Levels Of Secreted Protein Acidic And Rich In Cysteine Research Articles

Small interfering RNA inhibition of SPARC attenuates the profibrotic effect of transforming growth factor β1 in cultured normal human fibroblasts

SPARC (secreted protein, acidic and rich in cysteine), or osteonectin, is a matricellular protein. Recently, it was observed to be overexpressed in fibroblasts obtained from the skin of patients with scleroderma, as well as in different tissues from patients with several other fibrotic disorders. Moreover, a genetic polymorphism in SPARC has been associated with susceptibility to scleroderma. Transforming growth factor beta1 (TGFbeta1) is a profibrotic cytokine that stimulates excessive collagen production in patients with scleroderma or other fibrotic diseases. The purpose of this study was to examine whether specific inhibition of SPARC can influence the expression of type I collagen and ameliorate the profibrotic activity of TGFbeta1 on normal human fibroblasts. Fibroblasts obtained from the skin of 4 healthy individuals were cultured and transfected with SPARC small interfering RNA (siRNA). TGFbeta was used as a fibrosis stimulus in cultured fibroblasts. Real-time quantitative reverse transcriptase-polymerase chain reaction and Western blotting were used to measure transcription and protein levels of SPARC and type I collagen, respectively. The fibroblasts transfected with SPARC siRNA showed decreased expression of both SPARC and type I collagen. Exogenous TGFbeta1 induced increased expression of both SPARC and type I collagen in cultured normal human fibroblasts, but this response was significantly blunted in the fibroblasts transfected with SPARC siRNA. TGFbeta1 can induce increased expression of both SPARC and type I collagen. Specific inhibition of SPARC led to decreased expression of type I collagen and attenuated the profibrotic effect of TGFbeta1 in cultured normal human fibroblasts. Use of siRNA to silence SPARC represents a potential therapeutic approach to fibrotic disorders such as scleroderma.

Development of UV-induced squamous cell carcinomas is suppressed in the absence of SPARC.

SPARC (Secreted Protein Acidic and Rich in Cysteine) is a multifunctional glycoprotein belonging to a group of matrix-associated factors that mediate cell-extracellular matrix interactions but have no structural roles. In the present study we investigated the contribution of SPARC to factors that influence the development of skin tumors in response to UV irradiation. A hairless SPARC-null mouse was developed and compared to control SKH1 hairless mice in terms of skin tumor induction and extracellular matrix changes occurring in response to UV-irradiation. Following 23 weeks of exposure to UVB totaling 14.5 J per cm(2), tumor development in the wild-type mice was severe, with an average of over 20 tumors per mouse, many of which were squamous cell carcinomas. Conversely, the SPARC-null mice were strikingly tumor-resistant, developing no squamous cell carcinomas and averaging less than one small papilloma per mouse. SPARC was undetectable immunohistochemically in skin from the non-irradiated control group yet was present in relatively high quantities in the basal and superficial areas of the tumor mass. The SPARC-null mice also exhibited a limited contact hypersensitivity response and were refractory to UV induced immune suppression. In conclusion, SPARC appears to have a crucial role in mediating tumor formation in response to UV irradiation.

Compromised Production of Extracellular Matrix in Mice Lacking Secreted Protein, Acidic and Rich in Cysteine (SPARC) Leads to a Reduced Foreign Body Reaction to Implanted Biomaterials

SPARC (secreted protein, acidic and rich in cysteine), a matricellular glycoprotein, modulates the interaction of cells with the extracellular matrix (ECM). Recently, accelerated cutaneous wound closure and altered deposition of collagen were reported in SPARC-null mice. Herein we asked whether SPARC might influence the foreign body reaction to biomaterial implants. Polydimethylsiloxane (silicone rubber) disks and cellulose Millipore filters were implanted into wild-type and SPARC-null mice. In wild-type animals, significant levels of SPARC were observed in the cells and the ECM comprising the capsules around the implants. After 4 weeks, SPARC-null mice exhibited a significant decrease in the thickness of the foreign body capsule, as compared to that observed in wild-type mice. A significant reduction in capsular vascular density was also associated with the silicone implants in the SPARC-null animals. Electron microscopy revealed that collagen fibers in the capsules produced by SPARC-null mice were smaller and more uniform in size than those in wild-type animals. Furthermore, staining with picrosirius-red showed that the collagen fibers were less mature in SPARC-null than in wild-type mice. The altered ECM resulting in decreased capsular thickness, indicative of an altered foreign body reaction in SPARC-null mice, implicates SPARC as an important modulator of the encapsulation of implanted biomaterials.

ANALYSIS OF THE GENE EXPRESSION OF SPARC AND ITS PROGNOSTIC VALUE FOR BLADDER CANCER

We analyzed the gene expression of the glycoprotein termed secreted protein, acidic and rich in cysteine (SPARC), also called osteonectin and BM40, in bladder cancer and its relationship with conventional clinical-histopathological manifestations, evaluated its prognostic value for patient outcome and determined the possible mechanism underlying the effect of SPARC on bladder cancer progression. Tissue samples from 63 patients with bladder cancer were used for analysis. Gene expression levels of SPARC and matrix metalloproteinase-2 were analyzed using reverse transcription-polymerase chain reaction. Correlations of the expression of SPARC with histopathological findings or patient outcome and with matrix metalloproteinase-2 were evaluated. Significantly higher expression of SPARC was observed in grades 3 and 2 than in grade 1 tumors (p <0.001 and <0.05, respectively). Stage T2 or greater invasive tumors expressed a significantly higher level of SPARC than stages T1 or less superficial tumors (p <0.0001). Patients in whom the lesions showed high SPARC expression had a significantly worse prognosis than those with low SPARC expression disease (p <0.0001). Even in those with invasive bladder cancer high SPARC expression was associated with significantly worse survival than low expression (p <0.01). Moreover, gene expression of SPARC significantly correlated with matrix metalloproteinase-2 gene expression (p <0.0001), implying that regulation of matrix metalloproteinase-2 expression may be a possible mechanism underlying the effect of SPARC on bladder cancer progression. A significant correlation was detected of the gene expression level of SPARC with histological grade, pathological stage and bladder cancer prognosis. SPARC may have an important role in bladder cancer progression and provide some additional information in patients with bladder cancer.

Effects of ageing on proliferative ability, and the expressions of secreted protein, acidic and rich in cysteine (SPARC) and osteoprotegerin (osteoclastogenesis inhibitory factor) in cultures of human periodontal ligament cells

Secreted protein, acidic and rich in cysteine (SPARC) has been suggested to play an important role in wound repair and mineralization. Osteoprotegerin/osteoclastogenesis inhibitory factor (OPG/OCIF) is a secreted protein that inhibits the maturation, activity and survival of osteoclasts. An examination of the changes in expression of these proteins as well as their proliferative ability according to ageing in cultured cells may elucidate characteristic changes in periodontal tissues induced by ageing. In the present study, proliferative ability and the expression of SPARC and OPG/OCIF were compared between cultures of human periodontal ligament (HPL) cells obtained from young and senior donors (in vivo cellular ageing) as well as in cultures of HPL cells at early and late passages (in vitro cellular ageing). Cumulative population doubling levels and cell population doubling time of HPL cells from young donors were greater and shorter, respectively, than those of HPL cells from senior donors. Levels of SPARC mRNA in HPL cells increased with cellular ageing in vivo. No change in the levels of OPG/OCIF mRNA in HPL cells with cellular ageing in vivo was observed. The changes in proliferative ability and the mRNA levels of SPARC and OPG/OCIF with cellular ageing in vitro were similar to those with ageing in vivo. This study demonstrated for the first time a relationship between in vivo and in vitro cellular ageing in the functional changes in HPL cells. These findings suggest that the impairment of periodontal ligament repair with ageing is due to the decrease in proliferative ability in HPL cells with ageing. Furthermore, the increase in SPARC with ageing may be related to changes in metabolism of periodontal ligament that occur with ageing.

SPARC, a matricellular glycoprotein with important biological functions.

SPARC (secreted protein, acidic and rich in cysteine) is a unique matricellular glycoprotein that is expressed by many different types of cells and is associated with development, remodeling, cell turnover, and tissue repair. Its principal functions in vitro are counteradhesion and antiproliferation, which proceed via different signaling pathways. SPARC consists of three domains, each of which has independent activity and unique properties. The extracellular calcium binding module and the follistatin-like module have been recently crystallized. Specific interactions between SPARC and growth factors, extracellular matrix proteins, and cell surface proteins contribute to the diverse activities described for SPARC in vivo and in vitro. The location of SPARC in the nuclear matrix of certain proliferating cells, but only in the cytosol of postmitotic neurons, indicates potential functions of SPARC as a nuclear protein, which might be involved in the regulation of cell cycle progression and mitosis. High levels of SPARC have been found in adult eye, and SPARC-null mice exhibit cataracts at 1-2 months of age. This animal model provides an excellent opportunity to confirm and explore some of the properties of SPARC, to investigate cataractogenesis, and to study SPARC-related family proteins, e.g., SC1/hevin, a counteradhesive matricellular protein that might functionally compensate for SPARC in certain tissues.(J Histochem Cytochem 47:1495-1505, 1999)

SPARC Is Expressed by Ganglion Cells and Astrocytes in Bovine Retina

SPARC (secreted protein, acidic and rich in cysteine)/osteonectin is a matricellular, counteradhesive glycoprotein that disrupts cell-matrix interactions, interacts with growth factors and components of extracellular matrix, and modulates the cell cycle, but appears to subserve only minor structural roles. SPARC is expressed in a variety of tissues during embryogenesis and remodeling and is believed to regulate vascular morphogenesis and cellular differentiation. Although usually limited in normal adult tissues, SPARC is expressed at significant levels in the adult central nervous system. Using a monoclonal antibody against bovine bone osteonectin, we have determined the localization of SPARC in newborn (3-day-old) and adult (4-8-year-old) normal bovine retinas. SPARC was present in the soma of ganglion cells and strong reactivity was found in ganglion cell axons. Muller cells displayed no immunoreactivity, but SPARC was present in retinal astrocytes that were identified by the astrocyte marker glial fibrillary acidic protein (GFAP). Newborn calf retina showed a staining pattern similar to that of adult retina but exhibited significantly reduced levels of SPARC. Minimal levels of SPARC protein were also detected in some capillaries of the inner retina of both newborn and adult animals, whereas large vessels were negative. The presence of SPARC in the retina was confirmed by Western blotting of retinal extracts. These data indicate that SPARC originating from bot h neurons and glia of the inner retina may be an important modulator of retinal angiogenesis. The increased expression of SPARC in adult relative to newborn retinal tissue also indicates that SPARC has an ongoing role in the maintenance of retinal functions.

The Caenorhabditis elegans homologue of the extracellular calcium binding protein SPARC/osteonectin affects nematode body morphology and mobility.

The extracellular matrix-associated protein, SPARC (osteonectin [Secreted Protein Acidic and Rich in Cysteine]), modulates cell adhesion and induces a change in cell morphology. SPARC expression in mammals is developmentally regulated and is highest at sites of extracellular matrix assembly and remodeling such as parietal endoderm and bone. We have isolated cDNA and genomic DNA clones encoding the Caenorhabditis elegans homologue of SPARC. The gene organization is highly conserved, and the proteins encoded by mouse, human, and nematode genes are about 38% identical. SPARC consists of four domains (I-IV) based on predicted secondary structure. Using bacterial fusion proteins containing nematode domain I or the domain IV EF-hand motif, we show that, like the mammalian proteins, both domains bind calcium. In transgenic nematodes expressing a SPARC-lacZ fusion gene, beta-galactosidase staining accumulated in a striated pattern in the more heavily stained muscle cells along the body. Comparison of the pattern of transgene expression to unc-54-lacZ animals demonstrated that SPARC is expressed by body wall and sex muscle cells. Appropriate levels of SPARC are essential for normal C. elegans development and muscle function. Transgenic nematodes overexpressing the wild-type SPARC gene were abnormal. Embryos were deformed, and adult hermaphrodites had vulval protrusions and an uncoordinated (Unc) phenotype with reduced mobility and paralysis.