Biomedical subjects

Paul Bornstein

Publications and source records attributed to Paul Bornstein.

At least 19 recordsLinked to original sources

PubMed2007

Thrombospondin-1 inhibits VEGF levels in the ovary directly by binding and internalization via the low density lipoprotein receptor-related protein-1 (LRP-1).

VEGF is a potent pro-angiogenic factor whose effects are opposed by a host of anti-angiogenic proteins, including thrombospondin-1 (TSP-1). We have previously shown that VEGF has important extravascular roles in the ovary and that VEGF and TSP-1 are inversely expressed throughout the ovarian cycle. To date, however, a causal interaction between TSP-1 and VEGF has not been identified. Here, we show that TSP-1 has a direct inhibitory effect on VEGF by binding the growth factor and internalizing it via LRP-1. Mice lacking TSP-1 are subfertile and exhibited ovarian hypervascularization and altered ovarian morphology. Treatment of ovarian cells with TSP-1 decreased VEGF levels and rendered the cells more susceptible to TNFalpha-induced apoptosis. Knockdown of TSP-1, through RNA interference, resulted in overexpression of VEGF and reduced cytokine-induced apoptosis. In conclusion, we demonstrate a direct inhibitory effect of TSP-1 on VEGF in the ovary. TSP-1's regulation of VEGF appears to be an important mediator of ovarian angiogenesis and follicle development.

Animals↗

PubMed2006

Glycosylation mediates up-regulation of a potent antiangiogenic and proatherogenic protein, thrombospondin-1, by glucose in vascular smooth muscle cells.

Accelerated development of atherosclerotic lesions remains the most frequent and dangerous complication of diabetes, accounting for 80% of deaths among diabetics. However, our understanding of the pathways mediating glucose-induced gene expression in vascular cells remains controversial and incomplete. We have identified an intracellular metabolic pathway activated by high glucose in human aortic smooth muscle cells that mediates up-regulation of thrombospondin-1 (TSP-1). TSP-1 is a potent antiangiogenic and proatherogenic protein that may represent an important link between diabetes and vascular complications. Using different glucose analogs and metabolites sharing distinct, limited metabolic steps with glucose, we demonstrated that activation of TSP-1 transcription is mediated by the hexosamine pathway of glucose catabolism, possibly resulting in modulation of the activity of nuclear proteins activity through their glycosylation. Specific inhibitors of glutamine: fructose 6-phosphate amidotransferase (GFAT), an enzyme controlling the hexosamine pathway, as well as direct inhibitors of protein glycosylation efficiently inhibited TSP-1 transcription and the activity of a TSP-1 promoter-reporter construct stimulated by high glucose. Overexpression of recombinant GFAT resulted in increased TSP-1 levels. Pharmacological inhibition of GFAT or protein glycosylation inhibited increased proliferation of human aortic smooth muscle cells caused by glucose. We have demonstrated that the hexosamine metabolic pathway mediates up-regulation of TSP-1 by high glucose. Our results suggest that the hexosamine pathway and intracellular glycosylation may control important steps in initiation and development of atherosclerotic lesions.

Angiogenesis Inhibitors↗

PubMed2006

The NH2-terminal propeptide of type I procollagen acts intracellularly to modulate cell function.

The function of the NH(2)-terminal propeptide of type I procollagen (N-propeptide) is poorly understood. We now show that a recombinant trimeric N-propeptide interacts with transforming growth factor-beta1 and BMP2 and exhibits functional effects in stably transfected cells. The synthesis of N-propeptide by COS-7 cells results in an increase in phosphorylation of Akt and Smad3 and is associated with a marked reduction in type I procollagen synthesis and impairment in adhesion. In C2C12 cells, N-propeptide inhibits the osteoblastic differentiation induced by BMP2. Our data suggest that these effects are mediated by the interaction of N-propeptide with an intracellular receptor in the secretory pathway, because they are not observed when recombinant N-propeptide is added to the culture medium of either COS-7 or C2C12 cells. Both the binding of N-propeptide to cytokines and its functional properties are entirely dependent on the exon 2-encoded globular domain, and a mutation that substitutes a serine for a highly conserved cysteine in exon 2 abolishes its function. Our findings suggest that N-propeptide performs an important feedback regulatory function and provides a rationale for the prominence of a homotrimeric form of type I procollagen (alpha1 trimer) during vertebrate development.

Animals↗

PubMed2006

Reduced expression of thrombospondins and craniofacial dysmorphism in mice overexpressing Fra1.

UNLABELLED: Fra1 transgenic (Tg) mice develop osteosclerosis and exhibit altered expression of bone matrix proteins. We found that expression of Thbs1 and Thbs2 was reduced in Fra1 Tg osteoblasts. Fra1 Tg and non-osteosclerotic Thbs1-/-Thbs2-/- mice share an edge-to-edge bite. Therefore, reduced expression of thrombospondins may contribute to craniofacial dysmorphism independently of osteosclerosis. INTRODUCTION: Tg mice overexpressing Fra1, a component of the transcription factor activator protein-1 (AP-1), show progressive osteosclerosis caused by cell autonomous abnormalities in osteoblasts. The expression of several bone matrix proteins, including matrix gla protein, is dysregulated in Fra1 Tg osteoblasts. MATERIALS AND METHODS: In osteoblastogenic cultures, altered bone matrix production by Fra1 overexpression was monitored using Alizarin red staining, quantitative RT-PCR, and Western blotting. Responsiveness to ovariectomy was examined by bone histomorphometry. Craniofacial parameters were measured on radiographs and using CT. RESULTS: Thrombospondin-1 (Thbs1) and thrombospondin-2 (Thbs2) were reduced in Fra1 Tg osteoblasts differentiated in vitro and in bones from Fra1 Tg mice. Despite alterations in bone matrix proteins, ovariectomy induces high turnover bone loss in Fra1 Tg mice as in wildtype mice. Fra1 Tg mice, as well as Thbs1-/- Thbs2-/- mice, which do not show osteosclerosis, exhibit an edge-to-edge bite phenotype associated with craniofacial dysmorphism. CONCLUSIONS: These data suggest that reduced expression of thrombospondins in Fra1 Tg mice underlies craniofacial dysmorphism, independent of osteosclerosis.

Animals↗

PubMed2006

Thrombospondins deployed by thrombopoietic cells determine angiogenic switch and extent of revascularization.

Thrombopoietic cells may differentially promote or inhibit tissue vascularization by releasing both pro- and antiangiogenic factors. However, the molecular determinants controlling the angiogenic phenotype of thrombopoietic cells remain unknown. Here, we show that expression and release of thrombospondins (TSPs) by megakaryocytes and platelets function as a major antiangiogenic switch. TSPs inhibited thrombopoiesis, diminished bone marrow microvascular reconstruction following myelosuppression, and limited the extent of revascularization in a model of hind limb ischemia. We demonstrate that thrombopoietic recovery following myelosuppression was significantly enhanced in mice deficient in both TSP1 and TSP2 (TSP-DKO mice) in comparison with WT mice. Megakaryocyte and platelet levels in TSP-DKO mice were rapidly restored, thereby accelerating revascularization of myelosuppressed bone marrow and ischemic hind limbs. In addition, thrombopoietic cells derived from TSP-DKO mice were more effective in supporting neoangiogenesis in Matrigel plugs. The proangiogenic activity of TSP-DKO thrombopoietic cells was mediated through activation of MMP-9 and enhanced release of stromal cell-derived factor 1. Thus, TSP-deficient thrombopoietic cells function as proangiogenic agents, accelerating hemangiogenesis within the marrow and revascularization of ischemic hind limbs. As such, interference with the release of cellular stores of TSPs may be clinically effective in augmenting neoangiogenesis.

Animals↗

PubMed2005

Mice lacking thrombospondin 2 show an atypical pattern of endocortical and periosteal bone formation in response to mechanical loading.

Thrombospondin 2 (TSP2) is an extracellular matrix (ECM) protein localized to bone. Since mice with a targeted disruption of the TSP2 gene (TSP2-null) have increased bone formation, we hypothesized that mice lacking TSP2 would show an enhanced osteogenic response to mechanical loading. We addressed our hypothesis by subjecting wild-type (WT) and TSP2-null mice to mechanical loading using the non-invasive murine tibia loading device, and statistical comparisons were made between loaded and unloaded bones within genotype, between genotypes, and between the periosteal and endocortical surfaces within genotype. Right tibiae of WT and TSP2-null mice received 5 days of a low-magnitude loading protocol. This low-magnitude loading (inducing approximately 900 and 500 muepsilon at periosteal and endocortical surfaces of WT bones, respectively) affected neither periosteal nor endocortical bone formation rate (BFR/BS) when comparing loaded to intact bones in either WT or TSP2-null mice, nor did it result in any significant differences between WT and TSP2-null. As well, there was no difference between loaded endocortical and periosteal surfaces in WT mice; however, endocortical BFR/BS in TSP2-null loaded tibia was significantly elevated relative to the periosteal BFR/BS-despite peak periosteal strains being significantly greater than endocortical strains in TSP2-null mice (690 versus 460 muepsilon). To confirm this counterintuitive surface-specific response in TSP2-null mice and to induce significant periosteal bone formation, osteogenic potency of the loading protocol was amplified by doubling the number of loading bouts (10 loading days) and loading magnitude (1 Hz, resulting in 1400 and 900 muepsilon peak strain at the periosteal and endocortical surfaces, respectively). Under load, both WT and TSP2-null mice showed significantly increased periosteal mineralizing surface (by nearly three-fold and five-fold, respectively), but mineral apposition rate (MAR) was not statistically changed. The increased MS/BS resulted in a five-fold increase in WT periosteal BFR/BS, but the TSP2-null periosteal BFR/BS was unchanged. Furthermore, this increase in WT loaded periosteal BFR/BS was statistically greater than the WT endocortical BFR/BS. At the endocortical surface of WT mice, loading did not significantly increase bone formation parameters (versus intact). In contrast, at the endocortical surface of TSP2-null mice, loading induced a significant two-fold increase in BFR/BS (versus intact), that was also significantly greater than the endocortical BFR/BS of loaded WT mice. Thus, exogenous loading of TSP2-null mice resulted in highly variable responses that did not reflect the induced strains at the periosteal and endocortical surfaces. While in WT mice, loading resulted in increased periosteal BFR/BS that was greater than the endocortical BFR/BS, in TSP2-null mice loading resulted in endocortical (not periosteal) BFR/BS that was elevated. This reversal in envelope-specific bone formation in TSP2-null mice occurred despite periosteal strains being significantly greater than endocortical (1290 versus 775 muepsilon) and strain distributions being similar to that of WT. These results show that the disruption of a single gene can lead to a reversal in normal pattern of load induced bone formation, and more specifically, that the functional interaction of TSP2 with mechanical loading is highly contextual and specific to the cortical bone envelope examined.

Animals↗

PubMed2005

Akt1 regulates pathological angiogenesis, vascular maturation and permeability in vivo.

Akt kinases control essential cellular functions, including proliferation, apoptosis, metabolism and transcription, and have been proposed as promising targets for treatment of angiogenesis-dependent pathologies, such as cancer and ischemic injury. But their precise roles in neovascularization remain elusive. Here we show that Akt1 is the predominant isoform in vascular cells and describe the unexpected consequences of Akt1 knockout on vascular integrity and pathological angiogenesis. Angiogenic responses in three distinct in vivo models were enhanced in Akt1(-/-) mice; these enhanced responses were associated with impairment of blood vessel maturation and increased vascular permeability. Although impaired vascular maturation in Akt1(-/-) mice may be attributed to reduced activation of endothelial nitric oxide synthase (eNOS), the major phenotypic changes in vascular permeability and angiogenesis were linked to reduced expression of two endogenous vascular regulators, thrombospondins 1 (TSP-1) and 2 (TSP-2). Re-expression of TSP-1 and TSP-2 in mice transplanted with wild-type bone marrow corrected the angiogenic abnormalities in Akt1(-/-) mice. These findings establish a crucial role of an Akt-thrombospondin axis in angiogenesis.

Actins↗

PubMed2005

Low-density lipoprotein receptor-related protein contributes to the antiangiogenic activity of thrombospondin-2 in a murine glioma model.

Host antiangiogenesis factors defend against tumor growth. The matricellular protein, thrombospondin-2 (TSP-2), has been shown to act as an antiangiogenesis factor in a carcinogen-induced model of skin cancer. Here, using an in vivo malignant glioma model in which the characteristics of the tumors formed after intracerebral implantation of GL261 mouse glioma cells are assessed, we found that tumor growth and microvessel density were significantly enhanced in tumors propagated in TSP-2(-/-) mice. Mechanistically, matrix metalloproteinase (MMP)-2 has been associated with neoangiogenesis and it has been proposed that the levels of available MMP-2 may be down-regulated by formation of a complex with TSP-2 that is internalized by low-density lipoprotein receptor-related protein 1 (LRP1). We found elevated expression of MMP-2 and MMP-9 in tumors propagated in TSP-2(-/-) mice, with a preferential localization in the microvasculature. In wild-type mice, MMP-2 was coexpressed with TSP-2 in the tumor microvasculature. In vitro, addition of recombinant (rec) TSP-2 to mouse brain microvessel endothelial cells reduced MMP-2 levels and invasion through mechanisms that could be inhibited by a competitive inhibitor of ligand binding to LRP1 or by siLRP1. Thus, the antiangiogenic activity of TSP-2 is capable of inhibiting the growth of gliomas in part by reducing the levels of MMP-2 in the tumor microvasculature. This mechanism is mediated by LRP1.

Animals↗

PubMed2005

Oncogenes and Angiogenesis: down-regulation of thrombospondin-1 in normal fibroblasts exposed to factors from cancer cells harboring mutant ras.

The onset of angiogenesis in cancer often involves down-regulation of endogenous angiogenesis inhibitors, of which thrombospondin-1 (TSP-1) is a paradigm. As this effect is thought to occur under the influence of transforming genetic lesions (e.g., expression of the mutant ras oncogene), its nature is regarded as intrinsic to cancer cells themselves. Here, we show that ras-transformed cancer cells can also induce TSP-1 down-regulation in their adjacent nontransformed stromal fibroblasts, but not in endothelial cells, in a paracrine and distance-dependent manner. Indeed, several H-ras-expressing fibrosarcoma (528ras1, B6ras, and NIH3T3Ras) and carcinoma (DLD-1 and IEC18Ras3) cells were found to release soluble factors capable of suppressing TSP-1 protein, mRNA, and promoter activity in nontumorigenic, immortalized dermal fibroblastic cell lines in culture (e.g., in fibroblasts expressing enhanced green fluorescent protein/TSP-1 reporter). This effect was abrogated in Id1-/- fibroblasts. At least two low molecular weight (<3 kDa), heat-labile, and trypsin-resistant mediators of TSP-1 suppression were found to be released from 528ras1 cells. Their effects on normal fibroblasts were inhibited (albeit to different extents) by pertussis toxin and, in one case, by dimethylsphingosine, none of which affected TSP-1 expression by 528ras1 cells. Collectively, our study suggests that the effect of mutant ras on tumor neovascularization is not limited to changes in angiogenic properties of cancer cells themselves. Rather, mutant ras, through a different signaling mechanism, may modulate the properties of the adjacent normal stroma, thus eliciting a proangiogenic field effect.

Animals↗

PubMed2005

Thrombospondins are astrocyte-secreted proteins that promote CNS synaptogenesis.

The establishment of neural circuitry requires vast numbers of synapses to be generated during a specific window of brain development, but it is not known why the developing mammalian brain has a much greater capacity to generate new synapses than the adult brain. Here we report that immature but not mature astrocytes express thrombospondins (TSPs)-1 and -2 and that these TSPs promote CNS synaptogenesis in vitro and in vivo. TSPs induce ultrastructurally normal synapses that are presynaptically active but postsynaptically silent and work in concert with other, as yet unidentified, astrocyte-derived signals to produce functional synapses. These studies identify TSPs as CNS synaptogenic proteins, provide evidence that astrocytes are important contributors to synaptogenesis within the developing CNS, and suggest that TSP-1 and -2 act as a permissive switch that times CNS synaptogenesis by enabling neuronal molecules to assemble into synapses within a specific window of CNS development.

Animals↗

PubMed2005

Proteolysis of cell-surface tissue transglutaminase by matrix metalloproteinase-2 contributes to the adhesive defect and matrix abnormalities in thrombospondin-2-null fibroblasts and mice.

Thrombospondin (TSP)-2-null dermal fibroblasts display an attachment defect that results from increased matrix metalloproteinase (MMP)-2 levels in their conditioned media. To investigate the molecular mechanisms responsible for this defect, we analyzed the activity of tissue transglutaminase (tTG) in TSP-2-null dermal fibroblasts and in tissues of TSP-2-null mice. tTG functions as a co-receptor for beta1 and beta3 integrins and stabilizes extracellular matrix proteins by introduction of isopeptide cross-links. Cell-surface tTG activity was reduced in TSP-2-null cells (0.50 +/- 0.05 arbitrary units versus 0.84 +/- 0.07 for wild type; P < or = 0.05), and addition of MMP-2 to the culture medium of wild-type cells caused a 35% reduction in cell-surface tTG activity. tTG was susceptible to proteolysis by MMP-2 in vitro, and addition of the MMP inhibitor TIMP-2 to TSP-2-null cells restored tTG activity (0.3 +/- 0.08 for untreated cells; 0.71 +/- 0.09 with TIMP-2). TSP-2-null mice had reduced tTG activity in skin, as measured by incorporation of fluorescein isothiocyanate-labeled cadaverine, and a threefold increase in acetic acid-extracted dermal collagen. Furthermore, isopeptide cross-links were reduced in both uninjured skin and in excisional wounds of TSP-2-null mice, as determined by morphometric immunohistochemical analysis, indicating that isopeptide cross-links are important for the stabilization of the collagenous matrix in dermis. These findings provide a mechanism for the reduced adhesion of TSP-2-null fibroblasts and an explanation for the increased collagen solubility and fragility of TSP-2-null skin.

Animals↗

PubMed2005

Mice with a disruption of the thrombospondin 3 gene differ in geometric and biomechanical properties of bone and have accelerated development of the femoral head.

Thrombospondin 3 (TSP3) is structurally similar to cartilage oligomeric matrix protein (COMP/TSP5), but its function is unknown. To determine the functional significance of TSP3, we generated mice with a targeted disruption of Thbs3. TSP3-null mice are viable and fertile and show normal prenatal skeletal patterning, based on Alcian blue/Alizarin red S staining. However, subtle and transient abnormalities were detected in the developing postnatal skeleton. Young adult TSP3-null mice are heavier than controls, and analyses of the geometric and biomechanical properties of long bones show increases in the moments of inertia, endocortical and periostal radii, and failure load. The bones of 9-week-old TSP3-null male mice also have a significantly greater cortical area. Most of these differences were no longer detected in 15-week-old mice. Micro-computed tomography scans showed that the trabecular bone proximal to the femoral head growth plate developed at an earlier time in TSP3-null mice than in wild-type mice. Thus, vascular invasion and ossification start in the femoral heads of TSP3-null mice at 9 weeks, whereas the wild-type femoral head is still composed of hypertrophic chondroctyes in a calcified matrix at 15 weeks. These results provide evidence for a role for TSP3 in the regulation of skeletal maturation in mice.

Animals↗

PubMed2005

SPARC-thrombospondin-2-double-null mice exhibit enhanced cutaneous wound healing and increased fibrovascular invasion of subcutaneous polyvinyl alcohol sponges.

Secreted protein acidic and rich in cysteine (SPARC) and thrombospondin-2 (TSP-2) are structurally unrelated matricellular proteins that have important roles in cell-extracellular matrix (ECM) interactions and tissue repair. SPARC-null mice exhibit accelerated wound closure, and TSP-2-null mice show an overall enhancement in wound healing. To assess potential compensation of one protein for the other, we examined cutaneous wound healing and fibrovascular invasion of subcutaneous sponges in SPARC-TSP-2 (ST) double-null and wild-type (WT) mice. Epidermal closure of cutaneous wounds was found to occur significantly faster in ST-double-null mice, compared with WT animals: histological analysis of dermal wound repair revealed significantly more mature phases of healing at 1, 4, 7, 10, and 14 days after wounding, and electron microscopy showed disrupted ECM at 14 days in these mice. ST-double-null dermal fibroblasts displayed accelerated migration, relative to WT fibroblasts, in a wounding assay in vitro, as well as enhanced contraction of native collagen gels. Zymography indicated that fibroblasts from ST-double-null mice also produced higher levels of matrix metalloproteinase (MMP)-2. These data are consistent with the increased fibrovascular invasion of subcutaneous sponge implants seen in the double-null mice. The generally accelerated wound healing of ST-double-null mice reflects that described for the single-null animals. Importantly, the absence of both proteins results in elevated MMP-2 levels. SPARC and TSP-2 therefore perform similar functions in the regulation of cutaneous wound healing, but fine-tuning with respect to ECM production and remodeling could account for the enhanced response seen in ST-double-null mice.

Animals↗

PubMed2004

Thrombospondin-2 is essential for myocardial matrix integrity: increased expression identifies failure-prone cardiac hypertrophy.

Cardiac hypertrophy can lead to heart failure (HF), but it is unpredictable which hypertrophied myocardium will progress to HF. We surmised that apart from hypertrophy-related genes, failure-related genes are expressed before the onset of failure, permitting molecular prediction of HF. Hearts from hypertensive homozygous renin-overexpressing (Ren-2) rats that had progressed to early HF were compared by microarray analysis to Ren-2 rats that had remained compensated. To identify which HF-related genes preceded failure, cardiac biopsy specimens were taken during compensated hypertrophy and we then monitored whether the rat progressed to HF or remained compensated. Among 48 genes overexpressed in failing hearts, we focused on thrombospondin-2 (TSP2). TSP2 was selectively overexpressed only in biopsy specimens from rats that later progressed to HF. Moreover, expression of TSP2 was increased in human hypertrophied hearts with decreased (0.19+/-0.01) versus normal ejection fraction (0.11+/-0.03 [arbitrary units]; P<0.05). Angiotensin II induced fatal cardiac rupture in 70% of TSP2 knockout mice, with cardiac failure in the surviving mice; this was not seen in wild-type mice. In TSP2 knockout mice, angiotensin II increased matrix metalloproteinase (MMP)-2 and MMP-9 activity by 120% and 390% compared with wild-type mice (P<0.05). In conclusion, we identify TSP2 as a crucial regulator of the integrity of the cardiac matrix that is necessary for the myocardium to cope with increased loading and that may function by its regulation of MMP activity. This suggests that expression of TSP2 marks an early-stage molecular program that is activated uniquely in hypertrophied hearts that are prone to fail.

Angiotensin II↗

PubMed2004

The role of thrombospondins 1 and 2 in the regulation of cell-matrix interactions, collagen fibril formation, and the response to injury.

Thrombospondins (TSPs) 1 and 2 are extracellular modular glycoproteins that are best known for their anti-angiogenic properties and their ability to modulate cell-matrix interactions. However, these proteins, and in particular TSP2, are pleiotropic in function and affect processes as disparate as bone growth and hemostasis. In recognition of their ability to influence a wide variety of cell functions, and in the absence of convincing evidence for their participation as integral components of extracellular structures, the term 'matricellular' has been applied to these and a small group of functionally related proteins. In this review, we focus on the role of TSP1 and 2 in two forms of injury in mice, excisional skin wounds and subcutaneously implanted biomaterials, and take advantage of mice with targeted disruptions of one or both genes to identify likely biochemical mechanisms that could account for the characteristics of the injury response in these knockout mice. In work that stems largely from our own laboratory, we show that pericellular levels of the matrix metalloproteinase, MMP2, are controlled to a large extent by TSP2 (and potentially also by TSP1), and that elevated levels of MMP2 are likely to account in part for defects as diverse as reduced cellular adhesion, abnormal collagen fibril structure, and increased endothelial cell and vascular proliferation.

Animals↗

PubMed2004

Thrombospondin 2 levels are increased in aged mice: consequences for cutaneous wound healing and angiogenesis.

The inhibitor of angiogenesis, thrombospondin 2 (TSP2), belongs to a group of matricellular proteins that are induced in response to injury and modulate the healing of dermal wounds. Thus, TSP-2-null mice display abnormal connective tissue architecture and increased angiogenesis in the dermis, and heal wounds at an accelerated rate. In this study, we report that the content of TSP2 is increased in the uninjured skin of aged mice. Furthermore, in primary dermal fibroblasts, TSP2 expression is increased both as a function of the age of the donor and days in culture. To determine the significance of the increased TSP2 in aged mice (two years or older), we performed full-thickness excisional wounds and compared their healing in aged and young (3-4 months) wild-type and TSP2-null mice. Gross morphological examination of wounds indicated that aged TSP2-null mice healed faster than their aged wild-type counterparts, but healing in aged mice was always sub-optimal in comparison to that in young animals. Surprisingly, despite the increase in TSP2, a potent inhibitor of angiogenesis, in wounds in aged mice, the vascular density of these wounds was not reduced in comparison to that in young animals. However, immunohistochemical analysis of healing wounds revealed a shift in the peak content of TSP2, from day 10 in young mice to day 14 or later in aged mice, and there was a corresponding delay in the expected increase in matrix metalloproteinase (MMP) 2 levels in aged TSP2-null mice. We suggest that the delay in expression of TSP2 and MMP2 in the wounds of aged mice could contribute to their impaired rate of wound healing.

Aging↗

PubMed2004

The CC chemokine ligand, CCL2/MCP1, participates in macrophage fusion and foreign body giant cell formation.

The foreign body reaction (FBR) develops in response to the implantation of almost all biomaterials and can be detrimental to their function. The formation of foreign body giant cells (FBGC), which damage the surface of biomaterials, is considered a hallmark of this reaction. FBGC derive from blood-borne monocytes that enter the implantation site after surgery in response to the release of chemotactic signals. In this study, we implanted biomaterials subcutaneous (s.c.) in mice that lack the monocyte chemoattractant CC chemokine ligand 2 (CCL2) and found that biomaterials were encapsulated despite reduced FBGC formation. The latter was due to compromised macrophage fusion rather than migration. Consistent with the reduction in FBGC formation, biodegradable biomaterials sustained reduced damage in CCL2-null mice. Furthermore, blockade of CCL2 function by localized gene delivery in wild-type mice hindered FBGC formation, despite normal monocyte recruitment. The requirement for CCL2 in fusion was confirmed by the ability of both a CCL2 inhibitory peptide and an anti-CCL2 Ab to reduce FBGC formation from peripheral blood monocytes in an in vitro assay. Our findings demonstrate a previously unreported involvement of CCL2 in FBGC formation, and suggest that FBGC are not the primary determinants of capsule formation in the FBR.

Animals↗

PubMed2004

Roles of thrombospondin-1 and -2 in regulating corneal and iris angiogenesis.

PURPOSE: Thrombospondin (TSP)-1 and -2 are important antiangiogenic factors thought to be involved in maintaining corneal avascularity (angiogenic privilege). This study was undertaken to investigate whether deficiencies of these factors altered developmental and inflammation-induced angiogenesis in the cornea and developmental angiogenesis of the iris of mice. METHODS: Expression of TSP-1 and -2 mRNA and protein was assayed in cornea and iris stroma by RT-PCR and Western blot. Corneas and irides of TSP-1(-/-), TSP-2(-/-), and TSP-1,2(-/-) mice aged 2, 3, and 6 months, and wild-type control mice, were analyzed for spontaneous angiogenesis biomicroscopically, histologically, and with CD31 immunohistochemistry. The mouse model of suture-induced, inflammatory corneal neovascularization was used to evaluate the lack of TSP-1,2 and both TSPs on induced-corneal angiogenesis. Seven days after intrastromal placement of three 11-0 sutures, vascularized areas were analyzed morphometrically on CD31-stained corneal flatmounts. RESULTS: Corneas and irises from normal mouse eyes constitutively expressed TSP-1 and -2 mRNAs and proteins. Corneas of TSP-1(-/-), -2(-/-), and -1,2(-/-) mice displayed no evidence of spontaneous developmental-postnatal angiogenesis, although irises of these mice contained significantly increased iris vessel density compared with wild-type animals (P < 0.01). One week after suturing, corneas of all TSP(-/-) mice had significantly greater corneal angiogenesis than those of control mice (P < 0.05). TSP-1(-/-) had a significantly greater effect on induced corneal neovascularization than did TSP-2(-/-), with the opposite being the case in developmental iris angiogenesis (P < 0.01). CONCLUSIONS: Corneal avascularity during development is redundantly regulated, shown by the fact that lack of the antiangiogenic factors TSP-1 and/or -2 resulted in no spontaneous corneal angiogenesis. By contrast, TSP-1, more than TSP-2, helps to suppress inflammation-induced corneal angiogenesis postnatally, implying that angiogenic privilege in the cornea is actively maintained.

Animals↗