Matricellular homologs in the foreign body response: hevin suppresses inflammation, but hevin and SPARC together diminish angiogenesis

Proximal deposition of collagen IV by fibroblasts contributes to basement membrane formation by colon epithelial cells in vitro

The basement membrane (BM) underlying epithelial tissue is a thin layer of extracellular matrix that governs tissue integrity and function. Epithelial BMs are generally assembled using BM components secreted from two origins: epithelium and stroma. Although de novo BM formation involves self-assembly processes of large proteins, it remains unclear how stroma-derived macromolecules are transported and assembled, specifically in the BM region. In this study, we established an in vitro co-culture model of BM formation in which DLD-1 human colon epithelial cells were cultured on top of collagen I gel containing human embryonic OUMS-36T-2 fibroblasts as stromal cells. A distinct feature of our system is represented by OUMS-36T-2 cells which are almost exclusively responsible for synthesis of collagen IV, a major BM component. Exploiting this advantage, we found that collagen IV incorporation was significantly impaired in culture conditions where OUMS-36T-2 cells were not allowed to directly contact DLD-1 cells. Soluble collagen IV, once diluted in the culture medium, did not accumulate in the BM region efficiently. Live imaging of fluorescently tagged collagen IV revealed that OUMS-36T-2 cells deposited collagen IV aggregates directly onto the basal surface of DLD-1 cells. Collectively, these results indicate a novel mode of collagen IV deposition in which fibroblasts proximal to epithelial cells exclusively contribute to collagen IV assembly during BM formation.

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.

Matricellular Protein SPARCL1 Regulates Blood Vessel Integrity and Antagonizes Inflammatory Bowel Disease

BACKGROUND

The understanding of vascular plasticity is key to defining the role of blood vessels in physiologic and pathogenic processes. In the present study, the impact of the vascular quiescence marker SPARCL1 on angiogenesis, capillary morphogenesis, and vessel integrity was evaluated.

METHODS

Angiogenesis was studied using the metatarsal test, an ex vivo model of sprouting angiogenesis. In addition, acute and chronic dextran sodium sulfate colitis models with SPARCL1 knockout mice were applied.

RESULTS

This approach indicated that SPARCL1 inhibits angiogenesis and supports vessel morphogenesis and integrity. Evidence was provided that SPARCL1-mediated stabilization of vessel integrity counteracts vessel permeability and inflammation in acute and chronic dextran sodium sulfate colitis models. Structure-function analyses of purified SPARCL1 identified the acidic domain of the protein necessary for its anti-angiogenic activity.

CONCLUSIONS

Our findings inaugurate SPARCL1 as a blood vessel-derived anti-angiogenic molecule required for vessel morphogenesis and integrity. SPARCL1 opens new perspectives as a vascular marker of susceptibility to colitis and as a therapeutic molecule to support blood vessel stability in this disease.

EMID1, a multifunctional molecule identified in a murine model for the invasion independent metastasis pathway

EMI Domain Containing 1 (EMID1) was identified as a potential candidate metastasis-promoting gene. We sought to clarify the molecular function of EMID1 and the protein expression. Overexpression and knockdown studies using mouse tumor cell lines identified two novel functions of EMID1: intracellular signaling involving enhancement of cell growth via cell cycle promotion and suppression of cell motility, and inhibition of cell–matrix adhesion by extracellularly secreted EMID1. EMID1 deposited on the culture dish induced self-detachment of cells that overexpressed the protein and inhibited adhesion of additionally seeded cells. This multifunctional property involving both intracellular signaling and the extracellular matrix suggests that EMID1 may be a matricellular proteins. Expression analysis using immunohistochemical staining revealed expression of EMID1 that was limited to chief cells of the gastric fundic gland and β cells of the pancreatic islets in normal adult human tissues, implying cell-specific functions of this molecule. In addition, increased expression of EMID1 protein detected in some cases of human cancers implies that EMID1 might be a new therapeutic target for cancer treatment.

Developmental onset of enduring long-term potentiation in mouse hippocampus

Analysis of long-term potentiation (LTP) provides a powerful window into cellular mechanisms of learning and memory. Prior work shows late LTP (L-LTP), lasting >3 hr, occurs abruptly at postnatal day 12 (P12) in the stratum radiatum of rat hippocampal area CA1. The goal here was to determine the developmental profile of synaptic plasticity leading to L-LTP in the mouse hippocampus. Two mouse strains and two mutations known to affect synaptic plasticity were chosen: C57BL/6J and Fmr1^-/y on the C57BL/6J background, and 129SVE and Hevin^-/- (Sparcl1^-/- ) on the 129SVE background. Like rats, hippocampal slices from all of the mice showed test pulse-induced depression early during development that was gradually resolved with maturation by 5 weeks. All the mouse strains showed a gradual progression between P10-P35 in the expression of short-term potentiation (STP), lasting ≤1 hr. In the 129SVE mice, L-LTP onset (>25% of slices) occurred by 3 weeks, reliable L-LTP (>50% slices) was achieved by 4 weeks, and Hevin^-/- advanced this profile by 1 week. In the C57BL/6J mice, L-LTP onset occurred significantly later, over 3-4 weeks, and reliability was not achieved until 5 weeks. Although some of the Fmr1^-/y mice showed L-LTP before 3 weeks, reliable L-LTP also was not achieved until 5 weeks. L-LTP onset was not advanced in any of the mouse genotypes by multiple bouts of theta-burst stimulation at 90 or 180 min intervals. These findings show important species differences in the onset of STP and L-LTP, which occur at the same age in rats but are sequentially acquired in mice.

Species-, organ- and cell-type-dependent expression of SPARCL1 in human and mouse tissues

SPARCL1 is a matricellular protein with anti-adhesive, anti-proliferative and anti-tumorigenic functions and is frequently downregulated in tumors such as colorectal carcinoma or non-small cell lung cancer. Studies have identified SPARCL1 as an angiocrine tumor suppressor secreted by tumor vessel endothelial cells, thereby exerting inhibitory activity on angiogenesis and tumor growth, in colorectal carcinoma. It is unknown whether SPARCL1 may exert these homeostatic functions in all organs and in other species. Therefore, SPARCL1 expression was comparatively analysed between humans and mice in a systematic manner. Murine Sparcl1 (mSparcl1) is most strongly expressed in the lung; expressed at an intermediate level in most organs, including the large intestine; and absent in the liver. In human tissues, SPARCL1 (hSPARCL1) was detected in all organs, with the strongest expression in the stomach, large intestine and lung, mostly consistent with the murine expression pattern. A striking difference between human and murine tissues was the absence of mSparcl1 expression in murine livers, while human livers showed moderate expression. Furthermore, mSparcl1 was predominantly associated with mural cells, whereas hSPARCL1 was detected in both mural and endothelial cells. Human SPARCL1 expression was downregulated in different carcinomas, including lung and colon cancers. In conclusion, this study revealed species-, organ- and cell-type-dependent expression of SPARCL1, suggesting that its function may not be similar between humans and mice.

Ex Vivo and In Vivo Biocompatibility Assessment (Blood and Tissue) of Three-Dimensional Bacterial Nanocellulose Biomaterials for Soft Tissue Implants

Bacterial nanocellulose (BNC) is a promising biomedical material. However, the haemocompatibility (haemolysis and thrombogenicity) and acute and sub-chronic immune responses to three-dimensional (3D) BNC biomaterials have not been evaluated. Accordingly, this manuscript focused on the effect of 3D microporosity on BNC haemocompatibility and a comparison with 2D BNC architecture, followed by the evaluation of the immune response to 3D BNC. Blood ex vivo studies indicated that compared with other 2D and 3D BNC architectures, never-dried 2D BNC presented antihemolytic and antithrombogenic effects. Nevertheless, in vivo studies indicated that 3D BNC did not interfere with wound haemostasis and elicited a mild acute inflammatory response, not a foreign body or chronic inflammatory response. Moreover, compared with the polyethylene controls, the implant design with micropores ca. 60 µm in diameter showed a high level of collagen, neovascularization and low fibrosis. Cell/tissue infiltration increased to 91% after 12 weeks and was characterized by fibroblastic, capillary and extracellular matrix infiltration. Accordingly, 3D BNC biomaterials can be considered a potential implantable biomaterial for soft tissue augmentation or replacement.

Domesticating the foreign body response: Recent advances and applications

The foreign body response is an immunological process that leads to the rejection of implanted devices and presents a fundamental challenge to their performance, durability, and therapeutic utility. Recent advances in materials development and device design are now providing strategies to overcome this immune-mediated reaction. Here, we briefly review our current mechanistic understanding of the foreign body response and highlight new anti-FBR technologies from this decade that have been applied successfully in biomedical applications relevant to implants, devices, and cell-based therapies. Further development of these important technologies promises to enable new therapies, diagnostics, and revolutionize the management of patient care for many intractable diseases.

Biological response to self-etch adhesive after partial caries removal in rats

OBJECTIVES

The purposes of this study were to evaluate a model of slow caries progression and to investigate the performance of a self-etch adhesive system for partial caries removal.

MATERIALS AND METHODS

Rat molars were infected with Streptococcus sobrinus 6715 culture. Different time points were analyzed: days 78, 85, and 95 (± 2). After this, the samples were processed for morphological analysis. Additionally, the first molars were restored with zinc oxide and eugenol (IRM™; Dentsply; Brazil) or adhesive system (Clearfil SE Bond™; Kuraray Medical; Japan) 78 days after caries induction. After, 3 or 15 days post-treatment, the animals were euthanized, and their mandibles were processed for morphological analysis, classified by means of scores, and submitted to statistical analysis. Subsequently, immunohistochemical analysis was performed for osteonectin (OSN) and transforming growth factor-ß1 (TGF-ß1) expression.

RESULTS

According to the caries induction model used, on day 95 greater inflammatory infiltration (p < 0.001), and more extensive degradation of secondary/primary dentin were demonstrated than on day 78 (p < 0.05). Furthermore, the restorative materials presented similar performance (p > 0.05) and proved to be fundamental to control the carious lesion. The TGF-ß1 and OSN were shown to be active during the caries process.

CONCLUSIONS

The slow caries lesion model was feasible for morphological analysis of the dentin-pulp complex. The self-etch adhesive system triggered no acute inflammatory infiltration or pulp necrosis, instead it seemed to stimulate early pulp repair.

CLINICAL RELEVANCE

Clearfil SE Bond™ applied directly on caries-affected dentin did not predispose to pulp inflammation; instead, it appeared to provide early biological benefits.

Embracing the complexity of matricellular proteins: the functional and clinical significance of splice variation

Matricellular proteins influence wide-ranging fundamental cellular processes including cell adhesion, migration, growth and differentiation. They achieve this both through interactions with cell surface receptors and regulation of the matrix environment. Many matricellular proteins are also associated with diverse clinical disorders including cancer and diabetes. Alternative splicing is a precisely regulated process that can produce multiple isoforms with variable functions from a single gene. To date, the expression of alternate transcripts for the matricellular family has been reported for only a handful of genes. Here we analyse the evidence for alternative splicing across the matricellular family including the secreted protein acidic and rich in cysteine (SPARC), thrombospondin, tenascin and CCN families. We find that matricellular proteins have double the average number of splice variants per gene, and discuss the types of domain affected by splicing in matricellular proteins. We also review the clinical significance of alternative splicing for three specific matricellular proteins that have been relatively well characterised: osteopontin (OPN), tenascin-C (TNC) and periostin. Embracing the complexity of matricellular splice variants will be important for understanding the sometimes contradictory function of these powerful regulatory proteins, and for their effective clinical application as biomarkers and therapeutic targets.

Is SPARC an Evolutionarily Conserved Collagen Chaperone?

The construction of collagen fiber scaffolds, which provide the structural integrity of the extracellular matrix of connective tissues and basement membranes, is initiated by a complex mechanism of protein-folding, whereby pro-collagen α-chains are assembled into triple-helical procollagen molecules. This unique assembly of the procollagen molecules is guided by several endoplasmic reticulum resident molecular chaperones, including HSP47, which dissociates from procollagen molecules prior to their transport from the endoplasmic reticulum into the cis-Golgi network. SPARC, an evolutionarily conserved collagen-binding glycoprotein, which is frequently co-expressed with collagen in rapidly remodeling tissues, binds to the triple-helical region of procollagen molecules. Analysis of data from genome projects indicates that specific amino acids and sequences in SPARC that are critical for collagen binding are evolutionarily conserved in organisms ranging from nematodes to mammals. Studies of invertebrates, which do not encode HSP47, indicate that SPARC expression is required for the deposition of collagen IV in basal lamina during embryonic development. In mammals, defects in collagen deposition have been observed in normal and wound-healing tissues in the absence of SPARC expression. Based on these and other observations, we propose that intracellular SPARC acts as a collagen molecular chaperone in the endoplasmic reticulum, and that in higher organisms, SPARC acts in concert with HSP47 to ensure that only correctly folded procollagen molecules exit the endoplasmic reticulum. In contrast to HSP47, SPARC is transported from the endoplasmic reticulum through the Golgi network and into secretory vesicles for exocytosis at the plasma membrane. Hence, SPARC may also play a role in regulating post-endoplasmic reticulum events that promote collagen fibrillogenesis.

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.

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.

Biomedical implant capsule formation: lessons learned and the road ahead

Clinicians and investigators have been implanting biomedical devices into patients and experimental animals for centuries. There is a characteristic complex inflammatory response to the presence of the biomedical device with diverse cell signaling, followed by migration of fibroblasts to the implant surface and the eventual walling off of the implant in a collagen capsule. If the device is to interact with the surrounding tissues, the collagen envelope will eventually incapacitate the device or myofibroblasts can cause capsular contracture with resulting distortion, migration, or firmness. This review analyzes the various tactics used in the past to modify or control capsule formation with suggestions for future investigative approaches.

Molecular Characterization of Macrophage-Biomaterial Interactions

Implantation of biomaterials in vascularized tissues elicits the sequential engagement of molecular and cellular elements that constitute the foreign body response. Initial events include the non-specific adsorption of proteins to the biomaterial surface that render it adhesive for cells such as neutrophils and macrophages. The latter undergo unique activation and in some cases undergo cell-cell fusion to form foreign body giant cells that contribute to implant damage and fibrotic encapsulation. In this review, we discuss the molecular events that contribute to macrophage activation and fusion with a focus on the role of the inflammasome, signaling pathways such as JAK/STAT and NF-κB, and the putative involvement of micro RNAs in the regulation of these processes.

Revisiting the matricellular concept

The concept of a matricellular protein was first proposed by Paul Bornstein in the mid-1990s to account for the non-lethal phenotypes of mice with inactivated genes encoding thrombospondin-1, tenascin-C, or SPARC. It was also recognized that these extracellular matrix proteins were primarily counter or de-adhesive. This review reappraises the matricellular concept after nearly two decades of continuous investigation. The expanded matricellular family as well as the diverse and often unexpected functions, cellular location, and interacting partners/receptors of matricellular proteins are considered. Development of therapeutic strategies that target matricellular proteins are discussed in the context of pathology and regenerative medicine.

TGF-β2-mediated ocular hypertension is attenuated in SPARC-null mice

PURPOSE

Transforming growth factor-β2 (TGF-β2) has been implicated in the pathogenesis of primary open-angle glaucoma through extracellular matrix (ECM) alteration among various mechanisms. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein that regulates ECM within the trabecular meshwork (TM), and is highly upregulated by TGF-β2. We hypothesized that, in vivo, SPARC is a critical regulatory node in TGF-β2-mediated ocular hypertension.

METHODS

Empty (Ad.empty) or TGF-β2-containing adenovirus (Ad.TGF-β2) was injected intravitreally into C57BL6-SV129 WT and SPARC-null mice. An initial study was performed to identify a stable period for IOP measurement under isoflurane. The IOP was measured before injection and every other day for two weeks using rebound tonometry. Additional mice were euthanized at peak IOP for immunohistochemistry.

RESULTS

The IOP was stable under isoflurane during minutes 5 to 8. The IOP was significantly elevated in Ad.TGF-β2-injected (n = 8) versus Ad.empty-injected WT (n = 8) mice and contralateral uninjected eyes during days 4 to 11 (P < 0.03). The IOPs were not significantly elevated in Ad.TGF-β2-injected versus Ad.empty-injected SPARC-null mice. However, on day 8, the IOP of Ad.TGF-β2-injected SPARC-null eyes was elevated compared to that of contralateral uninjected eyes (P = 0.0385). Immunohistochemistry demonstrated that TGF-β2 stimulated increases in collagen IV, fibronectin, plasminogen activator inhibitor-1 (PAI-1), connective tissue growth factor (CTGF), and SPARC in WT mice, but only PAI-1 and CTGF in SPARC-null mice (P < 0.05).

CONCLUSIONS

SPARC is essential to the regulation of TGF-β2-mediated ocular hypertension. Deletion of SPARC significantly attenuates the effects of TGF-β2 by restricting collagen IV and fibronectin expression. These data provide further evidence that SPARC may have an important role in IOP regulation and possibly glaucoma pathogenesis.

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.

Matricellular proteins and biomaterials

Biomaterials are essential to modern medicine as components of reconstructive implants, implantable sensors, and vehicles for localized drug delivery. Advances in biomaterials have led to progression from simply making implants that are nontoxic to making implants that are specifically designed to elicit particular functions within the host. The interaction of implants and the extracellular matrix during the foreign body response is a growing area of concern for the field of biomaterials, because it can lead to implant failure. Expression of matricellular proteins is modulated during the foreign body response and these proteins interact with biomaterials. The design of biomaterials to specifically alter the levels of matricellular proteins surrounding implants provides a new avenue for the design and fabrication of biomimetic biomaterials.

Hevin plays a pivotal role in corneal wound healing

Background

Hevin is a matricellular protein involved in tissue repair and remodeling via interaction with the surrounding extracellular matrix (ECM) proteins. In this study, we examined the functional role of hevin using a corneal stromal wound healing model achieved by an excimer laser-induced irregular phototherapeutic keratectomy (IrrPTK) in hevin-null (hevin^-/-) mice. We also investigated the effects of exogenous supplementation of recombinant human hevin (rhHevin) to rescue the stromal cellular components damaged by the excimer laser.

Methodology/Principal Findings

Wild type (WT) and hevin^-/- mice were divided into three groups at 4 time points- 1, 2, 3 and 4 weeks. Group I served as naïve without any treatment. Group II received epithelial debridement and underwent IrrPTK using excimer laser. Group III received topical application of rhHevin after IrrPTK surgery for 3 days. Eyes were analyzed for corneal haze and matrix remodeling components using slit lamp biomicroscopy, in vivo confocal microscopy, light microscopy (LM), transmission electron microscopy (TEM), immunohistochemistry (IHC) and western blotting (WB). IHC showed upregulation of hevin in IrrPTK-injured WT mice. Hevin^-/- mice developed corneal haze as early as 1-2 weeks post IrrPTK-treatment compared to the WT group, which peaked at 3-4 weeks. They also exhibited accumulation of inflammatory cells, fibrotic components of ECM proteins and vascularized corneas as seen by IHC and WB. LM and TEM showed activated keratocytes (myofibroblasts), inflammatory debris and vascular tissues in the stroma. Exogenous application of rhHevin for 3 days reinstated inflammatory index of the corneal stroma similar to WT mice.

Conclusions/Significance

Hevin is transiently expressed in the IrrPTK-injured corneas and loss of hevin predisposes them to aberrant wound healing. Hevin^-/- mice develop early corneal haze characterized by severe chronic inflammation and stromal fibrosis that can be rescued with exogenous administration of rhHevin. Thus, hevin plays a pivotal role in the corneal wound healing.

The Juxtacanalicular Region of Ocular Trabecular Meshwork: A Tissue with a Unique Extracellular Matrix and Specialized Function

The trabecular meshwork (TM) is a filter-like tissue located in the anterior segment of the eye. It is composed of a series of fenestrated beams through which aqueous humor flows to exit the anterior chamber via Schlemm's canal. The primary function of the TM is to regulate the flow of aqueous humor in order to establish intraocular pressure (IOP). Dysregulated aqueous humor outflow causes elevated IOP, which is a primary risk factor for glaucoma. The region of the TM implicated in establishing IOP lies adjacent to Schlemm's canal and is called the juxtacanalicular tissue (JCT) or cribriform region. Recent advanced light microscopy studies suggest that the JCT can be subdivided into inner and outer zones based on the localization of certain extracellular matrix (ECM) molecules. By comparing the ECM of the JCT to other connectives tissues and disease processes, this review outlines the evidence for two new concepts in TM biology: (1) continuous maintenance ECM remodeling, which may be critical in order to preserve open aqueous humor flow channels by releasing trapped debris and associated ECM fragments from the outflow pathways; (2) the JCT ECM as a barrier to functionally isolate the aqueous outflow channels. The ECM surrounding the outflow channels in the JCT may function to sequester small active regulatory molecules and prevent them from aberrantly modulating outflow resistance. These adaptations point to a distinctive tissue that has evolved transient ECM remodeling processes in order to regulate aqueous humor outflow and maintain rigorous control of IOP.

Pro-angiogenic and anti-inflammatory regulation by functional peptides loaded in polymeric implants for soft tissue regeneration

Inflammation and angiogenesis are inevitable in vivo responses to biomaterial implants. Continuous progress has been made in biomaterial design to improve tissue interactions with an implant by either reducing inflammation or promoting angiogenesis. However, it has become increasingly clear that the physiological processes of inflammation and angiogenesis are interconnected through various molecular mechanisms. Hence, there is an unmet need for engineering functional tissues by simultaneous activation of pro-angiogenic and anti-inflammatory responses to biomaterial implants. In this work, the modulus and fibrinogen adsorption of porous scaffolds were tuned to meet the requirements (i.e., ~100 kPa and ~10 nm, respectively), for soft tissue regeneration by employing tyrosine-derived combinatorial polymers with polyethylene glycol crosslinkers. Two types of functional peptides (i.e., pro-angiogenic laminin-derived C16 and anti-inflammatory thymosin β4-derived Ac-SDKP) were loaded in porous scaffolds through collagen gel embedding so that peptides were released in a controlled fashion, mimicking degradation of the extracellular matrix. The results from (1) in vitro coculture of human umbilical vein endothelial cells and human blood-derived macrophages and (2) in vivo subcutaneous implantation revealed the directly proportional relationship between angiogenic activities (i.e., tubulogenesis and perfusion capacity) and inflammatory activities (i.e., phagocytosis and F4/80 expression) upon treatment with either type of peptide. Interestingly, cotreatment with both types of peptides upregulated the angiogenic responses, while downregulating the inflammatory responses. Also, anti-inflammatory Ac-SDKP peptides reduced production of pro-inflammatory cytokines (i.e., interleukin [IL]-1β, IL-6, IL-8, and tumor necrosis factor alpha) even when treated in combination with pro-angiogenic C16 peptides. In addition to independent regulation of angiogenesis and inflammation, this study suggests a promising approach to improve soft tissue regeneration (e.g., blood vessel and heart muscle) when inflammatory diseases (e.g., ischemic tissue fibrosis and atherosclerosis) limit the regeneration process.

Proteolysis of the matricellular protein hevin by matrix metalloproteinase-3 produces a SPARC-like fragment (SLF) associated with neovasculature in a murine glioma model

The matricellular SPARC-family member hevin (Sparc-like 1/SPARCL-1/SC1/Mast9) contributes to neural development and alters tumor progression in a range of mammalian models. Based on sequence similarity, we hypothesized that proteolytic digestion of hevin would result in SPARC-like fragments (SLF) that affect the activity and/or location of these proteins. Incubation of hevin with matrix metalloproteinase-3 (MMP-3), a protease known to cleave SPARC, produced a limited number of peptides. Sequencing revealed the major proteolytic products to be SPARC-like in primary structure. In gliomas implanted into murine brain, a SLF was associated with SPARC in the neovasculature but not with hevin, the latter prominent in the astrocytes encompassed by infiltrating tumor. In this model of invasive glioma that involves MMP-3 activity, host-derived SLF was not observed in the extracellular matrix adjacent to tumor cells. In contrast, it occurred with its homolog SPARC in the angiogenic response to the tumor. We conclude that MMP-3-derived SLF is a marker of neovessels in glioma, where it could influence the activity of SPARC.

Down-regulated SPARCL1 is associated with clinical significance in human gastric cancer

BACKGROUND

SPARC-like protein 1 (SPARCL1), a member of extracelluar matrix glycoprotein, is involved in many physiological functions.

METHODS

Tissue microarray (TMA) blocks were constructed based on 1,072 Chinese patients, containing both gastric cancer (GC) tissues and adjacent normal mucosa tissues. We analyzed the expression of SPARCL1 from both mRNA and protein level, using Real-time quantitative polymerase chain reaction (qRT-PCR), semi-quantitative PCR, immunohistochemistry (IHC), and Western blotting. Loss of heterozygosity analysis at the SPARCL1 gene locus was carried out using ten paired tumor and matched normal tissues.

RESULTS

SPARCL1 mRNA was significantly reduced in tumor specimens compared with normal tissues. Down-regulation of SPARCL1 protein was detected in 413 cases (38.7%) of 1,072 primary gastric tumor tissues. Kaplan-Meier survival curves demonstrated that SPARCL1-positive patients had better median survival time than SPARCL1-negative patients (59 months vs. 28 months, P = 0.001). Multivariate survival analysis revealed that SPARCL1 was an independent prognostic factor in gastric adenocarcinoma patients with no metastasis and well/moderately differentiated. The incidence of LOH for each individual marker was 12.5% (1/8) for D4S2462, 20% (2/10) for D4S2929, and 33.3% (3/9) for SPARCL1.

CONCLUSIONS

Our study revealed the clinical significance of SPARCL1 expression, providing a basis that the loss of SPARCL1 is a negative event in GC progression and prognosis. Furthermore, SPARCL1 protein might be considered to be a potential differentiation marker.

SPARC: a key player in the pathologies associated with obesity and diabetes

SPARC (secreted protein acidic and rich in cysteine, also known as osteonectin or BM-40) is a widely expressed profibrotic protein with pleiotropic roles, which have been studied in a variety of conditions. Notably, SPARC is linked to human obesity; SPARC derived from adipose tissue is associated with insulin resistance and secretion of SPARC by adipose tissue is increased by insulin and the adipokine leptin. Furthermore, SPARC is associated with diabetes complications such as diabetic retinopathy and nephropathy, conditions that are ameliorated in the Sparc-knockout mouse model. As a regulator of the extracellular matrix, SPARC also contributes to adipose-tissue fibrosis. Evidence suggests that adipose tissue becomes increasingly fibrotic in obesity. Fibrosis of subcutaneous adipose tissue may restrict accumulation of triglycerides in this type of tissue. These triglycerides are, therefore, diverted and deposited as ectopic lipids in other tissues such as the liver or as intramyocellular lipids in skeletal muscle, which predisposes to insulin resistance. Hence, SPARC may represent a novel and important link between obesity and diabetes mellitus. This Review is focused on whether SPARC could be a key player in the pathology of obesity and its related metabolic complications.

Blood flow in the foreign-body capsules surrounding surgically implanted subcutaneous devices

BACKGROUND

Surgically implanted devices initiate inflammatory mechanisms and wound healing events and result in the formation of a thick fibrotic capsule that surrounds the device. To investigate the foreign-body response to devices of clinically relevant size, we used microspheres to determine regional blood flow patterns in the foreign-body capsule (FBC) and surrounding subcutaneous tissue after device implantation.

MATERIALS AND METHODS

In 10 canines, we implanted 40 subcutaneous devices (polysulfone n = 20, silicone-coated n = 10, titanium n = 10). Via thoracotomy, animals were instrumented with left atrial and aortic vascular access catheters for serial microsphere injections and reference blood sampling. Regional blood flow was repeatedly determined in the FBC, subcutaneous fascia surrounding the FBC, and subcutaneous fascia distal to the surgical site up to 19 wk after device implantation (n = 55 determinations).

RESULTS

Compared with normal blood flow in subcutaneous fascia distal to the surgical site, blood flow increased in FBCs surrounding each device material (polysulfone P = 0.0035, silicone-coated P < 0.0001, titanium P < 0.0001). Additionally, blood flow increased in the subcutaneous fascia within half a centimeter of fibrous capsules encasing polysulfone (P = 0.0081) but not silicone (P = 0.3706) or titanium (P = 0.8160) devices. The time-course of measured blood flow changes within FBCs were similar for polysulfone and silicone but not for titanium.

CONCLUSIONS

Surgically implanted subcutaneous devices of clinically relevant size elicit increases in blood flow in the FBC as well as surrounding fascia. Device material may influence regional blood flow patterns.

Processing of the matricellular protein hevin in mouse brain is dependent on ADAMTS4

The matricellular SPARC family member hevin (SPARC-like 1/SPARCL-1/SC1/Mast9) contributes to neural development and alters tumor progression in a range of mammalian models. The distribution of hevin in mouse tissues was reexamined with a novel monoclonal antibody that discriminates between hevin and its ortholog SPARC. We now report proteolysis of hevin in many tissues, with the most extensive processing in the brain. We demonstrate a cleavage site within the hevin sequence for the neural tissue proteinase ADAMTS4. Digestion of hevin by ADAMTS4 in vitro produced fragments similar to those present in brain lysates. Monoclonal antibodies revealed a SPARC-like fragment generated from hevin that was co-localized with ADAMTS4 in vivo. We show that proteolysis of hevin by ADAMTS4 in the mouse cerebellum is important for the normal development of this tissue. In conclusion, we have identified the fragmentation of hevin by ADAMTS4 in the mouse brain and propose that this specific proteolysis is integral to cell morphology and extracellular matrix deposition in the developing brain.

Norrin, frizzled-4, and Lrp5 signaling in endothelial cells controls a genetic program for retinal vascularization

Disorders of vascular structure and function play a central role in a wide variety of CNS diseases. Mutations in the Frizzled-4 (Fz4) receptor, Lrp5 coreceptor, or Norrin ligand cause retinal hypovascularization, but the mechanisms by which Norrin/Fz4/Lrp signaling controls vascular development have not been defined. Using mouse genetic and cell culture models, we show that loss of Fz4 signaling in endothelial cells causes defective vascular growth, which leads to chronic but reversible silencing of retinal neurons. Loss of Fz4 in all endothelial cells disrupts the blood brain barrier in the cerebellum, whereas excessive Fz4 signaling disrupts embryonic angiogenesis. Sox17, a transcription factor that is upregulated by Norrin/Fz4/Lrp signaling, plays a central role in inducing the angiogenic program controlled by Norrin/Fz4/Lrp. These experiments establish a cellular basis for retinal hypovascularization diseases due to insufficient Frizzled signaling, and they suggest a broader role for Frizzled signaling in vascular growth, remodeling, maintenance, and disease.

Matricellular proteins in the trabecular meshwork

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

SPARC is expressed by macroglia and microglia in the developing and mature nervous system

SPARC (secreted protein, acidic and rich in cysteine) is a matricellular protein that is highly expressed during development, tissue remodeling, and repair. SPARC produced by olfactory ensheathing cells (OECs) can promote axon sprouting in vitro and in vivo. Here, we show that in the developing nervous system of the mouse, SPARC is expressed by radial glia, blood vessels, and other pial-derived structures during embryogenesis and postnatal development. The rostral migratory stream contains SPARC that becomes progressively restricted to the SVZ in adulthood. In the adult CNS, SPARC is enriched in specialized radial glial derivatives (Müller and Bergmann glia), microglia, and brainstem astrocytes. The peripheral glia, Schwann cells, and OECs express SPARC throughout development and in maturity, although it appears to be down-regulated with maturation. These data suggest that SPARC may be expressed by glia in a spatiotemporal manner consistent with a role in cell migration, neurogenesis, synaptic plasticity, and angiogenesis.

A prototypic matricellular protein in the tumor microenvironment--where there's SPARC, there's fire

Within the tumor microenvironment is a dynamic exchange between cancer cells and their surrounding stroma. This complex biologic system requires carefully designed models to understand the role of its stromal components in carcinogenesis, tumor progression, invasion, and metastasis. Secreted protein acidic and rich in cysteine (SPARC) is a prototypic matricellular protein at the center of this exchange. Two decades of basic science research combined with recent whole genome analyses indicate that SPARC is an important player in vertebrate evolution, normal development, and maintenance of normal tissue homeostasis. Therefore, SPARC might also play an important role in the tumor microenvironment. Clinical evidence indicates that SPARC expression correlates with tumor progression, but tightly controlled animal models have shown that the role of SPARC in tumor progression is dependent on tissue and tumor cell type. In this Prospectus, we review the current understanding of SPARC in the tumor microenvironment and discuss current and future investigations of SPARC and tumor-stromal interactions that require careful consideration of growth factors, cytokines, proteinases, and angiotropic factors that might influence SPARC activity and tumor progression.

Reduced foreign body reaction to implanted biomaterials by surface treatment with oriented osteopontin

The foreign body reaction (FBR), which leads to the encapsulation of implanted biomaterials, has been implicated in the failure of many medical devices. The protein layer that is nonspecifically adsorbed onto the implant surface immediately after implantation is thought to dictate this reaction. It is hypothesized that biomaterial surfaces having specific proteins with precisely controlled orientations will decrease the FBR. Previously, we have reported that osteopontin (OPN) adsorbed on positively charged surfaces has a preferable orientation for in vitro cell adhesion and spreading as compared to negatively charged surfaces. It is expected that coating a layer of OPN in its preferred orientation on an implant surface will decrease the FBR. In this work, in vivo studies were performed to test this hypothesis. A positively charged polymer (p(HEMA-co-AEMA)) and a negatively charged polymer (p(HEMA-co-CEA)) coated with OPN were implanted subcutaneously in wild-type mice for 7 or 28 days. Uncoated polymers were used as control. For the 7-day implants, cells on OPN-coated p(HEMA-co-AEMA) spread more than cells on the other three materials. Following 28 days of implantation the implants were explanted and the capsule thickness and vascularity around the implants were characterized. Additionally, the macrophage and foreign body giant cells (FBGCs) around the implants were quantified. It was found in this study that the modification of the positively charged polymer surface with OPN in a controlled orientation led to a reduction in the foreign body reaction as determined by capsule thickness. Our finding provides valuable information for designing better biocompatible biomaterials with improved in vivo performance.

Searching the principal genes for neural differentiation of mouse ES cells by factorizing eigengenes of clusters

A time-series microarray experiment is useful to study the changes in the expression of a large number of genes over time. Many methods for clustering genes using gene expression profiles have been suggested, but it is not easy to interpret the biological significance of the results or utilize these methods for understanding the dynamics of gene regulatory systems. In this study, we introduce an algorithm for readjusting the boundaries of clusters by adopting the advantages of both k-means and singular value decomposition (SVD). In addition, we suggest a methodology for searching the principal genes that can be the most crucial genes in regulation of clusters. We found 34 principal genes from 171 clusters having strong concentratedness in their expression patterns and distinct ranges of oscillatory phases, by using a time-series microarray dataset of mouse embryonic stem (ES) cells after induction of dopaminergic neural differentiation. The biological significance of the principal genes examined in the literature supports the feasibility of our algorithms in that the hierarchy of clusters may lead the manifestation of the phenotypes, e.g., the development of the nervous system.

Altered tissue repair in hevin-null mice: inhibition of fibroblast migration by a matricellular SPARC homolog

Matricellular proteins such as hevin, secreted protein acidic and rich in cysteine, and thrombospondin-2 play an important role during tissue repair through their influence on fundamental cellular activities such as adhesion, migration, proliferation, and extracellular matrix synthesis/reorganization. We have investigated the role played by hevin during excisional and incisional cutaneous wound repair in hevin-null mice. Hevin-null animals both close and heal their skin wounds faster than wild-type animals, as evidenced by enhanced macrophage infiltration of wound beds at early time points, the earlier appearance of mature extracellular matrix, and the overall higher maturity score. In addition, fibrovascular invasion of polyvinyl alcohol sponges was more robust in hevin-null mice, a result indicating that differences in cell migration might underlie the observed alterations in wound repair. Experiments in vitro showed that hevin induced the deadhesion and inhibited the migration of primary dermal fibroblasts in a Rac-1-dependent manner. These findings indicate that the differences in wound repair between hevin-null and wild-type animals can be attributed in part to the deadhesive function of hevin and reduced cell migration within dermal wound beds in which this protein is expressed.

Localization of the extracellular matrix protein SC1 coincides with synaptogenesis during rat postnatal development

SC1 is an extracellular matrix protein that belongs to the SPARC family of matricellular molecules. This anti-adhesive protein localizes to synapses in the adult rat brain and has been postulated to modulate synapse shape. In this study, increased levels of SC1 were detected from postnatal days 10-20, with a peak at postnatal day 15, a period of intense synaptogenesis. During this time, increased colocalization of SC1 with the synaptic marker synaptophysin was observed in synapse-rich regions of the cerebellum and the cerebral cortex. These findings indicate that the pattern of SC1 localization coincided with synaptogenesis during rat postnatal development.

Analysis of the extracellular matrix protein SC1 during reactive gliosis in the rat lithium-pilocarpine seizure model

When the nervous system is subjected to stressful stimuli, reactive gliosis often ensues. This phenomenon consists of the hypertrophy of astrocyte processes as well as the proliferation of these cells. In this study, the lithium-pilocarpine model of temporal lobe epilepsy was employed to study the effects of status epilepticus (SE) on the localization of SC1 protein in reactive astrocytes. SC1 is an anti-adhesive extracellular matrix protein strongly expressed in the mammalian brain. At 1 day following SE, SC1 transiently localized to hypertrophied astrocyte processes that were closely associated with neurons and blood vessels. SC1 was also detected at 7 days post-SE in proliferating astrocytes labeled with the cell division marker PCNA. These findings indicate that the anti-adhesive protein SC1 is ideally localized to create an environment conducive to process extension and cellular proliferation in reactive astrocytes.

Tumor-suppressor function of SPARC-like protein 1/Hevin in pancreatic cancer

SPARC-like protein 1 (SPARCL1), a member of the SPARC family, is downregulated in various tumors. In the present study, the expression and localization of SPARCL1 were analyzed in a wide range of nontumorous and neoplastic pancreatic tissues by quantitative reverse transcription-polymerase chain reaction, laser capture microdissection, microarray analysis, and immunohistochemistry. For functional analysis, proliferation and invasion assays were used in cultured pancreatic cancer cells. Pancreatic ductal adenocarcinoma (PDAC) and other pancreatic neoplasms exhibited increased SPARCL1 mRNA levels compared to those of the normal pancreas. SPARCL1 mRNA levels were low to absent in microdissected and cultured pancreatic cancer cells, and promoter demethylation increased SPARCL1 levels only slightly in three of eight cell lines. SPARCL1 was observed in small capillaries in areas of inflammation/tumor growth and in some islet cells. In PDAC, 15.4% of vessels were SPARCL1-positive. In contrast, the percentage of SPARCL1-positive vessels was higher in chronic pancreatitis and benign and borderline pancreatic tumors. Recombinant SPARCL1 inhibited pancreatic cancer cell invasion and exerted moderate growth-inhibitory effects. In conclusion, SPARCL1 expression in pancreatic tissues is highly correlated with level of vascularity. Its anti-invasive effects and reduced expression in metastasis indicate tumor-suppressor function.

The fur seal-a model lactation phenotype to explore molecular factors involved in the initiation of apoptosis at involution

Mammary gland involution requires co-ordination of milk production, immune responses, apoptosis and remodeling. Initiation and progression of each of these components involves integral control by the mammary gland. Although cell-based culture models and genetically manipulated animals have shed light on these processes, the factors controlling each step in the involution cascade are still poorly understood. The fur seal displays a unique lactation phenotype. During the lactation cycle the mammary gland downregulates milk production and initiates an immune response but fails to initiate the apoptotic phase of involution, allowing the female fur seal to undertake long foraging trips of up to 28 days between suckling bouts. Upon return to shore the female continues feeding her pup following resumption of lactation and milk production. Expression profiling of genes involved in this lactation cycle provides valuable tools for investigation of the factors responsible for the initiation of apoptosis at involution.

SPARC and Hevin expression correlate with tumour angiogenesis in hepatocellular carcinoma

Both Secreted Protein Acidic and Rich in Cysteine (SPARC) and Hevin are multifunctional matricellular glycoproteins. Recent experimental studies suggested that Hevin and SPARC together diminish angiogenesis, but their significance in hepatocellular carcinoma (HCC) remains unclear. This study aimed to correlate SPARC and Hevin expression with angiogenesis and clinicopathological features in HCC. SPARC and Hevin protein and mRNA expression in HCC specimens were assessed by immunostaining, immunoblotting, and quantitative reverse transcriptase-polymerase chain reaction. Tumour microvessel density (MVD) was assessed by CD34 immunostaining. The role of SPARC and Hevin in HCC was further assessed in an in vivo nude mice xenograft model. Both SPARC and Hevin mRNA levels were significantly higher in tumours than in non-tumourous livers. A significant correlation between tumour SPARC and Hevin mRNA levels was found. Moreover, SPARC protein localized in the tumour sinusoidal area correlated significantly with Hevin protein localized in HCC cells. Truncated forms of SPARC and Hevin proteins were detected in clinical samples. Truncated SPARC protein localized in the tumour sinusoidal area correlated significantly with tumour MVD. On the other hand, overexpression of full-length SPARC in tumour xenografts in athymic nude mice significantly delayed tumour growth, and this delay was related to a decrease in tumour angiogenesis. Expression of Hevin protein within HCC cells was related to the presence of tumour encapsulation and the absence of hepatitis B surface antigen in clinical samples. Overexpression of Hevin in tumour xenografts also significantly delayed tumour growth. In conclusion, this study has shown that SPARC and Hevin are upregulated in HCC compared with non-tumourous liver, and that they are inter-related at both mRNA and protein levels. Moreover, both SPARC and Hevin were related to HCC angiogenesis and tumour progression.

Matricellular hevin regulates decorin production and collagen assembly

Matricellular proteins such as SPARC, thrombospondin 1 and 2, and tenascin C and X subserve important functions in extracellular matrix synthesis and cellular adhesion to extracellular matrix. By virtue of its reported interaction with collagen I and deadhesive activity on cells, we hypothesized that hevin, a member of the SPARC gene family, regulates dermal extracellular matrix and collagen fibril formation. We present evidence for an altered collagen matrix and levels of the proteoglycan decorin in the normal dermis and dermal wound bed of hevin-null mice. The dermal elastic modulus was also enhanced in hevin-null animals. The levels of decorin protein secreted by hevin-null dermal fibroblasts were increased by exogenous hevin in vitro, data indicating that hevin might regulate both decorin and collagen fibrillogenesis. We also report a decorin-independent function for hevin in collagen fibrillogenesis. In vitro fibrillogenesis assays indicated that hevin enhanced fibril formation kinetics. Furthermore, cell adhesion assays indicated that cells adhered differently to collagen fibrils formed in the presence of hevin. Our observations support the capacity of hevin to modulate the structure of dermal extracellular matrix, specifically by its regulation of decorin levels and collagen fibril assembly.

Novel Function of Alternatively Activated Macrophages: Stabilin-1-Mediated Clearance of SPARC

The matricellular protein SPARC (secreted protein acidic and rich in cysteine) has been implicated in development, differentiation, response to injury, and tumor biology by virtue of its regulation of extracellular matrix production/assembly and its antiadhesive and antiproliferative effects on different cell types. Despite numerous biological activities described for SPARC, cell surface receptors for this protein have not been identified. By phage display and in vitro-binding assays, we now show that SPARC interacts with stabilin-1, a scavenger receptor expressed by tissue macrophages and sinusoidal endothelial cells. The interaction is mediated by the extracellular epidermal growth factor-like region of stabilin-1 containing the sequence FHGTAC. Using FACS analysis and confocal microscopy, we demonstrate that stabilin-1 internalizes and targets SPARC to an endosomal pathway in Chinese hamster ovary cells stably transfected with this receptor. In human macrophages, stabilin-1 expression is required for receptor-mediated endocytosis of SPARC. SPARC was efficiently endocytosed by alternatively activated macrophages stimulated by IL-4 and dexamethasone, but not solely by Th1 or Th2 cytokines. A time course of ligand exposure to alternatively activated macrophages revealed that stabilin-1-mediated endocytosis of SPARC was followed by its targeting for degradation, similar to the targeting of acetylated low density lipoprotein, another stabilin-1 ligand. We propose that alternatively activated macrophages coordinate extracellular matrix remodeling, angiogenesis, and tumor progression via stabilin-1-mediated endocytosis of SPARC and thereby regulate its extracellular concentration.

Loss of SPARC-mediated VEGFR-1 suppression after injury reveals a novel antiangiogenic activity of VEGF-A

VEGF-A promotes angiogenesis in many tissues. Here we report that choroidal neovascularization (CNV) incited by injury was increased by excess VEGF-A before injury but was suppressed by VEGF-A after injury. This unorthodox antiangiogenic effect was mediated via VEGFR-1 activation and VEGFR-2 deactivation, the latter via Src homology domain 2-containing (SH2-containing) tyrosine phosphatase-1 (SHP-1). The VEGFR-1-specific ligand placental growth factor-1 (PlGF-1), but not VEGF-E, which selectively binds VEGFR-2, mimicked these responses. Excess VEGF-A increased CNV before injury because VEGFR-1 activation was silenced by secreted protein, acidic and rich in cysteine (SPARC). The transient decline of SPARC after injury revealed a temporal window in which VEGF-A signaling was routed principally through VEGFR-1. These observations indicate that therapeutic design of VEGF-A inhibition should include consideration of the level and activity of SPARC.

ST7-mediated suppression of tumorigenicity of prostate cancer cells is characterized by remodeling of the extracellular matrix

Multiple lines of evidence have provided compelling evidence for the existence of a tumor suppressor gene (TSG) on chromosome 7q31.1. ST7 may be the target of this genetic instability but its designation as a TSG is controversial. In this study, we show that, functionally, ST7 behaves as a tumor suppressor in human cancer. ST7 suppressed growth of PC-3 prostate cancer cells inoculated subcutaneously into severe combined immunodeficient mice, and increased the latency of tumor detection from 13 days in control tumors to 23 days. Re-expression of ST7 was also associated with suppression of colony formation under anchorage-independent conditions in MDA-MB-231 breast cancer cells and ST7 mRNA expression was downregulated in 44% of primary breast cancers. Expression profiling of PC-3 cells revealed that ST7 predominantly induces changes in genes involved in re-modeling the extracellular matrix such as SPARC, IGFBP5 and several matrix metalloproteinases. These data indicate that ST7 may mediate tumor suppression through modification of the tumor microenvironment.

Bionic grandma

Aging takes a toll on organs and tissues. Skin rumples, hearts fail, and muscles weaken. Drugs and other interventions can sometimes slow the devastation but rarely repair existing damage. Furthermore, although transplants can replace ruined organs, demand for donors outstrips supply, and immune rejection is a risk. To circumvent these problems, researchers are working to create tissues in the lab that can substitute for defective ones in the body. Building on previous success in designing simple tissues such as skin and bone, they are seeking new biomaterials and methods to craft more complicated ones.