESULTS

A cDNA microarray identified SPARC as being upregulated in primary gastric carcinoma tissue and the corresponding lymph node metastasis compared with the nonneoplastic mucosa. SPARC was expressed in fibroblasts and, occasionally, in tumor cells. However, the level of immunoreactivity was particularly strong in stromal cells surrounding the tumor. The level of expression of SPARC, determined by immunohistochemistry, correlated in intestinal-type gastric cancer with the local tumor growth, nodal spread, and tumor stage according to the International Union Against Cancer.

CONCLUSIONS

Our study provides transcriptional and translational evidence for the differential expression of SPARC in gastric cancer tissue. On the basis of our observations and those made by others, we hypothesize that SPARC is a promising novel target for the treatment of gastric cancer.