Biomedical subjects

E Helene Sage

Publications and source records attributed to E Helene Sage.

48 records · Page 3Linked to original sources

PubMed2003

Amelioration of diabetic nephropathy in SPARC-null mice.

SPARC (Secreted Protein, Acidic and Rich in Cysteine) is a matricellular protein that inhibits mesangial cell proliferation and also affects production of extracellular matrix (ECM) by regulating transforming growth factor-beta1 (TGF-beta1) and type I collagen in mesangial cells. This study is an investigation of the role of SPARC in streptozotocin (STZ)-induced diabetic nephropathy (DN) of 6-mo duration in wild type (WT) and SPARC-null mice. SPARC expression was evaluated by immunohistochemistry (IHC) and by in situ hybridization (ISH). Deposition of type I and IV collagen and laminin was evaluated by IHC, and TGF-beta 1 mRNA was assessed by ISH. Renal function studies revealed no significant difference in BUN between diabetic SPARC-null mice and diabetic WT mice, whereas a significant increase in albumin excretion was detected in diabetic WT relative to diabetic SPARC-null mice. Diabetic WT animals exhibited increased levels of SPARC mRNA and protein in glomerular epithelial cells and in interstitial cells, in comparison with nondiabetic WT mice. Neither SPARC mRNA nor protein was detected in SPARC-null mice. Morphometry revealed a significant increase in the percentage of the glomerular tufts occupied by ECM in diabetic WT compared with nondiabetic WT mice, although there was no difference in the mean glomerular tuft area among groups. In contrast, diabetic SPARC-null mice did not show a significant difference in the percentage of the glomerular tufts occupied by ECM relative to nondiabetic null mice. Tubulointerstitial fibrosis was ameliorated in diabetic SPARC-null mice compared with diabetic WT animals. Further characterization of diabetic SPARC-null mice revealed diminished glomerular deposition of type IV collagen and laminin, and diminished interstitial deposition of type I and type IV collagen correlated with decreases in TGF-beta 1 mRNA compared with WT diabetic mice. These observations suggest that SPARC contributes to glomerulosclerosis and tubulointerstitial damage in response to hyperglycemia through increasing TGF-beta 1 expression in this model of chronic DN.

Animals↗

PubMed2003

Enhanced growth of tumors in SPARC null mice is associated with changes in the ECM.

SPARC, a 32-kDa glycoprotein, participates in the regulation of morphogenesis and cellular differentiation through its modulation of cell-matrix interactions. Major functions defined for SPARC in vitro are de-adhesion and antiproliferation. In vivo, SPARC is restricted in its expression to remodeling tissues, including pathologies such as cancer. However, the function of endogenous SPARC in tumor growth and progression is not known. Here, we report that implanted tumors grew more rapidly in mice lacking SPARC. We observed that tumors grown in SPARC null mice showed alterations in the production and organization of ECM components and a decrease in the infiltration of macrophages. However, there was no change in the levels of angiogenic growth factors in comparison to tumors grown in wild-type mice, although there was a statistically significant difference in total vascular area. Whereas SPARC did inhibit the growth of tumor cells in vitro, it did not have a demonstrable effect on the proliferation or apoptosis of tumor cells in vivo. These data indicate that host-derived SPARC is important for the appropriate organization of the ECM in response to implanted tumors and highlight the importance of the ECM in regulating tumor growth.

Animals↗

PubMed2003

Expression of the matricellular protein SPARC in murine lens: SPARC is necessary for the structural integrity of the capsular basement membrane.

SPARC (Secreted Protein, Acidic and Rich in Cysteine) is a matricellular glycoprotein that modulates cell proliferation, adhesion, migration, and extracellular matrix (ECM) production. Although SPARC is generally abundant in embryonic tissues and is diminished in adults, we have found that the expression of SPARC in murine lens persists throughout embryogenesis and adulthood. Our previous studies showed that targeted ablation of the SPARC gene in mice results in cataract formation, a pathology attributed partially to an abnormal lens capsule. Here we provide evidence that SPARC is not a structural component of the lens capsule. In contrast, SPARC is abundant in lens epithelial cells, and newly differentiated fiber cells, with stable expression in wild-type mice up to 2 years of age. Pertubation of the lens capsule in animals lacking SPARC appears to be a consequence of the invasion of the lens cells situated beneath the capsule. Immunoreactivity for SPARC in the lens cells was uneven, with minimal reactivity in the epithelial cells immediately anterior to the equator. These epithelial cells appeared essentially noninvasive in SPARC-null mice, in comparison to the centrally located anterior epithelial cells, in which strong labeling by anti-SPARC IgG was observed. The posterior lens fibers exhibited cytoplasmic extensions into the posterior lens capsule, which was severely damaged in SPARC-null lenses. The expression of SPARC in wild-type lens cells, together with the abnormal lens capsule in SPARC-null mice, indicated that the structural integrity of the lens capsule is dependent on the matricellular protein SPARC. The effects of SPARC in the lens appear to involve regulation of lens epithelial and fiber cell morphology and functions rather than deposition as a structural component of the lens capsule.

Animals↗

PubMed2003

Osteonectin-null mutation compromises osteoblast formation, maturation, and survival.

Osteonectin, also known as SPARC (secreted protein acidic and rich in cysteine) or BM-40, is one of the most abundant noncollagenous proteins in bone. Analysis of osteonectin-null mice revealed that osteonectin is necessary for the maintenance of bone mass and normal remodeling, as osteonectin-null mice have decreased osteoblast number and bone formation rate. Cultures of bone marrow stromal cells and osteoblasts from control and osteonectin-null mice were used to determine the cellular basis for the mutant phenotype. We found that marrow stroma from osteonectin-null mice contains fewer osteoblastic precursors than that of control mice, and the osteonectin-null mutation did not affect the proliferation rate of stromal cells or osteoblasts. Whereas osteonectin-null cells could adopt an osteoblastic phenotype, a smaller proportion of these cells expressed markers of a fully differentiated osteoblast. Mutant cells exhibited decreased formation of mineralized nodules, as well as diminished expression of osteocalcin mRNA and response to PTH. Furthermore, osteonectin-null cells showed an increased tendency to form adipocytes, with enhanced expression of the adipocytic markers adipsin and CCAAT/enhancer binding protein delta. Osteonectin-null cells were also more susceptible to environmental stresses. These data indicate that osteonectin is important for osteoblast formation, maturation, and survival.

Animals↗

PubMed2002

Alterations in the lens capsule contribute to cataractogenesis in SPARC-null mice.

The lens capsule, which is also called the lens basement membrane, is a specialized extracellular matrix produced anteriorly by the lens epithelium and posteriorly by newly differentiated fiber cells. SPARC (secreted protein, acidic and rich in cysteine) is a matricellular glycoprotein that regulates cell-cell and cell-matrix interactions, cellular proliferation and differentiation, and the expression of genes encoding extracellular matrix components. SPARC-null mice exhibit lens opacity 1 month after birth and mature cataract and capsular rupture at 5-7 months. In this study, we report disruption of the structural integrity of the lens capsule in mice lacking SPARC. The major structural protein of basement membrane, collagen type IV, in the lens capsule was substantially altered in the absence of SPARC. The lens cells immediately beneath the capsule showed aberrant morphology, with numerous protrusions into the lens basement membrane. SPARC-null lenses at 1 month of age exhibited an increased penetration of dye or radioactive tracer through the capsule, as well as a higher content of water than their wild-type counterparts. Moreover, SPARC-null fibers exhibited swelling as early as 1 month of age; by 3 months, all the fiber cells appeared swollen to a marked degree. By contrast, the absence of SPARC had no apparent morphological effect on the early stages of lens formation, cell proliferation or fiber cell differentiation. Degradation of crystallins and MIP 26, or changes in the levels of these proteins, were not detected. These results underscore the importance of the capsular extracellular matrix in the maintenance of lens transparency and indicate that SPARC participates in the synthesis, assembly and/or stabilization of the lens basement membrane.

Animals↗

PubMed2002

Inhibition of PDGF-stimulated and matrix-mediated proliferation of human vascular smooth muscle cells by SPARC is independent of changes in cell shape or cyclin-dependent kinase inhibitors.

Interactions among growth factors, cells, and extracellular matrix regulate proliferation during normal development and in pathologies such as atherosclerosis. SPARC (secreted protein, acidic, and rich in cysteine) is a matrix-associated glycoprotein that modulates the adhesion and proliferation of vascular cells. In this study, we demonstrate that SPARC inhibits human arterial smooth muscle cell proliferation stimulated by platelet-derived growth factor or by adhesion to monomeric type I collagen. Binding studies with SPARC and SPARC peptides indicate specific and saturable interaction with smooth muscle cells that involves the C-terminal Ca2+-binding region of the protein. We also report that SPARC arrests monomeric collagen-supported smooth muscle cell proliferation in the late G1-phase of the cell cycle in the absence of an effect on cell shape or on levels of cyclin-dependent kinase inhibitors. Cyclin-dependent kinase-2 activity, p107 and cyclin A levels, and retinoblastoma protein phosphorylation are markedly reduced in response to the addition of exogenous SPARC and/or peptides derived from specific domains of SPARC. Thus, SPARC, previously characterized as an inhibitor of platelet-derived growth factor binding to its receptor, also antagonizes smooth muscle cell proliferation mediated by monomeric collagen at the level of cyclin-dependent kinase-2 activity.

Amino Acid Sequence↗

PubMed2002

Matricellular proteins: extracellular modulators of cell function.

The term 'matricellular' has been applied to a group of extracellular proteins that do not contribute directly to the formation of structural elements in vertebrates but serve to modulate cell-matrix interactions and cell function. Our understanding of the mode of action of matricellular proteins has been advanced considerably by the recent elucidation of the phenotypes of mice that are deficient in these proteins. In many cases, aspects of these phenotypes have illuminated previously unsuspected consequences of the lack of appropriate interactions of cells with their environment.

Animals↗

PubMed2002

Localization of SPARC in developing, mature, and chronically injured human allograft kidneys.

BACKGROUND: The matricellular protein SPARC (secreted protein acidic and rich in cysteine) is expressed during development, tissue remodeling and repair. It functions as an endogenous inhibitor of cell proliferation, regulates angiogenesis, regulates cell adhesion to extracellular matrix, binds cytokines such as platelet derived growth factor and stimulates transforming growth factor-beta (TGF-beta) production. This study describes the expression of SPARC during human renal development, in normal kidneys and during renal allograft rejection. METHODS: A total of 60 renal specimens, including normal areas from tumor nephrectomies (N = 24), fetal kidneys (N = 27) and explanted renal allografts (N = 9), were included in the study. SPARC protein was localized by immunohistochemistry using two different antibodies. On consecutive sections SPARC mRNA was detected by in situ hybridization. RESULTS: In the normal adult kidney SPARC protein was expressed by visceral and parietal epithelial cells, collecting duct epithelium (CD), urothelium, smooth muscle cells of muscular arteries and focally in interstitial cells. During renal development immature glomeruli demonstrated a polarized SPARC expression in visceral epithelial cells at their surface abutting the capillary basement membranes. In the fully differentiated glomeruli the expression pattern mirrored that of the adult kidney. Furthermore, SPARC was abundantly expressed by derivatives of the ureteric bud, and smooth muscle cells of arterial walls. During chronic allograft rejection SPARC is expressed in neointimal arterial smooth muscle cells, infiltrating inflammatory cells as well as by interstitial myofibroblasts in areas of interstitial fibrosis. SPARC mRNA synthesis detected by in situ hybridization mirrored these protein expression patterns. CONCLUSION: These studies co-localize SPARC to several sites of renal injury previously shown to be sites of PDGF B-chain expression and/or activity. We speculate that SPARC could function as an accessory molecule in chronic PDGF-mediated sclerosing interstitial and vascular injury. SPARC localization to glomerular epithelial cells corresponds to similar findings in rodents, and may reflect its role in cell adhesion and /or regulation of cell shape.

Adult↗

PubMed2002

Fractal analysis of region-based vascular change in the normal and non-proliferative diabetic retina.

PURPOSE: Evaluation of normal and abnormal vascular pattern in the human retina using a novel method: quantitative region-based fractal analysis. METHODS: Binary (black/white) vascular patterns of the human retina originating at the optic disc were obtained by semi-automatic computer processing of digital images from 60-degree fundus fluorescein angiography of 5 normal eyes and 5 eyes with non-proliferative diabetic retinopathy (NPDR). As determined by image resolution, vascular patterns included vessels with diameters >or=50 microm and excluded small vessels and capillaries. The density of linearized (i.e., skeletonized) vascular patterns in the macular region versus paramacular region (termed "region-based" linearized vascular pattern) was quantified with the fractal dimension (D(f)) and confirmed by grid intersection (rho(v)). RESULTS: By region-based quantification, D(f) and rho( v) were significantly higher in the normal macular region than in the NPDR macular region (p = 0.008 and p = 0.019, respectively). However, differences in D(f) and rho(v) between the normal and NPDR paramacular regions were not strongly significant (p = 0.168 and p = 0.337, respectively). CONCLUSIONS: Results from the retrospective analytical study demonstrate the feasibility of using quantitative region-based fractal analysis of early-stage vascular disease in the human retina. The results are encouraging for a broader study of diverse patient populations.

Diabetic Retinopathy↗

PubMed2002

SPARC-null mice exhibit accelerated cutaneous wound closure.

Expression of SPARC (secreted protein acidic and rich in cysteine; osteonectin, BM-40), an extracellular matrix (ECM) associated protein, is coincident with matrix remodeling. To further identify the functions of SPARC in vivo, we have made excisional wounds on the dorsa of SPARC-null and wild-type mice and monitored closure over time. A significant decrease in the size of the SPARC-null wounds, in comparison to that of wild-type, was observed at Day 4 and was maximal at Day 7. Although substantial differences in the percentage of proliferating cells were not apparent in SPARC-null relative to wild-type wounds, primary cultures of SPARC-null dermal fibroblasts displayed accelerated migration, relative to wild-type fibroblasts, in wound assays in vitro. Although the expression of collagen I mRNA in wounds, as measured by in situ hybridization (ISH), was not significantly different in SPARC-null vs wild-type mice, the collagen content of unwounded skin appeared to be substantially lower in the SPARC-null animals. By hydroxyproline analysis, the concentration of collagen in SPARC-null skin was found to be half that of wild-type skin. Moreover, we found an inverse correlation between the efficiency of collagen gel contraction by dermal fibroblasts and the concentration of collagen within the gel itself. We propose that the accelerated wound closure seen in SPARC-null dermis results from its decreased collagen content, a condition contributing to enhanced contractibility.

Animals↗

PubMed2002

Altered phosphodiesterase 3-mediated cAMP hydrolysis contributes to a hypermotile phenotype in obese JCR:LA-cp rat aortic vascular smooth muscle cells: implications for diabetes-associated cardiovascular disease.

Cardiovascular diseases represent a significant cause of morbidity and mortality in diabetes. Of the many animal models used in the study of non-insulin-dependent (type 2) diabetes, the JCR:LA-cp rat is unique in that it develops insulin resistance in the presence of obesity and manifests both peripheral and coronary vasculopathies. In this animal model, arterial vascular smooth muscle cells (VSMCs) from homozygous obese (cp/cp) rats, but not from age-matched healthy (+/+ or + /cp, collectively defined +/?) littermates, display an " activated" phenotype in vitro and in vivo and have an elevated level of cAMP phosphodiesterase (PDE) activity. In this report, we confirm that cp/cp rat aortic VSMCs have an elevated level of PDE3 activity and show that only particulate PDE3 (PDE3B) activity is elevated. In marked contrast to results obtained in + /? VSMCs, simultaneous activation of adenylyl cyclase and inhibition of PDE3 activity in cp/cp VSMCs synergistically increased cAMP. Although PDE3 inhibition did not potentiate the antimigratory effects of forskolin on +/? VSMCs, PDE3 inhibition did markedly potentiate the forskolin-induced inhibition of migration of cp/cp-derived VSMCs. Although PDE3 activity was elevated in cp/cp rat aortic VSMCs, levels of expression of cytosolic PDE3 (PDE3A) and PDE3B in +/? and cp/cp VSMCs, as well as activation of these enzymes following activation of the cAMP-protein kinase A signaling cascade, were not different. Our data are consistent with an increased role for PDE3 in regulating cAMP-dependent signaling in cp/cp VSMCs and identify PDE3 as a cellular activity potentially responsible for the phenotype of cp/cp VSMCs.

1-Methyl-3-isobutylxanthine↗

PubMedDate not supplied

A role for decorin in cutaneous wound healing and angiogenesis.

Decorin is known to influence tissue tensile strength and cellular phenotype. Therefore, decorin is likely to have an impact on tissue repair, including cutaneous wound healing. In this study, cutaneous healing of both excisional and incisional full-thickness dermal wounds was studied in decorin-deficient (Dcn(-/-)) animals. A statistically significant delay in excisional wound healing in the Dcn(-/-) mice occurred at 4 and 10 days postwounding and, in incisional wounds at 4, 10, and 18 days when compared with wild-type (Dcn(-/-)) controls. Fibrovascular invasion into polyvinylalcohol sponges was significantly increased by day 18 in Dcn(-/-) mice relative to Dcn(+/+) mice. The 18-day sponge implants in the Dcn(-/-) mice showed a marked accumulation of biglycan when compared with the corresponding implants in Dcn(+/+) mice. Thus, regulated production of decorin may serve as an excellent therapeutic approach for modifying impaired wound healing and harmful foreign body reactions.

Animals↗